The tetrabutylammonium ferrate(1-), n-Bu₄N[Fe(CO)₃NO] (TBAF), was prepared by the reaction of Fe(CO)₅ with NaNO₂ in benzene-water in the presence of n-Bu₄NBr. TBAF was stable to air and moisture and applied to the synthesis of a variety of (η³-allyl)dicarbonylnitrosyliron complexes. The reaction of allylic halides with TBAF gave (η³-allyl)iron complexes which can be converted to 1, 5-diene derivatives and β, γ-unsaturated carbonyl compounds by treatment with allylic halides and acyl or alkoxycarbonyl halides, respectively. The reaction of alkyl halides with TBAF in the presence of conjugated dienes gave acylmethylsubstituted (η³-allyl)iron complexes which can be converted to conjugated dienone derivatives and homoallyl alcohols by treatment with NaOCH₃ and LiAlH₄, respectively. The mechanistic features of these reactions are discussed.

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Desulfurization reaction of 4, 5-diaryl-1, 3-dioxolene-2-thione [ 1 ], namely vinylene trithiocarbonates, with an equimolar amount of hexacarbonylmolybdenum, Mo(CO)₆, in refluxing toluene afforded pentacarbonyl(4, 5-diaryl-1, 3-dioxolen-2-ylidene)molybdenum[ 2 ] in low yields, accompanied by the formation of acetylenes [ 3 ]J, vinylene carbonates [ 4 ], and 1, 2ethanediones [ 5 ]. Yields and selectivities in the formation of the dioxocarbene complexes [2 ]J were much improved by the addition of excess amount of Mo(CO)₆ to [ 1]. In the presencoef triphenylphosphteintrea, c arbony51-d(4ia, r y13--1d, i oxolen-2-yli(dterinpeh)e nylphosphine)molybdenum [ 6 ] was obtained in the isolated yield of 30% by the reaction! of [ 1 ] (aryl =Ph) with Mo(CO)₆.
The dioxocarbene complex [ 2 ]J w as thermally decomposed in refluxing decalin to give riot tetracarbonylbis(4, 5-diaryl-1, 3-dioxolen-2-ylidene)molybdenum [ 9 ] or the carbene dimer, but [ 3 ], [ 4 ], and [ 5 ]. However, [ 2 ] was converted to the bis (dioxocarbene) complex [ 9 ] in the co-presence of trithiocarbonate such as [ 1 ] or 1, 3 -dithiolane-2-thione [ 10 ], In the latter case, [ 10 ] reacted also with [ 2 ] to form the vinylene trithiocarbpnate [ 1 ] in a moderate yield. The dioxocarbene complex [ 2 ] reacted with oxygen and elemental sulfur to afford [ 4 ] and [ 1 ], respectively.
The desulfurization reaction of [ 1 ] with hexacarbonyl-chromium or -wolfrum failed and the starting materials were recovered in almost quantitative yields.

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π-Allylpalladium complexes were prepared from s-trans conjugated dienes, such as 3-methylenecyclohexene [7 a], and 6-methyl [7 b]1 6-isopropyl [7 c] and 6-t-butyl [7 d]analogs. The structures of the complexes were examined by ¹H and ¹³C NMR spectroscopy. Reactions of dienes with sodium tetrachloropalladate(II) in methanol at 0°C gave the exo-cyclic complexes [10], in which a methoxyl uoup is incorporated onto the endo-cyclic terminal carbon of the conjugated system. Endo-cyclic complexes, [11 c] and [11 d], in which a hydrogen is incorporated onto the exo-cyclic terminal of the diene were formed from [7 c] and [7 d], respectively, while [10 a] and [10 b] from [7 a] and [7 b] respectively, when the reaction was carried out in methanol at 50∼60°C. In tetrahydrofuran [7 b] was converted to [11 b]. The results indicate that π-allylpalladium complexes are formed directly from s-trans conjugated dienes. The hydrogen atom, which is incorporated onto the diene, is proved to come from the excess diene, which converts to the aromatic compound by double bond migration and dehydrogenation. The mechanism of complex formation is discussed.

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An efficient method for the nucleophilic addition of organometallic reagents to imines is reported. RCu⋅BF₃, generated in situ from Grignard reagents, CuI and BF₃⋅Et₂, was added to aldimines without deprotonation of a-hydrogen to afford secondary amines in good yields, , (57∼85%). Boron trifluoride complex of dialkylcuprate( I ) gave essentially the same re sults with wider application. Furthermore, alkynyltrifluoroborates, prepared in situ from alkynyllithium and BF₃⋅OEt₂, were added to aldimines containing α-hydrogens to afford α-(1alkynyl)amines in good yields (57∼82%).

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For the purpose of developing the synthetic application of aryliminodimagnesium reagent (ArN(MgBr)₂, IDMg), the reactions of ethylmagnesium bromide (EtMgBr) with ami ne hydrochlorides as well as hydroxy- and amino-substituted anilines were examined. Aniline hydrochloride and o-phenylenediamine gave IDMg-type reagent on the treatment with three molar equivalents of EtMgBr.
When the latter reag ent [B] was allowed to react with p-methyl-, p-methoxy-, p-chloro-, and o-hydroxy-nitrobenzenes, o'-amino-azobenzene derivatives were obtained as the major product in 30∼40% yields. The yield of the desired o-aminoazobenzenes was not improved in contrast to the high combined yields of unsymmetrical azoxy- and azo-benzenes obtained previously by the reaction of typical aryl-IDMg and nitrobenzenes. On the basis of the working hypothesis proposed recently for the explanation of the reaction profiles of organomagnesium reagents, the yield distribution of the o-aminoazobenzene and five types of minor products was discussed in terms of the high electron-donating ability of reagent [B] as well as its sterically hindered hisntdruecretudre.

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Bromomagnesium thioureide complex underwent fixation of carbon dioxide and the resulting carbamate complex transferred the carboxylato group to active methylene compounds. The carbamate complexes, prepared from 6- and 7-membered cyclic thioureas, were particularly excellent in the carboxylafing ability, which carboxylated esters as well as ketones under mild conditions.
The monocarbamate complex was less effective in the carboxylation than the dicarbamate complex.

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The reactions of diethylzinc, trimethylaluminum, triethylaluminum and triisobutylaluminum with aliphatic ketones including 2-alkanones and 3-alkanones, and cyclic ketones have been carried out to examine the effect of their alkyl substituents on the reaction mode. Diethylzinc gave meither addition nor reduction products but gave condensation products when heated to 90°C. The reaction of AlR₃(R =Me, Et) with 2-alkanone gave 2: 1 addition products at 30°C. Further addition of 2-alkanone to the addition product resulted in the formation of the condensation product at>80°C. (E)/(Z)-ratios of the aluminumenolates obtained from various ketones were analyzed by means of NMR spectra. Catalysis of EtZn(OZn)_nEt or Et₂Al(OAlEt)_nEt for isomerization of α, β-to β, γ-unsarurated ketones was also examined.

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The pronounced solvent as well as temperature effects on the course of trialkylaluminuminduced cyclization of unsaturated aldehydes were observed. Thus, unimolecular decomposition of the 1: 1 complex of trimethylaluminum-citronellal at -78°C to room temperature led to the formation of an acyclic methylated compound, isopulegol as a cyclization-deprotonation product, and/or a methylated cyclization product depending on the choice of solvents. The acyclic compound was obtained predominantly in hexane, while isopulegol was produced exclusively in 1, 2-dichloroethane. Furthermore, the methylated cyclization product was formed with the highest selectivity using excess trimethylaluminum at low temperature. In contrast with trimethylaluminum, the 1: 1 complex of other trialkylaluminum-citronellal decomposed upon warming to room temperature to furnish a reduction product, citronellol as a major product. Another aldehyde showed a similar variation in reactivity under the apove conditions.

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Epoxy resins were photocured with a new type of photoinitiation catalyst which consists of aluminum complex and (o-nitrobenzyloxy)triphenyl silane and the properties of the epoxy resins photocured were examined. Photocure time of epoxy resin varied by the structure of the aluminum complex and the silyl ether. The catalyst activity was best when using tris (ethyl acetoacetato) aluminum as aluminum complex and tris(4-chlorophenyl) (o-nitrobenzyloxy)silane as silyl ether. The catalyst activity increased with an increase in temperature. The epoxy resins photocured with this catalyst have excellent electrical properties, which have not been observed for epoxy resins cured with any other catalysts. Volume resistivity of epoxy resin cured with this catalyst is 100 times higher than that cured with strong acid type catalyst, such as onium salt of SbF6-. Corrosiveness of epoxy resin photocured with this catalyst was 10³ times lower, compared to in case of strong acid type catalyst.

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The reactions of trialkylgermyl anions, R₃Ge^-, with aryltins, ArSnR'₃, have been investigated. Trimethylgermyl anion reacted with aryltins in HMPAJether at -30°C for 5 min to give the corresponding substitution products, ArGeMe₃, reduction products, ArH. Most of these substitution products were converted to the reduction products when dicyclohexylphosphine, a trapping agent for free radicals was present in the reaction mixture. These results are consistent with free radical mechanism involving aryl radicals.

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A new method for desulfonation of vinyl sulfones utilizing organostannyl compounds is is reported. Vinyl sulfones, on treatment with (tributylstannyl) lithium in tetrahydrofuran at -78°C, give the Michael type addition products, βtributylstannyl sulfones, and their successive β-elimination by reaction with silica gel affords the desulfonated olefins in good yields. On the desulfonation of both of (E)-and (Z)-7-phenylsulfonyl-7--tetradecene [10 f] the (E)-7-tetradecene[15 f]is found to be a major product. Utilizing the procedure of this additionelimination sequence, the sulfonyl group of vinyl sulfones is substituted by electrophilic rea gents. Stereoselectivity of the reaction is also discussed.

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A series of homologous tin(IV) compounds having leaving groups at the ω-position were synthesized, and their behavior towards Lewis acids was examined.1, 2-Type compounds such as [10] and [14] underwent 1, 2-elimination producing olefins [11] and [13], while 1, 3-type compounds such as [17] underwent 1, 3-elimination producing cyclopropanes [18] With compounds having leaving groups at positions separated by more than three carbons, such as and [37], 1, 5- or 1, 6-hydride shift producing terminal or internal olefins [33], [38] or [39 ]proceeded selectively, provided that the starting materials have hydrogen atom at th e[3 9]appropriate positions. With compounds in which these hydrogens are not available, cyclization to three- or five-membered ring system proceeded. With compounds in which neither the hydride shifts nor cyclization to the ring systems is not possible, the reaction became complicated.

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Lewis acid (BF3. OEt2) mediated allylation of 1, 2-naphthoquinones [1] and o-benzoquinones with allyltin reagent (allyltributylstannane [2] and trans-2-butenyltributylsta[9]a ne [3])gives 4-allylated products in high yields. In the reaction of [1] with [3] the regioselectivity of the addition of the crotyl moiety was affected by the electronic characteristics of the substituent in position 3 of the quinone. The quinone having a electron-donating group afforded a-adduct, but a electron-attracting group exerted the opposite influence on the selectivity to give preferentially 6gamma;-adduct. Other Lewis acids (SnCl₄, TiCl₄, AlCl₃) slightly affected the regioselectivity: increasing the strength of the acid tends to increase the formation of γ-adduct, but in low yield.
In contrast to p-quinones, o-quinones reacted with [3] even in the absence of Lewis acid, and α-adduct was selectively obtained regardless of the nature of the substituent on the quinone. The stereoselectivity was also affected by Lewis acid. In the presence of Lewis acid, the crotyl moiety was introduced into quinonoid nucleus in high stereoselectivity, but in low selectivity in the absence of Lewis acid.
o-Benzoquinone afforded a-adduct in the reaction with [3] while p-benzoquinone gave γ-adduct. This remakable selectivity between these two quinones may be interpreted in terms of the different reaction processes: Michael addition for o-benzoquinone and 1, 2addition followed by allyl migration for p-benzoquinone.

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N -(2-Hydroxyethyl)ethylenediamine-N, N', N'-triacetato(hydroxymethyl)chromium(III)complex, [Cr(CH₂OH)(hedtra)]^-, reacts with chloropentaamminecobalt(III) in an aqueous solution to give [Cr(hedtra)(H₂O)] and cobalt(II). The reaction proceeded through a biphasic process; (i) formation of an intermediate species and (ii) the decomposition of the intermediate species accompanied by the cleavage of the chromium-carbon bond and the reduction of cobalt(III) to cobalt(II). Kinetic measurements for the second step were made at =1.0 (LiClO₄) and 25.0°C. The reaction obeyed the rate law, -d[intermediate]idt={k[H⁺]/(K+[H⁺])}[intermediate] and the k and K values were k= (5.1±0.3) × 10^-2 s^-1 and K= (3.80.3) × 10^-5 mol⋅ dm^-3.

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The visible light-induced reaction of molecular nitrogen with the polymer-metal complex membrane prepared from copolymerization of (vinylmethylcyclopentadienyl)tricarbonylmanganese (VMeCpMn(CO)₃) and styrene has been investigated by means of IR and visible absorption spectra. The results indicated that a mixture of a dinitrogen complex of the manganese moieties, -MeCpMn(CO)₂(N₂), and another unknown chemical species bound to th e polymer were produced. The latter was found to be the same species produced by the visible light irradiation of VMeCpMn-co-styrene under argon atmosphere.

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(t-BuOO)Co(salen)prepared by the oxidation of Co(salen)with t-butylihydroperoxide oxidized 2, 6-di-t-butylphenols to generate the corresponding phenoxyl radicals, which were detected and identified by ESR. The oxidation of the phenols seemed to take place by hydrogen abstraction by t-butylperoxyl radical produced by homolysis of the Co-O bond in(t-BuOO)Co (salen), although a possibility of homolytic cleavage of a (phenolato)Co^III(salen) complex formed by an acid-base reaction between the phenols and (t-BuOO)Co(salen)may not be ruled out. Addition of t-butyl hydroperoxide to the resulting phenoxyl radical solution resulted in the quantitative incorporation of the t-butyldioxy group into the radicals, giving 4-tbutyldioxy2, 6-di-t-butylcyclohexadienones. These results suggest that (t-BuOO)Co(salen)can catalyze the t-butylperoxylation of the phenols with t-butyl hydroperoxide. Actually, when a solution of 4-substituted 2, 6-di-t-butylphenol and t-butyl hydroperoxide (mol/mol=1/2) in dichloromethane was stirred in the presence of a catalytic amount of (t-BuOO)Co(salen)(0.1 eq.) at room temperature, the reaction was completed normally in 1 h to give 4-substituted 4-t-butyldioxy-2, 6-di-t-butyl-2, 5-cyclohexadienone in an excellent yield. The same results were obtained when Co(salen) was used as the catalyst in place of (t-BuOO)Co(salen).
Similar chemical behavior of (t-BuOO)Co(salen) was observed for 4-nitro phenylhydrazones of ketones, where the t-butyldioxy group was incorporated into. the carbon atom of the C=N group in the hydrazones to give 1-(t-butyldioxy)-1-(4-nitrophenylazo) compounds as the main product along with small amounts of 1-(t-butyldioxy)-1-(4-nitrophenylazoxy) compounds. Interestingly, the reaction of (t-BuOO)Co(salen) with 4-methoxyacetophenone 4nitrophenylhydrazone under nitrogen gave an appreciable amount of a stereoisomer (Z-form)of the starting hydrazone (E-form) in addition to the azo peroxidic product. The results are rationalized, by a strong interaction between the substrate radical and the cobalt complex, since no reaction took place when the hydrazone substrate was treated with Co(salen) itself under nitrogen or with t-BuOK.

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Hydroxylation reactions of olefins were carried out using a catalyst system, Cobalt(II) complex NaBH₄-O₂, as a model for monoxygenase enzymes. The catlyst system showed only a hydroxylation activity for styrene and its derivatives among the olefins tried. [Co^II(tpp)] was more active than a Sciff base complex of Cobalt(III), and the order of olefins to be hydroxylated was styrene> β-methylstyrene _??_α-methylstyrene. In the case of a standard reaction system including, for example, styrene, the main product was only 1-phenylethanol, but acetophenone and poly(styrene peroxide) were also formed when the porphyrin complex having a substituted phenyl group was used as a catalyst or when a ratio of NaBH₄/Co(II) was decreased. The use of the Schiff base complexes of Cobalt(II) having asymmetric ligands is found to induce an enantioexcess of the alcohol, depending on the ligand; e. e. of 8.1%was attained for (R)-(+)-1-phenylethanol with the [Co^II(sal₂-R-chxda)]-NaBH₄-O₂ system. Reaction mechanism including the asymmetric induction is estimated.

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Ethylbis(2, 2'-bipyridyl)cobalt( I ), [Co(Et)(bpy)₂], was prepared by dissolving diethylbis (2, 2'-bipyridyl)cobalt (III) tetraethylaluminate in polar ethers (THF, 1, 2-dimethoxyethane etc. ). Conjugated dienes were selectively hydrogenated to the corresponding monoenes by [Co(Et)(bpy)₂] where internal cis-olefins were the main products (>80%). The inductio n period disappeared by treating the cobalt( I ) complex with dienes for 30 min. The hydrogenation of 1, 3-butadiene was of first order in the cobalt concentration, of first order in the hydrogen pressure and independent of the butadiene concentration. The rate of hydrogenation increased with the increasing concentration of pretreated butadiene. The increase was more pronounced as the cobalt concentration became lower. The lower stability of the cobalt( I ) complexes with internally methyl-substituted 1, 3-butadienes caused a slight decomposition to metals and a decrease in selectivity. Nortricyclene was initially formed as the main product in the hydrogenation of 2, 5-norbornadiene with [Co(Et)(bpy)₂]but the selectivity of nortricyclene decreased with the elapse of time due to its isomerization into norbornene. The hydridocobalt( I) formed by the dissociation of ethylene from [Co(Et)(bpy)₂] is thought to react with butadiene to give anti-[1-3-η-(1-methylallyl)]cobalt which then is hydrogenated to afford mainly cis-2-butene.

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A thermally stable complex [CoH{PPh (OEt)₂}₄] was irradiated with a 400 W high-pressure Hg lamp equipped with a Pyrex filter to generate a coordinatively unsaturated active hydrido species "CoH{PPh(OEt)₂}₃". The species catalyzed intramolecular hydrogen transfer of 2cyclohexen-1-ol to give cyclohexanone. The reaction of 2-cyclohexen-1-ol yielded four byproducts: 3-cyclohexen-1-ol through double-bond migration and small amounts of cyclohexanol, 2-cyclohexen-1-one, and 3-cyclohexen-1-one through intermolecular hydrogen transfer. The reaction was virtually "photoassisted" rather than "true photocatalytic". Upon interuption of irradiation, the coordinatively unsaturated hydrido species was assumed to be recombined with the photodissociated phosphonite to give the stable starting complex. In the photoassisted catalytic reaction of 2-cyclohexen-1-ol, addition of free phosphonite decreased the conversion to cyclohexanone.
The reciprocal in itial rate of cyclohexanone formation was plotted against the reciprocal concentration of the substrate charged, and a linear relationship was observed between them at several reaction temperatures. From the Arrhenius equation, a value of 29.6 kJ⋅mol-1was obtained as the overall activation energy of the present reaction.

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Thermal decomposition of solid aquamethylcobalt (III) complexes with quadridentate Schiff base ligands as N, N'-ethylenebis(salicylideneamine) and its analogues was investigated by TG, DSC, and pyrolysis gas-chromatographic (PGC) analyses. The coordinated water was eliminated in the temperature range of 68∼116°C, and then, the methyl group was dissociated in the range of 138∼218°C accompanied by partial conversion into methane and ethane. The PGC analysis indicated that the molar ratio of methane and ethane evolved varied depending on the nature of the Schiff base. The results were discussed in comparison with those reported for the solution reaction.

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The addition of hydrogen cyanide to propadiene and 1, 2-hexadiene in the presence of a catalytic amount of [Ni{P(OPh)₃}₄][Ni(tpp)₄] or [Ni{P(OPh)₃}₃(CO)][Ni(tpp)₃C0] was investigated. [Ni(tpp)₄] was more effective for the hydrocyanation than [Ni(tpp)₃CO]. With [Ni(tpp)₄], the hydrocyanation products were obtained in 46% yield from propadiene ( Ni=3.6 mmol, propadiene: NCN: Ni=50: 50: 1, in 20 ml toluene) at 180°C (Table 1) and in 65% yield from 1, 2-hexadiene (Ni=1 mmol, 1, 2-hexadiene: FICN: Ni=-30: 30: 1) at 60°C (Table 2). In the hydrocyanation, the attack of CN group on the C(1) and C(3) of the allenic linkage occurred predominantly to give allylic products, in contrast to the carboxylation of allenes catalyzed by nickel carbonyl (Ref.8). A high 1, 2-hexadiene/Ni and HCN/Ni ratio caused the decrease in the reaction rate and yield (Table 3). The oligomerization and polymerization of the substrates, being main side reactions, resulted in lowering of the yield. At the high temperatures, the isomerization of the carbon-carbon double bond of the products, especially allylic products, proceeded in a high degree.
A reaction mechanism, in which [Ni(CN)(H){P(OPh)₃}₂] is considered to be the active species, is proposed for the hydrocyanation with [Ni(tpp)₄]catalyst to account for the experimental results.

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Aryl, 1-alkenyl and heterocyclic sulfides reacted with aryl and alkyl Grignard reagents in the presence of nickel complexes to afford the coupling products in high yields. Generally, the use of 3 mol% nickel complexes gave the best results (Table 1 and 2). T h e most effective catalysts were [NiCl₂(PPh₃)₂] [6] J for sterically hindered sulfides (run 21 in Table6) and aryl Grignard reagents and [NiCl₂(Ph₂PCH₂CH₂CH₂PPh₂)] [8] J for primary alkyl and simple aryl Grignard reagents (see Table 6). But, for secondary alkyl Grignard reagent s, this nickel catalyzed coupling reaction was impractical because of side reactions, reductive desulfurization and isomerization (run 3 and 4 in Table 6 and Fig.5). By the com petitive reaction with butylmagnesium bromide; the reactivity order C₆ > H₅I> C₆H₅SeCH₃ > C₆H₅Br > C₆H₅Cl > C₆H₅SCH₃ was observed (Table 5). The reaction me chanism and the scope and limitation of this coupling reaction are also discussed.

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Based on the facile reactivity of π-allylic nickel complexes toward alkyl halides in aprotic polar solvents, synthesis of macrocyclic lactones via intramolecular alkylation of π-allylic nickel complexes was investigated. (Z)-5-Bromo-3-pentenyl ω-chloroalkanoates [12]pr e pared from (Z)-5-[(tetrahydro-2 H-pyran-2-yl)oxy]-3-penten-1-ol in several steps, were allowed to react with nickel carbonyl in benzene to form the corresponding π-allylic nickel complexes [13], which were then treated with sodium iodide in N-methyl-2-pyrrolidon e affording unsaturated lactones [14] in trans-form in good to fair yields as shown in Table 1. Some of the lactones thus prepared were converted to natural fragrance compounds, e.g.exaltolide [16] and (Z)-9-dodecen-12-olide [7], by hydrogenation and isomerization, respeCtively.
The present method of lactone formation was further applied to the facile synthesis of (±)-recifeiolide [8] as shown in Scheme 4. Thus, (Z)-6-bromo-4-hexen-2-yl 6-halohexanoate (21), prepared from propargyl tetrahydropyranyl ether in five steps, was cyclized via the π-allylic nickel complex to give [8] in 32% yield.

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Bis(1, 2-diaryl-1, 2-ethylenedithiolato)nickel complexes (X-DTNi; where X represents the substituent in the aryl moiety in the ligand) are efficient quenchers for singlet oxygen.
The formation of 2, 5-dimethyl-2-hydroperoxy-5-methoxy-2, 5-dihydrofuran in the reaction. of 2, 5-dimethylfuran with ¹O₂ generated from H₂O₂ and NaC1O is suppressed more by 'X-DTNi with electron-donating X than by X-DTNi with electron-accepting X (Fig.1). Quenching of ¹O₂ by X-DTNi is not linear to the concentration of X-DTNi, and quenching is more efficient in higher concentrations of X-DTNi than in their lower concentrations. (Fig.1 and Table 2).
The durabilities of X-DTNi with electron-donating X against ¹O₂ are lower than those with electronaccentinu X (Fin.2).

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The reactions of copper ( I ) diethyl malonate [1] with sodium salts of N-acetyl- [2a], N-propionyl- [2b], and N-benzoyl-o-bromoaniline [2'c] afforded diethyl 2, 2 '-dioxo-3, indoline-3, 3-dicarboxylate [3] in 15∼22% yields. Activation of the aroma tic substitution observed for the sodium salts is attributed to the coordination of the anionic amide nitrogen to copper ( I ), leading to the formation of 3-ethoxycarbonyl-2-oxo-3-indolinyl-copper ( I )which subsequently undergoes thermal dimerization to give [3] J. Active methylene carbanions substituted with o-bromoanilino group cyclized in the presence of copper ( I ) salt to give indole derivatives.3-Acetyl-2-hydroxyindole [7a] and N-methyl-2-indolinone [7c] were obtained in 13 and 25% yield, respectively, when copper ( I ) complexes of N-acetoacetyl-obromoaniline [6a]and N-ethoxycarbonylacetyl-N-methyl-o-bromoaniline [6] cp were allowed to react.3-Acetyl-2-methylindole [9a] and 3-ethoxycarbony1-2-methylindole [9b] were isolated in 14 and 46% yield, respectively, from the reactions of copper ( I ) complexes of N(2-acety1-1-methylethylidene)-o-br omoaniline [8 a] and N-(2-ethoxycarbonyl-1-methylethylidene)o-bromoaniline [8b]. The relatively high yield of [9 b], the ease with which starting material [8b] is prepared, and the simple reaction procedu re make the aromatic nucleophilic cyclization reaction useful for the synthesis of 2-alkyl-3-(ethoxycarbonyl)indoles.

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Organocerium(III) reagents were conveniently generated by the reaction of organolithium compounds with anhydrous cerium(III) chloride. The reagents are less basic than organolithiums and Grignard reagents, and they react readily at -78°C with easily eno lizable ketones such as 2-tetralone to afford addition products in high yields. Cerium (III) enolates were also generated from lithium enolates and cerium (III) chloride. The cerium (111) e nolates undergo aldol addition with ketones or sterically crowded aldehyde to give the corresponding β-hydroxy ketones in good to high yields.

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The reactions of α-azidostyrene derivatives [13] or 3-aryl-2 H-azirines [14] with Mo(CO)₆in protic or aprotic media were investigated. In the reactions of [13] 2, 5-diarylpyrroles and acetophenone derivatives [16] were obtained in good yields. The [1y5ie] lds of [15]were found to increase in aprotic media, while those of [16] decreased. Reactions of [14]with Mo(CO)₆ were found to give 2, 4-diarylpyrroles [17] and 2, 5-diarylpyrazines [18] in addition to [15] and [16]. The (1-arylvinyl)nitrene complex [22] was postulated as a common intermediate for the formation of [15], [16], or [17] in the reaction of [13] and [14]. Dimerization of [22] would lead to [15] while simple reduction of [22] in protic solvents or in the presence of stray water followed by hydrolysis would give [16]. The formation of [17] could be explained by an addition of [22] with the azirine [17] A cornplexed nitrile ylide intermediate [33]or a metathetic type reaction of [14] seemed to be responsible for the formation of [18]. To elucidate the chemical behavior of the complexed nitrene intermediate in protic media, the reaction of azidobenzene [19] with Mo(CO)₆ in methanol or moist acetonitrile was also investigated. Aniline [20] was obtained in good yield.

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Dinitrogen complex, trans-[Mo(N₂)₂(dpe)₂][1](dpe=Ph₂PCH₂CH₂PPh₂) reacted in toluene at room temperature with aliphatic dinitriles NC(CH2)aCN (adiponitrile (n=4) and succinonitrile (n=2)) to give the mononuclear nitrile complex, [Mo(N₂){NC(CH₂)nCN}(dep)₂] ([2 ](n=4) and [4] (n=2)), and the dinitrile-bridged dinuclear complex, [Mo(N₂)(dPe)₂]₃{u-NC(CH₂)CN} ([3] (n=4) and [5] (n=2)), accompanied by evolution of dinitrogen (1mole per [1] reacted).
The nitrile complexes [2]∼[5] thus-formed were characterized by means of IR (Figs.1 and 2) and NMR spectroscopies, and elemental analyses. The toluene-soluble mononuclear complexes [2] and [4] were found to be formed selectively when excess of dinitriles were employed in these reactions, whereas the insoluble dinuclear complexes [3] and [5] were formed selectively by using half mole of dinitriles (Tables 1 and 2). The mononuclear complexes were fairly unstable in a solution. Thus, disproportionation of [2]in toluene to yield dinuclear complex [3] accompanied by release of adiponitrile was observed. Standing a toluene solution of [4] at room temperature for a few days led to its partial decomposition, yielding noncoordinated dpe as evidenced by ³¹PNMR spectroscopy of the solution. The feature of the present reactions suggests the stepwise formation of the nitrile complexes: the primary formation of the mononuclear complexes and [4] followed by the formation of the dinuclear complexes [3] and [5]. [2] Mononuclear adiponitrile complex [2] in toluene was allowed to react with CO (1 atm) at room temperature to give some carbonyl complexes.

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Ru₂Cl₄((-)-DIOP)₃ (DIOP =2, 2-dimethyl-4, 5-bis(diphenylphosphinomethyl)-1, 3-dioxolane), in the presence of triethylamine, was found to be an efficient catalyst for t h e hydrogen transfer to alkenes from 1, 4- or 1, 5-diols which have the prochiral center or t h e meso structure to afford optically active γ- or δ-lactones with the optical purity up to 16.9 %. This reaction belongs to the enantiotopos-differentiating reaction, in which one of the enantiotopic hydroxymethyl group of prochiral molecules is oxidized to give chiral lactone s. This type of reactions has been rarely reported for homogeneous transition metal complex catalysis, whereas the reactions of the similar type have been extensively investigat e d for enzyme-catalyzed reactions. The chiral induction was directed by the position of the su bstituent(S) of diol, i.e. 3-substituted 1, 5-diols gave (R)-δ-valerolactones and β, β'-dis u bstituted 1, 4- or 1, 5-diols gave γ- or δ-lactones which have S-configuration at the carbon center adjacent to the carbonyl group. It was also found that the two distinct mecha nisms of chiral induction took part in this reaction in a similar manner for the dehyd r ogenation of diols catalyzed by horse liver alcohol dehydrogenase; the first step is the se l ective dehydro. genation of one of the enantiotopic hydroxymethyl groups of a diol to give an optically active hemiacetal, and the second one is the subsequent selective dehydrogenation of one of the epimers of the hemiacetal to give the lactone (kinetic resolution).

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The hydrogenation of α, β-unsaturated carbonyl compounds and nitrile with carbon monoxide and water was investigated by using rhodium carbonyl cluster catalysts supported on resin beads containing polymer-bound amine moieties. The hydrogenation proceeded heterogeneously in dioxane-hexane (3:7) and no reaction took place in the solution after separation of the catalyst beads. However, rhodium species partially migrated during the reaction from the resin beads to the solution in tetrahydrofuran.
Amberlite IRA-93 and Amberlyst A-21, macrore cticular beads having N, N-dimethylbenzylamine moieties, were found to be the most excellent supports among the ion-exchange resins examined in terms of high activity and easy handling. Results of the hydrogenation with the catalyst supported on Amberlyst A-21 are shown in Table 1.
The carbon-carbon double bonds of α, β-unsaturated carbonyl compounds and nitrile were selectively hydrogenated and adjacent carbonyl and cyano groups were intact, although formyl group was hydrogenated to the corresponding alcohol. Simple aldehydes such as benzaldehyde and butyraldehyde were also hydrogenated to alcohols under these conditions.
The resin-supported catalysts were stable under nitrogen or carb on monoxide atmosphere and could be reused without any appreciable loss in catalytic activity and selectivity, as shown in Table 2. The effect of substitution with bulky groups or the number of substituents on the hydrogenation rates of olefins was more pronounced in the heterogeneous system than in homogeneous system (Table 3). The rates with the resin-supported catalysts were generally greater than those with the homogeneous catalyst (Table 4). Although the active species could not yet be identified, rhodium carbonyl cluster anions were detected in the reaction. It is believed that the first step probably involves the formation of a cluster anion from Rh₄(CO)₁₂ and the anion is bound to the resin to form heterogeneous catalyst.

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Under the pressure of carbon monoxide Rh₄(CO)₁₂-catalyzed reactions of various monosubstituted benzenes with methyl acrylate [1] gave three positional isomers of monosubstituted cinnamates [2]of which the ratio was affected by the substituent groups. The relative reactivity of monosubstituted benzene has been examined by competitive reactions with benzene. The order of reactivity was N, N-dimethylanilinecztoluene< methyl benzoate < benzyl acetate ≈ benzene < benzonitrile < phenyl acetate < fluorobenzene < anisole < diphenyl ether. The partial rate factors of the ortho position (f_o) in these compounds show a significant difference and the order was consistent with that of the reactivity. On the other hand, the values of f_m and f_p were similar. Using vinyl acetate as a hydrogen acceptor, xylene and naphthalene were reacted with [1] to give the corresponding products [2] in good catalytic yields. In this reaction system various disubstituted benzenes underwent facile alkenylation with [1] in which the ratios of positional isomers were compared with those from monosubstituted benzenes. t Rhodium Carbonyl-catalyzed Activation of Carbon-Hydrogen Bonds for Application in Organic Synthesis.

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For the purpose of eliminating the disadvantages of hydrophobic transition metal catalysts, the water-soluble phosphines, P[CHR(CH₂CH₂O)_nCH₃]₃(R=H, CH₃ n=1, 2, 3, ), having chemically stable side chains were synthesized. Their hydrophilicities were correlated with the number of the oxygen atom in the molecules on the basis of the measurements of the solubility in water and the distribution equilibrium between aqueous and organic phases. The usefulness of the phosphines as ligands for metal-catalyzed reactions in aqueous solution was studied in the water gas shift reaction under strong basic conditions as a model. The catalyst of W(CO)₆-L(L=water-soluble phosphine) showed high activity in aqueous solution, and the active species were proved to be water-soluble complexes, cis- and trans-W(CO)₄L₂. A catalyst system, [RhCl(cod)]₂-L, was effecient not only in aqueous solution but also under aqueous-organic two-phase conditions. The catalytic activity in the latter case was correlated with the distribution constant of the phosphine ligands. These facts suggest that the catalysis is attributed to the phosphine complex in aqueous phase. The rhodium-catalyzed hydroformylation of olefins with CO and H₂O could also be achieved under two-phase conditions. This reaction system had the advantage of simplifying the process of separating the catalyst from the organic products.

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The water gas shift reaction and its application to reduction of various functional groups and to carbonylation of olefins have been studied using rhodium carbonyl complex-amine (or pyridine) systems. Under the mild conditions (700 mmHg of CO and 100°C), Rh₆(CO)₁₆- ethylenediamine system has high catalytic activity for the water gas shift reaction. Heterogenization of Rh₆(CO)₁₆ using diaminated polystyrene increases the catalytic activity compared with the counterpart homogeneous systems. In the reduction of various functional groups, N-alkylated diamines are the best additives. Rh₆(CO)₁₆-N, N, N', N'-tetramethy1-1, 4-propropanediamine system reveals remarkably high catalytic activity of aldehyde reduction. Suitable choices of diamines and pyridines as additives attains selective reductions which can not be obtained in the case of H₂; in α, β-unsaturated aldehydes, pyridines lead to selective formation of olefin reduction products, while diamines give carbonyl reduction ones. In carbonylation of olefins, use ofRh₆(CO)₁₆-N-alkylated diamine system gives a high yield of alcohols from olefins via hydroformylation.

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Interconversion among anionic metal clusters(M=Ru, Os) formed in the basic water gas shift reactions has been studied under various conditions by using three kinds of bases, KOH, NEt₃ and DBU(1, 8-diazabicyclo[5.4.0]undece-7-ene). In the Ru-DBU system, [FIRu₃(CO)₁₁]- and [H₂Ru₄(CO)₁₂]^2- were mutually converted. The composition was found by IR spectroscopy to depend oh the relative ratio of the CO and H₂ partial pressure, and no [H₃Ru₄(CO)₁₂]^- was detected. The result is in contrast to the known interconversion between [EIRu₃(CO)₁₁]^- and [H₃Ru₄(CO)₁₂]^2- in the presence of the other bases. [H₂Os₄(CO)₁₂]² formed with DBU was stable when treated with carbon monoxide at 120°C for 5 h.

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The Water gas shift reaction (WGSR) was applied to an organic synthesis. The reaction was carried out with aldehydes. Reactions of ketones with formaldehyde or benzaldehyde under WGSR conditions (under 70 atm of CO initial pressure) at 180°C in the presence of base and a rhodium catalyst (0.1 mol% based on the ketone) gave α-methylated or α-benzylated products in good yields. 2- or 4-Ethylpyridines were obtained from α- and γ- picolines under the similar WGSR conditions as for formaldehyde. Aldehydes with two α-hydrogens were dimerized and hydrogenated into saturated alcohols. On the other hand, aldehydes with no or only one α-hydrogen were converted into corresponding alcohols.

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The phenylation reaction of allyl compounds with benzene using the Pd(OAc)₂, /AcOH and Pd(CF₃CO₂)₂/CF₃COOH systems has been investigated. The reaction of ally! esters su ch as allyl acetate [12] and benzoate [14] with benzene in the Pd(OAc)₂/AcOH system gave the usual phenylation products. The reaction of allyl halides, especially chloride [16]with benzene gave not only monophenylated product [17] but also di- and triphenylated products [18], [19], [20], [21] and [22]. Addition of PPh₃ resulted in the selective formation of [19]. On the other hand, the reaction with the Pd(CF₃CO₂)₂/CF₃COOH system gave the acyl-O bond fission-phenylation products; reactions of ally! acetate [12] and benzoate [14 ]with benzene gave cinnamaldehyde [29] and 3, 3-diphenylpropenal [32] Addition of pbenzoquinone as an oxidizing agent made the reaction catalytic with respect to palladium. The mechanisms of these reactions are also discussed.

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Palladium-catalyzed reaction of aryl bromide, ArBr, with aryltributyltin, Ar'SnBu₃, was found to be useful for the synthesis of the unsymmetrically-substituted biaryl, ArAr', except for the reaction with o-substituted aryl tributyltin. In some cases, a small amount of by-product, Ar'Ph, was formed by participation of the ligand, PPh3, on palladium. Substituent effects of substrates and reagents on the reaction rate were also investigated. The former was considerably large, whereas the latter was small.

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Diphenyliodonium bromide ([Ph₂I]Br) reacts readily with styrene in the presence of a palladium catalyst and a base to afford (E)-stilbene in good yields. Effects of catalyst, base and medium on the reactions have been examined. Both Pd( 0 ) and Pd ( II ) compounds were effective as a catalyst and sodium acetate was found to be the most efficient base. The reaction proceeded smoothly in zprotic polar solvents such as DMF and DMSO. By the reaction of [Ph₂I]Br with other olefinic compounds, various arylated vinyl compounds were prepared in good yields under mild conditions. Kinetic studies confirmed that the rate of stilbene formation is first order, with respect to the concentration of [Ph2I]Br, styrene and palladium catalyst. We propose the mechanism in which the rate-determining stage is the formation of PhCH₂CH(PdBr)Ph. The activation energy of this reaction was 18.3 kcal/mol.

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The reaction of butadiene with carbon dioxide by a palladium( 0 )-triphenylphosphine catalyst system was studied. The reaction at 60°C for 2 h in DMF solvent gave a six-membered lactone, (E)-2-ethylidene-6-hepten-5-olide [1] in 14% yield as a main product together wish a small amount of a mixture of C₉-carboxylic acids. The yield of the lactone [1]increased up to 50% by the addition of sodium acetate. On the other hand, another product, 2-vinyl--4, 6-heptadienoic acid, a C₉-carboxylic acid, was obtained selectively as the N-acylurea derivative in the presence of dicyclohexylcarbodiimide in 71% yield by the reaction at 80°C for 20 h.

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Organic halides were found to be catalytically carbonylated with terminal acetylenes by palladium complexes in the presence of bases under the conditions of P_(co) =20 atm and 120°C to give acetylenic ketones (eg. Equation 1). The basicity of phosphines as ligands for the palladium complex catalysts and, in case of diphosphines, the methylene chain length or the framework between the two phosphino groups profoundly affected the reactivity of the catalysts (Table 1). Arsines were found to accelerate the migratory insertion of carbon monoxide as compared to phosphines (Fig.1). Thus, in terms of the catalytic activity and the selectivity for 1, 3-dipheny1-2-propyn-1-one (DPP) in iodobenzene-phenylacetylene reactions, dppb, dbpb, dcpb, dppf, and dpaf were the ligands of choice. Although low pressure of carbon monoxide (eg.5 atm) was unfavorable for a high DPP selectivity in the PdCl₂(PPh₃)₂- catalyzed reaction, the use of PdCl₂(dppf) allowed the reaction to proceed with high selectivity for DPP even under atmospheric pressure of carbon monoxide (Table 2). Use of strong bases such as triethylamine and tripropylamine was essential for high yield synthesis of DPP (Table 3). This new reaction could be successfully applied to a variety of aromatic, heteroaromatic, and vinylic halides combined with terminal acetylenes except unsubstituted acetylene, which gave intractable tarry material (Table 4).

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The reaction of (diethylamino)tributyltin with aryl bromides in the presence of a catalytic amount of PdCl₂[P(o-tolyl)₃]₂ gave N, N-diethylaniline derivatives. The reaction was a new kind of amination different from ones through aryne or S_RN 1 mechanism. The scope and limitation of the reaction were surveyed. Application to the reaction of a variety of aminotin compounds has some limitations, and the relationship between the structure of aminotin compounds and the yield of the product was not cleared.

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1, 3-Dienes, such as 3-methyl-1, 3-butadienyl group [1], are important intermediates for sigmatropic reactions or Diels-Alder reactions. A new method of synthesizing [1] from prenyl group [2] via 2-chloro-3-methyl-3-butenyl group [3] was developed. The method consisted of ene-type chlorination with hypochlorous acid, and dehydrochlorination promoted by palladium-phosphine complex in the presence of sodium acetate. In the dehydrochlorination, the palladium complex catalyzed both the displacement of the chlorine atom in [3]with acetate ion and the elimination of acetic acid from the resulting acetates. Advantages of the dehydrochlorination were that 1) the reaction temperature was so high (150∼210°C)that thermal reactions of [1] occurred simultaneously 2) the reaction conditions were weakly acidic in contrast with the base-promoted dehydrochlorinations. Combinations of this method with [3, 3] sigmatropic reactions such as Thomas or Claisen rearrangements provided new routes to α, β-unsaturated aldehydes from prenyl allylic ethers. For example, citral was synthesized from diprenyl ether via 2-chloro-3-methyl-3-butenyl prenyl ether. On the other hand, this method coupled with intramolecular Diels-Alder reaction, afforded a new way for converting prenyl derivatives, having vinyl group in the molecules, into bicyclic compounds.

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Palladium-catalyzed arylation of allyl and 2-methylallyl alcohols with diaryliodonium salts has been investigated. The reaction proved to be useful in converting aromatic hy d r ocarbons to the corresponding arylpropanals in two steps. Thus, 3-(p-isopropylpheny1) - 2 methylpropanal(cyclamaeldne hyde)a nd 3-(p-isobutylphenyl)-2-methylpropanaall(dlielyhyde), which are perfume for soap and toilet, were obtained from isopropylbenzene and isobutylbenzene in 78 and 82% yields, respectively.

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Reductive elimination of ethane from trimethyl(triphenylphosphine)goldap is strongly accelerated by the addition of dimethyl acetylenedicarboxylate. S-shaped logistic time-yield curve suggests the autocatalytic property of this reaction. In fact, addition of the reaction. product, methyl(triphenylphosphine)gold( I ), into the reaction mixture diminish the induction period. A mechanism involving an unstable Au( III )-Au( I ) bimetallic species has been proposed.

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Polycarbosilane (PC) which consists of the skeleton of alternate carbon and silicon atoms has been used as a precursor for the ceramic materials containing silicon carbide, including silicon carbide fiber. However, it is difficult to control the properties of the ceramics produced from PC and to develop a new synthetic method of PC, because the structure of PC has not yet been clarified. Therefore, in the present study, three methods I) thermal decomposition and condensation of tetramethylsilane, II) thermal decomposition and condensation of poly(dimethylsilane) in an autoclave or III) at normal pressure were employed for synthesizing PCs. Also, molecular structures of PCs were studied by measurement of the intrinsic viscosity and IR, ¹H- and ²⁹Si-NMR spectral measurements. The silicon atoms forming the PC skeleton were represented by three simple elements; 1) silicon bonded with four carbon atoms (SiC₄), 2) silicon bonded with three carbon atoms and one hydrogen atom (SiC₃H) and 3) silicon bonded with x carbon atoms and (4-x) silicon atoms (SiC_xSi_4-x, x=1, 2 or 3). The fractions of these silicon atoms in each PC molecule were determined (Table 5). Further, from the differences in C-H/Si-H between the measured values and the values calculated on the assumption that the PCs are linear polymers ([1], [2] and ), (Table 3 and Table 5), the number of the linkages between linear chains in the unit consisting of ten silicon atoms in PC molecule was estimated as 3-4 ([4] and [5]. )This result was in agreement with the result from the intrinsic viscosity; it was found that the shape of PC molecule is planar and contains both ring structure and linear structure.

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The crystal structure of slant-bridged [ 4 ] (1, 1') [ 4 ] (3, 3') [ 3 ] (4, 5')ferrocenophane was determined by X-ray diffraction. The compound crystallizes in the monoclinic system, space group A 2/a with unit cell parameters a=21.825(5), b= 8.721(2), c=16.971(4) Å, p103.88(2)°, and z=8. Almost all of the C-C bond lengths and the C-C-C bond angles are in normal ranges. The two cyclopentadienyl (Cp) rings are in a staggard conformation and the dihedral angle between the two rings is 8.7°. The Cp-Fe-Cp distance (3.220 Å)is fairly short in comparison with the ones of tetramethylene-bridged ferrocenophanes.
The electronic absorption spectra of the compound and the related m ultibridged ferrocenophanes have been recorded in tetrahydrofuran and some correlations have been obtained between the d-d absorption band in the visible region and the structural parameters. The band undergoes a progressive hypsochromic shift with increase of the number of the tetramethylene bridges. An approximately linear relationship exists between the hypsochromic shifts of the band and the shortening of the Cp ring-Fe distances. The ring-tilt deformation of the ferrocene moiety also affects the d-d absorption shifts of the multibridged ferrocenophanes. The results are briefly discussed in relation to molecular orbital theory of metallocenes.

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Some ferrocene derivatives have been shown by Mossbauer spectroscopy to give an anomalous electronic state when treated with an oxidant or a Lewis acid. Two typical compounds among them, dibutylbiferricinium triiodide and iodotetramethyl[ 2 ] ferrocenophanium triiodide were subjected to an X-ray structural analysis, in order to clarify the mechanism for the formation of the unique electronic state in terms of the molecular strupture, conformation and counter anions in a solid.
Crystal str ucture of dibutylbiferricinium triiodide, which is known to exhibit temperaturedependent mixed valence state in Mössbauer spectrum, was determined at 150, 298 and 363 K. The averaged-valence state appeared in Mössbauer spectrum was attributed to an anisotropic molecular structure and interaction between iron atoms and iodide ions, which were slightly different from those in the trapped valence state observed at a lower temperature.
A part of iodotetramethyl[ 2 ] ferrocenophanium triiodide showed a lar ge quadrupole splitting in its Mössbauer spectrum, while the rest of the species showed the quadrupole splitting as small as that of ferricinium species. X-ray structural studies of a single crystal of this compound indicate that there are two kinds of iron atoms present at 298 K; i. e., 85% of iron atoms have a bond formation with iodide ions in a distance of 2.64Å and 15% of them are in the ferricinium state.

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In order to elucidate the effect of electron-donating and electron-withdrawing substituents on the cyclopentadienyl group in pianostuhl complexes, the (triphenylphosphine)dimethylcobalt (III) complexes of 1, 2, 3-trimethylcyclopentadienyl [1] J and methoxycarbonylcyclopentadienyl were prepared and their crystals were subjected to X[2-r]a y analyses (Table 2). The substituents were located trans to the phosphine ligand with respect to cobalt (Fig.1, Fig.2). The Co-Me and Co-P bond lengths are shorter in [2] than in [1] (Table 5), in accord. with our qualitative observation that [2] is more stable than [1]. Deviation of the cyclopentadienyl rings from a planar regular pentagon was observed. Geometries of the substituted cyclopentadienyls in the uncomplexed state were optimized by means of ab initio molecular orbital calculations and compared with those found in the complexes (Fig.3). Strong conjugation between the methoxycarbonyl group and the cyclopentadienyl ring was found. Deviation of the cyclopentadienyl group in [1] from planarity (Table 6), and short Co-C (14) distances in [1] and [2] (Table 5) were explained by strong interaction between the metal d_xz and cyclopentadienyl e- orbitals (Fig.4).

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Nuclear spin-spin coupling constants (¹J(RhP), ²J(RhP), ¹J(RhRh), ³J(PP)) in a carboxylatobridged dinuclear rhodium(II) phosphine complex have been studied with the extended Hilckel molecular orbital method in the framework of Pople-Santry theory (Fig.1, T able 2). A characteristic large value of ³J(PP) was found to relate to the presence of Rh-Rh σ and σ^* orbitals which were mainly composed of Rh(4 d_z2) atomic orbitals (Fig.2). Despite relatively small valence s-orbital coefficients therein, these two oribitals are located near the highest-occupied and lowest-unoccupied orbitals due to the dinuclearity, and thus give the large ³J(PP) value. This feature is in contrast to the case of ²J(PP)_trans in mononuclear complexes, where both the valence s-orbital coefficients and the orbital-energy difference are large (Fig.2).
In a model ca lculation, the variation of the electron-donating ability in substituted phosphines was taken as the change of Coulomb integral of the P atom of PH₃, and the character of the Rh-P bonding was evaluated in relation to the corresponding mutual polarizability of valence s-orbitals ¹π(RhP). Linear relationship was found not only between the ¹π(RhP)and Rh(5 s)-P(3 s) overlap populations (Fig.3) but also between ¹π(RhP) and Rh-P bond populations (Fig.4). Since the substituent effect on the observed ¹J(RhP) (Table 3) showed a parallel trend with ¹π(RhP), ¹J(RhP) itself is considered to be a good measure of the Rh-P σa-bond strength for this complex.

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An ab initio MO study was carried out on the bonding in [Li(C₂H₄)]⁺ and [HgH(C₂H₄)]⁺, and on the H₂O attack against these ethylene ligand. The effective core pote n tial of Topiol et al. was used for Hg and the usual 3-21 G basis set was employed for the ligand a t oms. The ethylene coordination in [Li(C₂H₄)]⁺ receives considerable stabilization from e l e ctrostatic interaction, and the ethylene coordination in [HgH(C₂H₄)]⁺ has larger donative in teraction than back donative interaction. Both considerably donative and back donative in teractions are contributing to stabilization in [PtCl₃(C₂H₄)]^-. The H₂O attack on free et hylene molecule results in remarkable destabilization of the reaction system. The H₂O app roach to [Li(C₂H₄)]⁺ presents energy stabilization at the H₂O-C distance of 2.5∼3.OÅ, whereas th e energy is destabilized at the shorter H2O-C distance. Thus, the H2O attack on [Li(C₂H₄)]⁺ is concluded to be difficult. The H₂O approach to [HgH(C₂H₄)]⁺ causes the energy stabilization at H₂O-C distance of 2.5∼1.5Å., suggesting that this nucleophilic reaction is facile and the H₂O molecule can approach the C₂H₄ moiety to make almost the C-O covalent bond with little barrier. The ease of the reaction can be explained in terms of the orbital mixing between ethylene π, π^*, and H₂O HOMO.

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