1999 年 57 巻 8 号 p. 698-707
In this article are summarized general properties, synthesis, reactivity, and catalysis of Group 4 transition metal amide complexes. Thermally robust but moisture sensitive compounds of the type M (NR2) 4 and MYn (NR2) 4-n CM = Ti, Zr, Hf ; R =H, alkyl, aryl ; Y = X (halogens), OR ; n=1-3) are generally synthesized from MX44 and amines or alkali metal amides, by disproportionation reactions of M (NR2) 4 with MY4, or by ligand exchange reactions of M (NR2) 4 and MYn (NR2) 4-n. Since nitrogen atoms in these compounds form both u- and it-donor bonds to the metal center, the amide complexes typically have planar MNR2 units with shorter M-N lengths.
The amide complexes are highly reactive towards carbonyl compounds or Brønsted acids such as cyclopentadiene. These reactions are useful for chemical transformation of carbonyl compounds and synthesis of metallocene derivatives ; some of the latter are excellent catalysts for olefin polymerization.
Besides metallocene derivatives, Group 4 transition metal amide complexes themselves have recently received much attention as catalysts for ethylene and α-olefins and for hydroamination of acetylenes.