Bulletin of the Chemical Society of Japan
Online ISSN : 1348-0634
Print ISSN : 0009-2673
Oxidative Addition of Allylic Substrates to Coordinatively Unsaturated Ruthenium Compounds, [Ru(η5-C5Me5)(η-amidinate)]: Preparation, Structure Elucidation, and Catalysis of Novel Ruthenium (IV)-η3-Allyl Complexes
Hideo KondoAkira KageyamaYoshitaka YamaguchiMasa-aki HagaKarl KirchnerHideo Nagashima
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Volume 74 (2001) Issue 10 Pages 1927-1937

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Abstract

Oxidative addition reactions of allylic halides, acetates, and carbonates with [Ru(η5-C5Me5)(η-amidinate)] [amidinate: iPrNC(Me)=NiPr (1a), tBuNC(Ph)=NtBu (1b)], which shows signs of coordinative unsaturation, gave novel cationic π-allyl ruthenium(IV) species. The compounds [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X were isolated by anion exchange of the products (X = PF6, BF4, BPh4), and were characterized by spectroscopic analysis. The crystallography of two of the [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X revealed a four-legged piano stool structure in which two nitrogen atoms in the amidinate ligand and two carbon atoms in the η3-allyl ligands occupy the positions of four legs; the orientation of the η3-allyl ligand was endo. Although cyclic voltammograms of the precursor, [Ru(η5-C5Me5)(η-amidinate)], indicated possible oxidative addition of organic halides other than allylic halides to [Ru(η5-C5Me5)(η-amidinate)], only allylic halides gave the corresponding Ru(IV) products. The importance of prior coordination of the carbon-carbon double bond of allylic substrates was evidenced by NMR observation of the intermediate in the reaction of 1a or 1b with allyl acetate. Addition of nucleophiles such as PhLi, dimethyl methylsodiomalonate, and piperidine to the [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X gave rise to allylation of these nucleophiles and regeneration of [Ru(η5-C5Me5)(η-amidinate)]. The reactions of allyl methyl carbonate with nucleophiles were also achieved by catalysis of either [Ru(η5-C5Me5)(η-amidinate)] or [Ru(η3-allyl)(η5-C5Me5)(η2-amidinate)]+X.

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© 2001 The Chemical Society of Japan
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