Synthesis of monohydridohexamethylbenzeneruthenium(II) complexes containing group V donor ligands. Isomerism arising from cyclometallation of a tertiary phosphine at aliphatic and aromatic carbon atoms

Abstract

The η-hexamethylbenzenehydridoruthenium(II) complexes RuHCl(η-C6Me6)L (L = PPh3 (11), AsPh3 (12), P(C6H4-p-F)3 (14), P(C6H4-p-Me)3 (15), P(C6H4-p-OMe)3 (16), P-t-BuPh2 (17), P-i-PrPh2 (18), P-i-Pr3 (19), PCy3 (20) and P-t-BuMe2 (21)) have been made by heating [RuCl2(η-C6Me6)]2, the ligand and sodium carbonate in propan-2-ol. The triarylphosphine complexes 11, 14 and 15 react with methyllithium to give aryl ortho-metallated hydridoruthenium(II) complexes such as RuH(o-C6H4PPh2)(η-C6Me6) (22) and 19 similarly gives the isopropyl cyclometallated complex RuH(CH2CHMeP-i-Pr2(η-C6Me6) (29) as a mixture of diastereomers. Reaction of 17 with methyllithium gives initially the t-butyl cyclometallated complex RuH(CH2CMe2PPh2)(η-C6Me6) (25) which isomerizes by a first order process (k 0 ̃.2 h-1 in C6D6 or THF-d8 at 50°C) to the aryl ortho-metallated complex RuH(o-C6H4P-t-BuPh)(η-C6Me6) (26). The similarly generated isopropyl cyclometallated complex RuH(CH2CHMePPh2)(η-C6Me6) (27) has not been isolated in a pure state owing to rapid isomerization to RuH(o-C6H4P-i-PrPh)(η-C6Me6) (28); both 27 and 28 exist as a pair of diastereomers. The formation of the cyclometallated complexes and the isomerizations are thought to involve intermediate 16-electron ruthenium(O) complexes Ru(η-C6Me6)L. Show more