Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part 30. Trimethylphosphine-chloro-, -acetato-, and -hydrido-complexes and related compounds of (hexamethylbenzene)ruthenium

Abstract

Reaction of the η⁵-pentamethylcyclopentadienyl-rhodium or -iridium complexes [{M(C₅Me₅)}₂Cl₄] or the (η⁶-hexamethylbenzene)ruthenium complex [{Ru(C₆Me₆)}₂Cl₄] with PMe₃ gave [M(C_nMe_n)Cl₂(PMe₃)](2a; M = Rh, n= 5), (2b; M = Ir, n= 5), and (2c; M = Ru, n= 6) which with silver acetate gave the complexes [M(C_nMe_n)(O₂CMe)₂(PMe₃)](3a)–(3c). The structures of complexes (3) were determined, by i.r. and n.m.r. spectroscopy, to contain monodentate acetates in the solid and in aprotic solvents. This was confirmed by an X-ray crystal-structure determination on (3a). In water there was rapid exchange between co-ordinated and free acetate in (3a) and (3b) but this was slower on the n.m.r. time-scale for (3c). Exchange took place via[M(C_nMe_n)(O₂CMe)(PMe₃)]⁺, the PF₆^– salts of which were obtained by reaction of (3) with KPF₆. The hydride complexes [Ir(C₅Me₅)H(Cl)(PMe₃)](6b) and [M(C_nMe_n)H₂(PMe₃)](7a)–(7c) were prepared from compounds (2); [Ir(C₅Me₅)H₂(PMe₃)] was stable to oxgen in solution but the others all decomposed rapidly giving Pme₃O and other products. Reactions with olefins or acetylenes were slow and such complexes are unlikely to be intermediates in catalytic hydrogen-transfer reactions.