Bimetallic cyano-bridged cations: preparation and hydride reduction of [(η⁵-C₅H₅)L₂Ru(µ-CN)ML′₂(η⁵-C₅H₅)]PF₆[L₂,L′₂=(PPh₃)₂,Ph₂PCH₂CH₂PPh₂; M = Ru or Fe]. Formation of [Ru(η⁵-C₅H₅)(PPh₃)H₃] and X-ray crystal structure of [(η⁵-C₅H₅)(Ph₂PCH₂CH₂PPh₂)Ru(µ-CN)Ru(PPh₃)₂(η₅-C₅H₅)]PF₆

Abstract

The cyano-complexes [Ru(η5-C5H5)L2(CN)][(1) L = PPh3 and (2) L2= dppe (Ph2PCH2CH2PPh2)] react with the corresponding chlorides (3) and (4) and with [Fe(η5-C5H5)(dppe)Br](9) to give the diruthenium cyano-bridged cations [(η5-C5H5)L2Ru(µ-CN)RuL′2(η5-C5H5)]+[L = L′= PPh3(5); L = PPh3, L′2= dppe (6); L2= dppe, L′= PPh3(7); L2= L′2= dppe (8)] and the mixed iron–ruthenium cation [(η5-C5H5)(dppe)Ru(µ-CN)Fe(dppe)(η5-C5H5)]+. An X-ray crystal structure of complex (7) shows the Ru–CN–Ru bridge to be essentially linear. Hydride reduction of these cyano-bridged cations results in the breakage of the metal-nitrogen bond to regenerate the original cyano-complexes (1) and (2) together with the required hydrido-complexes [M(η5-C5H5)(dppe)H][M = Ru (11) or Fe (12)] or [Ru(η5-C5H5)(PPh3)2H](13). For those reductions giving (13), the novel ruthenium trihydride [Ru(η5-C5H5)(PPh3)H3](14) was also isolated. Reduction of chloride (3) with sodium methoxide exclusively gave the monohydride (13), whereas reduction with lithium aluminium hydride in tetrahydrofuran gave a 1 : 4 mixture of the monohydride (13) and the trihydride (14). The mechanism for the formation of the trihydride (14) is discussed.