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.