The bimetallic complexes CpRu(P-P)X [Cp = n 5-C 5H 5; X = Cl, H; P-P = dppf (1,1′-bis(diphenylphosphino)ferrocene) , dppr (1,1′-bis(diphenylphosphino)ruthenocene), dppo (1,1′- bis(diphenylphosphino)-osmocene), dippf (1,1′-bis(diisopropylphosphino) ferrocene), dcpf (1,1′-bis(dicyclohexylphosphino)ferrocene)], Cp*Ru(P-P)X [Cp* = n 5-C 5Me 5; X = Cl, H; P-P = dppf, dippf, dppomf (1,1′-bis(diphenylphosphino) octamethylferrocene), dppc (1,1′-bis(diphenylphosphino)cobaltocene)], [Cp*Ru(P-P)X] + (X = H, CCPh; P-P = dppc +), and [Cp*Ru(P-P)L] 2+ (L = CH 3CN, t-BuCN; P-P = dppc -) have been synthesized. Most of the chloride and hydride complexes have been studied by cyclic voltammetry. The X-ray structures of [Cp*Ru(dppc)CH 3CN][PF6] 2 and [Cp*Ru(dppc)CCPh] [PF 6] have been determined. Protonation of [Cp*Ru(dppc)CCPh] + gives the vinylidene complex [Cp*Ru(dppc)CCHPh] 2+. The Co(III/II) potential of the dppc + ligand undergoes a cathodic shift upon coordination in [Cp*Ru-(dppc)H] + and an anodic shift upon coordination in [Cp*Ru(dppc)CH3CN] . The 1H NMR spectrum of Cp*Ru(dppc)H is consistent with its formulation as a Co(II)/Ru(II) complex. As gauged by their reactivity toward iminium cations, the hydride complexes are poor hydride donors; proton and electron transfer are dominant. CpRu(dippf)H and CpRu(dcpf)H deprotonate iminium cations with acidic a-hydrogens. Cp*Ru(dppc)H is oxidized by the N-(benzylidene)pyrrolidinium cation, giving [Cp*Ru-(dppc)H] - and the vicinal diamine 1,2-bis(N-pyrrolidino)-1,2-diphenylethane. Most of the hydride complexes give rraw-dihydride cations upon protonation; an exception is [Cp*Ru(dppc)H] +, which forms a dihydrogen complex [Cp*Ru(dppc)(H2)]2+ with surprising kinetic stability. This dihydrogen complex is more acidic and less thermodynamically stable than its dihydride isomer. The H 2 ligand in [Cp*Ru(dppc)-(H 2)] 2+ is readily replaced by nitriles; the reaction with t-BuCN occurs by a dissociative mechanism.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry