Ruthenium and osmium complexes of dihydroperimidine-based N-heterocyclic carbene pincer ligands.

Abstract

The reactions of N,N'-bis(phosphinomethyl)dihydroperimidine pro-ligands H2C(NCH2PR2)2C10H6 (R = Cy 1a, R = Ph 1b) with [RuCl2(PPh3)3] give markedly different products. Chelate-assisted double C-H activation in the former affords the perimidinylidene-based N-heterocyclic carbene (per-NHC) pincer complex [RuCl2(OC4H8){κ(3)-P,C,P'-C(NCH2PCy2)2C10H6}] (2), while the latter reaction provides the asymmetric PNP-coordinated complex [RuCl2(PPh3){κ(3)-P,N,P'-CH2(NCH2PPh2)2C10H6}] (3), in which no C-H activation has occurred. Subsequent reactions of the per-NHC complex 2 with carbon monoxide and mesityl isocyanide readily displaced the labile THF ligand to afford the complexes [RuCl2(CA){κ(3)-P,C,P'-C(NCH2PCy2)2C10H6}] (A = O 4, A = NC6H2Me35). Double C-H activation of 1a and 1b was significantly more facile on reaction with [OsCl2(PPh3)3], providing the per-NHC complexes [OsHCl(PPh3){κ(3)-P,C,P'-C(NCH2PR2)2C10H6}] (R = Cy 7a, R = Ph 7b, respectively), each as two isomers. The reactions of 1b with [Ru2(μ-Cl)2Cl2(η-C6H3Me3)2] or [AuCl(THT)] (THT = tetrahydrothiophene) provide the bimetallic complexes [Ru2{μ-H2C(NCH2PPh2)2C10H6}Cl4(η-C6H3Me3)2] (8) and [Au2{μ-H2C(NCH2PPh2)2C10H6}Cl2] (9) without C-H activation occurring.