Formation and reactivity of the cyclometallated N-heterocyclic carbene complexes [Ru(NHC)′(dppe)(CO)H]

Thermolysis of [Ru(PPh3)(dppe)(CO)HCl] (dppe = 1,2-bis(diphenylphosphino)ethane) with the N-heterocyclic carbenes IiPr2Me2 (1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene), IEt2Me2 (1,3-diethyl-4,5-dimethyl-imidazol-2-ylidene) or ICy (1,3-dicyclohexylimidazol-2-ylidene) gave the cyclometallated carbene complexes [Ru(NHC)′(dppe)(CO)H] (NHC = IiPr2Me2, 4; IEt2Me2, 5; ICy, 6). Dissolution of 4 in CH2Cl2 or CHCl3 gave the trans-Cl–Ru–P complex [Ru(IiPr2Me2)′(dppe)(CO)Cl] (7), which converted over hours at room temperature to the trans-Cl–Ru–CO isomer 7′. Chloride abstraction from 7 by NaBPh4 under an atmosphere of H2 produced the cationic mono-hydride complex [Ru(IiPr2Me2)(dppe)(CO)H][BPh4] (9), which could also be formed by protonating 4 with 1 eq HBF4·OEt2. Treatment of 4 with excess HBF4·OEt2 followed by extraction into MeCN produced the dicationic acetonitrile complex [Ru(IiPr2Me2)(dppe)(CO)(NCMe)2][BF4]2 (10). The structures of 6, 7, 7′ and 10 have been determined by X-ray crystallography.