Heterobimetallic ruthenium-zinc complexes with bulky N-heterocyclic carbenes: Syntheses, structures and reactivity

The ruthenium–zinc heterobimetallic complexes, [Ru(IPr)₂(CO)ZnMe][BArF₄] (7), [Ru(IBiox6)₂(CO)(THF)ZnMe][BArF₄] (12) and [Ru(IMes)′(PPh₃)(CO)ZnMe] (15), have been prepared by reaction of ZnMe₂ with the ruthenium N-heterocyclic carbene complexes [Ru(IPr)₂(CO)H][BArF₄] (1), [Ru(IBiox6)₂(CO)(THF)H][BArF₄] (11) and [Ru(IMes)(PPh₃)(CO)HCl] respectively. 7 shows clean reactivity towards H₂, yielding [Ru(IPr)₂(CO)(η²-H₂)(H)₂ZnMe][BArF₄] (8), which undergoes loss of the coordinated dihydrogen ligand upon application of vacuum to form [Ru(IPr)₂(CO)(H)₂ZnMe][BArF₄] (9). In contrast, addition of H₂ to 12 gave only a mixture of products. The tetramethyl IBiox complex [Ru(IBioxMe₄)₂(CO)(THF)H][BArF₄] (14) failed to give any isolable Ru–Zn containing species upon reaction with ZnMe₂. The cyclometallated NHC complex [Ru(IMes)′(PPh₃)(CO)ZnMe] (15) added H₂ across the Ru–Zn bond both in solution and in the solid-state to afford [Ru(IMes)′(PPh₃)(CO)(H)₂ZnMe] (17), with retention of the cyclometallation