Isolation of Bis‐ and Mono‐Cyclometallated Ru−IMes Complexes upon Reaction of [Ru(PPh3)3HCl], IMes and ZnMe2

Abstract Addition of an excess of ZnMe 2 to a mixture of [Ru(PPh 3 ) 3 HCl] and IMes (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) yields the bis‐cyclometallated complex, [Ru(IMes)“(PPh 3 ) 2 ] 2 , together with the mono‐cyclometallated, Ru−Zn heterobimetallic complex [Ru(IMes)′(PPh 3 ) 2 (ZnMe)] 3 . Treatment of 2 with H 2 , PhSiH 3 or pinacolborane yields the previously reported complex, [Ru(IMes)′(PPh 3 ) 2 H] 1 , the synthesis of which has been reinvestigated. Further studies of small molecule reactivity show that 1 adds H 2 to give [Ru(IMes)(PPh 3 ) 2 H 4 ] 4 , whilst 2 reacts with catecholborane to give [Ru(IMes‐Bcat)′(PPh 3 ) 2 H] 5 , in which (IMes‐Bcat)′ signifies a borylated NHC ligand that is singly‐metallated onto Ru. Treatment of 2 with CO gives the 18‐electron dicarbonyl product [Ru(IMes)”(PPh 3 )(CO) 2 ] 6 . Compounds 1 – 3 , 5 and 6 have been structurally characterised.