N-heterocyclic carbene and cyclic (alkyl)(amino)carbene complexes of molybdenum(IV) and tungsten(IV).

The synthesis and characterization of N-heterocyclic carbene (NHC) and cyclic (alkyl)(amino)carbene (cAAC) complexes of molybdenum(IV) and tungsten(IV) chloride is reported. Reaction of two equivalents of the NHCs IMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene), IDipp (1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and IiPr (1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene) with [MCl(SEt)] (M = Mo, W) in toluene afforded the bis-NHC complexes [MCl(NHC)] (M = Mo: NHC = IMes 1, NHC = IMes 2; M = W: NHC = IMes 3, NHC = IDipp 4, NHC = IiPr5). Mono-carbene complexes [MCl(NHC)(SEt)] 6-9 (M = Mo: NHC = IMes 6, NHC = IMes 7; M = W: NHC = IMes 8, NHC = IDipp 9) are available ligand dismutation of 1-4 with [MCl(SEt)].