SYNTHESIS AND CHARACTERIZATION OF A SERIES OF (PENTAMETHYLCYCLOPENTADIENYL)TUNGSTEN(V) AND (PENTAMETHYLCYCLOPENTADIENYL)TUNGSTEN(VI) AMINO, AMIDO, IMIDO, AND BRIDGING NITRIDO COMPLEXES AND MOLYBDENUM ANALOGS

Ammonia adds reversibly to [Cp*WMe4]PF6 (1) to give unstable [Cp*WMe4(NH3)]PF6 (2), which is readily deprotonated to form Cp*WMe4(NH2) (3a). Excess methylamine reacts with 1 to give Cp*WMe4(NHMe); bulkier amines such as tert-butylamine simply deprotonate 1. Aniline reacts with 1 to yield [Cp*WMe-(NHPh)(NPh)]PF6 (5), which is readily deprotonated to give Cp*WMe(NPh)2. Reaction of Cp*WMe(NPh)2 with anhydrous triflic acid gives Cp*WMe(OTf)2(NPh), whereas aqueous HCl yields Cp*WMe(O)2. Cp*WMe3(NPh) is formed upon alkylation of Cp*WMe(OTf)2(NPh). Ammonia adds to Cp*WMe3(OTf) to form two isolable adducts, [Cp*WMe3(NH3)]OTf and [Cp*WMe3(NH3)2OTf. Deprotonation of either yields Cp*WMe3(NH2) (8). Oxidation of 8 in the presence of a base yields Cp*WMe3(NH) (9a). 9a is deprotonated by alkyllithium reagents to give [Cp*WMe3(NLi)]x (9b), which reacts with water, MeOTf, or Me3SiCl to give Cp*WMe3(NR) (R = H, Me, SiMe3), respectively. Protonation of 9a or oxidation of 8 is proposed to form transient [Cp*WMe3(NH2)]+ (4), which decomposes to {[Cp*WMe3]2(mu-N)}+ and NH4+. Molybdenum analogues that have been prepared include [Cp*MoMe3(NH3)]OTf, [Cp*MoMe3(NH3)2]OTf, Cp*MoMe3(NH2), Cp*MoMe3(NH), and [Cp*MoMe3(NLi)]x.