The syntheses, structures and reactivity of bis(tert-butylcyclopentadienyl)molybdenum derivatives: nitrogenalkylation of an η2-acetonitrile ligand and influence of the chalcogen on the barrier to inversion of chalcogenoether adducts

Abstract

An investigation of the chemistry of the tert-butyl-substituted molybdenocene system, {(Cp^But)₂Mo} (Cp^But = C₅H₄Bu^t), has demonstrated that the η²-acetonitrile ligand in (Cp^But)₂Mo(η²-MeCN) may be alkylated by RI (R = Me, Et) at nitrogen to give iminoacyl derivatives, [(Cp^But)₂Mo(η²-MeCNR)]⁺, which is a new type of reactivity for mononuclear acetonitrile complexes. A series of chalcogenolate–hydride complexes (Cp^But)₂Mo(EPh)H (E = S, Se, Te) have been obtained by reaction of (Cp^But)₂MoH₂ with Ph₂E₂, and may be alkylated by MeI to give the chalcogenoether adducts [(Cp^But)₂Mo(PhEMe)H]I. Dynamic NMR studies on [(Cp^But)₂Mo(PhEMe)H]⁺ indicate that the barrier to inversion at the chalcogen increases in the sequence S < Se < Te. The oxo complex (Cp^But)₂MoO reacts with 2 equivalents of Me₃SiX (X = Cl, Br, I, O₂CMe, O₃SMe) to yield (Cp^But)₂MoX₂; for X = CN and NCS, (Cp^But)₂Mo(OSiMe₃)X, the product of reaction with 1 equivalent may be isolated. (Cp^But)₂Mo(OSiMe₃)X (X = CN, NCS) reacts with Me₃SiNCS to give the thiocyanate complex (Cp^But)₂Mo(SCN)X, rather than the isocyanate isomer, (Cp^But)₂Mo(NCS)X, thereby indicating that the reactions do not involve a simple metathesis of the Si–NCS bond. Other complexes that are reported include: (Cp^But)₂MoX₂ (X = H, Cl, Br, I, Me, CH₂Ph, CH₂SiMe₃), (Cp^But)₂MoL (L = CO, C₂H₄, C₂H₂, MeCN, PMe₃), [(Cp^But)₂Mo(μ-E)]₂, (Cp^But)₂Mo(η²–E₂) and (Cp^But)₂Mo(EPh)₂ (E = S, Se, Te).