Highly reduced organometailics. 7. The synthesis of alkyl and phenyl isocyanide and related monosubstituted vanadium carbonyl anions, V(CO)₅L, by the thermal substitution of (amine)pentacarbonylvanadate(1-), v (CO)₅NH₃-

(Amine)pentacarbonylvanadate(l-) reacts with various isocyanides, RNC (R = Me, c-Hx, t-Bu, Ph) to form [V(CO)₅CNR]^- in high yields (60-85%). These anions have been characterized by elemental analysis and infrared and 1 H NMR spectra and are the first examples of (isocyanide)pentacarbonylvanadate ions. Treatment of Na[V(CO)₅NH₃] with NaCN in liquid ammonia provides, after cation exchange, up to 56% yields of [Et₄N]₂[V(CO)₅CN]. The reactions of [V(CO)₅NH₃]- with n-BuNC and acetonitrile also provide V(CO)₅L^- species. On the basis of infrared spectra, these materials are formulated as [V(CO)₅CN-n-Bu]^- and V(CO)₅(CH₃CN)^-, respectively. The latter product was isolated in 30% yield as a thermally unstable Ph₄As⁺ salt.