Highly Reduced Organometallics. 8. The Synthesis of (Phosphine)pentacarbonylvanadate(1−) Anions, V(CO)₅PR₃ ⁻, by the Thermal Substitution of (Ammine)pentacarbonylvanadate(1-), V(CO)₅NH₃ ⁻

(Ammine)pentacarbonylvanadate(1-) reacts with various phosphines (L = Ph₃P, Ph₂P(CH₂)_nPPh₂ (n = 0–2), (p-ClC₆H₄)₃P, Me₃P, HPh₂P, F₃P) to provide moderate to high yields of V(CO)₅L⁻. Several of these materials have not been isolated previously and either are unavailable or are not easily prepared by other methods. Interestingly, the reaction of V(CO)₆NH₃ ⁻ with Ph₄P₂ in liquid ammonia provides high yields (70–75%) of previously unknown V(CO)₅Ph₂PNH₂ ⁻, isolated as the Et₄N⁺ salt, while the same reaction conducted in THF provides lower yields (35–45%) of V(CO)₅Ph₄P₂ ⁻, isolated as the Ph₄P⁺ and Ph₄As⁺ salts. Proton-decoupled ³¹P NMR has been used to unambiguously show that V(CO)₅Ph₂P(CH₂)_nPPh₂ ⁻ (n = 0–2) contain both ligated and unligated diphenylphosphino groups. Infrared and ¹H NMR spectra of the products are also discussed with respect to proposed structures. This “labile ligand method” represents the best method presently available for the synthesis of V(CO)₅PR₃ ⁻ species.