Highly Reduced Organometallics. 4. Syntheses and Chemistry of Pentacarbonylvanadate(3-) Ion, V(CO)53-

Article abstract of DOI:10.1021/ja00410a019

Alkali-metal reductions of various salts containing V(CO)6^- in liquid ammonia provide high yields of the super-reduced species V(CO)5^3- which contains vanadium in its lowest known formal oxidation state.Although salts of V(CO)5^3- containing lithium, sodium, and various onium cations rapidly decompose above 0 deg C, the trianion has been isolated and characterized as rather thermally stable rubidium and cesium salts, Rb3V(CO)5 and Cs3V(CO)5.A treacherously shock sensitive potassium salt, K3V(CO)5, is also described.Treatment of liquid ammonia solutions of Na3V(CO)5 with bis(triphenylphosphin)iminium chloride and tetraphenylphosphonium chloride provides thermally unstable, ammonia-insoluble solids believed to contain V(CO)5^3-.These decompose on warming to room temperature to provide V(CO)5PPh3^-.Main-group 4 electrophiles, including R3EX (R = alkyl, aryl; E = Sn, Pb; X = halide), react with V(CO)5^3- to provide moderate to high yields of the new organometallic derivatives, (R3Sn)V(CO)5^2- and (R3E)2V(CO)5^1-.The dianions are the first reported organotin derivatives containing a transition metal in a formally negative oxidation state.Reactions of V(CO)5^3- in liquid ammonia with weak Broensted acids including water, ammonium cation, and acetonitrile are also described.High yields (85 - 95percent) of V(CO)5NH3^- are obtained by treatment of V(CO)5^3- in liquid ammonia with 2 or more equiv of ammonium chloride.This amine-substituted anion is quite unstable in solution at room temperature but may be isolated as thermally stable Ph4As⁺ or Ph4P⁺ salts.