Tungsten(IV) Imido Complexes from Oxidation of a Protected Zero-Valent NitrenePrecursor

摘要

Treatment of the zwitterionic complex (CO)5WNPhNPhC(OMe)Ph (1b) with oneequivalent of I2(iodine) leads to formation of the iodo-bridged tungsten (IV) imido dimer (CO)2W(NPh)I22 (2) and PhN=C(OMe)Ph. Iodination of the W(O) center of 1b is followed by rapid cleavage of the N-N bond to form I2(CO)3WNPh, which dimerizes with loss of CO. Cleavage of 2 with THF or pyridine leads to formation of the monomeric compounds (CO)2W(NPh)I2L (3a,b). Addition of excess PR3 (R = Me, OMe) to 2 or 3 gives W(NPh)2(CO)(PR3)2 (4a,b) in 90% yield. Conversion of 1b to a series of tungsten (IV) imido complexes is equivalent to oxidizing the highly unstable zero-valent nitrene complex (CO)5W=NPh. The zwitterionic ligand in 1b serves as a protected imido group during oxidation of the metal center. (jg).