Organoimido complexes of tungsten-(VI) and -(V): correlation between relative orientation of π-donor ligands and electron configuration of the metal

Abstract

The high-yield synthesis of the monomeric five-co-ordinate arylimido complex [WCl ₃ (NPh)(OC ₆ H ₃ Pr ⁱ ₂ -2,6)] was achieved starting from [{WCl ₃ (NPh)} ₂ (µ-Cl) ₂ ]. The adducts [WCl ₃ (NPh)(OC ₆ H ₃ Pr ⁱ ₂ -2,6)L] (L = tetrahydrofuran, pyridine (py) or 4-tert-butylpyridine) of the monoalkoxide have been synthesized and the constitution of the pyridine adduct determined by X-ray crystallography. The reduction of the monoalkoxide with 1 equivalent of sodium amalgam in the presence of pyridine or triethylphosphine leads to the paramagnetic adducts [WCl ₂ (NPh)(OC ₆ H ₃ Pr ⁱ ₂ -2,6)L ₂ ] (L = py or PEt ₃ ) which were characterized. A trans configuration was found for the two chlorine atoms and the two σ-donor ligands in the structure analysis. Reorganization of the two π-donor ligands (aryloxide and NPh) from a cis arrangement in the complex with d ⁰ electron configuration to a trans arrangement in the d ¹ configurated complexes is found and verified by X-ray diffraction analyses.