Substituted carbonyl derivatives of the Group VI transition metals. I. Complexes with Bis(diphenylarsino)methane

Abstract

The reactions of the potentially bidentate ditertiary arsine ligand bis-(diphenylarsino)methane, dam, with the hexacarbonyls of the Group VI transition metals have been investigated. N.m.r, spectroscopy has been used to determine the mode of coordination of the ligand. In the compounds M(CO)₅(dam), M(CO)₄(dam)₂, and M(CO)₃(dam)₃ [M = Cr, Mo, W], dam is acting as a monodentate ligand, but in M(CO)₄(dam) it is acting as a normal chelate coordinating to the metal through both arsenic atoms. In the cases of molybdenum and chromium, only, a further type of complex M(CO)₂(dam) has been isolated. The results of N.M.R., infrared, and mass spectrometry, together with other physical measurements, can only be explained on the assumption that the ligand was coordinated to the metal by an arene π-linkage and by one arsenic atom. This novel structure has been confirmed by a single crystal X-ray diffraction study on the chromium compound.