Syntheses and Structures of Transition Metal Complexes with Phosphanylphosphinidene Chalcogenide Ligands

The reactivity of the phosphanylphosphinidene complex [(DippN)₂W(Cl)(η²-P-P tBu₂)]^- (1) toward chalcogens (Ch = Se, S) was studied. Reactions of stoichiometric amounts of 1 with chalcogens in DME yielded monomeric tungsten complexes with phosphanylphosphinidene chalcogenide ligands of the formula tBu₂P-P-Ch (Ch = Se (in 2) and S (in 5)), which can be regarded as products of the addition of a chalcogen atom to a P═W bond in starting complex 1. The dissolution of selenophosphinidene complex 2 in nondonor solvents led to the formation of a dinuclear complex of tungsten (3) bearing a tBu₂P(Se)-P ligand together with [ tBuSe₂Li(dme)₂]₂ and polyphosphorus species. Under the same reaction conditions, thiophosphinidene complex 5 dimerized via the formation of transient complex 7, possessing a thiotetraphosphane-diido moiety tBu₂P(S)-P-P-P tBu₂. The elimination of the tBu₂PS group from 7 yielded stable dinuclear tungsten complex 8 with an unusual phosphinidene tBu₂P-P-P ligand. The reaction of 1 with excess chalcogen led to the cleavage of the P-P bond in the tBu₂P-P ligand and the formation of [(DippN)₂W(PCh₄)]₂^2- and [ tBuCh₂Li(dme)₂]₂. The isolated compounds were characterized by NMR spectroscopy and X-ray crystallography. Furthermore, the calculated geometries of the free selenophosphinidenes, tBu₂P-P-Se and tBu₂P(Se)-P, were compared with their geometries when serving as ligands in complexes 2 and 3.