Syntheses and Structures of Transition Metal Complexes with Phosphanylphosphinidene Chalcogenide Ligands

The reactivity of the phosphanylphosphinidene complex [(DippN)₂W­(Cl)­(η²-P-PtBu₂)]⁻ (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–PtBu₂. 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.