Carbonyl halides of the Group VI transition metals. XIX. Iodocarbonyl complexes of molybdenum and tungsten with Bis(diphenylarsino)methane

Abstract

Complexes of the general formulae M(CO)₃(dam)I₂, M(CO)₃(dam)₂I₂, and M(CO)₂(dam)₂I₂ have been prepared and characterized [M = Mo, W; dam = bis(diphenylarsino)methane]. All of the compounds are diamagnetic and non-electrolytes in acetone solution. The tungsten derivatives were prepared by direct interaction of dam with diiodotetracarbonyltungsten(11), but the molybdenum analogues were obtained by iodine oxidation of the zero-valent complex Mo(CO)₄(dam)₂ whose preparation is reported for the first time in this paper. The bis(dam)tricarbonyl complexes, M(C0)₃(dam)₂I₂, are unstable in solution giving M(CO)₂(dam)I₂ and free dam in equilibrium with undissociated complex. The bis(dam)tricarbonyl complexes also readily lose carbon monoxide, especially in the case of molybdenum, to give M(CO)_z(dam)₂I₂. These dicarbonyl complexes readily absorb carbon monoxide to re-form the tricarbonyl complexes to give a reversible carbon monoxide carrying system. Overall, these systems may be represented by the general equations : M(CO)₃(dam)I₂ + dam ↔ M(CO)₃(dam)₂I₂ + CO These equilibria have been studied using both infrared and nuclear magnetic resonance techniques.