Carbonyl halides of the Group VI transition metals. XIII. Diiodotetracarbonyls of molybdenum and tungsten and some of their derivatives

Abstract

Diiodotetracarbonyls of molybdenum and tungsten(II) have been prepared for the first time by the direct interaction of the parent hexacarbonyls with iodine at room temperature under the influence of ultraviolet radiation. Reaction of the iodocarbonyls with donor ligands such as triphenylphosphine, triphenylarsine, and triphenylstibine generally gives neutral substitution products, but the reaction between the molybdenum compound and triphenylphosphine yielded the previously reported triphenylphosphonium salt of the triiodotricarbonyl(triphenylphosphine)-molybdate(II) ion.     Diiodotricarbonylbis(triphenylphosphine)tungsten(II) loses carbon monoxide on heating under vacuum to give the corresponding blue dicarbonyl compound. The dicarbonyl dissolved in dichloromethane readily absorbs carbon monoxide to reform the tricarbonyl and the compounds therefore represent a further carbon monoxide carrying system.