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Potassium oxopentacyanomolybdate(IV), [Mo(0)(CN)5]K3-2H20, is prepared either through a disproportionation process of the molybdenum(V) cyano intermediate or by controlled hydrolysis of the octacyanomolybdate(IV). The tetraphenylphosphonium salt obtained under phase-transfer conditions reacts readily with dioxygen to give tetraphenylphosphonium oxoperoxotetracyanomolybdate(VI) [Mo(0)(02)(CN)4][PPh4]2, whose structure is determined by an X-ray analysis. The crystalline compound belongs to triclinic space group Pi with a = 10.951 (2) A, b = 22.597 (6) A, c = 10.283 (2) A, a = 97.66 (2)°, /3 = 116.24 (2)°, and y = 84.43 (2)°. The volume of the unit cell is 2260 (2) A3 with Z = 2. The structure was refined to R = 3.1%. The reactivity of the peroxo complex toward triphenylphosphine is studied and is shown to give 1.5 mol of phosphine oxide/mol of peroxo complex. This unusual stoichiometry is rationalized in terms of a classical oxidation of 1 mol of phosphine by the peroxo moiety followed by an oxo transfer involving 2 mol of the dioxomolybdenum(VI) intermediate. The plausible implications that such a process could have on the catalytic oxidation on metal oxide surfaces is given. The poor reactivity of the oxoperoxomolybdenum dianion toward olefins is dramatically increased in the presence of silver salts. A monoanionic species, stabilized by hexamethylphosphoramide, [Mo(0)(02)(CN)3-HMPA] [(PhCH2)Ph3P], is isolated and characterized by an X-ray analysis. The crystalline compound belongs to monoclinic space group P2Jn with a = 9.801 (2) A, b = 13.613 (3) A, c = 27.597 (8) A, and d = 90.56 (2)°. The volume of the unit cell is 3682 (2) A3 with Z = 4. The structure was refined to R = 7.12%.

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A novel double carbonylation of styrene oxides occurs on treatment of the heterocycle with carbon monoxide, methyl iodide, NaOH (0.5 M), C6H6, CO*(CO)~ as the metal catalyst, and cetyltrimethylammonium bromide as the phase transfer agent.