Steric and “Indenyl” Effects in the Chemistry of Alkylidyne Complexes of Tungsten and Molybdenum

Abstract

Reaction between LiC5Me5 or KC9H7 and [M(≡C6H3Me2-2,6)(CO)2(NC5H4Me-4)2Br] affords the complexes [M(≡CC6H3Me2-2,6)(CO)2L] (L = η-C5Me5, M = W (1a); Mo (1b); L = η5-C9H7, M = Mo (1c)). The complexes 1a and 1b react with PMe3 to give η2-ketenyl compounds [M{η2-C(O)CC6H3Me2-2,6}(CO)(PMe3)(η-C5Me5)] (M = W (2a), Mo (2b)) while the reaction of 1c with PMe3 or P(OMe)3 gives [Mo(≡CC6H3Me2-2,6)(CO)L'(η5-C9H7)] (L' = PMe3 (3a), P(OMe)3 (3b)). Thermolysis of 2a provides 1a rather than the anticipated complex [W(≡CC6H3Me2-2,6)(CO)(PMe3)(η-C5Me5)]. Compound lb has been employed to prepare the range of heterobimetallic compounds [MoFe(η-CC6H3Me2-2,6)(CO)5(η-C5Me5)] (4), [MoFe(μ-CC6H3Me2-2,6)(CO)3(μ-dppm)(η-C5Me5)] (5), [MoFe(μ-η2-SeCC6H3Me2-3,6)(CO)5-(η-C5Me5)] (6), and [MoCu(μ-CC6H3Me2-2,6)(CO)(μ-CO)(η-C5Me5)2] (8b), with bonds between molybdenum and iron or copper supported by the xylylmethylidyne unit, to assess the effects of steric encumbrance on bridge-assisted cluster asembly.