Comparative photochemistry of tricarbonyl(η5-cyclopentadienyl)methyl- and -ethyl-molybdenum and -tungsten in poly(vinyl chloride) film matrices at 12–298 K
Abstract
The photoreactions of [M(η5-C5H5)(CO)3(CH3)] and [M(η5-C5H5)(CO)3(C2H5)] complexes (M = Mo or W) in poly(vinyl chloride)(pvc) film matrices over a wide temperature range have been monitored using i.r. spectroscopy. At 298 K the methyl complexes dealkylate on irradiation (λ > 300 nm) to form [M(η5-C5H5)(CO)3 Cl], [M(η5-C5H5)(CO)3H], and [M2(η5-C5H5)2(CO)6]. Photolysis at 12 K leads primarily to the formation of [M(η5-C5H5)(CO)2(CH3)]. In the case of molybdenum, M–CH3 bond cleavage also occurs at 12 K and the complexes [Mo(η5-C5H5)(CO)3Cl] and [Mo(η5-C5H5)(CO)3H] are generated on warming the matrices. Photolysis of [M(η5-C5H5)(CO)3(C2H5)] at 12 K proceeds with the formation of [M(η5-C5H5)(CO)2(C2H5)] which rearranges photochemically or thermally to form trans-[M(η5-C5H5)(CO)2(C2H4)H]. The cis-ethylene–hydride complex is also observed for tungsten at temperatures below ca. 50 K. At 298 K, photolysis of [W(η5-C5H5)(CO)3(C2H5)] leads directly to trans-[W(η5-C5H5)(CO)2(C2H4)H] which reacts further to form [W(η5-C5H5)(CO)3H], [W(η5-C5H5)(CO)2(C2H4)Cl], [W(η5-C5H5)(CO)3Cl], and [W2(η5-C5H5)2(CO)6]. However, on photolysis of [Mo(η5-C5H5)(CO)3(C2H5)] at 298 K the main product observed is [Mo(CO)6] with trace amounts of [Mo(η5-C5H5)(CO)3H], [Mo(η5-C5H5)(CO)3Cl], and [MO2(η5-C5H5)2(CO)6].