Solution and Nujol matrix photochemistry of (η5-C5H5)2Os2(CO)4 and Nujol matrix photochemistry of (η5-C5H4CH3)2Ru2(CO)4 and (η5-C5H5)M(CO)2H, where M = Ru and Os

Lowering the temperature of a Nujol solution of (eta (5)-C5H4CH3)(2)Ru-2(CO)(4) containing bands of the trans- and cis-bridging and trans-nonbridging isomers from room temperature to ca. 90 K results in complete disappearance of the bands of the trans-terminal isomer. The photochemistry of (eta (5)-C5H4CH3)(2)Ru-2(CO)(4) in frozen Nujol at 90 K differs subtly from that of (eta (5)-C5H5)(2)Ru-2(CO)(4) in inert gas matrixes at 12 K in that the trans-bridging isomer is found to undergo photolysis at high energy (lambda (irr) > 250 nm) to yield both the triply bridged carbonyl-loss species, (eta (5)-C5H4CH3)(2)Ru-2(mu -CO)(3), and the cis-bridged species isomer. There is no evidence for formation of the trans-nonbridged isomer upon photolysis as observed for (eta (5)-C5H5)(2)Ru-2(CO)(4) The solution photochemistry of (eta (5)-C5H5)(2)Os-2(CO)(4) is shown to closely parallel that of (eta (C5H5)-C-5)(2)Ru-2(CO)(4). Photolysis of (eta (5)-C5H5)(2)OS2(CO)(4) in CBCl3 yields (eta (5)-C5H5)Os(CO)(2)Cl, while photolysis in benzene yields hydride products believed to arise from metal-to-ring coupling of radicals. Photolysis of (eta (5)-C5H5)(2)Os-2(CO)(4), which exists only in a nonbridged form, in frozen Nujol (90 K) results in CO loss; and formation of (eta (5)-C5H5)(2)Os-2(mu -CO)(3) as the only photoproduct. Photolysis of (eta (5)-C5H5)M(CO)(2)H, where M = Ru or Os, in frozen Nujol yields (eta (5)-C5H5)M(CO)H and a second product that;appears to be either (ys; C5H6)M(CO)(2) or the (eta (5)-C5H5)M(CO)(2) radical.