Mechanistic study of the photofragmentation of the clusters [Os-3(CO)(10)(diene)] (diene = cis-1,3-butadiene, 1,3-cyclohexadiene): direct observation of the open-triangle primary photoproduct with nanosecond time-resolved infrared and UV-Vis spectros

摘要

The photochemistry of the clusters [Os-3(CO)(10)(diene)] (diene = cis-1,3-butadiene, 1,3-cyclohexadiene) was studied in detail. Upon near-UV irradiation photofragmentation occurs to give mononuclear [O-3(CO)(3)(diene)]. The second fragmentation product [Os-2(CO)(7)] was trapped by reaction with CO, or with alkenes at low temperatures, to produce the dinuclear complexes [Os-2(CO)(7)(L)(2)] (L = CO, ethene, 1-octene). The fragmentation was studied further with nanosecond time-resolved W-Vis and IR spectroscopy and was found to proceed via the initial formation of a triosmium photoproduct with a lifetime of about 100 ns in hexane. From the spectroscopic data we infer that this intermediate has a coordinatively unsaturated open-triangle structure with two bridging carbonyl groups, one bridging the split (CO)(4)Os-Os(CO)(2)(diene) bond. (C) 2000 Elsevier Science S.A. All rights reserved. [References: 28]