Photolysis of metal carbonyls

It is not our intention in this section to provide a comprehensive review of flash photolysis of organometallic species rather, we summarize some key experiments which establish the timescales of different types of reactions. Understandably, much more work has been done on the flash photolysis of metal carbonyls in solution than in the gas phase, and so we begin with solution experiments. 

Flash photolysis of metal carbonyls in solution was pioneered by Kelly and Koerner von Gustorf 30). The most complete of these studies has been carried out on the photolysis of Cr(CO)6 30). The historical development of these experiments, which forms an intriguing story in its own right, has been recently retold (2). The salient features are as follows ... 

Spectroscopists also saw the potential of reacting ligands with transition metal under matrix isolation conditions. Photolysis of metal carbonyls in organic (383 or inert gas matrices (39) had already been done, but atoms offered the possibility of step-wise addition of ligands. DeKock (40), Turner (41 ), and Moskovits and Ozin (42) made early contributions, but the work of the last two became dominant (32). By 1972, there were the two distinct branches in transition metal atom chemistry, the preparative and matrix spectroscopic studies. 

Caution. Metal carbonyls are volatile and toxic. The photolysis of metal carbonyls in THF solvent produces toxic carbon monoxide. Hence all reactions should be carried out in a well-ventilated hood. 

The use of supercritical fluids as reaction media for organometallic species is also investigated. Reactions include photochemical replacement of carbon monoxide with N2 and H2 in metal carbonyls, where the reaction medium is supercritical xenon. Also, photochemical activation of C-H bonds by organometallic complexes in supercritical carbon dioxide is investigated. More recent studies on photochemical reactions also include laser flash photolysis of metal carbonyls in supercritical carbon dioxide and ethane and laser flash photolysis of hydrogen abstraction reaction of triplet benzophenone in supercritical ethane and... 

Photolyses in frozen N2 matrices result in the substitution of N2 for CO yielding M(CO) j(N2)x, CpM(CO) x(N2)x/ i or (C6H6)Cr(CO) x(N2)x i photoproducts. N2 species can also be observed by photolysis of metal carbonyls impregnated in polyethylene films followed by exposure of the films to N2. Similar routes to H2 species will be described below. Fe(CO)4(N2), CpMn(CO)2(N2) and (C6H6)Cr(CO)2(N2) have been observed by time-resolved IR spectroscopy in the gas phase. 

Me). Photolysis of metal carbonyls in liquefied noble gases has been a successful approach in the charaterization of a range of highly reactive dihydrogen complexes including V(GO)s(H2), M(Gp)(GO)3(H2) (M = V or Nb), ... 

Top Electron promotion initially thought to occur upon photolysis of an octahedral oP complex. Bottom Mixing of excited states that are now thought to more accurately reflect the t/ents that occur after photolysis of metal-carbonyl compounds, such as = Cr,Mo,andW). 

Methods to generate the unsaturated intermediate that adds alkane include photolysis of metal-carbonyl or -dihydride complexes, thermolysis of alkyl hydride complexes, and abstraction of halide with a cationic reagent or protonation of an alkyl group with an acid containing a weakly coordinating anion. For example, the photolysis of Cp Ir(CO)j or Cp IrfPMejJHj generates Cp Ir(L) (L = CO or and photolysis of the... 

Carbonyl complexes in thin films of polystyrene and other polymers have been studied by Butler et. Polymer films arise again in a paper by Bronshtein et al dealing with the general issue of the photolysis of metal carbonyls in thin films. This technique has become a common and reliable method for exploring metal carbonyl photochemistry. 

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