Metal carbonyls, TRIR spectroscopy

More recently, Weitz and co-workers studied the bonding of Xe and Kr atoms to M(CO)5 fragments [M = Cr and Mo (Xe only) and W] in the gas phase using TRIR spectroscopy (52). The IR v(C—O) bands of metal carbonyls in the gas phase are much broader than those in solution or... 

Time-resolved Infrared spectroscopy (TRIR), a combination of UV flash photolysis and fast IR spectroscopy (ns), has been outstandingly successful in identifying reactive intermediates [5] and excited states [6] of metal carbonyl complexes in solution at room temperature. We have used infrared spectroscopy to probe the mechanism of photo-17] and electrochemical [8] catalytic reduction of COj. We have used TRIR to study organometallic reactions in supercritical fluids on a nanosecond time-scale [9-10]. 

Another method found to be useful for the direct observation of alkane metal complexes is fast time-resolved infrared (TRIR) spectroscopy.- - - Upon UV irradiation of a metal-carbonyl complex, such as Cp Rh(CO)2 in liquid rare gases, an intermediate is formed, which, in the presence of an alkane, forms a weakly bound alkane complex [Eq. (6.93)]. Finally, the latter complex rapidly transforms through the transition state 112 into the alkyl hydride [Eq. (6.94)]. 

Time-resolved infrared spectroscopy (TRIR) has been outstandingly successful in identifying reactive intermediates and excited states of both metal carbonyl [68,69] and organic complexes in solution [70-72]. Some time ago, the potential of TRIR for the elucidation of photochemical reactions in SCFs was demonstrated [73]. TRIR is particularly suited to probe metal carbonyl reactions in SCFs because v(CO) IR bands are relatively narrow so that several different species can be easily detected. Until now, TRIR measurements have largely been performed using tunable IR lasers as the IR source and this has restricted the application of TRIR to the specialist laboratory [68]. However, recent developments in step-scan FTIR spectroscopy promise to open up TRIR to the wider scientific community [74]. 

The value of vCO in (36) is 1907 cm ie. very high for a bridging carbonyl -ascribed to the semibridging nature of the bonding. TRIR spectroscopy of transition metal carbonyls, e.g. W(CO)5py, showed that MLCT excited states gave broad vCO bands due to solvent-solute interactions. ... 

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