Matrix isolation studies of some group V1 and group V11 substituted metal carbonyl complexes

Photoprocesses, both photochemical and photophysical, have been studied for a variety of substituted metal carbonyls of groups VI and VII isolated at low temperature in frozen gas matrices. Infrared spectroscopic evidence, including 13CO labelling and energy-factored force field fitting for CH3Mn(CO)5 and CH 3 MM(CO)4$ is presented to show that on photolysis of RMn(CO)5 (R = CH3, CH0)t complexes at high dilutions in CH4, Ar and CO matrices at 10K, news pecies RMn(CO)4, with the R ligand occupying an equatorial position in a trigonal bipyramid and having C2v symmetry, are produced. The results indicate that CH3Mn(C0)4 is fluxional and are discussed in terms of proposed mechanisms for carbonylation/decarbonylation reactions. Infrared spectroscopic evidence is presented to show that on photolysis of Mn(CO)5X (X = C1, Br, I) complexes in Ar and CH4 matrices at 10K, new coordinatively unsaturated species Mn(C0)4X are produced, with the X ligand occupying an equatorial position in a trigonal bipyramid and having C2v symmetry. The reaction is shown to be reversible. The results are related to the mechanistic pathway for substitution reactions. The photochemistry of W(CO)5L, (L = pyridine, 3-bromopyridine, ammonia, hydrogen sulphide) and M(CO) 5(pyridine), (M = Cr, Mo, W), has been studied in both 'inert' and 'reactive' matrices and it has been shown that photo ejection of L or CO can take place. In many cases either reaction can be promoted with virtual selectivity depending on excitation wavelength. All the reactions are shown to be reversible to a degree. Luminescence spectra have been obtained for M(CO)6, (M = Cr, Mo, W) t and M(CO)5(pyridine), (M = Mo or W) complexes in Ar and CH4 matrices at 1OK for the first time. The results are related to observed photochemical processes occurring under the same conditions.