SOLUTION PHOTOSUBSTITUTION CHEMISTRY OF TRIPHENYLPHOSPHINE DERIVATIVES OF MOLYBDENUM HEXACARBONYL
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The ligand photosubstitution chemistry of Mo(CO)5PPh3 has been demonstrated to proceed with a high quantum efficiency for CO loss (366=0.58). When this reaction was carried out in the presence of either PPh3 or 13CO both cis and trans primary photoproducts were observed, presumably resulting from incoming ligand trapping of the [Mo(CO)4PPh3] intermediate in its Cs or C4v isomeric forms, respectively. On the other hand, the quantum efficiency for unique ligand loss, PPh3, was only 0.11 at 366 nm. The trans-Mo(CO)4[PPh3]2 complex was found to undergo photoisomerization to the cis-Mo(CO)4-[PPh3]2 derivative via loss of PPh3 followed by subsequent rearrangement of the [Mo(CO)4PPh3] (C4V) intermediate to its Cs analogue prior to recapture of PPh3. Photolysis of either pure cis-or trans-Mo(CO)4[PPh3]2 in the presence of 13CO afforded primarily CM-Mo(CO)4(13CO)PPh3 with a smaller quantity of trans-Mo(CO)4(13CO)PPh3. The latter 13CO-labeled species was observed in larger quantities from photolysis of trans-Mo(CO)4[PPh3]2 with 13CO as would be anticipated. These experiments further demonstrate the facile rearrangement of the C4v structure of [Mo(CO)4PPh3] to the Cs structure prior to recombination with an incoming ligand. 1978, American Chemical Society. All rights reserved.