ELUCIDATING THE MECHANISM OF THE PHOTOCHEMICAL PAUSON-KHAND REACTION - MATRIX PHOTOCHEMISTRY OF PHENYLACETYLENEHEXACARBONYLDICOBALT

Short wavelength UV irradiation of (phenylacetylene)Co-2(CO)(6) (3) in argon matrices at 12 K results in loss of CO to form (phenylacetylene )Co-2(CO)(5) (4). Reversal of this reaction occurs on longer wavelengt h irradiation. When the reaction is instead carried out in mixed argon /nitrogen matrices (phenylacetylene)Co-2(CO)(5)(N-2) (5) is formed as an additional pro duct. Irradiation at lambda = 390 nm allows selectiv e reversal of photoproduct 4 to the parent species, leaving photoprodu ct 5 unaffected. When 3 is irradiated in pure nitrogen matrices photop roduct 4 is not formed, but two photoproducts containing coordinated d initrogen are observed. One of these may confidently be assigned as 5, but the identity of the second cannot at present be specified with ce rtainty. The results gained are discussed in the light of the much mor e widely studied and better understood thermal chemistry of such compl exes. (C) 1998 Elsevier Science S.A. All rights reserved.