The preparation and reactions of alkynylphosphonate hexacarbonyldicobalt complexes

The preparation of a series of hexacarbonyldicobalt alkynylphosphonate complexes, Co-2(CO)(6)[(RC)-C-1=CP(O)(OR2)(2)] is reported. They are found to be unreactive under a range of conditions and this is ascribed to a combination of electron deficiency and alkyne pi to phosphorus pi-acceptor orbital interactions. Complexes of alkynyl carboxylates are more reactive. Reaction of diethyl 1-propynylphosphonate with dicarbonylcyclopentadienylcobalt results in the formation of (eta(5)-cyclopentadienyl) (eta(4)-2,4-dimethylcyclopentadienone-3,5-diphosphonate tetraethyl ester)cobalt (I), the X-ray crystal structure of which has been determined. This is a rare example of an unsymmetrically substituted cyclopentadienone complex. (C) 1999 Elsevier Science S.A. All rights reserved.