摘要:
The complexes fac-(1-P,P',O)M(CO)3, where M = Mo or W and 1 is cis-1,5-bis((diphenylphosphino)-methyl)-3-oxabicyclo[3.3.0]octane, were found to react with the ligands L = acetonitrile, piperidine, pyridine, and P(OCH2)3CCH3 to yield two diastereomers of fac-(1-P,P')M(CO)3(L) in each case. H-1 and C-13 NMR spectroscopic data suggest that the major isomer in each product is that in which the added ligand occupies the site originally occupied by the ether oxygen of 1 and that the minor isomer contains the new ligand in the position trans to this site. Carbon monoxide reacts with the complexes fac-(1-P,P',O)M(CO)3 (M = Mo, W) to yield (1-P,P')M(CO)4. Using (CO)-C-13, these reactions stereoselectively yield two diastereomers of fac-(1-P,P')M(CO)3((CO)-C-13) in ratios of approximately 5:1 and 7:1 for M = Mo and W, respectively. A scheme involving the isomerization of diastereomeric five-coordinate square-pyramidal intermediates is discussed. The N-donor complexes fac-(1-P,P')M(CO)3L, where M = Mo and W and L = acetonitrile, pyridine, and piperidine, were observed by infrared and H-1 and P-31 NMR spectroscopy to partially dissociate in solution, equilibrating with free L and fac-(1-P,P',O)M(CO)3. This equilibrium was further substantiated by monitoring the exchange reaction between free and coordinated CD3CN in the presence of fac-(1-P,P')Mo(CO)3(NCCH3) using H-2 NMR spectroscopy.