ELECTRONIC-STRUCTURE AND REACTIVITY OF YLIDE SYSTEMS .18. X-RAY STRUCTURE-ANALYSIS OF A BIS(YLIDE)NICKEL CATALYST

Known differences in the activity and selectivity of ylide catalysts 1 and phosphine catalysts 2 made a comparison of the structures of 1-3 desirable. An X-ray structure determination of [NiPh(Ph2PCHCMeO)(i-Pr3PCH2)] (1a) confirms the presence of a structurally intact C-coordinated i-Pr3PCH2-ylide ligand in the trans position to the diphenylphosphino group of a Ph2PCHCMeO-arc PO chelate. The most striking finding is a dramatic increase in the NiO bond length to 1.95 angstrom as a consequence of a structurally intact coordinated ylide ligand.