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Zerovalent [Pd(NHC)(alkene)] complexes bearing expanded-ring N-heterocyclic carbene ligands in transfer hydrogenation of alkynes

Organometallics, ISSN: 0276-7333, Vol: 32, Issue: 1, Page: 131-140
2013
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Metrics Details

  • Citations
    60
    • Citation Indexes
      60
  • Captures
    30

Article Description

In search of more active catalysts for the transfer hydrogenation of alkynes, a series of [Pd(NHC)(MA)] (8-14) and [Pd(NHC)(dvtms)] complexes (1-7), in which the NHC ancillary ligands are expanded-ring N-heterocyclic carbenes (erNHC's), have been prepared. These very bulky, strong σ-donor ligands impart a highly constrained geometry on the complexes and in some cases enable the isolation of coordinatively and electronically unsaturated complexes (10 and 14). Their strong σ-donor character is reflected in a decrease in IR stretching frequency for the C=O bond of the maleic anhydride ligands (8-14) in comparison to their five-membered counterparts. Significantly enhanced catalytic activity in the transfer hydrogenation of 1-phenyl-1-propyne is observed using [Pd(erNHC)(dvtms)] complexes (1-7) as precatalysts. The catalysts show high initial selectivity toward (Z)-alkene. However, double-bond isomerization and over-reduction to the corresponding alkane occur when all the alkyne substrate is consumed; this feature reflects the very high efficiency of these catalysts in the transfer hydrogenation of alkynes as well as alkenes. © 2012 American Chemical Society.

Bibliographic Details

Peter Hauwert; Dorette S. Tromp; Cornelis J. Elsevier; Jay J. Dunsford; Kingsley J. Cavell; Jan J. Weigand; Martin Lutz

American Chemical Society (ACS)

Chemistry

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