Biscarbene palladium(II) complexes. reactivity of saturated versus unsaturated N-heterocyclic carbenes.
A series of designed palladium biscarbene complexes including saturated and unsaturated N-heterocyclic carbene (NHC) moieties have been prepared by the carbene transfer methods. All of these complexes have been characterized by (1)H and (13)C NMR spectroscopy as well as X-ray diffraction analysis. The reactivity of Pd-C((saturated NHC)) is distinct from that of Pd-C((unsaturated NHC)). The Pd-C((saturated NHC)) bonds are fairly stable toward reagents such as CF(3)COOH, AgBF(4) and I(2), whereas Pd-C((unsaturated NHC)) bonds are readily cleaved under the similar conditions. Notably, the catalytically activity of these palladium complexes on Suzuki-Miyaura coupling follows the order: (sat-NHC)(2)PdCl(2) > (sat-NHC)(unsat-NHC)PdCl(2 )> (unsat-NHC)(2)PdCl(2).
Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
Ching-Feng
CF
Fu
Chun-Chin
CC
Lee
Yi-Hung
YH
Liu
Shie-Ming
SM
Peng
Stefan
S
Warsink
Cornelis J
CJ
Elsevier
Jwu-Ting
JT
Chen
Shiuh-Tzung
ST
Liu