1095281-89-2Relevant academic research and scientific papers
Synthesis, X-ray structures, and catalytic applications of palladium(II) complexes bearing N-heterocyclic iminocarbene ligands
Netland, Kjetil Andreas,Krivokapic, Alexander,Schr?der, Markus,Boldt, Klaus,Lundvall, Fredrik,Tilset, Mats
, p. 3703 - 3710 (2008)
Two new Pd(II) N-heterocyclic iminocarbene complexes (C-N)PdCl2 that contain 5-membered chelate rings have been prepared by carbene transfer from a silver iminocarbene precursor to (COD)PdCl2. The new Pd imonocarbene complexes, as well as two that have been previously reported (altogether three 5-membered and one 6-membered chelate ring complexes) have been evaluated as catalysts for the Suzuki-Miyaura coupling reaction. The complexes were found to be active in the reaction, but without exceptional catalytic performances. The 5-membered chelate ring complexes appeared to be more robust and remained active for a longer time than the 6-membered ring congener. The catalytic performance of the 5-membered chelate ring complexes appeared to be rather insensitive to the steric demands of the imine-N-aryl group. The X-ray structure of one of the Ag iminocarbene complexes reveals the κ1(C) bonding of the iminocarbene moiety in a nearly linear Ag(I) complex; two monomeric units are associated through a weak Ag-Ag interaction. The X-ray structures of two new Pd iminocarbene complexes (C-N)PdCl2 confirm the chelating κ2(C,N) nature of the iminocarbene moiety; in both complexes, the Pd-Cl distances trans to carbene-C are slightly longer than those trans to imine-N.
Investigation of ligand steric effects on a highly cis-selective Rh(i) cyclopropanation catalyst
Rosenberg, Marianne Lenes,Langseth, Eirin,Krivokapic, Alexander,Gupta, Nalinava Sen,Tilset, Mats
, p. 2306 - 2313 (2011/12/03)
Four new Rh(i) complexes bearing chelating imine-functionalized N-heterocyclic carbene ligands have been synthesized and characterized. The catalytic activity of these new Rh(i) complexes has been tested in the cyclopropanation reaction between ethyl diazoacetate and styrene. One of the new complexes, having ethyl groups on the ligand N-aryl ring, exhibited a reactivity and a cis-diastereoselectivity that were comparable to our previously reported Rh(i) cyclopropanation catalyst of this type, and a higher yield and cis-diastereoselectivity were obtained at lower catalyst loadings and higher temperatures. The other new Rh(i) complexes were found to be inferior to the previously reported Rh(i) cyclopropanation catalyst. The catalytic study gave important information about the effect that changing the steric requirements of the substituents at the ligand system has on the efficiency and cis-diastereoselectivity of the complexes as cyclopropanation catalysts.
