Zincocene and Dizincocene N‐Heterocyclic Carbene Complexes and Catalytic Hydrogenation of Imines and Ketones |
| |
| Authors: | Dr Phillip Jochmann Prof?Dr Douglas W Stephan |
| |
| Affiliation: | 1. Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6 (Canada);2. Chemistry Department, Faculty of Science, King Abdulaziz University (KAU), Jeddah 21589 (Saudi Arabia) |
| |
| Abstract: | The N‐heterocyclic carbene (NHC) adducts Zn(CpR)2(NHC)] (CpR=C5HMe4, C5H4SiMe3; NHC=ItBu, IDipp (Dipp=2,6‐diisopropylphenyl), IMes (Mes=mesityl), SIMes) were prepared and shown to be active catalysts for the hydrogenation of imines, whereas decamethylzincocene ZnCp*2] is highly active for the hydrogenation of ketones in the presence of noncoordinating NHCs. The abnormal carbene complex Zn(OCHPh2)2(aItBu)]2 was formed from spontaneous rearrangement of the ItBu ligand during incomplete hydrogenation of benzophenone. Two isolated ZnI adducts Zn2Cp*2(NHC)] (NHC=ItBu, SIMes) are presented and characterized as weak adducts on the basis of 13C NMR spectroscopic and X‐ray diffraction experiments. A mechanistic proposal for the reduction of ZnCp*2] with H2 to give Zn2Cp*2] is discussed. |
| |
| Keywords: | carbene ligands homogeneous catalysis hydrogenation reaction mechanisms zinc |
|
|
