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Zincocene and Dizincocene N‐Heterocyclic Carbene Complexes and Catalytic Hydrogenation of Imines and Ketones
Author(s) -
Jochmann Phillip,
Stephan Douglas W.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402875
Subject(s) - carbene , imes , adduct , chemistry , catalysis , medicinal chemistry , benzophenone , ligand (biochemistry) , organic chemistry , biochemistry , receptor
The N‐heterocyclic carbene (NHC) adducts Zn(Cp R ) 2 (NHC)] (Cp R =C 5 HMe 4 , C 5 H 4 SiMe 3 ; NHC=I t Bu, 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(OCHPh 2 ) 2 (aI t Bu)] 2 was formed from spontaneous rearrangement of the I t Bu ligand during incomplete hydrogenation of benzophenone. Two isolated Zn I adducts [Zn 2 Cp* 2 (NHC)] (NHC=I t Bu, SIMes) are presented and characterized as weak adducts on the basis of 13 C NMR spectroscopic and X‐ray diffraction experiments. A mechanistic proposal for the reduction of [ZnCp* 2 ] with H 2 to give [Zn 2 Cp* 2 ] is discussed.