Organometallics 2009, 28, 819–823
819
Syntheses, Structures, and Catalytic Properties of Ruthenium(II)
Nitrosyl Complexes with Pyridine-Functionalized N-Heterocyclic
Carbenes
Yong Cheng,† Jia-Feng Sun,† Hong-Ling Yang,† Hui-Jun Xu,† Yi-Zhi Li,† Xue-Tai Chen,*,†
and Zi-Ling Xue‡
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing National
Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing UniVersity,
Nanjing 210093, People’s Republic of China, and Department of Chemistry, UniVersity of Tennessee,
KnoxVille, Tennessee 37996
ReceiVed August 17, 2008
Ruthenium(II) nitrosyl complexes with pyridine-functionalized N-heterocyclic carbenes [(L)Ru(NO)Cl3]
[L ) 3-tert-butyl-1-(2-pyridyl)imidazol-2-ylidene, 2a; 3-n-butyl-1-(2-pyridyl)imidazol-2-ylidene, 2b; 3-tert-
butyl-1-picolylimidazol-2-ylidene, 2c; 3-n-butyl-1-picolylimidazol-2-ylidene, 2d; and 3-benzyl-1-pico-
lylimidazol-2-ylidene, 2e] have been prepared by transmetalation from the corresponding silver carbene
complexes. Compounds 2a-c have been characterized by single-crystal X-ray crystallography. Compounds
2a-e show catalytic activities in transfer hydrogenation of ketones.
N-Heterocyclic carbenes (NHCs) have been receiving much
attention for their wide applications in coordination chemistry
and homogeneous catalysis.1 Many types of interesting NHC-
containing ligands have been designed to search for new efficient
catalysts. In particular, functionalized NHC ligands and catalytic
activities of their metal complexes have been the subject of
intensive studies.2 Incorporation of a classical donor into NHC
compounds offers vast opportunities in the design of the
functionalized NHC ligands. The noncarbon donor atom would
act as a hemilabile arm, capable of reversible dissociation from
the metal center. The hybrid NHC ligands containing nitrogen
donors have attracted considerable interest, among which the
bidentate pyridine-functionalized NHC ligands, L, have been
most extensively studied. So far, many metal complexes
including groups 9 (Rh,3 Ir3b-d,4), 10 (Ni,5 Pd6), and 11 (Cu,7
Ag3a,5a,8) complexes of L have been prepared, some of which
showed catalytic activities in hydrosilation of acetylenes,4b
cyclizatioin of acetylenic carboxylic acids,4b transfer hydrogena-
tion of ketones,4b reduction of nitrarenes,4c C-C coupling
reactions,6b,c and olefin polymerization.5a,6h However, group 8
metal complexes with L have been rarely studied. Sun and co-
workers have prepared dinuclear iron-carbonyl complexes with
L as the 2Fe2S hydrogenase model.9 The only known ruthenium
complex with L is the half-sandwich ruthenium containing 1,2-
dichalcogenolato-1,2-dicarba-closo-docecaborane, in which ligand
L (n ) 1, R ) Me) is coordinated with carbene carbon and
leaves the pyridyl nitrogen appeneded.3d Ruthenium nitrosyl
complexes have been extensively studied due to their interesting
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* To whom correspondence should be addressed. Tel: +86 25 83597147.
Fax: +86 25 83314502. E-mail: xtchen@netra.nju.edu.cn.
† Nanjing University.
‡ University of Tennessee.
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10.1021/om800791n CCC: $40.75
2009 American Chemical Society
Publication on Web 01/05/2009