Cyclopentadienyl molybdenum(II/VI) N-heterocyclic carbene complexes: Synthesis, structure, and reactivity under oxidative conditions
Type
ArticleKAUST Department
Biological and Environmental Sciences and Engineering (BESE) DivisionChemical Science Program
Homogeneous Catalysis Laboratory (HCL)
KAUST Catalysis Center (KCC)
Physical Science and Engineering (PSE) Division
Date
2010-04-26Permanent link to this record
http://hdl.handle.net/10754/561467
Metadata
Show full item recordAbstract
A series of N-heterocyclic carbene (NHC) complexes CpMo(CO) 2(NHC)X (NHC = IMe = 1,3-dimethylimidazol-2-ylidene, X = Br, 1; NHC = 1,3-dipropylimidazol-2-ylidene, X = Br, 2; NHC = IMes = 1,3-bis(2,4,6- trimethylphenyl)imidazol-2-ylidene, X = Br, 3; NHC = IBz = 1,3-dibenzylimidazol- 2-ylidene, X = Br, 4a, and X = Cl, 4b; NHC = 1-methyl-3-propylimidazol-2- ylidene, X = Br, 5) and [CpMo(CO)2(IMes)(CH3CN)][BF 4] (6) have been synthesized and fully characterized. The stability of metal-NHC ligand bonds in these compounds under oxidative conditions has been investigated. The thermally stable Mo(VI) dioxo NHC complex [CpMoO 2(IMes)][BF4] (9) has been isolated by the oxidation of the ionic complex 6 by TBHP (tert-butyl hydrogen peroxide). Complex 6 can be applied as a very active (TOFs up to 3400 h-1) and selective olefin epoxidation catalyst. While under oxidative conditions (in the presence of TBHP), compounds 1-5 decompose into imidazolium bromide and imidazolium polyoxomolybdate. The formation of polyoxomolybdate as oxidation products had not been observed in a similar epoxidation catalyzed by Mo(II) and Mo(VI) complexes. DFT studies suggest that the presence of Br- destabilizes the CpMo(VI) oxo NHC carbene species, consistent with the experimental observations. © 2010 American Chemical Society.Citation
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2010). Cyclopentadienyl Molybdenum(II/VI) N-Heterocyclic Carbene Complexes: Synthesis, Structure, and Reactivity under Oxidative Conditions. Organometallics, 29(8), 1924–1933. doi:10.1021/om900980aSponsors
We are grateful to the Ministry of Education (MOE) of Singapore Academic Research Fund (AcRF) Tier 1 Grant (WBS No. R-143-000-373-112). S.Y. L. also thanks National University of Singapore for the scholarship. K.W.H. acknowledges the support from KAUST baseline funding. We thank Ms. Geok Kheng Tan and Dr. Lip Lin Koh for determining the X-ray crystal structures.Publisher
American Chemical Society (ACS)Journal
OrganometallicsRelations
Is Supplemented By:- [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 748781: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cct457b. DOI: 10.5517/cct457b HANDLE: 10754/624609 - [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 748782: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cct458c. DOI: 10.5517/cct458c HANDLE: 10754/624610 - [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 748783: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cct459d. DOI: 10.5517/cct459d HANDLE: 10754/624611 - [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 748784: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cct45bf. DOI: 10.5517/cct45bf HANDLE: 10754/624612 - [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 748785: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/cct45cg. DOI: 10.5517/cct45cg HANDLE: 10754/624613 - [Dataset]
Li, S., Kee, C. W., Huang, K.-W., Hor, T. S. A., & Zhao, J. (2011). CCDC 810641: Experimental Crystal Structure Determination [Data set]. Cambridge Crystallographic Data Centre. https://doi.org/10.5517/ccw6jq9. DOI: 10.5517/ccw6jq9 HANDLE: 10754/624632
ae974a485f413a2113503eed53cd6c53
10.1021/om900980a