Organochromium Complexes Bearing Noninnocent Diimine Ligands

Authors

  • Kevin A. Kreisel,

    1. Department of Chemistry and Biochemistry, Center for Catalytic Science and Technology, University of Delaware, Newark, Delaware 19716, USA, Fax: +1-302-831-6335
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  • Glenn P. A. Yap,

    1. Department of Chemistry and Biochemistry, Center for Catalytic Science and Technology, University of Delaware, Newark, Delaware 19716, USA, Fax: +1-302-831-6335
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  • Klaus H. Theopold

    1. Department of Chemistry and Biochemistry, Center for Catalytic Science and Technology, University of Delaware, Newark, Delaware 19716, USA, Fax: +1-302-831-6335
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Abstract

We have prepared several anionic and neutral organochromium complexes featuring noninnocent α-diimine ligands. All neutral and anionic complexes refrain from insertion of the C=N bonds of the diimine ligand into the chromium–carbon bonds, presumably due to the reduced nature of the diimine ligand. However, insertion can be facilitated by one-electron oxidation. Thus, oxidation of [(HLiPr)CrR(THF)] [HLiPr = Ar–N=C(H)–(H)C=N–Ar in which Ar = 2,6-diisopropylphenyl and R = CH2SiMe3 or CH3] with [(C5H5)2Fe]+ presumably forms [(HLiPr)CrR(THF)]+, which contains a neutral diimine ligand coordinated to CrII. This cationic complex apparently undergoes immediate insertion of the C=N bond of the diimine ligand into the Cr–alkyl bond, followed by C–H activation of the isopropyl substituent of an N–aryl group on the diimine ligand. DFT calculations confirm that [(HLiPr)CrR(THF)]+ contains a neutral innocent diimine ligand that undergoes C=N bond insertion into the Cr–R bond.

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