Molecular Structure and Vinyl Chloride Insertion of a Cationic Zirconium(IV) Acyl Carbonyl Complex

Abstract

The reaction of vinyl chloride (VC) with the cationic Zr acyl complex [Cp2Zr{C(O)Me}(CO)][MeB(C6F5)3] (1a/b, O-inside and O-outside isomers) yields an unusual dinuclear dicationic μ-acyl μ-keto-alkoxide complex, [Cp2Zr{μ-C(O)Me}{μ-OCMe(CHCH2)C(O)Me}ZrCp2][MeB(C6F5)3]2 (3), which was characterized by NMR spectroscopy and X-ray crystallography. This reaction proceeds by 1,2 insertion into the Zr−acyl bond of Cp2Zr{C(O)Me}+ to yield Cp2Zr{CH2CHClC(O)Me}+, which undergoes β-Cl elimination to form methyl vinyl ketone (MVK) and Cp2ZrCl+ (8). The MVK is trapped by Cp2Zr{C(O)Me}+ to form [Cp2Zr{η2-C(O)Me}(MVK)][MeB(C6F5)3] (9), which rearranges to [Cp2Zr{κ2-OC(Me)(CHCH2)C(O)Me}][MeB(C6F5)3] (10). Intermediate 10 is trapped by Cp2Zr{C(O)Me}+ to form 3. 3 is also formed by the reaction of 1a/b with 0.5 equiv of MVK. 1,2 VC insertion of Cp2Zr{C(O)Me}+ is favored over 2,1 insertion by steric factors. The molecular structure of 1a was determined by X-ray crystallography.