ANSA-METALLOCENE DERIVATIVES .36. ANSA-VANADOCENE COMPLEXES - SYNTHESES, STRUCTURES AND LIGAND EXCHANGE REACTIONS

摘要

Tetramethylethano-blidged vanadocene dichlorides (CH3)(4)C-2(3-R-C5H3)(2)VCl2 with R = H, Me, t-Bu are obtained by reacting the corresponding ligand MgCl salts with vanadium(III) acetylacetonato compounds, followed by oxidation with PCl3 or AgCl. Smooth ligand exchange reactions of these ansa-vanadocene dichlorides afford acetylacetonato cations and binaphtholate complexes; from these, the dichlorides are regenerated by exposure to MgCl2 in THF solution. Separation of meso and rac isomers (as well as enantiomer separation) is achieved via corresponding binaphtholate complexes; conversion to the vanadium(III) diisonitrile cations (CH3)(4)C-2(3-R-C5H3)(2)V(CNt-Bu)(2)(+) allows an assessment of diastereoisomer ratios by H-1 NMR. Lewis-acidic bistriflate derivatives of these ansa-vanadocene complexes are obtained from the dichlorides by reaction with silver triflate. [References: 20]