ansa-Vanadocene Complexes - Syntheses, Structures and Ligand Exchange Reactions

Abstract

Tetramethylethano-bridged vanadocene dichlorides (CH3)4C2(3-R-C5H3)2VCl2 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)4C2(3-R-C5H3)2V(CNt-Bu)2+ allows an assessment of diastereoisomer ratios by 1H NMR. Lewis-acidic bistriflate derivatives of these ansa-vanadocene complexes are obtained from the dichlorides by reaction with silver triflate.

Synthesis, characterization and structure of the Bis(methyl-cyclopentadienyl)vanadium(IV) carboxylates

“…The bent metallocene dichlorides can be modified either by substitution of the chloride ligands [5,6] or by substitution on the cyclopentadienyl rings [7,8]. Some of the recently prepared titanocene dichloride derivatives showed significantly better activity and stability than corresponding non-substituded counterparts [9][10][11][12].…”

1,1′‐Dimethylvanadocene α‐amino acid complexes: synthesis, characterization and antimicrobial behavior toward Escherichia coli B

“…The cytotoxic behaviour of 1,1 -dimethylvanadocene amino acid complexes (3)(4)(5)(6)(7)(8)(9)(10) and their unsubstituted analogs (14)(15)(16)(17)(18)(19)(20)(21) toward Escherichia coli B was studied. All of the complexes show biological activity and evoke significant cell elongation.…”

“…The 1,1 -dimethylvanadocene amino acid complexes [MeVD(aa)]Cl (aa = glycine 3, L-alanine 4, L-valine 5, Lleucine 6, L-isoleucine 7, L-phenylalanine 8, L-histidine 9, L-tryptophane 10) were prepared by the reaction of 1,1dimethylvanadocene dichloride (MeVDC, 2) with appropriate amino acid in aqueous solution at neutral pH; see Scheme 1. The eight new complexes (3)(4)(5)(6)(7)(8)(9)(10) were isolated in reasonable yields after evaporating the solvent from the reaction mixture. These compounds are extremely soluble in polar solvents such is H 2 O or CH 3 OH and almost insoluble in non-polar organic solvents.…”

Ansa-vanadocene complexes with short interannular bridges

“…This method was previously successfully used for preparation of tetramethylethano- [21] and biphenyl-bridged vanadocene dichlorides [22].…”

“…Previously some efficient routes for preparation of ansavanadocene complexes were developed by Brintzinger et al [20][21][22]. Such studies were focused particularly on the catalytic properties of ansa-metallocenes toward polymerization of a-olefins.…”