Experimental and Theoretical Study of the First Vanadocene(IV) Complexes of α-Amino Acids Prepared from Vanadocene Dichloride

Abstract

The first bioinorganic vanadocene(IV) complexes of α-amino acids ([Cp2V(aa)]Cl, Cp = η5-C5H5, aa = glycine, L-alanine, L-valine) were prepared by reaction of vanadocene dichloride ([Cp2VCl2]) and α-amino acids in aqueous methanol. Analogous cationic complexes with PF6- counterions were obtained by metathetical reactions of the chloride precursors with KPF6. These compounds are of great interest as model systems for the vanadocene moiety binding to proteins. All complexes have been characterized by elemental analyses and IR, Raman and EPR spectroscopies. On the basis of EPR spectra, a chelate in all the studied complexes was proposed, formed by the carboxylato and amino groups. This structure has also been confirmed by density functional theory (DFT) calculations.

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

“…Some of the recently prepared titanocene dichloride derivatives showed significantly better activity and stability than corresponding non-substituded counterparts [9][10][11][12]. These findings prompted us to study water-soluble vanadocene compounds [13][14][15]. Here, we report the preparation and structural characterization of 1,1'-dimethylvanadocene complexes with monocarboxylic (C 5 H 4 CH 3 ) 2 V(OOCR 2 ) 2 (R=H, CCl 3 , CF 3 , C 6 H 5 ) and dicarboxylic acids (C 5 H 4 CH 3 ) 2 V(OOC-A-COO) (A= -, CH 2 ).…”

Ansa-vanadocene complexes with short interannular bridges

“…Vanadocene dichloride (3a) forms chelate complexes with a-amino acids [11]. The same type of coordination was proved for dimethylmethano-bridged vanadocene by EPR spectroscopy.…”

“…The compounds (CH 3 ) 2 C(C 5 H 4 ) 2 VX 2 [X = CN (5); X 2 = CO 3 (7), PO 4 H (8)] and [(CH 3 ) 2 C(C 5 H 4 ) 2 V(aa)]Cl [aa = gly (9), ala (10), val (11)] were prepared in small amount from compound 3 (5 mg) in similar way to their unbridged counterparts according to literature procedures [8,11,31]. These compounds were characterized in solution by EPR spectroscopy.…”

“…Past research in our group has been focused on the aqueous chemistry vanadocene dichloride [8][9][10][11] due to the large stability of [Cp 2 V] 2+ fragment [12]. An EPR spectroscopy was appeared as very efficient method for investigation of such paramagnetic d 1 -complexes.…”

Raman spectroscopic evidence for bent metallocene fragments [M(Cp)2]2+

“…14 A 1 g (3.40 mmol) quantity of sublimed niobocene dichloride was dissolved in 120 ml of dichloromethane. To the vigorously stirred solution, 0.24 ml (2.47 mmol) of boron tribromide was added.…”