The Structure of (l-histidinato)4V2O.2H2O

An unsupported oxo-bridged divanadium(III) complex with a bent bridge geometry





Singly bridged µ-oxo divanadium(III) complexes are almost always found with quasi-linear bridging geometries in which V-O-V angles range from 170 to 180°. This compound, however, has a distinctly bent geometry with a bridging V-O-V angle of approximately 154°. The explanation for this apparent anamoly lies in the two intramolecular hydrogen bonds formed between an imidazole proton from a histidinato group coordinated to one vanadium(III) center and a caboxylate oxygen from a histidinato group coordinated to the other vanadium(III) center. The bridge bends to aid formation of these hydrogen bonds in much the same way that it bends to accomodate bidentate bridging ligands in supported µ-oxo divanadium(III) complexes (see companion structure).

Of further interest is the fact that the chiral histidinato ligands force the molecule to crystallize in a non-centrosymmetric space group. Refinement of the two different enantiomeric structures yields a lower R value for the correct histidinato configuration. The structure also contains two water molecules that provide an interesting contrast in order and disorder. One is ordered and on a two-fold rotation axis. The other is highly disordered over two crystallographically independent positions and a total of four positions after consideration of the crystallographic two-fold rotation axis.

Literature reference: Czernuszewicz, R. S., Yan, Q., Bond, M. R., and Carrano, C. J. "Origin of the Unusual Bending Distortion in the mu-Oxo Divanadium Complex, [V2O(l-his)4]: A Reinvestigation" Inorg. Chem. 1994, 33, 6116-6119.

Companion Structure: [(HB(pz)3(mu-CH3CH2CO2V]2O.4CH3CN

Structure Determination Files by FTP

Download X-ray Data Set (mrb4.hkl)

Download X-ray Data Collection Parameters (mrb4.p4p)

Download Final Refinement Results (mrb4.res)

Last changed December 7, 1996

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