SYNTHESIS, CHARACTERIZATION AND CRYSTAL-STRUCTURE OF (HB(DMPZ)(3))VO(MU-ETA(5)-C5H4CO2)FE(ETA(5)-C5H5)] (HDMPZ EQUALS 3,5-DIMETHYLPYRAZOLE)

The complex {HB(dmpz)(3)}VO(mu-eta(5)-C5H4CO2)Fe(eta(5)-C5H5)] 1 (Hdmp z = 3,5-dimethylpyrazole) has been synthesized and its spectroscopic p roperties and crystal structure determined. It crystallizes in the tri clinic space group P (1) over bar, with a = 10.563(2), b = 12.460(4), c = 13.028(5) Angstrom, alpha = 95.16(3), beta = 38.93(2), gamma = 99. 59(2)degrees and Z = 2. The vanadium(IV) ion is in a distorted-octahed ral environment with nitrogen atoms of the borate ligand occupying thr ee facial sites and the other sites by an oxo group, an oxygen atom fr om the ferrocenecarboxylate, and a nitrogen atom from a neutral Hdmpz. The cyclic voltammogram in CH2Cl2 showed two oxidations at +0.70 and +1.41 V vs. Ag-AgCl, which are completely reversible at -30 degrees C. The first corresponds to oxidation of the ferrocenecarboxylate moeity , giving 1(+). The reversibility of 1 --> 1(+) has also been demonstra ted by electronic absorption and EPR resonance spectroscopies. Complex 1 is EPR active giving spectra as expected from an isolated vanadium( IV) centre, whilst 1(+) is EPR silent.