Structural and biological characterization of a novel spermicidal vanadium(IV) complex: bis(pi-cyclopentadienyl)-N,N-diethyl dithiocarbamato vanadium(IV) tetrafluoro borate, [VCp2(DeDtc)](BF4).

In a systematic search for vanadocene complexes with sperm immobilizing activity as a new class of contraceptive agents, we identified V(eta 5-C5H5)2((C2H5)2 NCS2)(BF4) (=VCp2(DeDtc)) as the most potent and stable spermicidal compound. Here we report the detailed biologic and physicochemical characterization of this lead spermicidal compound by computer-assisted sperm analysis, electron paramagnetic resonance spectroscopy, electrochemistry, and X-ray crystallography. VCp2(DeDtc) crystallized in the monoclinic space group P2(1)/c, with unit cell dimensions a = 7.0877(4) A, b = 22.2881(14) A, c = 11.8021(7) A, beta = 94.107(1) degree, V = 1859.6(2) A3. The final structure of VCp2(DeDtc) had an R factor of 0.0581 for 3191 independent reflections. The two sulfur atoms of the dithiocarbamate and centroids of the cyclopentadienyl rings in this vanadocene complex with unique contraceptive potential occupy four tetrahedral--like coordination sites about the central metal atom.