Metal pi complexes of benzene derivatives. 53 Tin in the periphery of bis(arene)metal complexes of vanadium and chromium

By means of metal-atom ligand-vapor cocondensation as well as via wet chemi cal methods (lithiation and follow-up reaction) the first organostannyl sub stituted bis(arene)metal complexes (R3Sn-eta(6)-C6H5)(2)M have been prepare d: 15 (R = Me, M = V), 16 (R = Ph, M = V). 13 (R = Me, M = V), 17 (R = Ph, M = Cr). Despite the bulkiness of the Ph3Sn groups the geometry of the cent ral sandwich unit in 17 deviates only marginally from that of the parent co mplex (C6H6)(2)Cr (2) The triclinic unit cell of 17 (space group: P (1) ove r bar; a = 9.414(4), b = 9.877(5), c = 11.012(13) Angstrom; alpha = 83.51(7 ), beta = 87.95(7), gamma = 72.67(4)degrees) contains one independent molec ule. Perturbation of the electronic structure of the bis(arene)metal unit b y organostannyl groups appears to be minute because EPR spectra of the M(d( 5)) species fail to reveal deviations from axial symmetry The potentials fo r reversible oxidation of the Me3Sn-substituted complexes 13 and 15 differ insignificantly (anodic shifts less than or equal to 20 mV) from those of t he parent species 1 and 2; reductions are irreversible in both cases. More sizeable anodic shifts are observed for the Ph3Sn-derivatives 16 and 17; he re as well, only the redox pairs 0/+ are reversible. The resistance of the neutral complexes to protic media contrasts to ready hydrodestannylation of the complex cations. By way of metal exchange, employing n-butyl lithium, 13 affords (Li-eta(6)-C6H5)(2)Cr strictly 1,1'-disubstituted and devoid of auxiliary base.