PREPARATION AND CHARACTERIZATION OF TETRAPHENYLARSONIUM TRANS-BIS(MU-ACETATO)-TETRACHLORODIMOLYBDATE(II) DISOLVATES, [(C6H5)4AS]2[MO2(O2CCH3)2CL4].2L (L=H2O OR CH3OH)

The preparation and isolation of [(C6H5)4As]2[Mo2(O2CCH3)2Cl4]•2L (L = H2O or CH3OH) are reported. The methanolate crystallizes in the triclinic space group P1 with a = 10.571 (2) Å, b = 11.330 (2), Å, c = 13.397 (2) Å, α = 75.16 (1)°, β = 67.19 (1)°, and γ = 64.24 (1)°,. The structure has been determined from 2165 X-ray counter intensities by Patterson and Fourier techniques and refined by full-matrix least-squares methods to R = 0.058 (0.073 weighted). The unit cell contains one centrosymmetric [Mo2(O2CCH3)2Cl4]2-, two [(C6H5)4As]+ions, and two CH3OH moieties. The anion has the trans configuration and closely approximates to D2hpoint symmetry with dimensions Mo-Mo = 2.086 (2), Mo-O = 2.120 (13), and Mo-Cl = 2.434 (4) Å; the methanol molecules are not coordinated to the molybdenum atoms. Vibrational and electronic spectral data are reported for this material. The v(Mo-Mo) stretching frequency of 380 cm-1and the position of the first absorption maximum at 20 200 cm-1are midway between the corresponding values of Mo2(O2CCH3)4and [Mo2Cl8]4-, even though the Mo-Mo bond length for [Mo2(O2CCH3)2Cl4]2-is the shortest of these three complexes. © 1979, American Chemical Society. All rights reserved.