STRUCTURE OF THE 17-ELECTRON CP-ASTERISK-MOCL2(DPPE) - AN UNEXPECTED TRANS GEOMETRY IN THE SOLID-STATE

Compound CpMoCl2(dppe) crystallizes in the monoclinic space group P2( 1)/c, a=16.9063(10), b=11.0118(8), c=18.6128(14) Angstrom, beta=111.71 3(6)degrees, V=3219.3(4) Angstrom(3), Z=4, D-calc=1.445 Mg m(-3), mu(M o K alpha) = 0.698 mm(-1), R1=0.0448, wR2 = 0.0906 for all data, R1=0. 0337, wR2=0.0839 for 4754 data with I>2 sigma(I). The geometry of the compound is a four-legged piano stool as typically found for this clas s of compounds, but the dppe ligand occupies relative trans position w hereas the previously reported CpMoBr2(dppe) has the more common cis g eometry, EPR spectroscopic investigations indicate that a mixture of i somers is present in solution and that the relative amounts of the iso mers are both solvent and temperature dependent.