REVERSIBLE INTERCONVERSION OF PERMETHYLSCANDOCENE TELLUROLATES AND TELLURIDES - X-RAY STRUCTURE OF [(C5ME5)2SC]2(MU-TE)

Permethylscandocene tellurolates were synthesized by insertion of tell urium into the scandium-carbon bonds of the corresponding alkyl comple xes. These tellurolates were found to be thermally unstable toward eli mination of TeR2, forming the dimeric scandium mu-telluride Cp2Sc-Te- ScCP2 (2). Photochemically induced reversion of the thermal reaction was observed when a mixture of 2 and TeR2 Was irradiated under a UV la mp through a Pyrex filter. X-ray analysis of 2 reveals an Sc-Te distan ce of 2.7528(12) angstrom and an Sc-Te-Sc angle of 172.07-degrees. The se data, coupled with allene-like orientation of the Cp rings about t he Sc-Te-Sc unit, suggest significant pi-bonding between scandium and tellurium in this compound. Crystal data for 2: tetragonal space group P42(1)cBAR, a = 15.0324(7) angstrom, c = 18.8884(14) angstrom, alpha, beta, gamma = 90-degrees, V = 4268.3(4) angstrom3, Z = 4, R = 0.040, R(w) = 0.034 for 2092 reflections with I > 3sigma(I).