SYNTHESIS AND CRYSTAL-STRUCTURE OF A PENTACOORDINATE 1,2-OXAGERMETANIDE

A pentacoordinate 1,2-oxagermetanide 1, K+ 4C(CF3)(2)O-]GePh[-CH(CH(2) (t)Bu)C(CF3)(2)O-]}(-), was quantitatively synthesized as a colourless block (m.p. 217-218 degrees C (decomp.)) by deprotonation of the corr esponding beta-hydroxygermane 2, [-C6H4C(CF3)(2)O-]GePhCH(CH(2)(t)Bu)C (CF3)(2)OH, which can be prepared by unique cycloelimination of benzen e from CF3)(2)CC(6)H(4)GePh(2)[CH(CH(2)(t)Bu)C(CF3)(2)OH] (3). On heat ing in CD3CN at 150 degrees C for 30 days, 1 equilibrates with another diastereomer 4 and then undergoes the Peterson-type reaction to give the corresponding olefin 5, (F3C)(2)C=CHCH(2)(t)Bu (13%), and its doub le-bond migrated isomer 6, (F3C)(2)CHCH=CH(t)Bu (33%). The yields of t he olefins 5 and 6 are not very high, because their polymerization tak es place under the reaction conditions. X-ray crystallographic analysi s of 1 shows that it has a distorted trigonal bipyramidal structure wi th two oxygen atoms at apical positions.