A TRIANGULAR HETEROMETALLIC SILOXIDE CONTAINING BARIUM

Reaction of KOSiPh3 with Ba3(OSiPh3)6(THF) in THF displaces barium from the triangular reagent to yield a colorless solid. Recrystallization in the presence of MeOC2H4OMe(DME) yields KBa2(OSiPh3)5(DME)2, characterized by H-1 and Si-29 NMR spectroscopy and X-ray diffraction. The molecule contains a triangular KBa2(mu-3-OSiPh3)2(mu-2-OSiPh3)3 core with eta-1- and eta-2-DME ligation on each barium. The benzene-soluble molecule is fluxional in solution at both the OSiPh3 and the DME groups. At -70-degrees-C in CH2Cl2/C6D6, both eta-1-DME/eta-2-DME site exchange and intramolecular siloxide migration have been slowed, and the spectra are in agreement with retention of the solid-state structure in solution. Crystallographic data for KBa2(OSiPh3)5(DME)2 (-159-degrees-C): a = 15.474 (3) angstrom, b = 26.466 (6) angstrom, c = 23.783 (5) angstrom, beta = 99.80 (1)-degrees with Z = 4 in space group P2(1)/n.