SYNTHESIS AND CHARACTERIZATION OF THE MONOMERIC DIGALLYLPHOSPHANE ANDDIGALLYLARSANE DERIVATIVES MESP(GA(TRIP)2)2.ET2O AND PHAS(GA(TRIP)2)2

The compounds MesP{Ga(TriP)2}2.Et2O, 1, and PhAs{Ga(TriP)2}2 (Trip = 2 ,4,6-i-Pr3C6H2), 2, were synthesized by the reaction of Li2ER (E = P a nd As and R = Mes and Ph, respectively) with 2 equiv of TriP2GaCl in t etrahydrofuran solution. They were characterized by X-ray crystallogra phy and variable temperature (VT) H-1 NMR and P-31 NMR spectroscopy. T he structure of 1 displays an almost eclipsed C2Ga-P(C)-GaC2 core arra y with trigonal planar coordination at phosphorus. In contrast, 2 has trigonal pyramidal coordination at arsenic and large angles between th e planes at Ga(1) or Ga(2) and the central AsGa2 Plane. These represen t the first structurally characterized examples of monomeric digallylp hosphanes and -arsanes. The detection of a rotational barrier around t he Ga-P bonds in 1 is attributed to weak delocalized Ga-P-Ga pi-bondin g in a manner analogous to that in the allyl cation. Crystal data with Mo Kalpha (lambda = 0.710 69 angstrom) at 130 K: 1, C70H103Ga2P, a = 15.641(5) angstrom, b = 20.112(5) angstrom, c = 22.278(6) angstrom, be ta = 97.61(2)-degrees, monoclinic, space group P2(1)/c, Z = 4, R = 0.0 63; 2, C66H90Ga2As, a = 13.395(5) angstrom, b = 14.438(7) angstrom, c = 18.693(7) angstrom, alpha = 105.80(3)-degrees, beta = 92.47(3)-degre es, gamma = 116.57(7)-degrees, triclinic, space group P1BAR, Z = 2, R = 0.054.