SYNTHESIS AND STRUCTURE OF [AU4(C6F5)2((PPH2)2CH)2(PPH3)2](CLO4)2.4CH2CL2, A COMPLEX WITH 2 DIRECT GOLD-GOLD BONDS

The oxidative addition of chlorine or bromine to [Au4(C6F5)2{(Ph2P)2CH }2] leads to [AU4(C6F5)2{(Ph2P)2Ch}2X2] (X = Cl, Br). Displacement of chlorine by reaction with [Ag(OClO3)L] gives the cationic complexes [A u4(C6F5)2{(Ph2P)2CH}2L2] (ClO4)2 (L = tht, PPh3, PPh2Me, P(tol)3). The structure of the PPh3 derivative has been determined by single-crysta l diffraction. It crystallizes with crystallographic 2-fold symmetry i n the monoclinic space group C2/c: a = 17.670(3) angstrom, b = 25.484- (5) angstrom, c = 22.651(5) angstrom, beta = 93.86(2)-degrees, Z = 4, T = -100-degrees-C. Its backbone is a linear chain of three four-coord inated gold atoms, in which the central gold atom is bonded to the oth ers with an Au-Au distance of 2.7305(11) angstrom. The formal charge o f the Au3unit is +5, but integral oxidation states consistent with nor mal coordination geometry cannot be assigned.