MODULATION OF THE B(3)-H-]RU DISTANCES IN 7,8-DICARBA-NIDO-UNDECARBORATE DERIVATIVES

The formation of B(3)-H-Ru bonds in 7,8-dicarba-nido-undecaborate deri vatives containing sulfur atoms connected to the cluster carbon atoms is described. The strength of the agostic bond is modulated by modifyi ng the length of the S,S' connecting chain. Shorter chains (more strai ned) produce shorter B(3)...Ru distances; longer chains produce longer B(3)...Ru distances. A relationship between the H-1 NMR B(3)-H hydrid e or the B(3) B-11 NMR signals and the external chain has also been di sclosed. Two extreme types of B(3)-H half arrow pointing right Ru agos tic bonds are described. The crystal structures of [RuCl(L5)(PPh3)2], [RuCl(L8)(PPh3)2].Me2CO, and [NMe4][RuCl(L6)2] are presented. The comp ound [RuCl(L5)(PPh3)2] (M(r) = 870.65) crystallizes in the monoclinic space group P2(1)/c, with a = 15.134(3) angstrom, b = 11.825(3) angstr om, c = 22.970(4) angstrom, alpha = 90.0-degrees, beta = 110.32(2)degr ees, gamma = 90.0-degrees, V = 4111(2) angstrom3, Z = 4, R = 0.058, an d R(w) = 0.041. The compound [RuCl(L8)(PPh3)2].Me2CO (M(r) = 970.80) c rystallizes in the triclinic space group P1BAR, with a = 12.187(4) ang strom, b = 17.163(3) angstrom, c = 8.196(2) angstrom, alpha = 95.73(1) degrees, beta = 95.51(2)degrees, gamma = 105.61(2)degrees, V = 2389(1) angstrom3, Z = 2, R = 0.041, and R(w) = 0.046. The compound [NMe4][Ru Cl(L6)2] (M(r) = 657.84) crystallizes in the orthorhombic space group Cmc2(1), with a = 19.423(4) angstrom, b = 13.028(2) angstrom, c = 12.1 42(2) angstrom, alpha = 90.0-degrees, beta = 90.0-degrees, gamma 90.0- degrees, V = 3073(1) angstrom3, Z = 4, R = 0.064, and R(w) = 0.064.