Modulation of the B(3)-H⇀Ru Distances in 7,8-Dicarba-nido-undecaborate Derivatives

The formation of B(3)-H⇀Ru bonds in 7,8-dicarba-nido-undecaborate derivatives containing sulfur atoms connected to the cluster carbon atoms is described. The strength of the agostic bond is modulated by modifying the length of the S,S′ connecting chain. Shorter chains (more strained) produce shorter B(3)⋯Ru distances; longer chains produce longer B(3)⋯Ru distances. A relationship between the 1H NMR B(3)-H hydride or the B(3) 11B NMR signals and the external chain has also been disclosed. Two extreme types of B(3)-H⇀Ru agostic bonds are described. The crystal structures of [RuCl(L5)(PPh3)2], [RuCl(L8)(PPh3)2]·Me2CO,and [NMe4][RuC1(L6)2] are presented. The compound [RuCl(L5)(PPh3)2] (Mr = 870.65) crystallizes in the monoclinic space group P21/c, with a = 15.134(3) Å, b = 11.825(3) Å, c = 22.970(4) Å, α = 90.0°, β = 110.32(2)°, γ = 90.0°, V = 4111(2) Å3, Z = 4, R = 0.058, and Rw = 0.041. The compound [RuCl(L8)(PPh3)2]·Me2CO (Mr = 970.80) crystallizes in the triclinic space group P1, with a = 12.187(4) Å, b = 17.163(3) Å, c = 8.196(2) Å, α = 95.73(1)°, β = 95.51(2)°, γ = 105.61(2)°, V = 2389(1) Å3,Z = 2, R = 0.041, and Rw = 0.046. The compound [NMe4][RuCl(L6)2] (Mr = 657.84) crystallizes in the orthorhombic space group Cmc21, with a = 19.423(4) Å, b = 13.028(2) Å, c = 12.142(2) Å, α = 90.0°, β = 90.0°, γ = 90.0°, V = 3073(1) Å3, Z = 4, R = 0.064, and Rw = 0.064. © 1994, American Chemical Society. All rights reserved.