Preparation, reactions, and nuclear magnetic resonance spectra of disubstituted derivatives of the octahydrotriborate(1-) ion, [B₃H₆XX′]^- (X = Cl, X′ = Cl, NCS, NCBH₃, or NCBH₂Cl); Molecular structure of [B₃H₆Cl₂]^- and partial structure of [B₃H₆Cl(NCS)]^-

The preparation of disubstituted derivatives of [B₃H₈]^- with halogen or pseudo-halogen is reported. Ions studied include [B₃H₆Cl₂]^- (1), [B₃H₆Cl(NCS)]^- (2), [B₃H₆Cl(NCBH₃)]^-, and [B₃H₆Cl(NCBH₂Cl)]^-. N.m.r. parameters show that the ions are fluxional in solution, and ¹¹B^-11B coupling is poorly resolved. The thermal stabilities, and chemical and electrochemical behaviour of representative compounds are described. The molecular structures, illustrated by [B₃H₆Cl₂]^- and [B₃H₆Cl(NCS)]^- relate to that of [B₃H₈]^- with trans substituents. Four molecules of [N(PPh₃)₂][B₃H₆Cl₂] crystallise in space group P2₁/c with a = 10.9552(14), b = 12.840(9), c = 24.236(5) Å, and β = 92.298(13)°. R = 0.0728 for 3 267 data measured at room temperature. The [B₃H₆Cl₂]^- ion has effective C₂ symmetry and markedly asymmetric H bridges. [N(PPh₃)₂][B₃H₆Cl(NCS)] crystallises from CH₂Cl₂ as a 1:1 solvate with Z = 2 in space group P1, with a = 11.2855(22), b = 14.4000(21), c = 15.708(4) Å, α = 120.680(17), β = 109.760(18), and γ = 65.971 (14)° at 185 ± 1 K. An approximate structure solution affords R = 0.1922 for 5 706 diffraction data.