Carbaborane derivatives of the late- and post-transition elements. Part 2. Dicarbaundecaboranyl compounds of copper(I), gold(I), and mercury(II); the crystal and molecular structure of 3-triphenylphosphine-3-mercura-1,2-dicarbadodecaborane(II), a pseudo-σ-bonded metallacarbaborane

Abstract

The novel d¹⁰ metallacarbaboranes B₉C₂^1,2[Hg(PPh₃)]³H₁₁(1), [AsPh₄][B₉C₂^1,2(HgMe)³H₁₁], B₉C₂^1,2[Au(PPh₃)]³(NC₅H₅)⁴H₁₀, B₉C₂^1,2[Cu(PPh₃)]³(NC₅H₅)⁴H₁₀, and [3.3′-{HgB₉C₂^1,2(NC₅H₅)⁴H₁₀}₂] have been prepared by reactions of [{HgCl₂(PPh₃)}₂] with Tl[B₉C₂^1,2Tl³H₁₁], [HgMe(O₂CMe)] with aqueous K[B₉C₂H₁₂]–K[OH], and Na[B₉C₂^7,8(NC₅H₅)⁹H₁₀] with [AuCl(PPh₃)], [{CuCl(PPh₃)}₄], and HgCl₂ respectively. The molecular structure of compound(1), as the 0.5-dioxan solvate, has been determined at –60 °C, and shows the mercury atom to be co-ordinated almost linearly by PPh₃ and the unique boron atom of the C₂B₃ face, implying a direct mercury–boron σ bond (Hg–B 2.20, Hg–P 2.39 Å, P–Hg–B 172°). The crystals are triclinic, space group P with cell dimensions a= 10.913 5(17), b= 11.188 3(19), c= 12.007 1(18)Å, α= 83.50(1), β= 86.98(1), γ= 61.55(1)°, and Z= 2, and the structure has been refined to R= 0.037 for 2 447 independent observed reflections.