Nine-vertex polyhedral monocarbaplatinaborane chemistry. Isolation, molecular structure and nuclear magnetic resonance properties of [6,6-(PPh3)2-arachno-6,4-PtCB7H11]

Abstract

Reaction between [Pt(PPh₃)₄] and nido-1-CB₈H₁₂1 results in the formation of [6,6-(PPh₃)₂-arachno-6,4-PtCB₇H₁₁]2 as a yellow crystalline solid in 26% yield. The product 2 is characterised by NMR spectroscopy and single-crystal X-ray diffraction analysis. Crystals (from CH₂Cl₂–hexane) are triclinic, space group P, with a= 974.3(2), b= 1237.5(2), c= 1771.3(3) pm, α= 95.26(1), β= 95.43(1), γ= 110.10(1)° and Z= 2. The structure has been refined to R(R′)= 0.0256 (0.0394) for 6324 reflections [F_o > 2.0σ(F_o)]. The molecular structure is based on a nine-vertex arachno cluster with the platinum and carbon atoms in projecting open face 6- and 4-positions respectively. The ¹¹B, ¹H and ³¹P NMR parameters have been measured and assigned to structural positions, and the ¹¹B and ¹H shielding patterns are compared to those of the related non-platinum species arachno-4,5-C₂B₇H₁₃7 and arachno-4,6-C₂B₇H₁₃8. Incidental to this work the previously unreported ¹H shielding behaviour of the carbaboranes 1, 7 and 8 have also been measured and assigned.