Protonation reactions of the salts [Na][Pt(PR3)2(η5-7-CB10H11)] (PR3 = PEt3 or PMe2Ph): synthesis and crystal structures of the platinacarborane complexes [PtCl(PMe2Ph)2(η5-7-CB10H11)], [Pt2{µ-σ,η5∶σ′,η5′-8,9′-(7-CB10H10)2}(PMe2Ph)4] and [Pt2(PEt3)4{η5∶η5′-9,9′-I(H)(7-CB10H10)2}]†

Abstract

Protonation of [Na][Pt(PMe₂Ph)₂(η⁵-7-CB₁₀H₁₁)] 1b with HCl in diethyl ether afforded a mixture of the complexes [PtX(PMe₂Ph)₂(η⁵-7-CB₁₀H₁₁)] (X = H 2b or Cl 3) and [Pt₂{µ-σ,η⁵∶σ′,η⁵′-8,9′-(7-CB₁₀H₁₀)₂}(PMe₂Ph)₄] 4. Single-crystal X-ray diffraction studies established the structures of 3 and 4. In the former the platinum atom is co-ordinated on one side by the open CBBBB face of the nido-7-CB₁₀H₁₁ cage and on the other by a chlorine atom and two PMe₂Ph molecules. In the molecule 4 two nido-icosahedral CB₁₀ cage frameworks, each η⁵-co-ordinated by their open CBBBB faces to a platinum atom, are joined by a B–B connectivity and by two relatively long Pt–B connectivities. The B–B link is formed between a boron atom in a β site in one CBBBB ring and a boron in an α site in the other CBBBB ring. Each boron involved in this connectivity also forms a B–Pt linkage to the platinum atom in the adjacent closo-2,1-PtCB₁₀ sub-cluster. Thus the two metal atoms and the two borons form a ‘butterfly’ arrangement with the platinums at the wing-tips. Treatment of [Na][Pt(PEt₃)₂(η⁵-7-CB₁₀H₁₁)] with HCl in diethyl ether gave [PtH(PEt₃)₂(η⁵-7-CB₁₀H₁₁)] 2a as expected, but a complex mixture of other products was also formed. Addition of [NEt₄]I to this mixture allowed isolation of a species [Pt₂(PEt₃)₄{η⁵∶η⁵′-9,9′-I(H)(7-CB₁₀H₁₀)₂}] 5. This unusual formulation is based principally on the results of an X-ray diffraction study which revealed that two icosahedral closo-2,1-PtCB₁₀ sub-clusters were bridged by an iodine atom.