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}]

Protonation of [Na][Pt(PMe2Ph)(2)(eta(5)-7-CB10H11)] 1b with HCl in diethyl ether afforded a mixture of the complexes [PtX(PMe2Ph)(2)(eta(5)-7-CB10H11)] (X = H 2b or Cl 3) and [Pt-2{mu-sigma,eta(5) : sigma' eta(5)'-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 coordinated 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 eta(5)-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 beta site in one CBBBB ring and a boron in an alpha 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)(eta(5)-7-CB10H11)] with HCl in diethyl ether gave [PtH(PEt3)(2)(eta(5)-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 [Pt-2(PEt3)(4)(eta(5) : eta(5)'-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.