Conversion of the amino group of 6-(2-aminophenyl)-2,2Ј-bipyridine to a thiol resulted not in the expected N,N,S-terdentate chelating ligand HL [6-(2-sulfhydryl)-2,2Ј-bipyridine] but in the oxidised disulfide 2,2Ј-bis-[6-(2,2Ј-bipyridyl)]diphenyldisulfide, L᎐L. This ligand contains two bipyridyl arms linked by a diphenyl disulfide bridge in such a way that they cannot be coplanar, but tend to co-ordinate to a single metal ion with a substantial dihedral angle between the two ligand planes giving a pseudo-tetrahedral geometry. The crystal structure of L᎐Lؒ0.5C 6 H 5 CH 3 shows the presence of near-linear N ؒ ؒ ؒ S᎐S interactions (non-bonded N ؒ ؒ ؒ S; 2.75 Å) in which the pyridyl lone pair interacts with the σ* orbital of the disulfide fragment. The complexes [Cu(L᎐L)][PF 6 ] and [Ag(L᎐L)][PF 6 ] were prepared and are isostructural, both having a distorted four-co-ordinate metal co-ordination environment in which the two chelating bipyridyl fragments have dihedral angles of between 70 and 80 ЊC between them (i.e. nearly mutually perpendicular). The electronic spectrum of the Cu I complex [Cu(L᎐L)][PF 6 ], and the EPR spectrum of its one-electron oxidised product [Cu(L᎐L)] 2ϩ , both confirm that the rigidity of the ligand donor set does not permit much variation in the co-ordination environment about the copper ion. The ligand therefore imposes a relatively rigid pseudo-tetrahedral geometry on the metal centres.

Protonation of [Na][Pt(PMe 2 Ph) 2 (η 5 -7-CB 10 H 11 )] 1b with HCl in diethyl ether afforded a mixture of the complexes [PtX(PMe 2 Ph) 2 (η 5 -7-CB 10 H 11 )] (X = H 2b or Cl 3) and [Pt 2 {µ-σ,η 5 : σЈ,η 5 Ј-8,9Ј-(7-CB 10 H 10 ) 2 }(PMe 2 Ph) 4 ] 4. Singlecrystal 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-CB 10 H 11 cage and on the other by a chlorine atom and two PMe 2 Ph molecules. In the molecule 4 two nido-icosahedral CB 10 cage frameworks, each η 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 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-PtCB 10 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(PEt 3 ) 2 (η 5 -7-CB 10 H 11 )] with HCl in diethyl ether gave [PtH(PEt 3 ) 2 (η 5 -7-CB 10 H 11 )] 2a as expected, but a complex mixture of other products was also formed. Addition of [NEt 4 ]I to this mixture allowed isolation of a species [Pt 2 (PEt 3 ) 4 {η 5 : η 5 Ј-9,9Ј-I(H)(7-CB 10 H 10 ) 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-PtCB 10 sub-clusters were bridged by an iodine atom.