The formation of nido [7,8-(PR2) 2-7,8-C2B9H10]- from closo 1,2-(PR2) 2-1,2-C2B10H10 (R = Ph, Et, iPr or OEt): A process enhanced by complexation

Article abstract of DOI:10.1016/0022-328X(95)05809-4

To gain insight into the mutual influence of an electron-rich element directly connected to the carborane cage, the coordination behavior of phosphorus atoms directly bonded to the cage has been studied. The reactivity of bisphosphines [7,8-(PR₂)₂-7,8-C₂B₉H₁₀]^- (R = Ph, Et, ⁱPr or OEt) has been investigated. These new chelating ligands exhibit some similarities to the much used 1,2-diphenylphos-phinoethane (diphos), such as the spacing between the two phosphorus atoms, and their five-membered ring chelating ability, but there are notable differences, and dissimilar ligating properties are expected. The differences are mainly due to the incorporated carborane cluster and can be summarized as follows: (1) the ligand is anionic, (2) the phosphorus atoms lie in an eclipsed conformation and (3) B(3)-H coordination to the metal is possible. To study the partial degradation of the closo clusters to the nido clusters enhanced by complexation, several metal complexes were treated with the closo ligands in ethanol. The crystal structures of [AuCl₂ {7,8-(P(ⁱPr₂)₂-7,8-C₂B₉H₁₀}] and [RuCl₂{7,8-(P(ⁱPr₂)₂-7,8-C₂B₉H₁₀}₂] have been determined.