THE FORMATION OF NIDO [7,8-(PR(2))(2)-7,8-C2B9H10](-) FROM CLOSO 1,2-(PR(2))(2)-1,2-C2B10H10 (R=PH, ET, PR-I OR OET) - A PROCESS ENHANCED BY COMPLEXATION

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 re activity of bisphosphines [7,8-(PR(2))(2)-7,8-C2B9H10](-)(R = Ph, Et,P r-i or OEt) has been investigated. These new chelating ligands exhibit some similarities to the much used 1,2-diphenylphosphinoethane (dipho s), such as the spacing between the two phosphorus atoms, and their fi ve-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 i n an eclipsed conformation and (3) B(3)-H coordination to the metal is possible. To study the partial degradation of the close clusters to t he nido clusters enhanced by complexation, several metal complexes wer e treated with the close ligands in ethanol. The crystal structures of [AuCl2{7,8-(P(Pr-i(2))(2)-7,8-C2B9H10}] and [RuCl2{7,8-(P(Pr-i(2))(2) -7,8-C2B9H10}(2)] have been determined.