Formation of B−P Bonds through the Reaction of nido-Monophosphinocarboranes with Palladium(II) Complexes. The First Example of a Chelating R2P−C−B−PR2 Diphosphine

Reaction of [NMe 4 ][7-PPh 2 -8-R-7,8-C 2 B 9 H 10 ] (R = Me, H, Ph) with cis -[PdCl 2 (PPh 3 ) 2 ] in ethanol yielded [PdCl(7-PPh 2 -8-R-11-PPh 2 -7,8-C 2 B 9 H 9 )(PPh 3 )] (R = Me, H, Ph). The Pd(II) is in a square-planar arrangement. The carborane ligand chelates the Pd through two phosphorus atoms, one from C−PPh 2 and the second from the generated B(11)−PPh 2 . The remaining two positions are filled by a PPh 3 and one chloride. In the complexation process, a previously nonexistent B(11)−P bond is generated in the ligand. This is unambiguously demonstrated by a doublet in the 11 B{ 1 H} NMR spectrum and a 1:1:1:1 quartet in the 31 P{ 1 H} spectrum. The structure was fully elucidated by a crystal diffraction analysis of [PdCl(7-PPh 2 -8-Me-11-PPh 2 -7,8-C 2 B 9 H 9 )(PPh 3 )]·C 7 H 8 . By this reaction the hitherto unknown R 2 P−C−B−PPh 2 chelating unit has been formed.