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 [NMe4][7-PPh2-8-R-7,8-C2B9H10] (R = Me, H, Ph) with cis-[PdCl2(PPh3)2] in ethanol yielded [PdCl(7-PPh2-8-R-11-PPh2-7,8-C2B9H9)(PPh3)] (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−PPh2 and the second from the generated B(11)−PPh2. The remaining two positions are filled by a PPh3 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 11B{1H} NMR spectrum and a 1:1:1:1 quartet in the 31P{1H} spectrum. The structure was fully elucidated by a crystal diffraction analysis of [PdCl(7-PPh2-8-Me-11-PPh2-7,8-C2B9H9)(PPh3)]·C7H8. By this reaction the hitherto unknown R2P−C−B−PPh2 chelating unit has been formed.