Formation of B−P Bonds through the Reaction of <i>nido</i>-Monophosphinocarboranes with Palladium(II) Complexes. The First Example of a Chelating R<sub>2</sub>P−C−B−PR<sub>2</sub> Diphosphine

Reaction of [NMe<sub>4</sub>][7-PPh<sub>2</sub>-8-R-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>10</sub>] (R = Me, H, Ph) with <i>cis</i>-[PdCl<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>] in ethanol yielded [PdCl(7-PPh<sub>2</sub>-8-R-11-PPh<sub>2</sub>-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>9</sub>)(PPh<sub>3</sub>)] (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<sub>2</sub> and the second from the generated B(11)−PPh<sub>2</sub>. The remaining two positions are filled by a PPh<sub>3</sub> 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 <sup>11</sup>B{<sup>1</sup>H} NMR spectrum and a 1:1:1:1 quartet in the <sup>31</sup>P{<sup>1</sup>H} spectrum. The structure was fully elucidated by a crystal diffraction analysis of [PdCl(7-PPh<sub>2</sub>-8-Me-11-PPh<sub>2</sub>-7,8-C<sub>2</sub>B<sub>9</sub>H<sub>9</sub>)(PPh<sub>3</sub>)]·C<sub>7</sub>H<sub>8</sub>. By this reaction the hitherto unknown R<sub>2</sub>P−C−B−PPh<sub>2</sub> chelating unit has been formed.