Study of the o-carboranyl fragment as an uncommon substituent. Crystal structures of [PdClMe(1,2-(PPh2)2-1,2-C2B10H10)]·CH2Cl2 and [PdClMe(1,2-(PiPr2)2-1,2-C2B10H10)]

The syntheses of two novel o-carboranyl palladium complexes [PdClMe(1,2-(PPh2)2-1,2-C2B10H10)] and [PdClMe(1,2-(PiPr2)2-1,2-C2B10H10)] are described and their crystal structures are determined. Both complexes were obtained in CH2Cl2 by two methods: (i) by replacement of 1,5-cyclooctadiene (cod) in [PdClMe(cod)] by 1,2-(PPh2)2-1,2-C2B10H10 and 1,2-(PiPr2)2-1,2-C2B10H10 and (ii) by the reaction of [PdCl2(1,2-(PR2)2-1,2-C2B10H10)] (R=Ph, iPr) with SnMe4. In both complexes the carborane cage is co-ordinated bidentately through P atoms to the Pd(II) ion, while the Cl ion and Me group in cis positions complete the distorted square-planar co-ordination around the metal. Differences in the 31P-NMR spectra of PdCl2 complexes of o-carboranyl diphosphines and of organic diphosphines with ethane and benzene backbones are discussed. The 31P-NMR spectra of o-carboranyl PdCl2 complexes have been compared with spectra of other complexes having same metal surrounding. The data obtained allowed an interpretation of the electronic characteristics of o-carborane and of the influence of these on co-ordination capacity.