Palladium and Platinum Units Grafted on the Periphery of Carbosilane Dendrimers

Abstract

The reaction of a series of phosphanyl-terminated carbosilane dendrimers with palladium and platinum complexes was carried out. The new metallodendrimers containing PdCl(η3-2-MeC3H4) and PtCl2 or Pt(C≡CPh)2 as peripheral groups were characterized by 1H, 13C, 29Si, 31P, and 195Pt NMR spectroscopy, and, in some cases, by mass spectrometry. The PtCl2-containing species of the second-generation carbosilane dendrimer displays only one of the two possible stereoisomers. By comparison with the 31P NMR spectra of the model compounds cis-[PtCl2(PPh2CH2SiMe3)2] (4) and cis-[PtCl2{Me2Si(CH2PPh2)2}] (5), it was deduced that the PtCl2 units are bound on the surface of the dendrimer through two phosphorus atoms belonging to the same branch. The palladium dendrimers were tested as catalysts in the hydrovinylation of styrene, and their activity was compared with that of the model catalyst [PdCl(η3-2-MeC3H4)(PPh2CH2SiMe3)]. The crystal structures of 4, 5, and [Pt(C≡CPh)2{Me2Si(CH2PPh2)2}] (6) were solved by X-ray diffraction analysis. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)