Synthesis, characterisation and catalytic application of sol-gel processedcationic palladium(II) complexes

The dicationic T-silyl functionalised bis(acetonitrile)(dppp)palladium(II) complex 2(T-0) (see Scheme 1) was sol-gel processed with different amounts (y) of the co-condensation agent MeSi(OMe)(2)(CH2)(6)(MeO)(2)SiMe (D-0-C-6- D-0) to give the new stationary phases 2a-h(T-n)(D-i-C-6-D-i)(y) (y = 0, 5, 10, 15, 20, 40, 80, and 100; n = 0-3, i = 0-2). The polysiloxane matrices and the integrity of the palladium(II) complex centres were investigated by means of solid state NMR (Si-29, C-13, P-31) and EXAFS spectroscopy. Dynam ic NMR investigations show an increasing mobility of the hybrid polymers on going from y = 0 to 10. For higher amounts of the co-condensation agent Me SiOi/2(OX)(2-i)(CH2)(6)O-i/2(XO)(2-i)SiMe (D-i-C-6-D-i) the mobility tends toward that of a matrix consisting of D-i-C-6-D-i (T/D = 0) only. NMR exper iments in suspension give further evidence for considerable mobility of the interphases (formed by the penetration of stationary and mobile phases on a molecular scale). Model reactions of 2a(T-n) with different isocyanides i n the interphase point to almost complete accessibility of the palladium(II ) centres, even if the reactants carry sterically demanding substituents (e .g. t-Bu). The activity of the hybrid catalysts 2a-h(T-n)(D-i-C-6-D-i)(y) i n the ethene/CO copolymerisation is markedly dependent on the temperature a nd the amount y of the co-condensation agent. A maximum of activity [1600 g (ECO) g(Pd)(-1) h(-1)] is achieved with y = 10 which is 75% of the activity of the analogous homogeneous catalyst.