Synthesis of Polysiloxane-Bound (Ether-phosphine)palladium Complexes. Stoichiometric and Catalytic Reactions in Interphases(1).
The reaction of two equiv of the monomeric ether-phosphine O,P ligand (MeO)(3)Si(CH(2))(3)(Ph)PCH(2)-Do [1a(T(0)()), 1b(T(0)())] {Do = CH(2)OCH(3) [1a(T(0)())], CHCH(2)CH(2)CH(2)O [1b(T(0)())]} with PdCl(2)(COD) yields the monomeric palladium(II) complexes Cl(2)Pd(P approximately O)(2) [2a(T(0)())(2)(), 2b(T(0)())(2)()]. The compounds 2a(T(0)())(2)() and 2b(T(0)())(2)() are sol-gel processed with variable amounts (y) of Si(OEt)(4) (Q(0)()) to give the polysiloxane-bound complexes 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() (Table 1) {P approximately O = eta(1)-P-coordinated ether-phosphine ligand; for T(n)() and Q(k)(), y = number of condensed T type (three oxygen neighbors), Q type (four oxygen neighbors) silicon atoms; n and k = number of Si-O-Si bonds; n = 0-3; k = 0-4; 2a(T(n)())(2)()(Q(k)())(y)(), 2b(T(n)())(2)()(Q(k)())(y)() = {[M]-SiO(n)()(/2)(OX)(3)(-)(n)()}(2)[SiO(k)()(/2)(OX)(4)(-)(k)()](y)(), [M] = (Cl(2)Pd)(1/2)(Ph)P(CH(2)Do)(CH(2))(3)-, X = H, Me, Et}. The complexes 2b(T(n)())(2)()(Q(k)())(y)() (y = 4, 12, 36) show high activity and selectivity in the hydrogenation of 1-hexyne and tolan. The dicationic complexes [Pd(P&arcraise;O)(2)][SbF(6)](2) [3a(T(0)())(2)(), 3b(T(0)())(2)()] are formed by reacting Cl(2)Pd(P approximately O)(2) with 2 equiv of a silver salt {P&arcraise;O = eta(2)-O&arcraise;P-coordinated ether-phosphine ligand; 3a(T(0)())(2)(), 3b(T(0)())(2)() = [M]-SiOMe(3); [M] = {[Pd(2+)](1/)(2)P(Ph)(CH(2)CH(2)OCH(3))(CH(2))(3)-}{SbF(6)} (a), {[Pd(2+)](1/)(2)P(Ph)(CH(2)CHCH(2)CH(2)CH(2)O)(CH(2))(3)-}{SbF(6)} (b)}. Their polysiloxane-bound congeners 3a(T(n)())(2)(), 3b(T(n)())(2)() {[M]-SiO(n)()(/2)(OX)(3)(-)(n)} are obtained if a volatile, reversible bound ligand like acetonitrile is employed during the sol-gel process. The bis(chelate)palladium(II) complexes 3a(T(n)())(2)(), 3b(T(n)())(2)() are catalytic active in the solvent-free CO-ethene copolymerization, producing polyketones with chain lengths comparable to those obtained with chelating diphosphine ligands. The polysiloxane-bound palladium(0) complexes 5a(T(n)())(2)()(Q(k)())(4)(), 5b(T(n)())(2)()(Q(k)())(4)() {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)}(2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [(dba)Pd](1/)(2)P(Ph)(CH(2)Do)(CH(2))(3)-} undergo an oxidative addition reaction with iodobenzene in an interphase with formation of the complexes PhPd(I)(P approximately O)(2).4SiO(2) [6a(T(n)())(2)()(Q(k)())(4)(), 6b(T(n)())(2)()(Q(k)())(4)()] {[M]-SiO(n)()(/)(2)(OX)(3)(-)(n)](2)[SiO(k)()(/2)(OX)(4)(-)(k)](4), [M] = [PhPd(I)](1/2)P(Ph)(CH(2)Do)(CH(2))(3)-}, which insert carbon monoxide into the palladium-aryl bond even in the solid state.
Lindner
Ekkehard
E
Institut für Physikalische und Theoretische Chemie der Universität, Auf der Morgenstelle 8, 72076 Tübingen, Germany.
Schreiber
Rudolf
R
Schneller
Theodor
T
Wegner
Peter
P
Mayer
Hermann A.
HA
Göpel
Wolfgang
W
Ziegler
Christiane
C