Synthesis of Polysiloxane-Bound (Ether−phosphine)palladium Complexes. Stoichiometric and Catalytic Reactions in Interphases1

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Abstract
The reaction of two equiv of the monomeric ether−phosphine O,P ligand (MeO)3Si(CH2)3(Ph)PCH2−Do [1a(T 0), 1b(T 0)] {Do = CH2OCH3 [1a(T 0)], CHCH2CH2CH2O [1b(T 0)]} with PdCl2(COD) yields the monomeric palladium(II) complexes Cl2Pd(P∼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∼O = η1-P-coordinated ether−phosphine ligand; for Tn and Qk, 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]-SiOn/2(OX)3-n}2[SiOk/2 (OX)4-k]y, [M] = (Cl2Pd)1/2(Ph)P(CH2Do)(CH2)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⌒O)2][SbF6]2 [3a(T 0) 2, 3b(T 0) 2] are formed by reacting Cl2Pd(P∼O)2 with 2 equiv of a silver salt {P⌒O = η2-O⌒P-coordinated ether−phosphine ligand; 3a(T 0) 2, 3b(T 0) 2 = [M]−SiOMe3; [M] = {[Pd2+]1/2P(Ph)(CH2CH2OCH3)(CH2)3−}{SbF6} (a), {[Pd2+]1/2P(Ph)(CH2CHCH2CH2CH2O)(CH2)3−}{SbF6} (b)}. Their polysiloxane-bound congeners 3a(T n) 2, 3b(T n) 2 {[M]-SiOn/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]-SiOn/2(OX)3-n}2[SiOk/2(OX)4-k]4, [M] = [(dba)Pd]1/2P(Ph)(CH2Do)(CH2)3−} undergo an oxidative addition reaction with iodobenzene in an interphase with formation of the complexes PhPd(I)(P∼O)2·4SiO2 [6a(T n) 2 (Q k) 4 , 6b(T n) 2 (Q k) 4] {[M]-SiOn/2(OX)3-n]2[SiOk/2(OX)4-k]4, [M] = [PhPd(I)]1/2P(Ph)(CH2Do)(CH2)3−}, which insert carbon monoxide into the palladium−aryl bond even in the solid state.

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