POLYSILOXANE-BOUND ETHER PHOSPHINES AND RUTHENIUM COMPLEXES - A CHARACTERIZATION BY SOLID-STATE NMR-SPECTROSCOPY AND CATALYSIS

The monomeric ether-phosphine ligands (CH3O)3Si(CH2)3(Ph)PCH2D [D = CH 2OCH3 (1a), tetrahydrofuryl (1b), and 1,4-dioxanyl (1c)] and their P-c oordinated trimethoxysilyl- (T-) functionalized ruthenium(II) complexe s HRuCl(CO)(P approximately 0)3 (3a-c) were copolymerized with variabl e amounts of Si(OEt)4 (Q elements) under various sol-gel conditions to give the polysiloxane-bound ether-phosphine ligands 1a'(Q(n))x-1c'(Q( n))x and (ether-phosphine)ruthenium-(II) complexes 3a'(Q(n))x-3c'(Q(n) )x, [P approximately O: eta1-P-coordinated; (Q(n))x: x = number of coc ondensated Q type silicon atoms, n = 2-4, the number of Si-O-Si bonds] . Detailed P-31 and C-13 spin-lattice relaxation time studies (T1P, T1 C, T1rhoH) show that the noncomplexed ether-phosphine ligands strongly increase their mobilities in the gels at rising temperatures, while t he coordinated ligands in the complexes are less mobile and rigidly bo und to ruthenium. Solid-state Si-29 NMR spectroscopy has been used to determine the relative amounts of the T and Q silyl species and the de gree of condensation. Moreover, the molecular mixing of the copolymeri zed components in the samples has been investigated and the transition to the silica gel attached system 3c'-silica gel elucidated. The mate rials, obtained by the different sol-gel variants, differ in their amo unt of Q species, degree of condensation, and their particle sizes, wh ich strongly influence their catalytic behavior. Although the BET surf aces are in the range of the external surface of the gels, a high cata lytic activity has been found when small particle sizes have been comb ined with a low content of Q silicon moieties. This can be traced back to a high flexibility of such materials, which allows swelling and an increase of the surface during hydrogenation of n-butyraldehyde to bu tanol within the gel. The undesired tendency to form highly swollen ge ls in alcohols after catalysis, which complicate the separation of the catalysts from the products, has been suppressed without loss of cata lytic activity by the use of a modified matrix containing small amount s of insoluble ionic magnesium silicates. Constant elemental analyses of this material after three identical catalytic runs demonstrate the. possibilities of this system, which unifies the advantages of organic and inorganic polymer networks and those of homogeneous and heterogen eous catalyses.