Synthesis and characterization of poly(alumosiloxane)-bound (ether-phosphine)ruthenium(II) complexes

The trimethoxysilyl-(T)-functionalized ruthenium(II) complex cis-Cl(H)Ru(CO)(P similar to O)(3) [2(T-0)(3)] (P similar to O: P-coordinated ether-phosphine) is sol-gel processed with tetraethoxysilane (TEOS, Q(0)) and aluminum 2-propanolate [Al(OiPr)(3)]. All components are simultaneously polycondensed to result in the poly(alumosiloxane)-bound ruthenium complexes A and B with various amounts of aluminum. From P-31 and C-13 CP MAS NMR as well as IR spectroscopy it can be concluded that the complex fragment cis-Cl(H)Ru(CO)(P similar to O)(3) is preserved during the immobilization. Polymers A and B show a remarkable number of Si-O-Al bonds in the Si-29 solid state NMR spectra. The aluminum is incorporated as tetrahedrally coordinated AlO4 units with a formal negative charge. The 6-fold coordinated AlO6 groups containing water and hydroxide groups as ligands are sited as interstitials and act as their counterions. Stoichiometric formulas of A and B derived by Al-27 and Si-29 solid state NMR spectroscopy and energy dispersive X-ray spectroscopy (EDX) suggest that the amount of aluminum can be adjusted by the applied stoichiometry. The two materials A and B act as hydrogenation catalysts of trans-crotylaldehyde and are easy to separate from the reaction mixture by simple centrifugation.