Stoichiometric and Catalytic Reactions of the Polysiloxane‐Bound (Ether‐Phosphine)Rhodium(I) Complex [ClRh(PO)(P ∼ O)] in Interphases

The reaction of four equivalents of the monomeric trimethoxysilyl(T)‐functionalized ether‐phosphine ligand CyP(CH 2 CH 2 OCH 3 )(CH 2 ) 3 SiR 3 (R = OMe [ 1 a(T 0 )], Me [ 1 b ]) with [{μ‐ClRh(COE) 2 } 2 ] yielded the monomeric pseudo 14 electron rhodium(I) complexes [ClRh(PO)(P∼O)] ( 2a(T 0 ) 2 , 2 b ). For the sol‐gel process the complex 2 a(T 0 ) 2 was protected by introduction of the volatile, reversibly binding ligand pyridine. Thus, the monomeric compound 2 a(T 0 ) 2 was co‐condensed with two and eight equivalents of the co‐condensation agent MeSi(OMe) 2 (CH 2 ) 6 (MeO) 2 SiMe ( D 0 ‐C 6 ‐D 0 ) to give the polysiloxane‐bound congeners 2(T n ) 2 ( D i ‐C 6 ‐D i ) y ( y = 2 and 8, respectively; i = 0–2; n = 0–3). The polysiloxane‐bound complex 2(T n ) 2 ‐( D i ‐C 6 ‐D i ) 2 was treated with a variety of small molecules in the gas/solid and liquid/solid interphases. It was shown that a facile cleavage of the Rh‐O bond in the ether‐phosphine chelate occurred even in the solid state. The reaction of 2(T n ) 2 ‐( D i ‐C 6 ‐D i ) 2 with carbon monoxide, carbon disulfide, and diphenylacetylene resulted in the irreversible coordination of the molecule to the metal. In the presence of pyridine, the polysiloxane‐bound complex 2(T n ) 2 ‐( D i ‐C 6 ‐D i ) 2 oxidatively added hydrogen to give the octahedrally configurated complex [ClRhH 2 (Py)(P ∼ O) 2 ] [ 6(T n ) 2 ( D i ‐C 6 ‐D i ) 2 ]. Treatment of dry 2(T n ) 2 ‐( D i ‐C 6 ‐D i ) 2 with ethene led to the reversible formation of the corresponding complex. Although the materials display low surface areas, at least 75% of the rhodium centers within the matrix are accessible to the rather bulky tolan molecules. The complexes 2(T n ) 2 ( D i ‐C 6 ‐D i ) y ( y ( y = 2, 8) show high activities and selectivities in the hydrogenation of tolan. The conversion was found to depend markedly on the amount of co‐condensate ( D 0 ‐C 6 ‐D 0 ) and on the polarity of the solvent. The polysiloxane‐bound complexes 2(T n ) 2 ( D i ‐C 6 ‐D i ) y are more active than their monomeric congener 2 a(T 0 ) 2 .