Abstract
A silica-supported triisopropylphosphine complex of Rh, prepared by phosphine-induced reductive elimination of allyl ligands, is proposed to be dimeric, on the basis of the
31
P
MAS spectrum. It reacts with H
2 to give a supported Rh hydride complex and the resulting material hydrogenates butene without hydrogenolysis.
The reaction of the silica-supported complex (SiO)(SiOX)Rh(η
3-C
3H
5)
2, where X is H or Si, with excess P
iPr
3 leads to the formation of the chemisorbed bis(phosphine) Rh(I) complex [SiORh(P
iPr
3)
2]
x
, proposed to be dimeric (
x=2) on the basis of the
31
P
MAS NMR spectrum. The phosphine complex irreversibly binds H
2 to give a hydride complex, SiORh(P
iPr
3)
2(H)
2, characterized by IR and
31
P
MAS NMR spectroscopy as well as D-exchange. The coordinatively unsaturated hydride complex is inferred to be the active site for hydrogenation of olefins under mild conditions.