(699a) The Influences of Grafting Solvent and Surface-Linking Groups On the Structure-Function Relationships of Surface Organometallic Catalysts

The Influences of Grafting Solvent
and Surface-Linking Groups on the Structure-Function Relationships of Surface
Organometallic Catalysts

Eric G. Moschetta and Robert M. Rioux^*

Department of Chemical Engineering

The Pennsylvania State University, University Park, PA 16802

^*rioux@engr.psu.edu

Surface organometallic catalysts are
synthesized to mimic their homogeneous counterparts in the hopes that they behave
with similar activity and selectivity while adding the benefit of facile
separation and recyclability. The surface-linking group can impart different
effects due to the nature of the linking atom (e.g. P, N) and the flexibility
or rigidity of the tethering backbone. A more subtle influence is present in
the form of the grafting solvent used as the medium to transfer the
organometallic species to the surface-modified support, which can alter the
structure of the organometallic species, thereby altering the nature of the
active site.

We present studies of the
hydrothiolation of thiophenol and phenylacetylene as a model reaction using
Wilkinson's catalyst (RhCl(PPh₃)₃) supported on
functionalized SBA-15 using various surface-linking groups and grafting
solvents to compare catalytic activities and selectivities. We also present
results for homogeneously catalyzed reactions using Wilkinson's catalyst in
each grafting solvent under otherwise identical hydrothiolation conditions as
the heterogeneous reactions. Additionally, we characterize the supported
catalysts using techniques such as solid-state NMR. Finally, we compare the
structures of the synthesized catalysts and use the obtained kinetic data, both
homogeneous and heterogeneous, to draw conclusions regarding the role of each
grafting solvent and the different ligand tethers on the resulting activity and
selectivity of each catalyst.