Convergent Synthesis of a Metal–Organic Framework Supported Olefin Metathesis Catalyst

Synthesis
of a metal–organic framework (MOF)-supported olefin
metathesis catalyst has been accomplished for the first time following
a new, convergent approach where an aldehyde-functionalized derivative
of Hoveyda’s recently reported ruthenium catecholate olefin
metathesis catalyst is condensed with an amine-functionalized IRMOF-74-III.
The resulting material, denoted MOF-Ru, has well-defined, catalytically active ruthenium centers
confined within channels having a ca. 20 Å diameter. MOF-Ru is
a recyclable, single-site catalyst for self-cross-metathesis and ring-closing
metathesis of terminal olefins. Comparison of this heterogeneous catalyst
with a homogeneous analogue shows different responses to substrate
size and shape suggestive of confinement effects. The MOF-Ru catalyst
also displays greater resistance to double-bond migration that can
be attributed to greater catalyst stability. For the preparation of
well-defined, single-site heterogeneous catalysts where catalyst purity
is essential, the convergent approach employed here, where the catalytic
center is prepared ex situ and covalently linked to an intact MOF,
offers an attractive alternative to in situ catalyst preparation as
currently practiced in MOF chemistry.