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Research in the Rosenberg group
We have focused on organophosphorus and
organosilicon chemistry, with emphasis on
homogeneous catalysis using transition metal
complexes, mechanistic aspects of P-H and Si-H
activation, catalytic hydrophosphination and
phosphine dehydrcopoupling, and the synthesis of
functionalized oligo- and polysilanes.
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Metal-mediated
P-C & P-P bond formation
We develop metal catalysts for the
efficient, selective preparation of phosphines,
which play an important role in fine chemicals
synthesis. We studied the participation of
highly reactive terminal phosphido complexes of
ruthenium in addition and substitution reactions
of the P-H bond in secondary phosphines. This Ru
system allowed us to probe "outer-sphere"
mechanisms of catalytic hydrophosphination in
great detail, identifying critical features for
the design of more active catalysts. A "next generation" catalyst based on
Co shows unusually broad phosphine substrate
scope in hydrophosphination and also catalyzes
the dehydrogenative coupling of primary and
secondary phosphines, apparently via a new,
metal-ligand cooperative P-H activation step.
Our recent investigation of the possible role of
electrophilic Mo phosphenium complexes in P-H
activation chemistry has introduced umpolung
into both hydrophosphination and phosphine
dehydrocoupling, widening unsaturated substrate
scope in the former and providing high, room
temperature activity in the latter.
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Synthetic
routes to functionalized oligosilanes
Methods abound for the
construction of organic molecules containing new
C-C bonds, but synthetic strategies for
incorporating Si-Si bonds are not nearly so well
established. We can use metal catalysts to make
organosilicon reagents of variable chain length,
and then selectively incorporate new side chains
via residual Si-H bonds using a Lewis acidic
borane catalyst. We have explored the scope of
these strategies in the production of new
reagents and polymers based on silicon. Recently
we also discovered a new thermolytic method for
converting linear polysilanes to novel
polysilyne materials.
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