TOWARD SILICON METATHESIS

ORGANOMETALLICS: Chemists accomplish essential steps in quest regarding a silicon form of classic synthesis

METATHESIS REACTIONS with regard to making compounds that include carbon-carbon multiple bonds are one of by far the most vital sets of processes in the chemical industry. The alkene or alkyne products are extensively made use of, regarding instance, in polymerizations to produce plastics.

Chemists have already been interested in extending metathesis methods to carbon??s heavier analogs, which include silicon, which one particular day could result in new varieties of polymeric supplies. The holdup has been the lack of suitable silicon precursors. A analysis group led by Vladimir Ya. Lee and Akira Sekiguchi from the University of Tsukuba, in Japan, has now cleared that hurdle ( J. Am.Chem. Soc., DOI: 10.1021/ja401072j ).

To produce their precursors, they coupled a bicyclic tetrasilicon molecule to titanocene dichloride to type a Ti=Si complex known as a silylene. This species is actually a heavy analog with the alkylidene metal complexes that happen to be catalysts for alkene and alkyne metathesis reactions.

When they tried mimicking alkyne metathesis by having an alkyne to their silylene, the researchers generated a silicon analog on the key cyclobutane metathesis intermediate intended for the very first time.

With regard to now, this cyclic silicon compound is often a "frozen" intermediate on the metathesis procedure, Sekiguchi explains. That's since the team hasn't figured out exactly ways to prompt the intermediate to finish the catalytic cycle and shed the final product, he states. This molecule would be a Ti=C-CC=Si species, which may possibly possibly react additional with an alkene to kind a new sort of a single,3-diene having a C=C-CC=Si core.


"That is a substantial report, in that it gives direct observation of the [2 2] cycloaddition involving a silylene complex with an alkyne," says T. Don Tilley of the University of California, Berkeley. Tilley's group has reported the opne other instance of the silylene cycloaddition, which involved a ruthenium silylene along with a nonmetathesis mechanism.

"This sort of reaction has long been postulated regarding metal-mediated silylene-transfer reactions," Tilley adds. "It's good to see a well-characterized instance." Sekiguchi is optimistic in regards to the prospects of working with the strategy to make heavy alkenes and dienes containing silicon, or perhaps extending the strategy a single row lower on the periodic table to germanium. -STEVE RITTER

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