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首页> 外文期刊>Organometallics >Geometric Control of Carbon-Carbon Reductive Elimination from a Platinum(IV) Pincer Complex
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Geometric Control of Carbon-Carbon Reductive Elimination from a Platinum(IV) Pincer Complex

机译：Geometric Control of Carbon-Carbon Reductive Elimination from a Platinum(IV) Pincer Complex

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摘要

In five-coordinate transition metal complexes, isomerization between square-pyramidal and trigonal-bipyramidal geometries is generally assumed to be rapid relative to reactions such as reductive elimination. Herein we report a system in which two square-pyramidal isomers of the same compound, (NCN)Pt(Me)(ap)(Ph)(ba)OTf and (NCN)Pt(Ph)(ap)(Me)(ba)OTf (ap = apical, ba = basal), undergo reductive elimination to form different products. For (NCN)Pt-(Me)(ap)(Ph)(ba)OTf, methyl migration to the pincer aryl group occurs to form the sigma-agostic complex (N(C-Me)N)Pt(Ph)OTf. In contrast, reductive elimination from (NCN)Pt(Ph)(ap)(Me)(ba)OTf affords toluene and (NCN)Pt(OTf). The observation of distinct products from these isomers demonstrates that isomerization between five-coordinate structures is slower than reductive elimination. DFT studies indicate that the barriers to these C-C couplings are dominated by the need for aryl groups to adopt a "face-on" configuration during reductive elimination, the steric requirements of which are kinetically prohibitive for some pathways in this system. Although the calculated barrier to isomerization is low enough for isomerization to be rapid at room temperature as expected, the activation barriers leading to experimentally observed carbon-carbon reductive elimination products are lower still, in agreement with experiment.

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