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A bridge to somewhere: A series of pyridine dicarbene iridium “pincer” complexes is easily accessible when pyridine ring metalation is suppressed by methyl substitution (see structure; NHC=N-heterocyclic carbene). A new bridging binding mode of the imidazol-2-ylidene heterocycle, involving η2-alkene-like coordination, has been observed crystallographically.
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Danopoulos et al. (2008) studied this question.
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