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Carbene−Pnictinidene Adducts

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journal contribution
posted on 07.05.1997, 00:00 by Anthony J. Arduengo, Joseph C. Calabrese, Alan H. Cowley, H. V. Rasika Dias, Jens R. Goerlich, William J. Marshall, Bernhard Riegel
The syntheses, characterizations, and X-ray crystallographic structure determinations are described for adducts of stable nucleophilic carbenes with pnictinidenes. The adducts between 1,3-dimesitylimidazol-2-ylidene and phenylphosphinidene, phenylarsinidene, (trifluoromethyl)phosphinidene, and (pentafluorophenyl)arsinidene are reported. These carbene−pnictinidene adducts are formed by the direct reaction of a stable nucleophilic carbene with the corresponding pnictinidene cyclic oligomers. The synthesis and structure of the adduct between 1,3-dimesitylimidazolin-2-ylidene and phenylphosphinidene from the reaction of 1,3-dimesitylimidazolin-2-ylidene with phenylphosphorus dichloride are also reported. These carbene−pnictinidene adducts possess strongly polarized pnictinidene−carbene bonds. The C−Pn−C angles are all typically small at 97−102°, and there is only a 4% shortening of the nominal PnC double bond compared to the Pn−C single bond to the second substituent on the pnictogen. The 31P NMR shifts of the phosphorus adducts suggest strongly shielded phosphorus centers in accord with the polarized structures.

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