Publication Date:
2013-07-17
Description:
The new N -heterocyclic carbene (NHC) precursors 4, 5-dicyano-1, 3-dimesityl- ( 9 ) and 4, 5-dicyano-1, 3-dineopentyl-2-(pentafluorophenyl)imidazoline ( 14 ) were synthesized. The structure of 9 could be determined by X-ray crystallography. With the 2-pentafluorophenyl-substituted imidazolines 9 and 14 , the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO) 2 (NHC)] complexes [NHC = 4, 5-dicyano-1, 3-dimesitylimidazol-2-ylidene ( 3 ) and 4, 5-dicyano-1, 3-dineopentylimidazol-2-ylidene ( 4 )] were obtained. Crystal structures of [AgCl( 3 )] ( 15 ), [RhCl(COD)( 3 )] ( 17 ), [RhCl(COD)( 4 )] ( 18 ), and [RhCl(CO) 2 ( 3 )] ( 19 ) were solved and with the crystal data of 19 , the percent buried volume (% V bur ) of 31.8(±0.1) % was determined for NHC 3 . Infrared spectra of the imidazolines 9 and 14 and of the complexes 15 – 20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the Tolman electronic parameters of the newly obtained NHCs 3 (TEP: 2060 cm –1 ) and 4 (TEP: 2061 cm –1 ), thus proving that 1, 3-substitution of maleonitrile-NHCs does not have a significant effect for the high π-acceptor strength of these carbenes.
Print ISSN:
0044-2313
Electronic ISSN:
1521-3749
Topics:
Chemistry and Pharmacology
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