In:
Chemistry – A European Journal, Wiley, Vol. 15, No. 22 ( 2009-05-25), p. 5491-5502
Abstract:
Pincer carbene complexes : Comparison of the electronic structures of “pincer” Fe 0 pyridine bis(imidazol‐2‐ylidene) and pyridine diphosphine dicarbonyl complexes (see figure) show subtle differences that account for observed spectroscopic trends. Intermolecular CH activation has been observed in Fe pyridine dicarbene complexes. magnified image Reduction of [Fe(C‐ N ‐C)(Br) 2 ] or [Fe(C‐N Me ‐C)(I) 2 ] with Na/Hg under N 2 gave the Fe 0 complexes [Fe(C‐ N ‐C)(N 2 ) 2 ] and [Fe(C‐N Me ‐C)(N 2 ) 2 ] for which C‐ N ‐C=2,6‐bis(arylimidazol‐2‐ylidene)‐pyridine, C‐N Me ‐C=2,6‐bis(arylimidazol‐2‐ylidene)‐3,5‐dimethyl‐pyridine and aryl=2,6‐ i Pr 2 C 6 H 3 . Substitution of the coordinated N 2 by CO or CN(2,6‐xyl), xyl=2,6‐dimethylphenyl, took place readily to afford [Fe(C‐ N ‐C)(L) 2 ] and [Fe(C‐N Me ‐C)(L) 2 ], L=CO or CN(2,6‐xyl). The electronic characteristics of the N‐heterocyclic carbene and phosphine donors in the complexes [Fe(C‐ N ‐C)(CO) 2 ], [Fe(C‐N Me ‐C)(CO) 2 ] and [Fe(P‐ N ‐P)(CO) 2 ], P‐ N ‐P=2,6‐bis(di‐ tert ‐butylphosphinomethyl)‐pyridine, have been evaluated by spectroscopic, structural and computational methods. The unexpected reduced Fe 0 to CO backbonding in [Fe(C‐ N ‐C)(CO) 2 ] and [Fe(C‐N Me ‐C)(CO) 2 ] compared to [Fe(P‐ N ‐P)(CO) 2 ] is accounted for by backbonding from the FeN pyridine bond in the imidazol‐2‐ylidene complexes. Reduction of [Fe(C‐ N ‐C)(Br) 2 ] under Ar gave mixtures from which a complex with a metalated pyridine and a dangling imidazolium group was isolated. Photolysis of [Fe(C‐ N ‐C)(N 2 ) 2 ] in the presence of benzaldehyde phenylimine gave an ortho ‐metalated benzaldehyde phenylimine. The Fe II complex [Fe(C‐ N ‐C)(CO)(Br) 2 ] was prepared by the reaction of [Fe(C‐ N ‐C)(Br) 2 ] with CO or reduction of CO 2 with [Fe(C‐ N ‐C)(N 2 ) 2 ].
Type of Medium:
Online Resource
ISSN:
0947-6539
,
1521-3765
DOI:
10.1002/chem.200900027
Language:
English
Publisher:
Wiley
Publication Date:
2009
detail.hit.zdb_id:
1478547-X
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