Structural and reactivity studies of "pincer" pyridine dicarbene complexes of Fe-0: Experimental and computational comparison of the phosphine and NHC donors

Andreas A. Danopoulos, D. Pugh, Hayley Smith, Jorg Sassmannshausen

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Abstract

Pincer carbene complexes: Comparison of the electronic structures of pincer Fe0 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. Reduction of [Fe(C-N-C)(Br)2] or [Fe(C-NMe-C)(I)2] with Na/Hg under N2 gave the Fe0 complexes [Fe(C-N-C)(N2)2] and [Fe(C-NMe-C)(N2)2] for which C-N-C=2,6-bis(arylimidazol-2-ylidene)-pyridine, C-NMe-C=2,6-bis(arylimidazol-2-ylidene)-3,5-dimethyl-pyridine and aryl=2,6-iPr2C6H3. Substitution of the coordinated N2 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-NMe-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-NMe-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 Fe0 to CO backbonding in [Fe(C-N-C)(CO)2] and [Fe(C-NMe-C)(CO)2] compared to [Fe(P-N-P)(CO)2] is accounted for by backbonding from the FeNpyridine 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)(N2)2] in the presence of benzaldehyde phenylimine gave an ortho-metalated benzaldehyde phenylimine. The FeII 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 CO2 with [Fe(C-N-C)(N2)2].
LanguageEnglish
Pages5491-5502
Number of pages11
JournalChemistry - A European Journal
Volume15
Issue number22
DOIs
Publication statusPublished - 2009

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phosphine
Carbon Monoxide
pyridine

Keywords

  • density functional calculations
  • heterocyclic carbenes
  • iron
  • phosphanes
  • pincer complexes

Cite this

@article{b6851ee36ef94efabc89b32567a32e9f,
title = "Structural and reactivity studies of {"}pincer{"} pyridine dicarbene complexes of Fe-0: Experimental and computational comparison of the phosphine and NHC donors",
abstract = "Pincer carbene complexes: Comparison of the electronic structures of pincer Fe0 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. Reduction of [Fe(C-N-C)(Br)2] or [Fe(C-NMe-C)(I)2] with Na/Hg under N2 gave the Fe0 complexes [Fe(C-N-C)(N2)2] and [Fe(C-NMe-C)(N2)2] for which C-N-C=2,6-bis(arylimidazol-2-ylidene)-pyridine, C-NMe-C=2,6-bis(arylimidazol-2-ylidene)-3,5-dimethyl-pyridine and aryl=2,6-iPr2C6H3. Substitution of the coordinated N2 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-NMe-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-NMe-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 Fe0 to CO backbonding in [Fe(C-N-C)(CO)2] and [Fe(C-NMe-C)(CO)2] compared to [Fe(P-N-P)(CO)2] is accounted for by backbonding from the FeNpyridine 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)(N2)2] in the presence of benzaldehyde phenylimine gave an ortho-metalated benzaldehyde phenylimine. The FeII 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 CO2 with [Fe(C-N-C)(N2)2].",
keywords = "density functional calculations, heterocyclic carbenes, iron, phosphanes, pincer complexes",
author = "Danopoulos, {Andreas A.} and D. Pugh and Hayley Smith and Jorg Sassmannshausen",
year = "2009",
doi = "10.1002/chem.200900027",
language = "English",
volume = "15",
pages = "5491--5502",
journal = "Chemistry - A European Journal",
issn = "0947-6539",
number = "22",

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Structural and reactivity studies of "pincer" pyridine dicarbene complexes of Fe-0: Experimental and computational comparison of the phosphine and NHC donors. / Danopoulos, Andreas A.; Pugh, D.; Smith, Hayley; Sassmannshausen, Jorg.

In: Chemistry - A European Journal, Vol. 15, No. 22, 2009, p. 5491-5502.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Structural and reactivity studies of "pincer" pyridine dicarbene complexes of Fe-0: Experimental and computational comparison of the phosphine and NHC donors

AU - Danopoulos, Andreas A.

AU - Pugh, D.

AU - Smith, Hayley

AU - Sassmannshausen, Jorg

PY - 2009

Y1 - 2009

N2 - Pincer carbene complexes: Comparison of the electronic structures of pincer Fe0 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. Reduction of [Fe(C-N-C)(Br)2] or [Fe(C-NMe-C)(I)2] with Na/Hg under N2 gave the Fe0 complexes [Fe(C-N-C)(N2)2] and [Fe(C-NMe-C)(N2)2] for which C-N-C=2,6-bis(arylimidazol-2-ylidene)-pyridine, C-NMe-C=2,6-bis(arylimidazol-2-ylidene)-3,5-dimethyl-pyridine and aryl=2,6-iPr2C6H3. Substitution of the coordinated N2 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-NMe-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-NMe-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 Fe0 to CO backbonding in [Fe(C-N-C)(CO)2] and [Fe(C-NMe-C)(CO)2] compared to [Fe(P-N-P)(CO)2] is accounted for by backbonding from the FeNpyridine 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)(N2)2] in the presence of benzaldehyde phenylimine gave an ortho-metalated benzaldehyde phenylimine. The FeII 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 CO2 with [Fe(C-N-C)(N2)2].

AB - Pincer carbene complexes: Comparison of the electronic structures of pincer Fe0 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. Reduction of [Fe(C-N-C)(Br)2] or [Fe(C-NMe-C)(I)2] with Na/Hg under N2 gave the Fe0 complexes [Fe(C-N-C)(N2)2] and [Fe(C-NMe-C)(N2)2] for which C-N-C=2,6-bis(arylimidazol-2-ylidene)-pyridine, C-NMe-C=2,6-bis(arylimidazol-2-ylidene)-3,5-dimethyl-pyridine and aryl=2,6-iPr2C6H3. Substitution of the coordinated N2 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-NMe-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-NMe-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 Fe0 to CO backbonding in [Fe(C-N-C)(CO)2] and [Fe(C-NMe-C)(CO)2] compared to [Fe(P-N-P)(CO)2] is accounted for by backbonding from the FeNpyridine 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)(N2)2] in the presence of benzaldehyde phenylimine gave an ortho-metalated benzaldehyde phenylimine. The FeII 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 CO2 with [Fe(C-N-C)(N2)2].

KW - density functional calculations

KW - heterocyclic carbenes

KW - iron

KW - phosphanes

KW - pincer complexes

UR - http://dx.doi.org/10.1002/chem.200900027

U2 - 10.1002/chem.200900027

DO - 10.1002/chem.200900027

M3 - Article

VL - 15

SP - 5491

EP - 5502

JO - Chemistry - A European Journal

T2 - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 22

ER -