Unusual structural and spectroscopic features of some PNP-pincer complexes of iron

Elizabeth M. Pelczar, Thomas J. Emge, Karsten Krogh-Jespersen, Alan S Goldman

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

We report a structural, spectroscopic, and computational study of two tBuPNP (2,6-bis(di-tert-butylphosphinomethyl)pyridine) complexes of iron, (tBuPNP)FeCl2 (1) and (tBuPNP)Fe(CO) 2 (3). Complex 1, (tBuPNP)FeCl2, also independently synthesized by Milstein, has unusually long iron-ligand bond distances. DFT calculations show that these are clearly attributable to its high-spin electronic structure, and in particular to occupancy of the strongly antibonding dx2-y2 orbital. The crystal structure of 3 reveals two unusual aspects. (1) The geometry around the iron atom in 3 is much closer to square pyramidal (SQP; apical CO) than to trigonal bipyramidal (TBP), although five-coordinate Fe(O) complexes are generally expected to be TBP; moreover, Chirik et al. have reported that (iPrPNP)Fe(CO)2 has essentially a perfect TBP structure (iPrPNP = 2,6-bis(di-isopropyl-phosphinomethyl)pyridine). (2) The apical carbonyl ligand in 3 deviates significantly from linearity (Fe-C-O = 171.9°). Additionally, complex 3 is intensely blue in color, which is unusual for an Fe(O) complex and also significantly different from the red color of Chirik's ( iPrTNP)Fe(CO)2 species. Results from DFT calculations reproduce and explain these structural and spectroscopic aspects as well as the contrast between 3 and its iPrPNP analogue.

Original languageEnglish
Pages (from-to)5759-5767
Number of pages9
JournalOrganometallics
Volume27
Issue number22
DOIs
Publication statusPublished - Nov 24 2008

Fingerprint

Carbon Monoxide
pyridines
Iron
iron
Discrete Fourier transforms
Ligands
Color
color
ligands
Electronic structure
linearity
Crystal structure
pyridine
analogs
electronic structure
orbitals
Atoms
crystal structure
Geometry
geometry

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

Unusual structural and spectroscopic features of some PNP-pincer complexes of iron. / Pelczar, Elizabeth M.; Emge, Thomas J.; Krogh-Jespersen, Karsten; Goldman, Alan S.

In: Organometallics, Vol. 27, No. 22, 24.11.2008, p. 5759-5767.

Research output: Contribution to journalArticle

Pelczar, Elizabeth M. ; Emge, Thomas J. ; Krogh-Jespersen, Karsten ; Goldman, Alan S. / Unusual structural and spectroscopic features of some PNP-pincer complexes of iron. In: Organometallics. 2008 ; Vol. 27, No. 22. pp. 5759-5767.
@article{d60918f9ae9648b7b467c195a9679883,
title = "Unusual structural and spectroscopic features of some PNP-pincer complexes of iron",
abstract = "We report a structural, spectroscopic, and computational study of two tBuPNP (2,6-bis(di-tert-butylphosphinomethyl)pyridine) complexes of iron, (tBuPNP)FeCl2 (1) and (tBuPNP)Fe(CO) 2 (3). Complex 1, (tBuPNP)FeCl2, also independently synthesized by Milstein, has unusually long iron-ligand bond distances. DFT calculations show that these are clearly attributable to its high-spin electronic structure, and in particular to occupancy of the strongly antibonding dx2-y2 orbital. The crystal structure of 3 reveals two unusual aspects. (1) The geometry around the iron atom in 3 is much closer to square pyramidal (SQP; apical CO) than to trigonal bipyramidal (TBP), although five-coordinate Fe(O) complexes are generally expected to be TBP; moreover, Chirik et al. have reported that (iPrPNP)Fe(CO)2 has essentially a perfect TBP structure (iPrPNP = 2,6-bis(di-isopropyl-phosphinomethyl)pyridine). (2) The apical carbonyl ligand in 3 deviates significantly from linearity (Fe-C-O = 171.9°). Additionally, complex 3 is intensely blue in color, which is unusual for an Fe(O) complex and also significantly different from the red color of Chirik's ( iPrTNP)Fe(CO)2 species. Results from DFT calculations reproduce and explain these structural and spectroscopic aspects as well as the contrast between 3 and its iPrPNP analogue.",
author = "Pelczar, {Elizabeth M.} and Emge, {Thomas J.} and Karsten Krogh-Jespersen and Goldman, {Alan S}",
year = "2008",
month = "11",
day = "24",
doi = "10.1021/om800425p",
language = "English",
volume = "27",
pages = "5759--5767",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "22",

}

TY - JOUR

T1 - Unusual structural and spectroscopic features of some PNP-pincer complexes of iron

AU - Pelczar, Elizabeth M.

AU - Emge, Thomas J.

AU - Krogh-Jespersen, Karsten

AU - Goldman, Alan S

PY - 2008/11/24

Y1 - 2008/11/24

N2 - We report a structural, spectroscopic, and computational study of two tBuPNP (2,6-bis(di-tert-butylphosphinomethyl)pyridine) complexes of iron, (tBuPNP)FeCl2 (1) and (tBuPNP)Fe(CO) 2 (3). Complex 1, (tBuPNP)FeCl2, also independently synthesized by Milstein, has unusually long iron-ligand bond distances. DFT calculations show that these are clearly attributable to its high-spin electronic structure, and in particular to occupancy of the strongly antibonding dx2-y2 orbital. The crystal structure of 3 reveals two unusual aspects. (1) The geometry around the iron atom in 3 is much closer to square pyramidal (SQP; apical CO) than to trigonal bipyramidal (TBP), although five-coordinate Fe(O) complexes are generally expected to be TBP; moreover, Chirik et al. have reported that (iPrPNP)Fe(CO)2 has essentially a perfect TBP structure (iPrPNP = 2,6-bis(di-isopropyl-phosphinomethyl)pyridine). (2) The apical carbonyl ligand in 3 deviates significantly from linearity (Fe-C-O = 171.9°). Additionally, complex 3 is intensely blue in color, which is unusual for an Fe(O) complex and also significantly different from the red color of Chirik's ( iPrTNP)Fe(CO)2 species. Results from DFT calculations reproduce and explain these structural and spectroscopic aspects as well as the contrast between 3 and its iPrPNP analogue.

AB - We report a structural, spectroscopic, and computational study of two tBuPNP (2,6-bis(di-tert-butylphosphinomethyl)pyridine) complexes of iron, (tBuPNP)FeCl2 (1) and (tBuPNP)Fe(CO) 2 (3). Complex 1, (tBuPNP)FeCl2, also independently synthesized by Milstein, has unusually long iron-ligand bond distances. DFT calculations show that these are clearly attributable to its high-spin electronic structure, and in particular to occupancy of the strongly antibonding dx2-y2 orbital. The crystal structure of 3 reveals two unusual aspects. (1) The geometry around the iron atom in 3 is much closer to square pyramidal (SQP; apical CO) than to trigonal bipyramidal (TBP), although five-coordinate Fe(O) complexes are generally expected to be TBP; moreover, Chirik et al. have reported that (iPrPNP)Fe(CO)2 has essentially a perfect TBP structure (iPrPNP = 2,6-bis(di-isopropyl-phosphinomethyl)pyridine). (2) The apical carbonyl ligand in 3 deviates significantly from linearity (Fe-C-O = 171.9°). Additionally, complex 3 is intensely blue in color, which is unusual for an Fe(O) complex and also significantly different from the red color of Chirik's ( iPrTNP)Fe(CO)2 species. Results from DFT calculations reproduce and explain these structural and spectroscopic aspects as well as the contrast between 3 and its iPrPNP analogue.

UR - http://www.scopus.com/inward/record.url?scp=57049106301&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=57049106301&partnerID=8YFLogxK

U2 - 10.1021/om800425p

DO - 10.1021/om800425p

M3 - Article

VL - 27

SP - 5759

EP - 5767

JO - Organometallics

JF - Organometallics

SN - 0276-7333

IS - 22

ER -