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 language | English |
|---|---|
| Pages (from-to) | 5759-5767 |
| Number of pages | 9 |
| Journal | Organometallics |
| Volume | 27 |
| Issue number | 22 |
| DOIs | |
| Publication status | Published - Nov 24 2008 |
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ASJC Scopus subject areas
- Organic Chemistry
- Physical and Theoretical Chemistry
- Inorganic Chemistry
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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 journal › Article
}
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.
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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 -