N-Heterocyclic Carbene Complexes of Three- and Four-Coordinate Fe(I)

Ohki, Yasuhiro; Hoshino, Ryoko; Tatsumi, Kazuyuki

doi:10.1021/acs.organomet.5b01025

Cited by 15 publications

(5 citation statements)

References 81 publications

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“…2 ), anisotropic EPR signals are observed at around g =2, but no EPR signal is seen at around g =4, suggesting S =1/2. Reproducible EPR signals at g =2.6 and 2.2 are attributable to the EPR of 1 , which are similar to the previous EPR spectra observed for the low-spin iron(I) complexes with a square-planar geometry 30 . The complex 1 has a solution magnetic moment of 3.0±0.2 μ B at 298 K. The measured magnetic moment is larger than spin-only value for an S =1/2 spin state (1.73 μ B ), but still within the range of the reported low-spin square-planar iron(I) compounds 30 31 .…”

Section: Resultssupporting

confidence: 86%

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

et al. 2016

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Synthesis and reactivity of iron-dinitrogen complexes have been extensively studied, because the iron atom plays an important role in the industrial and biological nitrogen fixation. As a result, iron-catalyzed reduction of molecular dinitrogen into ammonia has recently been achieved. Here we show that an iron-dinitrogen complex bearing an anionic PNP-pincer ligand works as an effective catalyst towards the catalytic nitrogen fixation, where a mixture of ammonia and hydrazine is produced. In the present reaction system, molecular dinitrogen is catalytically and directly converted into hydrazine by using transition metal-dinitrogen complexes as catalysts. Because hydrazine is considered as a key intermediate in the nitrogen fixation in nitrogenase, the findings described in this paper provide an opportunity to elucidate the reaction mechanism in nitrogenase.

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Section: Resultssupporting

confidence: 86%

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

et al. 2016

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“…To further characterize compound 10 , we recorded its X-band EPR spectrum as a 2-Methf glass at 50 K (Figure ). As expected, the compound displayed a signal centered near g = 2 consistent with low-spin Fe(I) ( S = 1/2). − The signal appears to be axial with rich superhyperfine coupling and is markedly different than that reported for [Fe(N 2 )( t Bu PNP)] …”

Section: Resultsmentioning

confidence: 54%

A Pyrrole-Based Pincer Ligand Permits Access to Three Oxidation States of Iron in Organometallic Complexes

2017

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Treatment of FeCl2(thf)1.5 with the sodium salt of bis(dicyclohexylphosphinomethyl)pyrrole (NaCyPNP) in the presence of pyridine (py) affords the high-spin, five-coordinate iron(II) complex [FeCl(py)(CyPNP)]. The chloride complex serves as a starting point for a variety of organometallic iron(II) compounds including S = 1 square planar alkyls, [FeR(CyPNP)] (R = Me, Et, Bn, Ph). Treatment of [FeCl(py)(CyPNP)] with NaBEt3H does not generate an analogous square-planar hydride complex, but rather a bimetallic high-spin iron(II) species containing bridging hydride ligands. Analogous transmetalation reactions in the presence of carbon monoxide produced six-coordinate low-spin species [FeR(CO)2(CyPNP)] (R = Et, Ph, and H). Reduction of [FeCl(py)(CyPNP)] under CO afforded the low-spin iron(I) carbonyl complex [Fe(CO)2(CyPNP)]. This species could be further reduced with KC8 to afford the anionic iron(0) complex K[Fe(CO)2(CyPNP)]·thf. The breadth of coordination numbers, spin states, and valencies supported by this pyrrole-based PNP ligand demonstrates the flexibility afforded by this pincer framework.

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“…The Fe-C(carbene) distances (2.087(3) in average)i n1 are typical for high-spini ron(I)-NHC complexes. [11,14] Consistent with this, the fitting isomer shift (d = 0.54 mm s À1 )o fthe 57 Fe Mçssbauer spectrum of 1 and its measured magnetic moment However,l ow-energy N-N stretching vibrations (1967 cm À1 ,F igure S6, Supporting Information) are observedi nt he IR spectrum of 1,i mplying strong N 2 activation. For comparison, the IR frequency is significantly lower than those of the low-spin iron(I) complexes [((2-Ph 2 PC 6 H 4 ) 3 Si)Fe(N 2 )] (2041 cm À1 ), [15] [((Cy 2 PCH 2 CH 2 ) 3 P)Fe(N 2 )] [BPh 4 ]( 2059 cm À1 ), [16] and [(THF) 2 MgCl(m-H)(m-(N)-PNP)Fe(N 2 )] (2084 cm À1 ), [17] and is comparable to that of Harman's iron(I)-N 2 [(Tp Ad,Me )Fe(N 2 )] (1959 cm À1 ).…”

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confidence: 69%

High‐Spin Iron(I) and Iron(0) Dinitrogen Complexes Supported by N‐Heterocyclic Carbene Ligands

Ouyang

Cheng

Bao

et al. 2016

Chemistry A European J

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The use of 1,3-dicyclohexylimidazol-2-ylidene (ICy) as ligand has enabled the preparation of the high-spin tetrahedral iron(I)- and iron(0)-N2 complexes, namely [(ICy)3 Fe(N2 )][BPh4 ] (1) and [(ICy)3 Fe(N2 )] (2), the electronic structures of which have been established by various spectroscopic characterization and DFT calculations. The frequency of the N-N stretching resonance of the iron(0)-N2 complex is the lowest among the reported terminal N2 complexes of iron, signifying the beneficial roles of strongly σ-donating ligands in combination with the high-spin low-valent iron center in promoting N2 -activation. The iron(0)-N2 complex can convert reversibly to the low-spin iron(II)-N2 hydride complex [(ICy)2 (ICy')Fe(N2 )(H)] (4).

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N-Heterocyclic Carbene Complexes of Three- and Four-Coordinate Fe(I)

Cited by 15 publications

References 81 publications

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

Catalytic transformation of dinitrogen into ammonia and hydrazine by iron-dinitrogen complexes bearing pincer ligand

A Pyrrole-Based Pincer Ligand Permits Access to Three Oxidation States of Iron in Organometallic Complexes

High‐Spin Iron(I) and Iron(0) Dinitrogen Complexes Supported by N‐Heterocyclic Carbene Ligands

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