A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover

Daniel L. Reger; Christine A. Little; Arnold L. Rheingold; Matthew Lam; Louise M. Liable-Sands; Brian Rhagitan; Thomas E. Concolino; Amitabh Mohan; Gary J. Long; Valérie Briois; Fernande Grandjean

doi:10.1021/ic001102t

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover

Daniel L. Reger
, Christine A. Little
, Arnold L. Rheingold
, Matthew Lam
, Louise M. Liable-Sands
, Brian Rhagitan
, Thomas E. Concolino
, Amitabh Mohan
, Gary J. Long
, Valérie Briois
, Fernande Grandjean

Chemistry

Research output: Contribution to journal › Article › peer-review

Abstract

The complexes {Fe[HC(3,5-Me ₂ pz) ₃ ] ₂ } (BF ₄ ) ₂ (1), {Fe[HC(pz) ₃ ] ₂ }(BF ₄ ) ₂ (2), and {Fe[PhC(pz) ₂ (py)] ₂ }(BF ₄ ) ₂ (3) (pz = 1-pyrazolyl ring, py = pyridyl ring) have been synthesized by the reaction of the appropriate ligand with Fe(BF ₄ ) ₂ ·6H ₂ O. Complex 1 is high-spin in the solid state and in solution at 298 K. In the solid phase, it undergoes a decrease in magnetic moment at lower temperatures, changing at ca. 206 K to a mixture of high-spin and low-spin forms, a spin-state mixture that does not change upon subsequent cooling to 5 K. Crystallographically, there is only one iron(II) site in the ambient-temperature solid-state structure, a structure that clearly shows the complex is high-spin. Mössbauer spectral studies show conclusively that the magnetic moment change observed at lower temperatures arises from the complex changing from a high-spin state at higher temperatures to a 50:50 mixture of high-spin and low-spin states at lower temperatures. Complexes 2 and 3 are low-spin in the solid phase at room temperature. Complex 2 in the solid phase gradually changes over to the high-spin state upon heating above 295 K and is completely high-spin at ca. 470 K. In solution, variable-temperature ¹ H NMR spectra of 2 show both high-spin and low-spin forms are present, with the percentage of the paramagnetic form increasing as the temperature increases. Complex 3 is low-spin at all temperatures studied in both the solid phase and solution. An X-ray absorption spectral study has been undertaken to investigate the electronic spin states of {Fe[HC(3,5-Me ₂ pz) ₃ ] ₂ } (BF ₄ ) ₂ and {Fe[HC(pz) ₃ ] ₂ }(BF ₄ ) ₂ . Crystallographic information: 2 is monoclinic, P2 ₁ /n, a = 10.1891(2) Å, b = 7.6223(2) Å, c = 17.2411(4) Å, ß = 100.7733(12)°, Z = 2; 3 is triclinic, P1 ^- , a = 12.4769(2) Å, b = 12.7449(2) Å, c = 13.0215(2) Å, α = 83.0105(8)°, ß = 84.5554(7)°, γ = 62.5797(2)°, Z = 2.

Original language	American English
Journal	Inorganic Chemistry
Volume	40
DOIs	https://doi.org/10.1021/ic001102t
State	Published - Feb 1 2001

Keywords

Iron Complex
Methane
Pyrazole Derivative
Pyridine Derivative
Chemical Reaction
Chemical Structure
Complex Formation
Crystallography
Magnetism
Reaction Analysis
Rotation
Spectroscopy
Synthesis
Temperature Sensitivity
X Ray Spectrometry
Ferrous Compounds
Molecular Structure
Pyrazoles
Spectrum Analysis

Disciplines

Chemistry

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https://doi.org/10.1021/ic001102t

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Reger, D. L., Little, C. A., Rheingold, A. L., Lam, M., Liable-Sands, L. M., Rhagitan, B., Concolino, T. E., Mohan, A., Long, G. J., Briois, V., & Grandjean, F. (2001). A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover. Inorganic Chemistry, 40. https://doi.org/10.1021/ic001102t

Reger, DL, Little, CA, Rheingold, AL, Lam, M, Liable-Sands, LM, Rhagitan, B, Concolino, TE, Mohan, A, Long, GJ, Briois, V & Grandjean, F 2001, 'A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover', Inorganic Chemistry, vol. 40. https://doi.org/10.1021/ic001102t

@article{53b646c0aa2f4743a1fe746246194604,

title = "A Synthetic, Structural, Magnetic, and Spectral Study of Several \{Fe[tris(pyrazolyl)methane]₂\}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover",

abstract = " The complexes \{Fe[HC(3,5-Me 2 pz) 3 ] 2 \} (BF 4 ) 2 (1), \{Fe[HC(pz) 3 ] 2 \}(BF 4 ) 2 (2), and \{Fe[PhC(pz) 2 (py)] 2 \}(BF 4 ) 2 (3) (pz = 1-pyrazolyl ring, py = pyridyl ring) have been synthesized by the reaction of the appropriate ligand with Fe(BF 4 ) 2 ·6H 2 O. Complex 1 is high-spin in the solid state and in solution at 298 K. In the solid phase, it undergoes a decrease in magnetic moment at lower temperatures, changing at ca. 206 K to a mixture of high-spin and low-spin forms, a spin-state mixture that does not change upon subsequent cooling to 5 K. Crystallographically, there is only one iron(II) site in the ambient-temperature solid-state structure, a structure that clearly shows the complex is high-spin. M{\"o}ssbauer spectral studies show conclusively that the magnetic moment change observed at lower temperatures arises from the complex changing from a high-spin state at higher temperatures to a 50:50 mixture of high-spin and low-spin states at lower temperatures. Complexes 2 and 3 are low-spin in the solid phase at room temperature. Complex 2 in the solid phase gradually changes over to the high-spin state upon heating above 295 K and is completely high-spin at ca. 470 K. In solution, variable-temperature 1 H NMR spectra of 2 show both high-spin and low-spin forms are present, with the percentage of the paramagnetic form increasing as the temperature increases. Complex 3 is low-spin at all temperatures studied in both the solid phase and solution. An X-ray absorption spectral study has been undertaken to investigate the electronic spin states of \{Fe[HC(3,5-Me 2 pz) 3 ] 2 \} (BF 4 ) 2 and \{Fe[HC(pz) 3 ] 2 \}(BF 4 ) 2 . Crystallographic information: 2 is monoclinic, P2 1 /n, a = 10.1891(2) {\AA}, b = 7.6223(2) {\AA}, c = 17.2411(4) {\AA}, {\ss} = 100.7733(12)°, Z = 2; 3 is triclinic, P1 - , a = 12.4769(2) {\AA}, b = 12.7449(2) {\AA}, c = 13.0215(2) {\AA}, α = 83.0105(8)°, {\ss} = 84.5554(7)°, γ = 62.5797(2)°, Z = 2.",

keywords = "Iron Complex, Methane, Pyrazole Derivative, Pyridine Derivative, Chemical Reaction, Chemical Structure, Complex Formation, Crystallography, Magnetism, Reaction Analysis, Rotation, Spectroscopy, Synthesis, Temperature Sensitivity, X Ray Spectrometry, Ferrous Compounds, Molecular Structure, Pyrazoles, Spectrum Analysis",

author = "Reger, \{Daniel L.\} and Little, \{Christine A.\} and Rheingold, \{Arnold L.\} and Matthew Lam and Liable-Sands, \{Louise M.\} and Brian Rhagitan and Concolino, \{Thomas E.\} and Amitabh Mohan and Long, \{Gary J.\} and Val{\'e}rie Briois and Fernande Grandjean",

year = "2001",

month = feb,

day = "1",

doi = "10.1021/ic001102t",

language = "American English",

volume = "40",

journal = "Inorganic Chemistry",

}

TY - JOUR

T1 - A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover

AU - Reger, Daniel L.

AU - Little, Christine A.

AU - Rheingold, Arnold L.

AU - Lam, Matthew

AU - Liable-Sands, Louise M.

AU - Rhagitan, Brian

AU - Concolino, Thomas E.

AU - Mohan, Amitabh

AU - Long, Gary J.

AU - Briois, Valérie

AU - Grandjean, Fernande

PY - 2001/2/1

Y1 - 2001/2/1

N2 - The complexes {Fe[HC(3,5-Me 2 pz) 3 ] 2 } (BF 4 ) 2 (1), {Fe[HC(pz) 3 ] 2 }(BF 4 ) 2 (2), and {Fe[PhC(pz) 2 (py)] 2 }(BF 4 ) 2 (3) (pz = 1-pyrazolyl ring, py = pyridyl ring) have been synthesized by the reaction of the appropriate ligand with Fe(BF 4 ) 2 ·6H 2 O. Complex 1 is high-spin in the solid state and in solution at 298 K. In the solid phase, it undergoes a decrease in magnetic moment at lower temperatures, changing at ca. 206 K to a mixture of high-spin and low-spin forms, a spin-state mixture that does not change upon subsequent cooling to 5 K. Crystallographically, there is only one iron(II) site in the ambient-temperature solid-state structure, a structure that clearly shows the complex is high-spin. Mössbauer spectral studies show conclusively that the magnetic moment change observed at lower temperatures arises from the complex changing from a high-spin state at higher temperatures to a 50:50 mixture of high-spin and low-spin states at lower temperatures. Complexes 2 and 3 are low-spin in the solid phase at room temperature. Complex 2 in the solid phase gradually changes over to the high-spin state upon heating above 295 K and is completely high-spin at ca. 470 K. In solution, variable-temperature 1 H NMR spectra of 2 show both high-spin and low-spin forms are present, with the percentage of the paramagnetic form increasing as the temperature increases. Complex 3 is low-spin at all temperatures studied in both the solid phase and solution. An X-ray absorption spectral study has been undertaken to investigate the electronic spin states of {Fe[HC(3,5-Me 2 pz) 3 ] 2 } (BF 4 ) 2 and {Fe[HC(pz) 3 ] 2 }(BF 4 ) 2 . Crystallographic information: 2 is monoclinic, P2 1 /n, a = 10.1891(2) Å, b = 7.6223(2) Å, c = 17.2411(4) Å, ß = 100.7733(12)°, Z = 2; 3 is triclinic, P1 - , a = 12.4769(2) Å, b = 12.7449(2) Å, c = 13.0215(2) Å, α = 83.0105(8)°, ß = 84.5554(7)°, γ = 62.5797(2)°, Z = 2.

AB - The complexes {Fe[HC(3,5-Me 2 pz) 3 ] 2 } (BF 4 ) 2 (1), {Fe[HC(pz) 3 ] 2 }(BF 4 ) 2 (2), and {Fe[PhC(pz) 2 (py)] 2 }(BF 4 ) 2 (3) (pz = 1-pyrazolyl ring, py = pyridyl ring) have been synthesized by the reaction of the appropriate ligand with Fe(BF 4 ) 2 ·6H 2 O. Complex 1 is high-spin in the solid state and in solution at 298 K. In the solid phase, it undergoes a decrease in magnetic moment at lower temperatures, changing at ca. 206 K to a mixture of high-spin and low-spin forms, a spin-state mixture that does not change upon subsequent cooling to 5 K. Crystallographically, there is only one iron(II) site in the ambient-temperature solid-state structure, a structure that clearly shows the complex is high-spin. Mössbauer spectral studies show conclusively that the magnetic moment change observed at lower temperatures arises from the complex changing from a high-spin state at higher temperatures to a 50:50 mixture of high-spin and low-spin states at lower temperatures. Complexes 2 and 3 are low-spin in the solid phase at room temperature. Complex 2 in the solid phase gradually changes over to the high-spin state upon heating above 295 K and is completely high-spin at ca. 470 K. In solution, variable-temperature 1 H NMR spectra of 2 show both high-spin and low-spin forms are present, with the percentage of the paramagnetic form increasing as the temperature increases. Complex 3 is low-spin at all temperatures studied in both the solid phase and solution. An X-ray absorption spectral study has been undertaken to investigate the electronic spin states of {Fe[HC(3,5-Me 2 pz) 3 ] 2 } (BF 4 ) 2 and {Fe[HC(pz) 3 ] 2 }(BF 4 ) 2 . Crystallographic information: 2 is monoclinic, P2 1 /n, a = 10.1891(2) Å, b = 7.6223(2) Å, c = 17.2411(4) Å, ß = 100.7733(12)°, Z = 2; 3 is triclinic, P1 - , a = 12.4769(2) Å, b = 12.7449(2) Å, c = 13.0215(2) Å, α = 83.0105(8)°, ß = 84.5554(7)°, γ = 62.5797(2)°, Z = 2.

KW - Iron Complex

KW - Methane

KW - Pyrazole Derivative

KW - Pyridine Derivative

KW - Chemical Reaction

KW - Chemical Structure

KW - Complex Formation

KW - Crystallography

KW - Magnetism

KW - Reaction Analysis

KW - Rotation

KW - Spectroscopy

KW - Synthesis

KW - Temperature Sensitivity

KW - X Ray Spectrometry

KW - Ferrous Compounds

KW - Molecular Structure

KW - Pyrazoles

KW - Spectrum Analysis

UR - https://scholarsmine.mst.edu/chem_facwork/753

UR - https://doi.org/10.1021/ic001102t

U2 - 10.1021/ic001102t

DO - 10.1021/ic001102t

M3 - Article

C2 - 11261958

VL - 40

JO - Inorganic Chemistry

JF - Inorganic Chemistry

ER -

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]₂}(BF₄)₂ Complexes: Observation of an Unusual Spin-State Crossover

Abstract

Keywords

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