Computing ligand field potentials and relative energies of d orbitals: A simple general approach

Krishnamurthy, R.; Schaap, Ward B.

doi:10.1021/ed046p799

Cited by 98 publications

(62 citation statements)

References 7 publications

(14 reference statements)

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“…The cis ‐N–Fe–N bond angles are evidence for a distorted octahedral arrangement, but the magnitude of the prismatic distortion expressed by the value Σ is smaller than the similar non‐methylated compound 4 (Table 3). 14 The distance from the methyl carbon to the nearest nitrogen of the adjacent pyridine ring is similar to the value found in the structure of 8 in LS state; it is equal to ca. 3.030 Å.…”

Section: Crystal Structures Of 1–5supporting

confidence: 77%

“…According to Gillum et al,13 pronounced M d –L π * ‐back‐bonding (confirmed by IR and UV/Vis spectroscopy, vide infra) can decrease the bond order of the C=N group by decreasing the rotational barrier of the bond, which explains the observed deviation. This is caused by the strong tendency of LS Fe II to form an energetically favorable pseudo‐octahedral arrangement of donor atoms,14 but this competes with the rigidity of the ligand, which prefers trigonal prismatic conformation.…”

Section: Crystal Structures Of 1–5mentioning

confidence: 99%

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Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Seredyuk

Gaspar

Kusz

et al. 2011

Zeitschrift anorg allge chemie

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The synthesis and characterization of a series of mononuclear tripodand‐based FeII complexes by means of Mössbauer andUV/Vis spectroscopic as well as magnetic methods is reported. The complexes were obtained from the reactions of FeII salt with heterocyclic aldehydes (imd = imidazole‐4(5)‐carboxaldehyde, py = picolinaldehyde, or 6‐Mepy = 6‐methylpicolinaldehyde) and a symmetric triamine [tren = tris(2‐aminoethyl)amine, tame = 2,2,2‐tris(aminomethyl)ethane, or tach = 1,3,5‐cis,cis‐cyclohexanetriamin]. Because of extreme rigidity of the capping triamine tach, the molecular structure of {Fe[tach(imd)3](BF4)2} (1) features an unprecedented tapered trigonal prismatic FeN6 polyhedron. The molecular structures of the complexes {Fe[tach(py)3](ClO4)2} (2), {Fe[tame(imd)3](ClO4)2} (3), {Fe[tame(py)3](ClO4)2} (4) and {Fe[tame(6‐Mepy)3](ClO4)2} (5) are quite similar and exhibit pseudo‐octahedral arrangements of the coordination polyhedron. Compound 1 is in the high spin state, whereas compounds 2–5 are in the low spin state at all investigated temperatures (10–400 K). Chemical modification of the ligands in 2–5 to introduce liquid crystalline properties is expected to decrease the ligand field strength sufficiently to transform the electronic LS ground state to spin crossover behavior in the room temperature region.

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Section: Crystal Structures Of 1–5supporting

confidence: 77%

Section: Crystal Structures Of 1–5mentioning

confidence: 99%

Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Seredyuk

Gaspar

Kusz

et al. 2011

Zeitschrift anorg allge chemie

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“…Previously, we argued that this trend was a consequence of increased crystal field stabilization that would be achieved by flattening to a D 2 d structure. 34 Interestingly, the trend reverses at Co (τ 4 = 0.59), which features a d 5 electronic configuration. Presumably, once a d 5 configuration is achieved, at least one d electron must occupy an anti-bonding or partially anti-bonding orbital, which results in a decrease of the crystal field stabilization.…”

Section: Resultsmentioning

confidence: 95%

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

et al. 2015

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Addition of 4 equiv of Li(N=CtBu2) to VCl3 in THF, followed by addition of 0.5 equiv I2, generates the homoleptic V(IV) ketimide complex, V(N=CtBu2)4 (1), in 42% yield. Similarly, reaction of 4 equiv of Li(N=CtBu2) with NbCl4(THF)2 in THF affords the homoleptic Nb(IV) ketimide complex, Nb(N=CtBu2)4 (2), in 55% yield. Seeking to extend the series to the tantalum congener, a new Ta(IV) starting material, TaCl4(TMEDA) (3), was prepared via reduction of TaCl5 with Et3SiH, followed by addition of TMEDA. Reaction of 3 with 4 equiv of Li(N=CtBu2) in THF results in a isolation of a Ta(V) ketimide complex, Ta(Cl)(N=CtBu2)4 (5), which can be isolated in 32% yield. Reaction of 5 with Tl(OTf) yields Ta(OTf)(N=CtBu2)4 (6) in 44% yield. Subsequent reduction of 6 with Cp*2Co in toluene generates the homoleptic Ta(IV) congener Ta(N=CtBu2)4 (7), although the yields are poor. All three homoleptic Group 5 ketimide complexes exhibit squashed tetrahedral geometries in the solid state, as determined by X-ray crystallography. This geometry leads to a dx2−y21 (2B1 in D2d) ground state, as supported by DFT calculations. EPR spectroscopic analysis of 1 and 2, performed at X- and Q-band frequencies (~9 and 35 GHz, respectively), further supports the 2B1 ground state assignment, while comparison of 1, 2, and 7 with related Group 5 tetra(aryl), tetra(amido) and tetra(alkoxo) complexes shows a higher M-L covalency in the ketimide-metal interaction. In addition, a ligand field analysis of 1 and 2 demonstrates that the ketimide ligand is both a strong π-donor and strong π-acceptor, an unusual combination found in very few organometallic ligands.

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“…This is still lacking in conventional ligand field theory, despite valiant attempts [13,14]. The simplicity can be illustrated with the example of a trans-CrA 4 B 2 complex.…”

Section: In the Beginningmentioning

confidence: 99%

Angular Overlap Model Parameters

Hoggard

2004

Structure and Bonding

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Since the introduction of the Angular overlap model (AOM) in the mid-1960s, expressing d orbital energies in terms of the s-and p-antibonding parameters e s and e p , the AOM has failed to supplant crystal field theory as the standard model to explain structure and electronic spectra in transition metal complexes. This is so despite the much more obvious connection in the AOM between structure and d orbital energies, the pictorial simplicity of the AOM approach, and the more consistent transferability of AOM parameters from one complex to another. The main reason is probably that AOM parameters cannot be determined uniquely when all the ligands are on the Cartesian axes. The scales for e s and e p must then be fixed arbitrarily, as is done automatically in the crystal field model. A number of experimental approaches have evolved to solve, or at least evade, the nonuniqueness problem, including: (a) the assignment of e p for saturated amines to zero, reflecting their inability to p-bond; (b) the simultaneous use of magnetic and spectroscopic data; (c) the inclusion of data from sharp, spinforbidden lines in Cr(III) spectra, along with application of the exact geometry and full d n configuration interaction in computations, or any combination of these; (d) the use of charge transfer bands involving dp orbitals to determine e p values. As of yet, the level of consistency among different techniques leaves something to be desired, and even with a common technique, reported AOM parameter values for particular metal-ligand combinations show a much higher variability than one would like, given even minimum expectations for transferability. Some of the variability can be ascribed to differences in the other ligands present. Even with these variations, AOM parameter sets can be usefully correlated with kinetic and thermodynamic data from both photochemical and thermal reactions.

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Computing ligand field potentials and relative energies of d orbitals: A simple general approach

Abstract: This approach to ligand field theory permits the derivation of the expressions for ligand field potentials and the quantitative evaluation of the energies of d orbitals in a large variety of geometrical situations.

Cited by 98 publications

References 7 publications

Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)

Angular Overlap Model Parameters

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Computing ligand field potentials and relative energies of d orbitals: A simple general approach

Abstract: This approach to ligand field theory permits the derivation of the expressions for ligand field potentials and the quantitative evaluation of the energies of d orbitals in a large variety of geometrical situations.

Cited by 98 publications

References 7 publications

Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Mononuclear Complexes of Iron(II) Based on Symmetrical Tripodand Ligands: Novel Parent Systems for the Development of New Spin Crossover Metallomesogens

Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═CtBu2)4 (M = V, Nb, Ta)

Angular Overlap Model Parameters

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Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C^tBu₂)₄ (M = V, Nb, Ta)