Re-examination of the Metal Carbonyl Complex Infrared Parameter, vco, and Phosphorus Ligand Parameters, pKa, Σχiand Σσph, in Relation to an Evaluation of σ and Ω Components of M-P Bonds

Alyea, Elmer C.; Song, Shuquan

doi:10.1080/02603599608032722

Cited by 24 publications

(14 citation statements)

References 65 publications

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“…Tolman himself realized that the bulkiness of a ligand can outweigh electronic factors, which was the reason why he introduced the cone angle θ as a measure for the steric requirements of the ligand. , The Lever electronic parameter (LEP) is based on the ratio of the redox potentials of closely related complexes such as those of Ru(III) and Ru(II), which can be electrochemically determined , and which can be set into relationship to the TEP . It has been disputed whether the molecular electrostatic potential can be used to derive the CO stretching frequencies of transition metal carbonyl complexes. , Alyea and co-workers suggested ways of differentiating between σ and π effects influencing the CO stretching frequencies by referring to thermochemical data such as p K a values. Giering combined electronic and steric effects to what he coined the Quantitative Analysis of Ligand Effects (QALE) model.…”

Section: Introductionmentioning

confidence: 99%

“…48 It has been disputed whether the molecular electrostatic potential can be used to derive the CO stretching frequencies of transition metal carbonyl complexes. 72,73 Alyea and co-workers 74 suggested ways of differentiating between σ and π effects influencing the CO stretching frequencies by referring to thermochemical data such as pK a values. Giering 73 combined electronic and steric effects to what he coined the Quantitative Analysis of Ligand Effects (QALE) model.…”

Section: Introductionmentioning

confidence: 99%

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Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

2016

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The Tolman electronic parameter (TEP) derived from the A 1symmetrical CO stretching frequency of nickel-tricarbonyl complexes L− Ni(CO) 3 with varying ligands L is misleading as (i) it is not based on a mode decoupled CO stretching frequency and (ii) a generally applicable and quantitatively correct or at least qualitatively reasonable relationship between the TEP and the metal−ligand bond strength does not exist. This is shown for a set of 181 nickel-tricarbonyl complexes using both experimental and calculated TEP values. Even the use of mode−mode decoupled CO stretching frequencies (L(ocal)TEPs) does not lead to a reliable description of the metal−ligand bond strength. This is obtained by introducing a new electronic parameter that is directly based on the metal−ligand local stretching force constant. For the test set of 181 nickel complexes, a direct metal−ligand electronic parameter (MLEP) in the form of a bond strength order is derived, which reveals that phosphines and related ligands (amines, arsines, stibines, bismuthines) are bonded to Ni both by σ-donation and π-back-donation. The strongest Ni−L bonds are identified for carbenes and cationic ligands. The new MLEP quantitatively assesses electronic and steric factors.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

2016

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“…The nature of the metal–phosphorus bond has been analyzed in detail by computational (including Suresh’s molecular electrostatic potential , ), structural, and a combined structural–computational approach and by the covalent/ionic method of Drago and the more widely applicable quantitative analysis of ligand effects (QALE) of Prock and Giering, who have also commented on the methods of Drago and Suresh . Perspectives are given by Song and Alyea, Kühl, and York …”

Section: Introductionmentioning

confidence: 99%

Iron-57 NMR and Structural Study of [Fe(η⁵-Cp)(SnPh₃)(CO)(PR₃)] (PR₃ = Phosphine, Phosphite). Separation of Steric and Electronic σ and π Effects

2014

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The complexes [Fe(Cp)(SnPh3)(CO)(PR3)] (PR3 = PMe3 (1), PnBu3 (2), PCy3 (3), PMe2Ph (4), PMePh2 (5), P(CH2Ph)3 (6), PPh3 (7), P(4-MeC6H4)3 (8), P(4-MeOC6H4)3 (9), P(4-FC6H4)3 (10), P(4-CF3C6H4)3 (11), P(NMe2)3 (12), P(OMe)3 (13), P(OPh)3 (14)), which have been characterized by X-ray crystallography (except for 1 and 4), infrared spectroscopy (carbonyl stretching frequency, νCO), and NMR spectroscopy (13C, 31P, 57Fe, 119Sn) offer some insight into the response of the iron nucleus to changes in the electronic and steric properties of the PR3 ligand. A fairly good correlation is found between the 57Fe chemical shift and the Tolman cone angle θ for PR3 and a rather poorer correlation between δ(57Fe) and νCO. However, for the subseries of complexes 7–11 having PR3 = P(4-XC6H4)3 (X = H, Me, MeO, F, CF3), the correlation between δ(57Fe) and νCO is very good. Since the steric properties of these ligands, from the point of view of the metal, are identical (θ = 145°), this provides a means of separating the steric and electronic contributions of PR3 to δ(57Fe). The electronic contribution of PR3 to δ(57Fe) can be further separated into σ and π components by making use of the finding that the π component of the Fe–P bond has a negligible influence on δ(57Fe), unlike its influence on νCO. The ligands PMe3, PnBu3, PCy3, PMe2Ph, PMePh2, and P(NMe2)3 are found to be “pure” σ donors, P(OMe)3 and P(OPh)3 are found to be π acceptors of differing strength, and P(4-XC6H4)3 is found to show weak but clearly distinguishable π acceptor properties.

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“…The electronic parameters considered in this study have been widely applied to other transition metal systems to describe either σ-donation or a combination of σ-donor and π-acceptor effects. Both p K a and Drago's E B − C B parameters have been reported to describe primarily σ-donor properties, , whereas the remaining parameters have been reported to represent a combination of σ and π effects. , …”

Section: Discussionmentioning

confidence: 99%

Use of Intraligand CH Coupling Constants to Assess Binding in Organometallic Compounds. Insight into Electronic and Steric Properties of Monodentate P-Donor Ligands

Moore

Marzillï

1998

Inorg. Chem.

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In a series of methylcobaloximes (LCo(DH)2CH3, where DH = monoanion of dimethylglyoxime), the influence of P-donor ligands (L) on 1 J CH values of the Co−CH3 moiety correlated well with the pK a of L except when L was bulky (Cy3P and i-Pr3P). In contrast, no single steric parameter of those known for the trivalent P donors examined could be used to describe the variance of 1 J CH. The results indicate that the dominant property of L influencing this 1 J CH is electron donation. Although poor, the best correlation with a steric parameter was found with calculated cone angles (CCA) determined by experimental methods on methanol-coordinated cobaloximes. Since the single parameter fits with pK a indicated a steric effect, multiparameter regressions were performed using various combinations of electronic and steric terms. Terms reflecting only σ-donor ability (e.g., pK a) gave better correlations than terms reflecting combinations of σ-donor and π-acceptor properties (e.g., Σχ). CCA values also resulted in better multiparameter fits of the data than other reported steric terms. Using a multiparameter approach also allowed for the simultaneous fit of data for L = phosphine and phosphite ligands. Correlations of this type were poor with single parameter fits. The sensitivity of 1 J CH to trans ligand electronic and steric effects indicates that small changes in the hybridization of the Co−CH3 moiety occur. This method allows us to probe the nature of Co−C bonding in the ground state. The other experimental methods for probing this bond (e.g., X-ray crystallography, FT-Raman spectroscopy, etc.) indicate that this bond is relatively insensitive to the trans ligand in the ground state. Thus, 1 J CH values may be a useful general method for examining B12 systems and also hold promise for other types of organometallic compounds.

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Re-examination of the Metal Carbonyl Complex Infrared Parameter, v_co, and Phosphorus Ligand Parameters, pKa, Σ_χiand Σσ^ph, in Relation to an Evaluation of σ and Ω Components of M-P Bonds

Cited by 24 publications

References 65 publications

Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

Iron-57 NMR and Structural Study of [Fe(η⁵-Cp)(SnPh₃)(CO)(PR₃)] (PR₃ = Phosphine, Phosphite). Separation of Steric and Electronic σ and π Effects

Use of Intraligand CH Coupling Constants to Assess Binding in Organometallic Compounds. Insight into Electronic and Steric Properties of Monodentate P-Donor Ligands

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Re-examination of the Metal Carbonyl Complex Infrared Parameter, vco, and Phosphorus Ligand Parameters, pKa, Σχiand Σσph, in Relation to an Evaluation of σ and Ω Components of M-P Bonds

Cited by 24 publications

References 65 publications

Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

Direct Measure of Metal–Ligand Bonding Replacing the Tolman Electronic Parameter

Iron-57 NMR and Structural Study of [Fe(η5-Cp)(SnPh3)(CO)(PR3)] (PR3 = Phosphine, Phosphite). Separation of Steric and Electronic σ and π Effects

Use of Intraligand CH Coupling Constants to Assess Binding in Organometallic Compounds. Insight into Electronic and Steric Properties of Monodentate P-Donor Ligands

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Re-examination of the Metal Carbonyl Complex Infrared Parameter, v_co, and Phosphorus Ligand Parameters, pKa, Σ_χiand Σσ^ph, in Relation to an Evaluation of σ and Ω Components of M-P Bonds

Iron-57 NMR and Structural Study of [Fe(η⁵-Cp)(SnPh₃)(CO)(PR₃)] (PR₃ = Phosphine, Phosphite). Separation of Steric and Electronic σ and π Effects