Absolute metal-ligand σ bond enthalpies in group 4 metallocenes. A thermochemical, structural, photoelectron spectroscopic, and ab initio quantum chemical investigation

Wayne A. King, Santo Di Bella, Antonino Gulino, Giuseppe Lanza, Ignazio L. Fragalà, Charlotte L. Stern, Tobin J Marks

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Absolute metal-ligand σ bond enthalpies have been determined for a series of titanocene, zirconocene, and hafnocene halides and dimethyls by iodinolytic titration calorimetry. Absolute metal-iodine bond disruption enthalpies were measured by iodination of the monomeric trivalent group 4 metallocenes Cp(tt)2TiI, (Me5C5)2TiI, Cp(tt)2ZrI, and Cp(tt)2HfI (Cp(tt) = η5-1,3-di-tert-butylcyclopentadienyl). Iodinolysis of Cp(tt)2ZrMe2 and Cp(tt)2HfMe2 in turn yields absolute Zr-Me and Hf-Me bond enthalpies. Derived values (kcal/mol) are D[Cp(tt)2Ti(I)-I] = 40.6(5); D[(Me5C5)2Ti(I)-I] = 52.3(6); D[Cp(tt)2Zr(I)-I] = 58.0(5); D[Cp(tt)2Hf(I)-I] = 61.2(4); D[Cp(tt)2Zr-Me2] = 43(1); and D[Cp(tt)2Hf- Me2] = 47.6(9). That D[Cp(tt)2Zr(I)-(I)] ≃ D(I3Zr-I) and D[(Me5C5)2Ti(I)-I] ≃ D(I3Ti-I), while D[Cp(tt)2Ti(I)-I] ≃ D(I3Ti-I) - 12 kcal/mol, argues for more reliable transferability of D(M(IV)-I) in sterically less congested metallocenes. The molecular structures of Cp2(tt)ZrI2, Cp2(tt)ZrI, and Cp2(tt)HfI were determined by X-ray diffraction. In Cp(tt)2ZrI2, the Zr ligation is pseudotetrahedral, and the ring tert-butyl groups 'straddle' the Zr-I bonds to minimize steric interactions. The geometry about Zr in Cp(tt)2ZrI is pseudotrigonal, with contracted Zr-ring centroid and Zr-I distances versus Cp(tt)2grI2, primarily reflecting substantially diminished ligand-ligand repulsive nonbonded interactions in the latter. Cp(tt)2HfI is isomorphous with Cp(tt)2ZrI, and the slightly different metrical parameters are in accord with Hf vs Zr ionic radii. The significant differences in interligand repulsive interactions in the trivalent versus tetravalent complexes are confirmed by van der Waals calculations. High-resolution UV PE spectra combined with ab initio relativistic effective core potential calculations provide details of electronic structure. Absolute ionization energy values indicate that iodine behaves as both a strong σ and π donor. Trends in the large Cp2MX(n) structural database can be understood in terms of the interplay between electronic and molecular structure factors, which are highly sensitive to the substitution patterns of the cyclopentadienyl ligands and, in particular, to competing σ vs π M-X bonding.

Original languageEnglish
Pages (from-to)355-366
Number of pages12
JournalJournal of the American Chemical Society
Volume121
Issue number2
DOIs
Publication statusPublished - Jan 20 1999

Fingerprint

Organometallics
Photoelectrons
Enthalpy
Metals
Ligands
Molecular Structure
Iodine
Molecular structure
Electronic structure
Calorimetry
Ionization potential
Halogenation
Chemical bonds
Titration
X-Ray Diffraction
Ligation
Substitution reactions
Databases
X ray diffraction
Geometry

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Absolute metal-ligand σ bond enthalpies in group 4 metallocenes. A thermochemical, structural, photoelectron spectroscopic, and ab initio quantum chemical investigation. / King, Wayne A.; Di Bella, Santo; Gulino, Antonino; Lanza, Giuseppe; Fragalà, Ignazio L.; Stern, Charlotte L.; Marks, Tobin J.

In: Journal of the American Chemical Society, Vol. 121, No. 2, 20.01.1999, p. 355-366.

Research output: Contribution to journalArticle

King, Wayne A. ; Di Bella, Santo ; Gulino, Antonino ; Lanza, Giuseppe ; Fragalà, Ignazio L. ; Stern, Charlotte L. ; Marks, Tobin J. / Absolute metal-ligand σ bond enthalpies in group 4 metallocenes. A thermochemical, structural, photoelectron spectroscopic, and ab initio quantum chemical investigation. In: Journal of the American Chemical Society. 1999 ; Vol. 121, No. 2. pp. 355-366.
@article{f783caea74d7482e86b9567bae3331f4,
title = "Absolute metal-ligand σ bond enthalpies in group 4 metallocenes. A thermochemical, structural, photoelectron spectroscopic, and ab initio quantum chemical investigation",
abstract = "Absolute metal-ligand σ bond enthalpies have been determined for a series of titanocene, zirconocene, and hafnocene halides and dimethyls by iodinolytic titration calorimetry. Absolute metal-iodine bond disruption enthalpies were measured by iodination of the monomeric trivalent group 4 metallocenes Cp(tt)2TiI, (Me5C5)2TiI, Cp(tt)2ZrI, and Cp(tt)2HfI (Cp(tt) = η5-1,3-di-tert-butylcyclopentadienyl). Iodinolysis of Cp(tt)2ZrMe2 and Cp(tt)2HfMe2 in turn yields absolute Zr-Me and Hf-Me bond enthalpies. Derived values (kcal/mol) are D[Cp(tt)2Ti(I)-I] = 40.6(5); D[(Me5C5)2Ti(I)-I] = 52.3(6); D[Cp(tt)2Zr(I)-I] = 58.0(5); D[Cp(tt)2Hf(I)-I] = 61.2(4); D[Cp(tt)2Zr-Me2] = 43(1); and D[Cp(tt)2Hf- Me2] = 47.6(9). That D[Cp(tt)2Zr(I)-(I)] ≃ D(I3Zr-I) and D[(Me5C5)2Ti(I)-I] ≃ D(I3Ti-I), while D[Cp(tt)2Ti(I)-I] ≃ D(I3Ti-I) - 12 kcal/mol, argues for more reliable transferability of D(M(IV)-I) in sterically less congested metallocenes. The molecular structures of Cp2(tt)ZrI2, Cp2(tt)ZrI, and Cp2(tt)HfI were determined by X-ray diffraction. In Cp(tt)2ZrI2, the Zr ligation is pseudotetrahedral, and the ring tert-butyl groups 'straddle' the Zr-I bonds to minimize steric interactions. The geometry about Zr in Cp(tt)2ZrI is pseudotrigonal, with contracted Zr-ring centroid and Zr-I distances versus Cp(tt)2grI2, primarily reflecting substantially diminished ligand-ligand repulsive nonbonded interactions in the latter. Cp(tt)2HfI is isomorphous with Cp(tt)2ZrI, and the slightly different metrical parameters are in accord with Hf vs Zr ionic radii. The significant differences in interligand repulsive interactions in the trivalent versus tetravalent complexes are confirmed by van der Waals calculations. High-resolution UV PE spectra combined with ab initio relativistic effective core potential calculations provide details of electronic structure. Absolute ionization energy values indicate that iodine behaves as both a strong σ and π donor. Trends in the large Cp2MX(n) structural database can be understood in terms of the interplay between electronic and molecular structure factors, which are highly sensitive to the substitution patterns of the cyclopentadienyl ligands and, in particular, to competing σ vs π M-X bonding.",
author = "King, {Wayne A.} and {Di Bella}, Santo and Antonino Gulino and Giuseppe Lanza and Fragal{\`a}, {Ignazio L.} and Stern, {Charlotte L.} and Marks, {Tobin J}",
year = "1999",
month = "1",
day = "20",
doi = "10.1021/ja9822815",
language = "English",
volume = "121",
pages = "355--366",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "2",

}

TY - JOUR

T1 - Absolute metal-ligand σ bond enthalpies in group 4 metallocenes. A thermochemical, structural, photoelectron spectroscopic, and ab initio quantum chemical investigation

AU - King, Wayne A.

AU - Di Bella, Santo

AU - Gulino, Antonino

AU - Lanza, Giuseppe

AU - Fragalà, Ignazio L.

AU - Stern, Charlotte L.

AU - Marks, Tobin J

PY - 1999/1/20

Y1 - 1999/1/20

N2 - Absolute metal-ligand σ bond enthalpies have been determined for a series of titanocene, zirconocene, and hafnocene halides and dimethyls by iodinolytic titration calorimetry. Absolute metal-iodine bond disruption enthalpies were measured by iodination of the monomeric trivalent group 4 metallocenes Cp(tt)2TiI, (Me5C5)2TiI, Cp(tt)2ZrI, and Cp(tt)2HfI (Cp(tt) = η5-1,3-di-tert-butylcyclopentadienyl). Iodinolysis of Cp(tt)2ZrMe2 and Cp(tt)2HfMe2 in turn yields absolute Zr-Me and Hf-Me bond enthalpies. Derived values (kcal/mol) are D[Cp(tt)2Ti(I)-I] = 40.6(5); D[(Me5C5)2Ti(I)-I] = 52.3(6); D[Cp(tt)2Zr(I)-I] = 58.0(5); D[Cp(tt)2Hf(I)-I] = 61.2(4); D[Cp(tt)2Zr-Me2] = 43(1); and D[Cp(tt)2Hf- Me2] = 47.6(9). That D[Cp(tt)2Zr(I)-(I)] ≃ D(I3Zr-I) and D[(Me5C5)2Ti(I)-I] ≃ D(I3Ti-I), while D[Cp(tt)2Ti(I)-I] ≃ D(I3Ti-I) - 12 kcal/mol, argues for more reliable transferability of D(M(IV)-I) in sterically less congested metallocenes. The molecular structures of Cp2(tt)ZrI2, Cp2(tt)ZrI, and Cp2(tt)HfI were determined by X-ray diffraction. In Cp(tt)2ZrI2, the Zr ligation is pseudotetrahedral, and the ring tert-butyl groups 'straddle' the Zr-I bonds to minimize steric interactions. The geometry about Zr in Cp(tt)2ZrI is pseudotrigonal, with contracted Zr-ring centroid and Zr-I distances versus Cp(tt)2grI2, primarily reflecting substantially diminished ligand-ligand repulsive nonbonded interactions in the latter. Cp(tt)2HfI is isomorphous with Cp(tt)2ZrI, and the slightly different metrical parameters are in accord with Hf vs Zr ionic radii. The significant differences in interligand repulsive interactions in the trivalent versus tetravalent complexes are confirmed by van der Waals calculations. High-resolution UV PE spectra combined with ab initio relativistic effective core potential calculations provide details of electronic structure. Absolute ionization energy values indicate that iodine behaves as both a strong σ and π donor. Trends in the large Cp2MX(n) structural database can be understood in terms of the interplay between electronic and molecular structure factors, which are highly sensitive to the substitution patterns of the cyclopentadienyl ligands and, in particular, to competing σ vs π M-X bonding.

AB - Absolute metal-ligand σ bond enthalpies have been determined for a series of titanocene, zirconocene, and hafnocene halides and dimethyls by iodinolytic titration calorimetry. Absolute metal-iodine bond disruption enthalpies were measured by iodination of the monomeric trivalent group 4 metallocenes Cp(tt)2TiI, (Me5C5)2TiI, Cp(tt)2ZrI, and Cp(tt)2HfI (Cp(tt) = η5-1,3-di-tert-butylcyclopentadienyl). Iodinolysis of Cp(tt)2ZrMe2 and Cp(tt)2HfMe2 in turn yields absolute Zr-Me and Hf-Me bond enthalpies. Derived values (kcal/mol) are D[Cp(tt)2Ti(I)-I] = 40.6(5); D[(Me5C5)2Ti(I)-I] = 52.3(6); D[Cp(tt)2Zr(I)-I] = 58.0(5); D[Cp(tt)2Hf(I)-I] = 61.2(4); D[Cp(tt)2Zr-Me2] = 43(1); and D[Cp(tt)2Hf- Me2] = 47.6(9). That D[Cp(tt)2Zr(I)-(I)] ≃ D(I3Zr-I) and D[(Me5C5)2Ti(I)-I] ≃ D(I3Ti-I), while D[Cp(tt)2Ti(I)-I] ≃ D(I3Ti-I) - 12 kcal/mol, argues for more reliable transferability of D(M(IV)-I) in sterically less congested metallocenes. The molecular structures of Cp2(tt)ZrI2, Cp2(tt)ZrI, and Cp2(tt)HfI were determined by X-ray diffraction. In Cp(tt)2ZrI2, the Zr ligation is pseudotetrahedral, and the ring tert-butyl groups 'straddle' the Zr-I bonds to minimize steric interactions. The geometry about Zr in Cp(tt)2ZrI is pseudotrigonal, with contracted Zr-ring centroid and Zr-I distances versus Cp(tt)2grI2, primarily reflecting substantially diminished ligand-ligand repulsive nonbonded interactions in the latter. Cp(tt)2HfI is isomorphous with Cp(tt)2ZrI, and the slightly different metrical parameters are in accord with Hf vs Zr ionic radii. The significant differences in interligand repulsive interactions in the trivalent versus tetravalent complexes are confirmed by van der Waals calculations. High-resolution UV PE spectra combined with ab initio relativistic effective core potential calculations provide details of electronic structure. Absolute ionization energy values indicate that iodine behaves as both a strong σ and π donor. Trends in the large Cp2MX(n) structural database can be understood in terms of the interplay between electronic and molecular structure factors, which are highly sensitive to the substitution patterns of the cyclopentadienyl ligands and, in particular, to competing σ vs π M-X bonding.

UR - http://www.scopus.com/inward/record.url?scp=0033585544&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033585544&partnerID=8YFLogxK

U2 - 10.1021/ja9822815

DO - 10.1021/ja9822815

M3 - Article

VL - 121

SP - 355

EP - 366

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 2

ER -