1,3-Ditungstacyclobutadienes. 2. The synthesis of alkoxide derivatives of W2(μ-CSiMe3)2(CH2SiMe 3)4 and investigations of the electronic structures of the M2(μ-CSiMe3)2 core as a function of dn-dn interactions (n = 0, M = Ta; n = 1, M = W; n = 2, M = Re)

Malcolm H. Chisholm, Joseph A. Heppert, Edward M. Kober, Dennis L Lichtenberger

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Abstract

W2(μ-CSiMe3)2(CH2SiMe 3)4 (I) reacts with t-BuOH in alkane solvents to produce a mixture of two isomers of W2(μ-CSiMe)2(O-t-Bu)2(CH 2SiMe3)2 from which the minor isomer can be isolated by fractional crystallization. The electronic structures of several related dimetallacyclobutadiene derivatives have been investigated by UV photoelectron spectroscopy, UV/visible spectrophotometry, and MO calculations. The M-M bonding configurations for the M2(μ-CSiMe3)2(CH2SiMe 3)4 molecules have been determined as σ0δ*0, σ2δ*0, and σ2δ*2 for M = Ta, W, and Re, respectively, by EHMO and Fenske-Hall MO calculations. This result is better reconciled with the previously observed M-M distances - Nb2 > Re2 > W2 - than with the original proposal of a σ2π2 configuration for the Re derivative. On replacement of the terminal alkyl ligands of the W complex by O-i-Pr ligands, the 2au LUMO (W-W δ*) and 2b2g W-μ-C π bond are strongly destabilized by antibonding interactions with pπ orbitals on oxygen. Destabilization of the 2b2g orbital results in the appearance of a clearly defined ionization representing this orbital at 7.2 eV in the PE spectrum of W2(μ-CSiMe3)2(O-i-Pr)4. Mulliken population analyses of the 6ag orbitals of I and W2(μ-CSiMe3)2(O-i-Pr)4 correctly predict that I prefers a shorter W-W distance of 2.54 Å, while the alkoxide-substituted compound prefers the longer W-W distance of 2.62 Å.

Original languageEnglish (US)
Pages (from-to)1065-1073
Number of pages9
JournalOrganometallics
Volume6
Issue number5
StatePublished - 1987

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alkoxides
Isomers
Electronic structure
electronic structure
Ligands
Derivatives
orbitals
Alkanes
Spectrophotometry
synthesis
Photoelectron spectroscopy
Crystallization
Ultraviolet spectroscopy
Ionization
isomers
interactions
Oxygen
ligands
Molecules
destabilization

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

Cite this

@article{04b68471b83a4cb9bb67fbe92aedfe09,
title = "1,3-Ditungstacyclobutadienes. 2. The synthesis of alkoxide derivatives of W2(μ-CSiMe3)2(CH2SiMe 3)4 and investigations of the electronic structures of the M2(μ-CSiMe3)2 core as a function of dn-dn interactions (n = 0, M = Ta; n = 1, M = W; n = 2, M = Re)",
abstract = "W2(μ-CSiMe3)2(CH2SiMe 3)4 (I) reacts with t-BuOH in alkane solvents to produce a mixture of two isomers of W2(μ-CSiMe)2(O-t-Bu)2(CH 2SiMe3)2 from which the minor isomer can be isolated by fractional crystallization. The electronic structures of several related dimetallacyclobutadiene derivatives have been investigated by UV photoelectron spectroscopy, UV/visible spectrophotometry, and MO calculations. The M-M bonding configurations for the M2(μ-CSiMe3)2(CH2SiMe 3)4 molecules have been determined as σ0δ*0, σ2δ*0, and σ2δ*2 for M = Ta, W, and Re, respectively, by EHMO and Fenske-Hall MO calculations. This result is better reconciled with the previously observed M-M distances - Nb2 > Re2 > W2 - than with the original proposal of a σ2π2 configuration for the Re derivative. On replacement of the terminal alkyl ligands of the W complex by O-i-Pr ligands, the 2au LUMO (W-W δ*) and 2b2g W-μ-C π bond are strongly destabilized by antibonding interactions with pπ orbitals on oxygen. Destabilization of the 2b2g orbital results in the appearance of a clearly defined ionization representing this orbital at 7.2 eV in the PE spectrum of W2(μ-CSiMe3)2(O-i-Pr)4. Mulliken population analyses of the 6ag orbitals of I and W2(μ-CSiMe3)2(O-i-Pr)4 correctly predict that I prefers a shorter W-W distance of 2.54 {\AA}, while the alkoxide-substituted compound prefers the longer W-W distance of 2.62 {\AA}.",
author = "Chisholm, {Malcolm H.} and Heppert, {Joseph A.} and Kober, {Edward M.} and Lichtenberger, {Dennis L}",
year = "1987",
language = "English (US)",
volume = "6",
pages = "1065--1073",
journal = "Organometallics",
issn = "0276-7333",
publisher = "American Chemical Society",
number = "5",

}

TY - JOUR

T1 - 1,3-Ditungstacyclobutadienes. 2. The synthesis of alkoxide derivatives of W2(μ-CSiMe3)2(CH2SiMe 3)4 and investigations of the electronic structures of the M2(μ-CSiMe3)2 core as a function of dn-dn interactions (n = 0, M = Ta; n = 1, M = W; n = 2, M = Re)

AU - Chisholm, Malcolm H.

AU - Heppert, Joseph A.

AU - Kober, Edward M.

AU - Lichtenberger, Dennis L

PY - 1987

Y1 - 1987

N2 - W2(μ-CSiMe3)2(CH2SiMe 3)4 (I) reacts with t-BuOH in alkane solvents to produce a mixture of two isomers of W2(μ-CSiMe)2(O-t-Bu)2(CH 2SiMe3)2 from which the minor isomer can be isolated by fractional crystallization. The electronic structures of several related dimetallacyclobutadiene derivatives have been investigated by UV photoelectron spectroscopy, UV/visible spectrophotometry, and MO calculations. The M-M bonding configurations for the M2(μ-CSiMe3)2(CH2SiMe 3)4 molecules have been determined as σ0δ*0, σ2δ*0, and σ2δ*2 for M = Ta, W, and Re, respectively, by EHMO and Fenske-Hall MO calculations. This result is better reconciled with the previously observed M-M distances - Nb2 > Re2 > W2 - than with the original proposal of a σ2π2 configuration for the Re derivative. On replacement of the terminal alkyl ligands of the W complex by O-i-Pr ligands, the 2au LUMO (W-W δ*) and 2b2g W-μ-C π bond are strongly destabilized by antibonding interactions with pπ orbitals on oxygen. Destabilization of the 2b2g orbital results in the appearance of a clearly defined ionization representing this orbital at 7.2 eV in the PE spectrum of W2(μ-CSiMe3)2(O-i-Pr)4. Mulliken population analyses of the 6ag orbitals of I and W2(μ-CSiMe3)2(O-i-Pr)4 correctly predict that I prefers a shorter W-W distance of 2.54 Å, while the alkoxide-substituted compound prefers the longer W-W distance of 2.62 Å.

AB - W2(μ-CSiMe3)2(CH2SiMe 3)4 (I) reacts with t-BuOH in alkane solvents to produce a mixture of two isomers of W2(μ-CSiMe)2(O-t-Bu)2(CH 2SiMe3)2 from which the minor isomer can be isolated by fractional crystallization. The electronic structures of several related dimetallacyclobutadiene derivatives have been investigated by UV photoelectron spectroscopy, UV/visible spectrophotometry, and MO calculations. The M-M bonding configurations for the M2(μ-CSiMe3)2(CH2SiMe 3)4 molecules have been determined as σ0δ*0, σ2δ*0, and σ2δ*2 for M = Ta, W, and Re, respectively, by EHMO and Fenske-Hall MO calculations. This result is better reconciled with the previously observed M-M distances - Nb2 > Re2 > W2 - than with the original proposal of a σ2π2 configuration for the Re derivative. On replacement of the terminal alkyl ligands of the W complex by O-i-Pr ligands, the 2au LUMO (W-W δ*) and 2b2g W-μ-C π bond are strongly destabilized by antibonding interactions with pπ orbitals on oxygen. Destabilization of the 2b2g orbital results in the appearance of a clearly defined ionization representing this orbital at 7.2 eV in the PE spectrum of W2(μ-CSiMe3)2(O-i-Pr)4. Mulliken population analyses of the 6ag orbitals of I and W2(μ-CSiMe3)2(O-i-Pr)4 correctly predict that I prefers a shorter W-W distance of 2.54 Å, while the alkoxide-substituted compound prefers the longer W-W distance of 2.62 Å.

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