Oxalate bridged triangles incorporating Mo24+ units. Electronic structure and bonding

Malcolm H. Chisholm, Nathan J. Patmore, Carly R. Reed, Namrata Singh

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The reactions between [Mo2L2(CH3CN) 6][BF4]2 compounds and [Bun 4N]2[O2CCO2] in CH3CN are shown to proceed under kinetic control to the formation of a mixture of molecular triangles and squares. The molecular triangles [L2Mo 2(O2CCO2)]3 I (L = DPhF, PhNCHNPh) and II (L = DAniF, p-MeO-C6H4NCHNC6H 4-p-OMe) are the major products, and when 0.75 equivalents of [Bun4N]2[O2CCO2] is employed, they are formed to the exclusion of the square. The molecular structure of II is reported based on a single crystal X-ray determination. The molecular triangles do not enter into an equilibrium with their molecular square counterparts in CH2Cl2, in contrast to their perfluoroterephthalate bridged counterparts. The compounds I and II are orange and have a strong electronic transition at λmax ∼ 460 nm assignable to metal-to-ligand charge transfer (1MLCT) involving the oxalate bridge. Electronic structure calculations employing density functional theory on model compounds [(HCO2)2Mo2(O 2CCO2)]3 and [(HNCHNH)2Mo 2(O2CCO2)]3 have been carried out and indicate the frontier occupied molecular orbitals are Mo2 δ combinations e4a2, and the lowest unoccupied are bridge π* for the formamidinates and δ* for formates as ancillary ligands. Compounds I and II show quasi-reversible oxidation waves in their cyclic voltammograms and oxidation of II in 2-methyl-THF by reaction with AgPF6 (1 equivalent) leads to a metal centered EPR signal, g ∼ 1.95. The electronic absorption spectrum shows a low-energy broad band centered at 6418 cm-1, which is assigned to an intervalence charge transfer (IVCT) band of a class III mixed valence ion.

Original languageEnglish
Pages (from-to)7116-7122
Number of pages7
JournalInorganic Chemistry
Volume49
Issue number15
Early online date1 Jul 2010
DOIs
Publication statusPublished - 2 Aug 2010
Externally publishedYes

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Oxalates
oxalates
triangles
Electronic structure
Charge transfer
Formates
Metals
electronic structure
Ligands
Oxidation
Molecular orbitals
charge transfer
Molecular structure
Density functional theory
Paramagnetic resonance
Absorption spectra
ligands
oxidation
formates
Single crystals

Cite this

Chisholm, Malcolm H. ; Patmore, Nathan J. ; Reed, Carly R. ; Singh, Namrata. / Oxalate bridged triangles incorporating Mo24+ units. Electronic structure and bonding. In: Inorganic Chemistry. 2010 ; Vol. 49, No. 15. pp. 7116-7122.
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abstract = "The reactions between [Mo2L2(CH3CN) 6][BF4]2 compounds and [Bun 4N]2[O2CCO2] in CH3CN are shown to proceed under kinetic control to the formation of a mixture of molecular triangles and squares. The molecular triangles [L2Mo 2(O2CCO2)]3 I (L = DPhF, PhNCHNPh) and II (L = DAniF, p-MeO-C6H4NCHNC6H 4-p-OMe) are the major products, and when 0.75 equivalents of [Bun4N]2[O2CCO2] is employed, they are formed to the exclusion of the square. The molecular structure of II is reported based on a single crystal X-ray determination. The molecular triangles do not enter into an equilibrium with their molecular square counterparts in CH2Cl2, in contrast to their perfluoroterephthalate bridged counterparts. The compounds I and II are orange and have a strong electronic transition at λmax ∼ 460 nm assignable to metal-to-ligand charge transfer (1MLCT) involving the oxalate bridge. Electronic structure calculations employing density functional theory on model compounds [(HCO2)2Mo2(O 2CCO2)]3 and [(HNCHNH)2Mo 2(O2CCO2)]3 have been carried out and indicate the frontier occupied molecular orbitals are Mo2 δ combinations e4a2, and the lowest unoccupied are bridge π* for the formamidinates and δ* for formates as ancillary ligands. Compounds I and II show quasi-reversible oxidation waves in their cyclic voltammograms and oxidation of II in 2-methyl-THF by reaction with AgPF6 (1 equivalent) leads to a metal centered EPR signal, g ∼ 1.95. The electronic absorption spectrum shows a low-energy broad band centered at 6418 cm-1, which is assigned to an intervalence charge transfer (IVCT) band of a class III mixed valence ion.",
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Oxalate bridged triangles incorporating Mo24+ units. Electronic structure and bonding. / Chisholm, Malcolm H.; Patmore, Nathan J.; Reed, Carly R.; Singh, Namrata.

In: Inorganic Chemistry, Vol. 49, No. 15, 02.08.2010, p. 7116-7122.

Research output: Contribution to journalArticle

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N2 - The reactions between [Mo2L2(CH3CN) 6][BF4]2 compounds and [Bun 4N]2[O2CCO2] in CH3CN are shown to proceed under kinetic control to the formation of a mixture of molecular triangles and squares. The molecular triangles [L2Mo 2(O2CCO2)]3 I (L = DPhF, PhNCHNPh) and II (L = DAniF, p-MeO-C6H4NCHNC6H 4-p-OMe) are the major products, and when 0.75 equivalents of [Bun4N]2[O2CCO2] is employed, they are formed to the exclusion of the square. The molecular structure of II is reported based on a single crystal X-ray determination. The molecular triangles do not enter into an equilibrium with their molecular square counterparts in CH2Cl2, in contrast to their perfluoroterephthalate bridged counterparts. The compounds I and II are orange and have a strong electronic transition at λmax ∼ 460 nm assignable to metal-to-ligand charge transfer (1MLCT) involving the oxalate bridge. Electronic structure calculations employing density functional theory on model compounds [(HCO2)2Mo2(O 2CCO2)]3 and [(HNCHNH)2Mo 2(O2CCO2)]3 have been carried out and indicate the frontier occupied molecular orbitals are Mo2 δ combinations e4a2, and the lowest unoccupied are bridge π* for the formamidinates and δ* for formates as ancillary ligands. Compounds I and II show quasi-reversible oxidation waves in their cyclic voltammograms and oxidation of II in 2-methyl-THF by reaction with AgPF6 (1 equivalent) leads to a metal centered EPR signal, g ∼ 1.95. The electronic absorption spectrum shows a low-energy broad band centered at 6418 cm-1, which is assigned to an intervalence charge transfer (IVCT) band of a class III mixed valence ion.

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