A Dinuclear Iridium(V,V) Oxo-Bridged Complex Characterized Using a Bulk Electrolysis Technique for Crystallizing Highly Oxidizing Compounds

Dimitar Y. Shopov, Liam S. Sharninghausen, Shashi Bhushan Sinha, Brandon Q. Mercado, David Balcells, Gary W Brudvig, Robert H. Crabtree

Research output: Contribution to journalArticle

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Abstract

We report a general method for the preparation and crystallization of highly oxidized metal complexes that are difficult to prepare and handle by more conventional means. This method improves typical bulk electrolysis and crystallization conditions for these reactive species by substituting oxidation-prone organic electrolytes and precipitants with oxidation-resistant compounds. Specifically, we find that CsPF6 is an effective inert electrolyte in acetonitrile, and appears to have general applicability to electrochemical studies in this solvent. Likewise, CCl4 is not only an oxidation-resistant precipitant for crystallization from MeCN but it also enters the lattice. In this way, we synthesized and characterized an Ir(V,V) mono-μ-oxo dimer which only forms at a very high potential (1.9 V vs NHE). This compound, having the highest isolated oxidation state in this redox-active system, cannot be formed chemically. DFT calculations show that the oxidation is centered on the Ir-O-Ir core and facilitated by strong electron-donation from the pyalk (2-(2-pyridinyl)-2-propanolate) ligand. TD-DFT simulations of the UV-visible spectrum reveal that its royal blue color arises from electron excitations with mixed LMCT and Laporte-allowed d-d character. We have also crystallographically characterized a related monomeric Ir(V) complex, similarly prepared by oxidizing a previously reported Ir(IV) compound at 1.7 V, underscoring the general applicability of this method.

Original languageEnglish
Pages (from-to)5684-5691
Number of pages8
JournalInorganic Chemistry
Volume57
Issue number9
DOIs
Publication statusPublished - May 7 2018

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Iridium
electrolysis
iridium
Electrolysis
Oxidation
Crystallization
oxidation
crystallization
Discrete Fourier transforms
Electrolytes
electrolytes
Electrons
Coordination Complexes
visible spectrum
Dimers
acetonitrile
electrons
dimers
Ligands
Color

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

A Dinuclear Iridium(V,V) Oxo-Bridged Complex Characterized Using a Bulk Electrolysis Technique for Crystallizing Highly Oxidizing Compounds. / Shopov, Dimitar Y.; Sharninghausen, Liam S.; Sinha, Shashi Bhushan; Mercado, Brandon Q.; Balcells, David; Brudvig, Gary W; Crabtree, Robert H.

In: Inorganic Chemistry, Vol. 57, No. 9, 07.05.2018, p. 5684-5691.

Research output: Contribution to journalArticle

Shopov, Dimitar Y. ; Sharninghausen, Liam S. ; Sinha, Shashi Bhushan ; Mercado, Brandon Q. ; Balcells, David ; Brudvig, Gary W ; Crabtree, Robert H. / A Dinuclear Iridium(V,V) Oxo-Bridged Complex Characterized Using a Bulk Electrolysis Technique for Crystallizing Highly Oxidizing Compounds. In: Inorganic Chemistry. 2018 ; Vol. 57, No. 9. pp. 5684-5691.
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AB - We report a general method for the preparation and crystallization of highly oxidized metal complexes that are difficult to prepare and handle by more conventional means. This method improves typical bulk electrolysis and crystallization conditions for these reactive species by substituting oxidation-prone organic electrolytes and precipitants with oxidation-resistant compounds. Specifically, we find that CsPF6 is an effective inert electrolyte in acetonitrile, and appears to have general applicability to electrochemical studies in this solvent. Likewise, CCl4 is not only an oxidation-resistant precipitant for crystallization from MeCN but it also enters the lattice. In this way, we synthesized and characterized an Ir(V,V) mono-μ-oxo dimer which only forms at a very high potential (1.9 V vs NHE). This compound, having the highest isolated oxidation state in this redox-active system, cannot be formed chemically. DFT calculations show that the oxidation is centered on the Ir-O-Ir core and facilitated by strong electron-donation from the pyalk (2-(2-pyridinyl)-2-propanolate) ligand. TD-DFT simulations of the UV-visible spectrum reveal that its royal blue color arises from electron excitations with mixed LMCT and Laporte-allowed d-d character. We have also crystallographically characterized a related monomeric Ir(V) complex, similarly prepared by oxidizing a previously reported Ir(IV) compound at 1.7 V, underscoring the general applicability of this method.

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