Peracid oxidation of inorganic chalcogen ligands in transition metal complexes

John E. Hoots, David A. Lesch, Thomas B. Rauchfuss

Research output: Contribution to journalArticlepeer-review

Abstract

The use of organic peracids as rapid, selective oxidation agents for coordinated chalcogens, η2-E2 (E = S, Se) and μ3-E (E = S, Se, Te), has been examined. Stepwise oxidation of [Ir(η2-S2)(dppe)2]PF6 with m-chloroperbenzoic acid (m-CPBA) yielded [Ir(η2-S2O)(dppe)2]PF6 (1) and [Ir(η2-S2O2)(dppe)2]PF 6 (2). Facile oxidation of [Ir(η2-Se2)(dppe)2]PF6 and Cp2Nb(η2-S2)Cl with peracetic acid produced [Ir(η2-Se2O)(dppe)2]PF6 (3) and Cp2Nb(η2-S2O)Cl (4). Similarly, reaction of Fe33-S)2(CO)9 and Fe2Pt(μ3-E)2(CO)6(PPh 3)2 (E = S, Se, Te) with m-CPBA produced the chalcogen monoxide complexes, Fe33-SO)(μ3-S)(CO)9 (5) and Fe2Pt(μ3-EO)(μ3-E)(CO) 6(PPh3)2 (6). The stereochemistry and reactivity of all of these complexes have been studied. Reaction of the η2-S2O complexes with nucleophiles (Nu = PPh3, CH3NC) revealed sulfur transfer as the favored reaction and the unsubstituted sulfur donor atom as the most reactive site. Attempted formation of η1- or η2-SO complexes by selective sulfur-abstraction reactions was unsuccessful, but an unsymmetrical dichalcogenide complex, [Ir(η2-SSe)(dppe)2]+ (7), was synthesized from [Ir(dppe)2]Cl and Cp2TiSxSe5-x (x ≈ 3). Examination of the oxygen-transfer capabilities of the iridium complexes revealed the following trend: Se2O ≫ S2O2 > S2O. In solution, the [Ir(Se2O)(dppe)2]PF6 complex spontaneously eliminates the exocyclic oxygen to yield [Ir(Se2)(dppe)2]+ and oxidizes C2H5SH to ethyl disulfide. In contrast, the [Ir(S2O)(dppe)2]Cl and Cp2Nb(S2O)Cl complexes show a pronounced tendency toward sulfur transfer to substrates but virtually no oxygen-transfer capability. The μ3-SO complexes proved to be virtually inert toward both O- and S-transfer reactions. Also described is the utility of chiral solvating and lanthanide shift reagents in the elucidation of the structure and stereochemistry of Cp2Nb(S2O)Cl using 1H NMR spectroscopy.

Original languageEnglish (US)
Pages (from-to)3130-3136
Number of pages7
JournalInorganic Chemistry
Volume23
Issue number20
DOIs
StatePublished - Jan 1984

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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