Monovalent copper as a potential catalyst for formation of acetaldehyde via the migration of methyl radicals to the coordinated carbonyl in the complex (CO)CuII-CH3+

Avraham Szulc, Dan Meyerstein, Haim Cohen

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Cu+aq forms stable complexes with carbon monoxide in aqueous solutions. Furthermore it reacts very fast with aliphatic radicals. The reaction of Cu(CO)+naq with methyl radicals, *CH3, was studied using the pulse-radiolysis technique. The results point out that methyl radicals react with Cu(CO)+aq to form an unstable intermediate with a CuII-C σ bond identified as (CO)CuII-CH3+, k=(1.1 ± 0.2) × 109 M-1 s-1. This intermediate has a strong LMCT charge transfer band (λmax=385 nm, εmax=2500 M-1 cm-1) which is similar to the absorption bands of other transient complexes with CuII-alkyl σ bonds. The coordinated carbon monoxide in (CO) CuII-CH3+ inserts into the copper-carbon bond (or rather the coordinated methyl migrates to the coordinated carbon monoxide ligand) at a rate of (3.0 ± 0.8) × 102 s-1 to form the copper-acetyl complex, (CO)mCuII-C(CH3)=O+max=480 nm, εmax=2100 M-1 cm-1). The rate of formation of (CO)CuII-CH3+ and of the insertion reaction are pH independent. The complex (CO)mCuII-C(CH3)=O+ is also unstable and decomposes heterolytically to yield acetaldehyde and Cu2+aq as the final stable products. This reaction is slightly pH dependent. The same reactivity pattern has been observed for the Cu(CO)+naq complexes (n=2 or 3). The results clearly point out that CO remains coordinated to transient complexes of the type CuII-alkyl.

Original languageEnglish
Pages (from-to)440-445
Number of pages6
JournalInorganica Chimica Acta
Volume270
Issue number1-2
DOIs
StatePublished - 2 Apr 1998

Keywords

  • Carbonyl complexes
  • Copper complexes
  • Kinetics and mechanism
  • Methyl complexes
  • Methyl migration

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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