From azobenzene coordination to aryl-halide bond activation by platinum

Olena Zenkina, Marc Altman, Gregory Leitus, Linda J W Shimon, Revital Cohen, Milko van der Boom

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


This contribution describes the reactivity of Pt(PEt3) 4 with (4-bromo-phenyl)-pyridin-4-yl-diazene. η2- Coordination of Pt(PEt3)2 to the N=N moiety is kinetically preferable and followed by an aryl-halide bond activation process. This quantitative transformation proceeds under mild reaction conditions in solution and in the solid state. Mechanistic studies in solution indicate that the metal insertion into the aryl-halide bond is the rate-determining step. The reaction obeys first-order kinetics in the η2-coordination complex with ΔG 298K = 24.6 ± 1.6 kcal/mol, ΔH = 26.5 ± 1.6 kcal/mol, and ΔS = 6.6 ± 5.0 eu. No effect on the reaction progress and NMR line shape has been observed in the presence of excess PEt3. However, competition experiments with the η-coordination complex and PhBr reveal that the product ratio can be altered by the presence of PEt3, indicating that the two aryl-halide bond activation processes proceed via different mechanistic pathways. Numerical analysis of a series of competition experiments fits a reaction scheme involving a unimolecular transformation from the η2-coordination complex to the product of aryl-halide oxidative addition. This "ring-walking" process is kinetically accessible as shown by density functional theory (DFT) calculations at the PCM:PBEO/SDB-cc-pVDZ/PBE0/SDD level of theory.

Original languageEnglish
Pages (from-to)4528-4534
Number of pages7
Issue number18
Publication statusPublished - Aug 27 2007

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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