Isomerization of Internal Alkynes to Iridium(III) Allene Complexes via C–H Bond Activation: Expanded Substrate Scope, and Progress towards a Catalytic Methodology

Molecules

Neha Phadke²  Michael Findlater¹ 

[1] Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, USA

关键词: iridium;    allenes;    pincer;    isomerization;    synthesis;    isolation;    crystal structure;   

DOI  :  10.3390/molecules201119686

来源: mdpi

【 摘 要 】

The synthesis of a series of allene complexes (POCOP)Ir(η²-RC==CR’) 1b–4b (POCOP = 2,6-bis(di-tert-butylphosphonito)benzene) via isomerization of internal alkynes is reported. We have demonstrated that the application of this methodology is viable for the isomerization of a wide variety of alkyne substrates. Deuterium labeling experiments support our proposed mechanism. The structures of the allene complexes 1b–4b were determined using spectroscopic data analysis. Additionally, the solid-state molecular structure of complex 2b was determined using single crystal X-ray diffraction studies and it confirmed the assignment of an iridium-bound allene isomerization product. The rates of isomerization were measured using NMR techniques over a range of temperatures to allow determination of thermodynamic parameters. Finally, we report a preliminary step towards developing a catalytic methodology; the allene may be liberated from the metal center by exposure of the complex to an atmosphere of carbon monoxide.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.