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Electronic and steric effects in rollover C–H bond activation

Maidich, Luca and Dettori, Gavina and Stoccoro, Sergio and Cinellu, Maria Agostina and Rourke, Jonathan P. and Zucca, Antonio (2015) Electronic and steric effects in rollover C–H bond activation. Organometallics, Vol. 34 (5), p. 817-828. ISSN 0276-7333. eISSN 1520-6041. Article.

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DOI: 10.1021/om500681u

Abstract

Steric and electronic factors in rollover C–H bond activation of substituted 2,2′-bipyridines, mediated by platinum(II), have been investigated by comparing the influence of two substituents, CH3 and CF3, on the progress of the reaction. The substituents were chosen to have similar steric hindrance but different electronic effects and were placed in position 6 (i.e., near one of the nitrogen atoms) or in position 5, which allows, in part, electronic and steric influence to be distinguished. The ligands studied, 6-methyl-2,2′-bipyridine, 5-methyl-2,2′-bipyridine, 6-trifluoromethyl-2,2′-bipyridine, and 5-trifluoromethyl-2,2′-bipyridine, were compared to unsubstituted 2,2′-bipyridine in the reaction with the electron-rich complex [Pt(Me)2(DMSO)2]. The electron-withdrawing CF3 group was found to have a significant effect in accelerating the cyclometalation reaction. The substituent in position 6 influences the stability of the intermediate adduct [Pt(N,N)(Me)2] (N,N = chelated bipyridine), as indicated by density functional theory calculations. The steric hindrance of substituted bipyridines was also evaluated by defining and measuring the angle ζ in [Pt(N,N)(Me)2] adducts. The presence of a substituent in position 6 causes destabilization of the adduct, acceleration of the cyclometalation reaction, and regioselectivity of C–H bond activation.

Item Type:Article
ID Code:10804
Status:Published
Refereed:Yes
Uncontrolled Keywords:Steric and electronic factors, rollover C–H bond activation, platinum(II)
Subjects:Area 03 - Scienze chimiche > CHIM/03 Chimica generale e inorganica
Divisions:001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:American Chemical Society
ISSN:0276-7333
eISSN:1520-6041
Deposited On:19 Feb 2015 12:46

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