Vinylic C–H Activation of Styrenes by an Iron–Aluminum Complex

Abstract

The oxidative addition of sp 2 C−H bonds of alkenes to single-site transition-metal complexes is complicated by the competing πcoordination of the C�C double bond, limiting the examples of this type of reactivity and onward applications. Here, we report the C−H activation of styrenes by a well-defined bimetallic Fe−Al complex. These reactions are highly selective, resulting in the (E)-β-metalation of the alkene. For this bimetallic system, alkene binding appears to be essential for the reaction to occur. Experimental and computational insights suggest an unusual reaction pathway in which a (2 + 2) cycloaddition intermediate is directly converted into the hydrido vinyl product via an intramolecular sp 2 C−H bond activation across the two metals. The key C−H cleavage step proceeds through a highly asynchronous transition state near the boundary between a concerted and a stepwise mechanism influenced by the resonance stabilization ability of the aryl substituent. The metalated alkenes can be further functionalized, which has been demonstrated by the (E)-selective phosphination of the employed styrenes.

Alkane Elimination Preparation of Heterobimetallic MoAl Tetranuclear and Binuclear Complexes Promoting THF Ring Opening

“…Aluminum-based heterobimetallic complexes are burgeoning as captivating entities in coordination chemistry [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], presenting unique structures and reactivities. The distinct properties of aluminum, such as its hard Lewis acidity or its large palette of coordination modes, coupled with the diverse reactivity of transition metals, pave the way for innovative catalytic and synthetic applications [15][16][17][18][19][20].…”