η 2 Coordination of Electron-Deficient Arenes with Group 6 Dearomatization Agents

• Published in: Organometallics 2020-07, Vol.39 (13), p.2493-2510
• Main Authors: Smith, Jacob A, Simpson, Spenser R, Westendorff, Karl S, Weatherford-Pratt, Justin, Myers, Jeffery T, Wilde, Justin H, Dickie, Diane A, Harman, W Dean
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.0c00277

The exceptionally -basic metal fragments {MoTp-(NO)(DMAP)} and {WTp(NO)(PMe )} (Tp = tris(pyrazolyl)borate; DMAP = 4-( , -dimethylamino)pyridine) form thermally stable -coordinated complexes with a variety of electron-deficient arenes. The tolerance of substituted arenes with fluorine-containing electron withdrawing groups (EWG; -F, -CF , -SF ) is examined for both the molybdenum and tungsten systems. When the EWG contains a bond (nitriles, aldehydes, ketones, ester), coordination occurs predominantly on the nonaromatic functional group. However, complexation of the tungsten complex with trimethyl orthobenzoate (PhC(OMe) ) followed by hydrolysis allows access to an -coordinated arene with an ester substituent. In general, the tungsten system tolerates sulfur-based withdrawing groups well (e.g., PhSO Ph, MeSO Ph), and the integration of multiple electron-withdrawing groups on a benzene ring further enhances the -back-bonding interaction between the metal and aromatic ligand. While the molybdenum system did not form stable -arene complexes with the sulfones or ortho esters, it was capable of forming rare examples of stable -coordinated arene complexes with a range of fluorinated benzenes (e.g., fluorobenzene, difluorobenzenes). In contrast to what has been observed for the tungsten system, these complexes formed without interference of C-H or C-F insertion.