The countercation effect on the reactivity of ambiphilic o-(fluorodimethylsilyl)phenyl anion was investigated by replacing Li in 1 with Cu (4 and 5), Mg (6), and Zn (7). The reactivity of the aryl metal species was estimated by the yields of dimerized product 3, which were monitored by GC. X-ray crystallographic analysis, DFT calculations, and AIM analysis of bis(aryl)zinc 7 were performed. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 24:53–57, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21062

o-C₆H₄(SiR_3−nH_n)(BMes₂) (1; R=Me, Ph; n=1, 2) undergo MesH (Mes=mesityl) ligand exchange between the silicon atom and the boron atom to form o-C₆H₄(SiMesR_3−nH_n−1)(BMesH) (6) upon heating. The resulting hydroborane intermediates (6) immediately react with benzaldehyde to afford their corresponding benzyloxyboranes (5). A DFT study of model compounds reveals the transition states of the ligand exchange. A hydride abstraction from the silicon atom by the boron center is key to reaching the transition states, which include the tricoordinate silyl-cation moiety and the tetracoordinate hydridoborate moiety.

Reactions of o-(HSiR₂)(BMes₂)C₆H₄ (R = Me (3a), Ph (3b)) with a fluoride ion afford [o-(FSiR₂)(HBMes₂)C₆H₄]⁻ (R = Me (5a), Ph (5b)), which involve the FSi⋅⋅⋅HB interaction to render the silicon atom pentacoordinate. The FSi⋅⋅⋅HB interaction in 5a was confirmed by X-ray crystallographic analysis and “atoms-in-molecules” (AIM) analysis. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:471–475, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20709