Dynamic Ion Speciation during the Hydrolysis of Aryltrifluoroborates**

Abstract

Organotrifluoroborates serve as coupling partners during transmetalation in the Suzuki–Miyaura reaction but require hydrolysis prior to the coupling reaction. Their anionic nature allows study of their hydrolysis by electrospray ionization mass spectrometry (ESI‐MS) through real‐time monitoring, complemented by pH analysis. The induction period varied according to the borates employed, and a dynamic series of equilibria for numerous ions was observed during hydrolysis. We found that the induction periods and reaction rates were sensitive to the R group of the borates, the shape of the reaction vessel, and stir rate.

Salt Metathesis: Tetrafluoroborate Anion Rapidly Fluoridates Organoboronic Acids to give Organotrifluoroborates

“…Yet establishing steady‐state concentrations is challenging as these are not observable by 19 F NMR spectroscopy (Figure 1), nor have they been observed in previous reports on their hydrolysis [15a] . A recent report on the solvolysis of RBF 3 − s used mass‐spectrometry to evidence low‐level speciation of mono‐ and difluorohydroxyborates, [15h] and corroborates earlier reports on the hydrolysis of BF 3 and H 3 O + BF 4 − , which reported complex mixtures inferred from pH titrations [21] . Also refractory to characterization is the nature of the boric acid product(s) given the fluxionality of boric acid clusters e.g., trimetaboric acid, tetraboric acid, linear acid polymers, hydrates, and methyl esters thereof [22] .…”

Primary trifluoroborate-iminiums enable facile access to chiral α-aminoboronic acids via Ru-catalyzed asymmetric hydrogenation and simple hydrolysis of the trifluoroborate moiety

“…33 This is associated with the fact that structurally diverse organic trifluoroborates exhibit notably different hydrolysis rates. 50,51 As we have shown recently, only Bode's SiCl 4 method 33 enabled the conversion of pTAMs to the aminoboronic acids while other methods failed. 35 However, huge excess (10 eq.)…”