O,N-chelated boron aminophenolate complexes. Crystal structure of BPh2(OC6H4(CH2NMe2)-2)

Two diphenylboron ortho-aminophenolate complexes, [BPh2(OC6H4(CH2NMe2)-2)] (2) and [BPh2(OC6H2(CH2NMe2)(2),-2,6-Me-4)] (6), have been prepared in a on e-pot procedure approach starting from B(OMe)(3). The starting material was reacted with two equivalents of phenylmagnesium bromide, followed by hydro lysis with HCl. The resulting borinic acid, BPh2(OH), was reacted with eith er HOC6H4(CH2NMe2)-2 or HOC6H2(CH2NMe2)(2)-2,6-Me-4 to give 2 or 6, respect ively. An X-ray structure determination of 2 showed it to be a four-coordin ate boron compound with a tetrahedral coordination geometry. The six-member ed chelate ring in 2 is puckered. Variable temperature H-1-NMR analysis of 6 showed the existence of two dynamic processes in solution, i.e. one proce ss involving flipping of the puckered chelate ring conformation (Delta G(do uble dagger) = 41 kJ mol(-1)) and a second, higher energy, process (Delta G (double dagger) = 65 kJ mol(-1)) in which exchange of coordinated and non-c oordinated amine functions occurs. The exchange is (at least partly) assist ed intermolecularly. (C) 2000 Elsevier Science S.A. All rights reserved.