Hydrogen-Bonded Dimeric Synthon of Fluoro-Substituted Phenylboronic Acids versus Supramolecular Organization in Crystals

Abstract

An analysis of crystal structures of a series of fluoro-substituted phenylboronic acids is presented. Interplay between the structure of a basic H-bonded dimeric R 2 2 (8) synthon and a higher-order supramolecular organization is highlighted. The elucidation of hydrogen bonds formed by the boronic B(OH) 2 moiety is supported by energy calculations based on a one-dimensional H-bond model as well as by Hirshfeld surface analysis. The results revealed that intramolecular O−H•••F hydrogen bonds are insignificant compared to O−H•••O ones in dimers in controlling the syn−anti conformation of the boronic group. Depending on the strength of H-bonds in the basic motif, forces constituting so-called large synthons change from O−H•••O hydrogen bonds to stacking interactions. This differentiation entails the twist of the boronic group with respect to the phenyl ring. The large synthons serve as main building blocks for three-dimensional structures either by their close packing or by the aid of weak secondary interaction such as C−H•••π, O−H•••F, or C−H•••F hydrogen bonds. The observed isomorphism and polymorphism are discussed in relation to the packing of one-dimensional large synthons.

Fluorinated Boronic Acids: Acidity and Hydrolytic Stability of Fluorinated Phenylboronic Acids

“…For the meta position, the resonance effect is much weaker, which causes increased acidity. In the case of the ortho derivative, an intramolecular B–O–H ··· F hydrogen bond is formed, which causes additional electron withdrawal from the boron center.…”

“…The exception is (2,6‐difluorophenyl)boronic acid ( 8 ), which displays a lower acidity than the 2,5 derivative 7 . It can be explained by the fact that in 2,6‐difluoro‐substituted phenylboronic acids, only one intramolecular hydrogen bond is formed, which was shown by X‐ray diffraction crystal structure determination for numerous compounds . Hence, the second ortho ‐fluorine substituent does not change the charge on the boron atom by hydrogen‐bond formation.…”

Geometry of trigonal boron coordination sphere in boronic acids derivatives – a bond-valence vector model approach

“…For example, in a series of variously fluoro-substituted phenylboronic catechol esters the para-fluoro derivative KIYZEZ (Madura et al, 2013) shows a substantially smaller v y value in comparison to other related compounds. Generally, the overall molecular geometry is similar in the whole series (both for molecules in crystals as well as in the gas phase), except for notable B-C shortening in the para derivative (Madura et al, 2014). Therefore, one can assume that in the para-fluorosubstituted case the mesomeric effect overcomes the inductive one and the -donation towards the B atom is observed.…”

Crystal structure of (2′,3,6′-trichlorobiphenyl-2-yl)boronic acid tetrahydrofuran monosolvate

“…The B-C [1.5907 (16) Å ] and B-O [1.3514 14, 1.3641 (14) Å ] bonds in the title compound (I) are within the expected range typically observed for boronic acids (Madura et al, 2014;Luliń ski et al, 2007;Maly et al, 2006;Shimpi et al, 2007;Durka et al, 2012). The molecular structure shows that the B(OH) 2 group adopts the usual syn-anti conformation (Fig.…”