Structural studies of organoboron compounds. XVI. Preparation and crystal and molecular structures of 4,4-dimethyl-2,5,5-triphenyl-1,3-dioxa-4-azonia-2-bora-5-boratacyclopentane and 4,4,5,5-tetramethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2-boratacyclopentane

Kliegel, Wolfgang; Motzkus, Hans‐Walter; Rettig, Steven J.; Trotter, James

doi:10.1139/v84-139

Cited by 8 publications

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“…Comparing the different O−B bond lengths in the heterobicycle, there is evidence of O−B pp (π) back-donation in the O−(sp 2 )B−O fragment of the seven-membered ring, the partial π-bond character causing short O−B bonds, especially at the O(11)−B(12) bond. The bond lengths of 1.431(5), 1.346(5), and 1.375(5) Å in the (sp 3 )B−O−(sp 2 )B−O portion are similar to corresponding bond lengths in five-membered heterocycles, where mean values of 1.471, 1.333, and 1.410 Å have been found, − although the (sp 3 )B−O and (sp 2 )B−O bond lengths are somewhat smaller. As compensation, the B(12)−C(30) bond length with 1.569(6) Å is slightly longer than the mean value for the above-mentioned compounds (1.554 Å). , Nevertheless, the B(12)−C(30) bond length is still indicative of some π-interaction between the phenyl group and the sp 2 -boron atom.…”

Section: Resultsmentioning

confidence: 52%

Synthesis and Study of Monomeric and Dimeric Boronates by Spectroscopic Methods and X-ray Crystallography

et al. 1998

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A series of 2-salicylideneamino ethanol derivatives with substituents in different positions have been brought to reaction with phenylboronic acid. Depending on the number and position of the substituents in the ligand, three boronate structure types have been obtained. Thereby, it could be shown that the formation of a macrocyclic dimeric boronate is preferred over the monomeric compound and a [5.4.0]heterobicyclic system with a B(4)-O-B(3) structural unit. The three structure types have been analyzed by X-ray crystallography, where a series of parameters such as NfB bond length, torsion angles, tetrahedral character at the boron atom, deviation of the boron atom from the mean plane and sum of bond angles in the heterocyclic rings have been evaluated in order to determine the factors for the preferred formation of each compound. Finally a new synthetic strategy is presented that permits the synthesis of other macrocyclic boronates in the future.

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