Structural studies of organoboron compounds LXIII. Reaction of ketoximes with aldehydes and diphenylborinic acid, and the crystal and molecular structures of two different types of boron chelates and one of the precursor aldehyde adducts

Abstract

The diphenylboron chelates of ketoxime adducts to formaldehyde and trichloroacetaldehyde (chloral) have been synthesized. The reactions were carried out as three-component one-pot reactions, and also as two-step reactions for the ketoxime chloral adducts, which were isolated and characterized before reaction with oxybis(diphenylborane) to form the diphenylboron chelates. One of the intermediate adducts and two of the diphenylboron chelates have been characterized by X-ray crystallographic analysis. Crystals of O-(2,2,2-trichloro-1-hydroxyethyl)-2-propanonoxime, 8d, are monoclinic, a = 7.010(2), b = 11.832(3), c = 11.684(2) Å, β = 90.48(2)°, Z = 4, space group P21/c; those of 4-isopropylidene-2,2-diphenyl-1,3-dioxa-4-azonia-2-boratacyclopentane, 9a, are orthorhombic, a = 11.098(2), b = 15.364(1), c = 8.715(2) Å, Z = 4, space group P212121; and those of 5-trichloromethyl-2-isopropylidene-3,3-diphenyl-1,4-dioxa-2-azonia-3-boratacyclopentane, 10d, are monoclinic, a = 9.164(2), b = 15.304(3), c = 13.859(2) Å, β = 105.28(1)°, Z = 4, space group P21/n. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R = 0.037, 0.044, and 0.040 (Rw = 0.041, 0.016, and 0.042) for 1082, 1256, and 3062 reflections with I ≥ 3σ(F2), respectively. The X-ray analyses show that the products from the reaction between acetonoxime, oxybis(diphenylborane), and formaldehyde or trichloroacetaldehyde, respectively, possess different boron chelate structures. With formaldehyde a COBON chelate ring is obtained and with trichloroacetaldehyde a BOCON chelate ring is formed. Keywords: boron chelates, boron compounds, organboron compounds, crystal structures.