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

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.

Structural studies of organoboron compounds. XXVIII. 5,5-Trimethylene-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane and 5,5-dimethyl-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane monohydrate

The preparation of the title compounds demonstrates the bis-N-alkylation of secondary amines by formaldehyde, these labile ammonium inner salts being captured as diphenylboron chelates. Crystals of 5,5-trimethylene-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane are orthorhombic, a = 8.8461(3), b = 10.7290(4), c = 15.8773(5) Å, Z = 4, space group P212121, and those of 5,5-dimethyl-2,2-diphenyl-1,3-dioxa-5-azonia-2-boratacyclohexane monohydrate are monoclinic, a = 6.2432(3), b = 17.1469(8), c = 14.3701(5) Å, β = 90.647(3)°, Z = 4, space group P21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.030 and 0.047 for 1400 and 2258 reflections with I ≥ 3σ(I), respectively. Both compounds have a B,N-betaine structure, the six-membered chelate rings adopting chair conformations. Libration-corrected bond lengths, O—B = 1.508(3)−1.522(3) and C—B = 1.612(4)−1.637(4) Å, indicate relatively strong binding of the diphenylboron moiety to the oxygen atoms of the O,O-chelating ligands.

Untersuchung des Substituenteneinflusses auf die Massenspektren von Diphenylborchelaten aus Salicylaldehyd-Azomethinen / Investigation on the Influence of the Substituent on the Mass Spectra - of Salicylaldehyde Azomethine Diphenylboron Chelates

Mass spectra of several substituted diphenylboron chelates derived from salicylaldehyde azomethines were compared with respect to the influence of the amine substituent R. The fragment ion M—C6H5 is the most intensive one. The abundance of the remaining fragment ions is poor. However, there are characteristic differences of corresponding ions depending on the influence of the substituent R.