Structure of Intramolecular Boron–Amine Complexes and Proposal of Tetrahedral Character for Correlation between Molecular Structure and Barrier to Dissociation of the N–B Bonds

Abstract

The molecular structures of a set of intramolecular boron-amine complexes, 9-[2-(dialkylaminomethyl)phenyl]-9-borabicyclo[3.3.1]nonanes (alkyl = Me and Et) and 2-[2-(dimethylaminomethyl)phenyl]-4,4-diphenyl-1,3,2-dioxaborolane, were determined by the X-ray analyses. The boron atom has a tetrahedral geometry and the five-membered ring is puckered with the nitrogen atom out of the plane in every complex. The distances of the N–B coordination bonds, which are in the range of 1.74–1.77Å, are not always correlated to the barrier to dissociation of the N–B bonds. In order to correlate the molecular structures to the strength of the N–B coordination bonds, the tetrahedral character, which is calculated from bond angles at a boron atom, is proposed. The usefulness as well as the limitation of this parameter are discussed.

Theoretical Characterization of Three 2,2-Diphenyl-1,3,2-oxazaborolidin-5-ones: Molecules with Fungicide Activities

“…According to the geometrical parameters, it appears that the bond length between B 2 N 3 atoms is short when an amino acid residue is present in position C 4 . Specifically, for these molecules, bond lengths were 1 (1.705 Å), 2 (1.667 Å) and 3 (1.682), distances that are consistent with values indicated in the literature (1.638-1.759 Å) [16][17][18][19][20]. The dihedral angles did not show significant differences around these atoms, and the bond angles (107°) around the boron atom were approximately tetrahedral.…”

Synthesis, characterization and X-ray studies of new chiral five-six-membered ring, [4.3.0] heterobicyclic system of monomeric boronates

“…The results from X-ray diffraction indicated high strain present in the five member rings of the molecules as well as the envelope conformation, the tetrahedral character of the boron atoms which is directly associated to the geometry [18,19] showed deviation from ideal values. The configurational stability at the boron atom is closely related to the size of the substituents attached to the aliphatic carbons in the ethanol amine residues.…”

Synthesis and characterization of novel intramolecularly base-stabilized BEt2 and BEt derivatives: molecular structures of 1-Et2BOCPh2-2-NMe2C6H4, 1-(CH3COO)EtBOCCy2-2-NMe2C6H4 and BEt(1-OCPh2CH2-2-NMe2C6H4)2

“…114.6(3) The B-N bond lengths of 4 and 6 are comparable to those of related dichloroborane derivatives [4] and those of dialkyl-or dialkoxyborane compounds with BC 3 N rings [17,18]. Also, the B-N bond lengths in 4 and 6 are larger than those of the adducts BCl 3 The bond lengths and angles of the organic fragment of 4 and 6 are similar to those observed for the corresponding organic compounds 1 and 2 [7].…”