Antimony lone electronic pair as a stereoelectronic barrier to stibatrane

Abstract

To examine the effect of 5s2 lone electron pair of antimony atom on the reaction of antimony trifluoride and triethanolamine in the presence of sodium methylate, the crystal structure of the reaction product -2-fluoro-6-(2-hydroxyethyl)-1,3-dioxa-6-aza-2-stibacy-cylooctane (1-fluoro-2-hydrostibatrane) FSb (OCH2CH2)2NCH2CH2OH) was confirmed. In the compound structure, the hydrogen atom of the 2-hydtoxyethyl group of each molecule forms an intermolecular hydrogen bond with the oxygen atom of one of the five-membered SbOCH2CH2N half-cycles in a neighbouring molecule. A geometry of both five-member N-C-C-O-Sb heterocycles, end-capped by transannular N→Sb bond in the 1-fluoro-2-hydrostibatrane molecule, is almost identical. C-O, C-C, N-C interatomic distances and valence angles in two endocyclic units (NCCOSb) are comparable to those observed in RSi(OCH2CH2)3N silatranes. A coordination polyhedron of the Sb atom can be represented as a transition from a bisphenoid to Sb(O3)N trigonal pyramid, with a nitrogen atom at the apex and three oxygen atoms in the base. The N→Sb transannular coordinate bond length is 2.402(4) Å, which is 0.40 Å greater than the Sb-N covalent bond standard length. The Sb-F bond (1.997(4) Å) is 0.12 Å longer than that in the SbF3 molecule, and insignificantly shorter than that of the Sb-Fax (2.028(3) Å) in the SbF3Gly crystalline complex. The fluorine atom substantially strays from the N→Sb axis to the direction of O(1) and O(2) atoms. The oxygen atom of the 2-hydroxyethyl group lies at a distance of 2.899(3) A from that of Sb, intermediate between the valence bond length and the sum of the Van der Waals radii of these atoms. Combined with the F atom position, one can assume the 1-fluoro-2-hydrostibatrane crystal structure as a “frozen” state of the SNi(Sb) type nucleophilic attack of the oxygen atom, uncompleted because of its repulsion by the 5s2 lone electronic pair of antimony atom.

Unveiling the Quantitative Relationships between Electron Distribution and Steric Hindrance of Organic Amines and Their Reaction Rates with Carbonyl Sulfur: A Theoretical Calculation Investigation

“…Under the inductive effects of electron-donating groups, the lone pair of electrons on the amine is more prone to transfer to the COS molecule. However, the excessively high electron density can result in the side reactions. , …”

“…However, the excessively high electron density can result in the side reactions. 48,49 The step 3 demonstrates the proton transfer from the nitrogen atom to the sulfur atom. This step represents the terminal process near the transition state peak in the overall reaction barrier.…”

The complicating role of pnictogen bond formation in the solution-phase and solid-state structures of the heavier pnictogen atranes

“…Attempts to isolate and characterize the simplest stibatrane from the reaction of antimony(III) sources with triethanolamine have not been successful. [8][9][10][11] In the original claim by Müller, the product was described as a white, sublimable substance, but no additional characterization was provided. 8,11 Another report detailed an attempt to use Sb (OEt) 3 as an antimony source, but the product was not structurally characterized.…”

“…The resulting product had two Sb-O bonds and one Sb-F bond, the final equivalent of 'HF' was not removed under these conditions. [8][9][10] The resulting structure was a tricyclic pseudo-atrane with one of the rings formed though a PnB between the Sb and the OH group (Fig. 2).…”