Experimental and theoretical conformational analysis of N-methyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, N-butyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide, and N-octyl-N-[2-(diphenylphosphoryl)ethyl]diphenylphosphorylacetamide was carried out by the methods of dipole moments, IR spectroscopy, and Density Functional Theory (DFT) B3PW91/6-311++G(df,p) calculations. In solution, these N,N-dialkyl substituted bisphosphorylated acetamides exist as a conformational equilibrium of several forms divided into two groups—with Z- or E-configuration of the carbonyl group and alkyl substituent, and syn or anti arrangement of the phosphoryl-containing fragments relative to the amide plane. The substituents at the phosphorus atoms have eclipsed cis- or staggered gauche-orientation relative to the P=O groups, and cis orientation of the substituents is due to the presence of intramolecular H-contacts P=O...H−C_phenyl or p,π conjugation between the phosphoryl group and the phenyl ring. Preferred conformers of acetamides molecules are additionally stabilized by various intramolecular hydrogen contacts with the participation of oxygen atoms of the P=O or C=O groups and hydrogen atoms of the methylene and ethylene bridges, alkyl substituents, and phenyl rings. However, steric factors, such as a flat amide fragment, the bulky phenyl groups, and the configuration of alkyl bridges, make a significant contribution to the realization of preferred conformers.

Conformational analysis of tris(3-methylphenyl)phosphine and its chalcogenides has been performed by methods of dipole moments, IR spectroscopy, and quantum chemistry [DFT B3PW91/6-31G(df,p)]. In...

The conformational analysis of bis[N-alkyl-N-(2-diphenylphosphorylethyl)]amides of diglycolic acid has been carried out using the methods of dipole moments, IR spectroscopy, and quantum-chemical DFT B3PW91/6-311++G(df,p) simulation. In solution, N,N-dimethyl-, N,N-dibutyl-, and N,N-dioctyl-substituted diamides of diglycolic acid exist as an equilibrium mixture of two groups of symmetrical or nonsymmetrical conformers, in some of which intramolecular contacts involving hydrogen atoms of the alkyl substituents and oxygen atoms of the ether bridge or carbonyl groups are possible.

The polarity and structure of tri(1- or 2-naphthyl)phosphines and their chalcogenides were determined by the methods of dipole moments, IR spectroscopy, and DFT quantum-chemical calculations at the B3PW91/6-311++G(df,p) level of theory. In solution, tri(1-naphthyl)phosphine prefers a single conformer with a gauche,gauche,gauche orientation of the substituents at the phosphorus. Tri(2-naphthyl)phosphine, as well as both phosphine chalcogenides exist as equilibrium mixtures of several forms with a propeller arrangement of the substituents and a cis or gauche orientation of the C_sp2‒C_sp2 and P=X (X = LEP, O, S, Se) bonds.

The mechanism of formation of N-methyl-2-(diphenylphosphoryl)acetamide was studied by DFT. The first stage, the reaction of trichlorophosphine with 2-(diphenylphosphoryl)acetic acid, involves three elementary steps, and the explicit inclusion of solvent makes it possible to reduce the activation energy of each of them. The second stage, the reaction of 2-(diphenylphosphoryl)acetyl chloride with a phosphoryl-substituted amine, involves one elementary step.

Tris(hetaryl)substituted phosphines and their chalcogenides are promising polydentate ligands for the design of metal complexes. An experimental and theoretical conformational analysis of tris[2-(4-pyridyl)ethyl]phosphine, tris[2-(2-pyridyl)ethyl]phosphine, and their chalcogenides was carried out by the methods of dipole moments, IR spectroscopy and DFT B3PW91/6-311++G(df,p) calculations. In solution, these compounds exist as an equilibrium of mainly non-eclipsed (synclinal or antiperiplanar) forms with a predominance of a symmetrical conformer having a gauche-orientation of the C_sp3–C_sp3 bonds of pyridylethyl substituents relative to the P=X bond (X = lone pair, O, S, Se) and a gauche-orientation of the pyridyl rings relative to the zigzag ethylene bridges. Regardless of the presence and nature of the chalcogen atom (oxygen, sulfur, or selenium) in the studied molecules with many axes of internal rotation, steric factors—the different position of the nitrogen atoms in the pyridyl rings and the configuration of ethylene bridges—determine the realization and spatial structure of preferred conformers.