E. A. Ishmaeva

Polarity and vibrational spectra of bis(2-phenylethyl)- and bis(2-phenylpropyl)phosphine selenides

There are quite limited published data on the structure, polarity, and vibrational spectra of organophosphorus compounds having a P=Se bond [1]. In the present communication we report on the dipole moments and vibrational spectra of bis(2-phenylethyl)phosphine selenide (I) and bis(2-phenylpropyl)phosphine selenide (II) which were synthesized from elemental phosphorus according to the Trofimov–Gusarova reaction [2] and were described for the first time in [3, 4]. Their dipole moments were determined in solution, and the IR spectra of II in different aggregate states, as well as in carbon tetrachloride and methylene chloride solutions, were recorded (see table). The dipole moments of phosphine selenides I and II fall into the range typical of four-coordinate phosphorus compounds (2.5–5.0 D) [5]. change of the number of absorption bands (freezingout) in going from liquid samples to solid, which may be attributed to both the presence of predominantly one conformer in liquid and in solution and similarity of the spectra of rotational isomers in the region 400– 1600 cm. It should be noted that the absorption band at 440 cm in the IR spectrum of II (assigned to P=Se bond vibrations [3]) does not change upon variation of the aggregate state. The same vibration gives rise to a strong band with its maximum at 442 cm in the Raman spectrum.

Polarity and structure of 2-(1-methylbenzimidazol-2-yl)-1-phenyl- and -1,2-diphenyl-1-nitroethenes

Polarity of 2-(1-methylbenzimidazol-2-yl)-1-phenyl- and -1,2-diphenyl-1-nitroethenes was determined and their structure was studied using electronic and 1H, 13C NMR spectroscopy, dipole moments measuring, XRD analysis, and quantum-chemical calculations. It was shown that the 2-(1-methylbenzimidazol-2-yl)-1-nitro-1-phenylethene has Z-configuration both in crystal and solution. The nitro group and benzimidazole substituent in its molecule are removed from the plane of the double bond. For 1,2-diphenyl-1-nitroethene E-structure is typical.

Conformational analysis of secondary arylalkylphosphine selenides

Conformational analysis of bis(2-phenylalkyl)phosphine selenides was performed by the dipole moment method and quantum-chemical calculations. Bis(2-phenylpropyl)phosphine selenide was found to exist as a mixture of several conformers, the most energetically favorable of which being characterized by gauche (non-eclipsed) orientation of the P=Se and

Conformational analysis of 4-methyl-2-trimethylsiloxy-1,3,2-dioxaphosphinane

C_{sp^3 } - C_{sp^3 }

Mechanism of the reaction of 3,3-dimethyl-1-trimethylsilyl-2-trimethylsiloxy-1-phosphabut-1-ene with chlorobis(o-phenylenedioxy)phosphorane

bonds.

Polarity and structure of 1,3,5,11-tetraoxa-8-aza-4-germaspiro [3,7]undecan-2-one

Conformational analysis of 4-methyl-2-trimethylsiloxy-1,3,2-dioxaphosphinane was performed by the dipole moment method and quantum-chemical calculations. The 1,3,2-dioxaphosphinane heteroring was found to adopt a chair conformation with equatorial orientation of the 4-methyl group and axial orientation of the irregular trimethylsiloxy substituent. The conformational equilibrium involves non-eclipsed gauche and trans conformers (the latter prevailing) interconvertible through rotation about the exocyclic P-O bond.

Conformational analysis of arylphosphine selenides

We have recently studied by quantum chemical methods the mechanism of the reaction of 3,3-dimethyl-2-trimethylsiloxy-1-trimethylsilyl-1-phosphabut-1ene (I) with diethyl phosphite [1]. There are no published data on mechanisms of reactions of compound I with electrophilic reagents. We previously reported [2] that compound I reacts with an equimolar amount of chlorobis(o-phenylenedioxy)phosphorane under mild conditions to give the product of electrophilic replacement at the two-coordinate phosphorus atom, 3,3-dimethyl-1-bis(o-phenylenedioxy)-λ-phosphanyl-2-trimethylsiloxy-1-phosphabut-1-ene (III), and chlorotrimethylsilane (Scheme 1). of the initial reactants, intermediate products, transition states, and final products were optimized. The structures localized on the potential energy surface were identified as minima or transition states by calculating the corresponding Hessian matrices (all positive eigenvalues for stable molecules and intermediates or at least one negative eigenvalue for transition states). The

Polarity and structure of diphosphorus-substituted isoxazole and 1,2,3-triazole

a Kazan (Volga Region) Federal University, Kremlevskaya ul. 18, Kazan, 420008 Russia e-mail: yavereshchagina@yahoo.com b Joint Supercomputer Center of the Russian Academy of Sciences (Kazan Branch), Kazan, Russia c Institute of Silicate Chemistry of the Russian Academy of Sciences, St. Petersburg, Russia d Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk, Russia

Mechanism of the reaction of 3,3-dimethyl-2-trimethylsiloxy-1-trimethylsilyl-1-phosphabut-1-ene with diethyl phosphite

We have carried out the conformational analysis by the methods of dipole moments and quantum chemistry [DFT B3PW91/6-31G(d), B3PW91/6-311++G(3df, 3pd)] of bis[(4-chlorophenyl)ethyl]phosphine selenide (I) and bis-[(4-tert-butylphenyl)ethyl]phosphine selenide (II), which are promising initial materials for the synthesis of various organophosphoselenium compounds. Their structural formulas are presented in the scheme. The coeffi cients of the calculation equations and the experimental dipole moments of phosphine selenides I, II are compiled in Table 1. The most probable conformers of compounds I, II according to the quantum-chemical calculations are given below (hydrogen atoms are not shown). The energies, theoretical dipole moments and those computed using the vector-additive scheme for the conformational isomers of compounds I, II are presented in Table 2. In phosphine selenide I according to the data of B3PW91/6-31G(d) the energy minimum corresponds to conformer IА possessing a symmetric structure. However the calculation in an extended basis indicates the energy prevalence of conformer IB. Taking into consideration that the dipole moment values of conformer IB calculated in both bases is in better agreement with the experimental fi nding than those of conformer IA the results of B3PW91/6-311++G(3df,3pd) concerning the energy preference of conformer IB apparently should be regarded Table 1. Coeffi cients of calculation equations and experimental dipole moments of compounds I, II

Polarity and structure of 1,1-dihalo-2,8-dioxa-5-azagermocanes

Diphosphorus-substituted isoxazole and 1,2,3-triazole were synthesized by a click chemistry method. Their polarity and structure were determined by the dipole moment method and quantum chemical calculations.