Andrey V. Mironov

Photochemical Synthesis of Phosphinolines from Phosphonium−Iodonium Ylides

We describe three different series of experiments which were undertaken to test our hypothesis that during irradiation of phosphonium-iodonium ylides (1a, 1b) an electrophilic carbene is generated. By opposing the assumed intermediate to monosubstituted alkynes, we observed in the case of electron-rich substituents at the triple bond a domination of a 1,3-dipolar cycloaddition of the intermediate with the triple bond to yield furans. In the case of electron poorer substituents, the formation of phosphinolines prevails. A second series of experiments was carried out with mixed ylides in which one phenyl ring at the triarylphosphonium group was replaced by a thienyl group. In this case, we observe only an intramolecular reaction with the thienyl ring to yield the phosphinolines 21-23. In a third test, we replaced in the mixed ylides 1a, 1b the COR group by a CN substituent. This modification leads to phosphinolines only and avoids a 1,3-dipolar cycloaddition.

Heterocycles from Phosphonium-Iodonium Ylides. Photochemical Synthesis of λ5-Phosphinolines

A photochemical reaction of mixed phosphonium-iodonium ylides with acetylenes yielding lambda(5)-phosphinolines, a rare class of phosphorus heterocycles hardly accessible by other methods, was found. The yields of lambda(5)-phosphinolines vary from 35% to 80%. The structures of two phosphinolines were established by single-crystal X-ray diffraction. The X-ray diffraction and NMR spectra data indicate the superposition of ylidic and aromatic structures for phosphinolines.

New complex oxides in RBaThCuO systems (R = LaGd)

Abstract The new complex oxides R2Ba1.33Th0.67Cu3O8+δ (R = La, Pr) and La0.67Ba1.33R2−xThxCu3O8+δ (R = NdGd, x = 0.5, 0.67) were synthesized. These compounds have a similar structure to the Ce-223 high-Tc oxides. The oxygen content (or δ) was varied over a wide range after annealing at high oxygen pressure (up to 90 atm). Unit cell parameters and δ values for all the new phases were determined. The resistivities of these semiconducting compounds obey the law ϱ = ϱoT−α. A single crystal of Nd2Ba1.5Th0.5Cu3−xAlxO8+δ (x = 0.3, δ = 0.8) was obtained and its structure was determined by X-ray single-crystal experiment (tetragonal system, space group I4 mmm , a = 3.9057(5) A, c = 28.569(4) A, Z = 2).

Comparative analysis of NdCaCoO4 phase formation from cryogel and from solid state precursors

In order to identify the reasons of the complicated synthesis of NdCaCoO4 by the cryogel method, the phase formation processes during thermal processing of precursors were investigated by in-situ X-ray diffraction analysis, Rietveld refinement and energy dispersive X-ray analysis of reaction products and intermediates. Formation of NdCaCoO4 from the cryogel precursor and from the mixture of oxides and CaCO3 is observed at 1000–1100 °C. The complicated phase formation from the cryogel precursor is associated with the low reactivity of (Nd,Ca)CoO3 intermediate of the precursor thermolysis. Precipitation by NaOH/Na2CO3 instead of KOH/K2CO3 results in the reduction of NdCaCoO4 formation temperature to 800 °C. According to energy dispersive X-ray analysis, the coprecipitation of Nd, Ca and Co is accompanied by the capture of Na ions followed by the formation of NaxCoO2 phase at 600–700 °C. The enhanced reactivity of (Nd,Ca)CoO3 in this case could be attributed to the enhanced ion mobility due to the simultaneous formation of NaxCoO2, CoO and NdCaCoO4 (Hedvall effect).Graphical Abstract