Dmitry B. Krivolapov

New Functional Cyclic Aminomethylphosphine Ligands for the Construction of Catalysts for Electrochemical Hydrogen Transformations

Eight-membered cyclic functional bisphosphines, namely 1,5-di-aryl-3,7-di(2-pyridyl)-1,5-diaza-3,7-diphosphacyclooctanes (aryl=2-pyridyl, m-tolyl, p-tolyl, diphenylmethyl, benzyl, (R)-(+)-(α-methyl)benzyl), with 2-pyridyl substituents on the phosphorus atoms have been synthesized by condensation of 2-pyridylphosphine, formaldehyde, and the corresponding primary amine. The structures of some of these bisphosphines have been investigated by X-ray crystallography. The bisphosphines readily form neutral P,P-chelate complexes [(κ(2)-P,P-L)MCl2], cationic bis-P,P-chelate complexes [(κ(2)-P,P-L)2 M](2+), or a five-coordinate complex [(κ(2)-P,P-L)2 NiBr]Br. The electrochemical behavior of two of the nickel complexes, and their catalytic activities in electrochemical hydrogen evolution and hydrogen oxidation, including the fuel-cell test, have been studied.

Synthesis of Novel Arylthio Derivatives of Mucochloric Acid

Stable reaction products of mucochloric acid with aromatic and heterocyclic thiols were synthesized and characterized. Under basic conditions the reactions proceeded with the substitution of the chlorine atom(s) by arylthiogroup(s), while in an acidic medium the hydroxy group at C 5 was substituted. Different types of new sulfur-containing products of di- and trisubstitution on the basis of mucochloric acid were obtained. In one case a new acyclic product—di-p-tolyl-2,3-bis-(p-tolylthio)butanedithioate—was isolated. The structure of all synthesized compounds was confirmed by IR, 1 H, and 13 C NMR spectroscopy; three compounds were characterized by single crystal X-ray diffraction.

An unusual conformation of 1,1′-dimethyl-isoindigo in crystals

The crystal and molecular structure of 1,1′-dimethyl-isoindigo is studied by single crystal X-ray diffraction analysis. It is shown that the molecules of 1,1′-dimethyl-isoindigo are nonplanar due to the rotation of two oxindole rings relative to the double bond.

Synthesis and Properties of Phosphabetaine Structures: III. Phosphabetaines Derived from Tertiary Phosphines and α,β-Unsaturated Carboxylic Acids. Synthesis, Structure, and Chemical Properties

Methods of synthesis of acylate phosphabetaines by reactions of triphenylphosphine with methacrylic, cinnamic, and p-methoxycinnamic acids are developed. The phosphabetaine form is proposed to exist in equilibrium with the σ5-oxaphospholane form. The features of methylation of the phosphabetaines are discussed.

Reactions of Allenylphosphonates with 2-Aminoethanol and Amines

Dialkyl 3-methyl-1,2-butadienylphosphonates take up 2-aminoethanol, butylamine, diethylamine, and morpholine in such a way that the amino nitrogen atom adds at the central carbon of the allene triad. The reactions with primary amines lead to the corresponding 1-phosphoryl-2-amino-1-butenes and isomeric 1-phosphoryl-2-iminobutanes, while secondary amines give rise to 1,2- and 2,3-enamines.

Synthesis and Properties of Phosphabetaine Structures: II. Synthesis and Molecular Structure of 3-(Triphenylphosphonio)propanoate and Its Alkylation Products

The structure of 3-(triphenylphosphonio)propanoate was studied, and the ability of proton-donor reagents to stabilize the betaine structure was demonstrated. The phosphobetaines are alkylated by alkyl halides to form (alkoxycarbonyl)alkyltriphenylphosphonium halides and acylated by acetyl bromides. Some features of the latter reactions were revealed.

Rearrangement of Quinoxalin-2-ones When Exposed to Enamines Generated in Situ from Ketones and Ammonium Acetate: Method for the Synthesis of 1-(Pyrrolyl)benzimidazolones

The reaction of 3-benzoylquinoxalin-2(1H)-ones with enamines (generated in situ from ammonium acetate and the corresponding methylaryl(hetaryl)ketones) proceeds smoothly to give the corresponding substituted 1-(pyrrolyl)benzimidazolone derivatives in moderate yields through the novel rearrangement of 3-benzoylquinoxalin-2(1H)-ones involving a dual cleavage of the C3═N4 and C2-C3 bonds under mild conditions.

Synthesis and properties of phosphabetaine structures: IV. 3-(triphenylphosphonio)propanoate in reactions with dipolar electrophilic reagents

Reactions of 3-(triphenylphosphonio)propanoate with heterocumulenes, such as phenyl isocyanate and dicyclohexylcarbodiimide, we studied under the assumption that they proceed by nucleophilic addition and 1,4-dipolar cycloaddition schemes. Quantum-chemical calculations show that the σ5-phosphorane cycloadduct of the betaine with isocyanate is thermodynamically preferred over its isomeric zwitter-ionic adduct. However, the experimental evidence suggests that the reaction with phenyl isocyanate involves nucleophilic addition of the betaine to isocyanate followed by hydrolysis to firm finally a complex of the starting betaine with diphenylurea. The structure of the complex was established by X-ray diffraction analysis. The revealed above controversy is explained by a high protophilicity of betaine structures, which is also confirmed by the results of the reaction of the betaine with carbodiimide.

Conformations and coordination properties of trialkyltrithiophosphites in copper(I) complexes

A series of complexes (RS)3P·CuBr with Ra Et, Pr, Bu, i-Pr as well as the complex of (PrS)3P·CuSCN were studied by X-ray single-crystal diffraction. Coordination properties of thiophosphites were found to be essentially different from their oxygen and nitrogen analogues and depend on the nature of the metal center, substituents at sulfur atoms, the conditions of reactions and of the crystal growth. All trithiophosphites in the studied copper(I) complexes except the isopropyl derivative exhibit bidentate coordination with both phosphorus and sulfur participating in coordination bonds with copper. Trithiophosphites increase their conformational multiformity upon complexation regardless of the coordination mode, propyl and butyl derivatives being conformationally inhomogeneous in crystals. Unusual cis-conformations about the P‐S bond, which are not observed for “free” trialkyltrithiophosphites or their phosphoryl and thiophosphoryl analogues, are realized in the complexes. The complexation results in the significant high-frequency shift of the symmetric and asymmetric PS3 stretching vibrations in the Raman spectra of complexes regardless of the coordination mode and in minor changes of the C‐S stretching vibrations in comparison with the spectra of the “free” ligands. q 2000 Elsevier Science B.V. All rights reserved.

Synthesis, Structure and Reactivity of Carboxylate Phosphabetaines

Abstract Triphenylphosphoniumethylcarboxylate 1 has been obtained in the reaction of triphenylphosphine with acrylic acid.