Vitalii V. Suslonov

Trinuclear (aminonitrone)ZnII complexes as key intermediates in zinc(ii)-mediated generation of 1,2,4-oxadiazoles from amidoximes and nitriles

Aliphatic and aromatic amidoximes RC(NH2)NOH (R = Et, tBu, Ph, o-ClC6H4) react with Zn(OAc)2·2H2O in Me2CO giving [Zn(OAc)2{RC(NH2)NOH}2] complexes bearing N-bound amidoximes, which are involved in a moderate strength (7.3–11.9 kcal mol−1 by the DFT calculations) intramolecular resonance-assisted hydrogen bonding between the oxime HO group and the oxo group of the acetate ligand. The complexes [Zn(OAc)2{RC(NH2)NOH}2] react with excess Zn(OTf)2 in acetone accomplishing trinuclear species [Zn3(μ2-OAc)2{μ2-RC(NH2)N(H)O}4(H2O)6](OTf)4 featuring both O-ligated amidoximes—stabilized in the aminonitrone tautomeric form—and bridging acetate ligands. The aminonitrone trinuclear species were also prepared directly via the reaction of the amidoximes with Zn(OTf)2 in EtOAc; ethyl acetate in this reaction plays the role of the acetate donor and OAc− is generated in situ via ZnII-mediated hydrolysis of EtOAc. Although [Zn(OAc)2{RC(NH2)NOH}2] are inactive toward dimethylcyanamide, the [Zn3(μ2-OAc)2{μ2-RC(NH2)N(H)O}4(H2O)6](OTf)4 complexes readily react with Me2NCN giving, as a result of ZnII-mediated amidoxime–cyanamide coupling, the O-carbamidine amidoxime complexes [Zn(OTf)2{RC(NH2)NOC(NMe2)NH}2]. All synthesized compounds were characterized by HRESI-MS, FTIR, 1H-, CP-MAS TOSS 13C{1H}-, and 13C{1H} NMR, and additionally by single-crystal X-ray diffraction for eight species. Different types of non-covalent interactions in the obtained solid-state structures were studied by DFT calculations (M06-2X/6-311+G(d,p) level of theory) and topological analysis of the electron density distribution within the formalism of Baders theory (QTAIM method).

A speedy route to sterically encumbered, benzene-fused derivatives of privileged, naturally occurring hexahydropyrrolo[1,2-b]isoquinoline

A series of 15 benzene-fused hexahydropyrrolo[1,2-b]isoquinolonic acids with substantial degree of steric encumbrance has been prepared via a novel variant of the Castagnoli–Cushman reaction of homophthalic anhydride (HPA) and various indolenines. The employment of a special kind of a cyclic imine component reaction allowed, for the first time, isolating a Mannich-type adduct between HPA and an imine component which has been postulated but never obtained in similar reactions.

Mechanism of generation of closo-decaborato amidrazones. Intramolecular non-covalent B–H⋯π(Ph) interaction determines stabilization of the configuration around the amidrazone CN bond

Three types of N(H)-nucleophiles, viz. hydrazine, acetyl hydrazide, and a set of hydrazones, were used to study the nucleophilic addition to the CN group of the 2-propanenitrilium closo-decaborate cluster (Ph3PCH2Ph)[B10H9NCEt], giving N-closo-decaborato amidrazones. A systematic mechanistic study of the nucleophilic addition is provided and included detailed synthetic, crystallographic, computational and kinetic work. As a result, two possible mechanisms have been proposed, which consist of firstly a consecutive incorporation of two Nu(H) nucleophiles, with the second responsible for a subsequent rapid proton exchange. The second possible mechanism assumes a pre-formation of a dinuclear [Nu(H)]2 species which subsequently proceeds with the nucleophilic attack on the boron cluster. The activation parameters for hydrazones indicate a small dependence on bond formation [ΔH‡ = 6.8–15 kJ mol−1], but significantly negative entropies of activation [ΔS‡ ranges from −139 to −164 J K−1 mol−1] with the latter contributing some 70–80% of the total Gibbs free energy of activation, ΔG‡. In the X-ray structure of (Z)-(Ph3PCH2Ph)[B10H9N(H)C(Et)NHNCPh2], very rare intramolecular non-covalent B–H⋯π(Ph) interactions were detected and studied by DFT calculations (M06-2x/6-311++G** level of theory) and topological analysis of the electron density distribution within the framework of Baders theory (QTAIM method). The estimated strength of these non-covalent interactions is 0.8–1.4 kcal mol−1.

Intermolecular hydrogen bonding H···Cl− in the solid palladium(II)-diaminocarbene complexes

Abstract Weak intermolecular non-covalent H···Cl− interactions in the solid chelated palladium(II)-diaminocarbene complex cis-[PdCl(CNXyl){C(NHXyl)=NHC6H2Me2NH2}]Cl (3; Xyl=2,6-Me2C6H3) were studied by XRD followed by appropriate DFT calculations. The N–H···Cl contacts for both NH groups in the carbene moiety are different (N1–H···Cl2 3.5258(19), N2–H···Cl2 3.0797(17) Å). The DFT calculations and topological analysis of the electron density distribution within the formalism of Bader’s theory (QTAIM method) were performed for a model cluster of the carbene complex 3. The theoretical data confirmed that the strength of intermolecular HB H···Cl− is different for two NH-protons of the carbene fragment. The influence of crystal packing effects on the formation of hydrogen bonds in the cluster of 3 is noticeable.

Halogen and chalcogen bonding in dichloromethane solvate of cyclometalated iridium(III) isocyanide complex

Abstract Solvent-rich dichloromethane solvate of cis-[Ir(bptz)2(CNXyl)2]BF4 (3, bptz is cyclometallated 4-(4-bromophenyl)-2-methylthiazole) is prepared via the reaction of chloro-bridged dimer [Ir(bptz)2(μ-Cl)]2 (1) with 2,6-dimethylphenyl isocyanide (CNXyl, 2) and AgBF4. Single crystal X-ray diffraction on the 3·3¼CH2Cl2 solvate showed the presence of numerous non-covalent interactions, including the C–S···F–B chalogen bonding (ChB), the C–Br···Br–C, C–Cl···Br–C, and C–Cl···S(C)–C halogen bonding (XB), and the C–H···F–B hydrogen bonding (HB). The nature of these short contacts was explored both experimentally by single-crystal X-ray diffraction and theoretically by DFT calculations on the empirical geometries followed by Bader’s topological electron density distribution analysis. The evaluated energies of XBs and ChBs are in range 1.3–2.2 kcal/mol indicating the non-covalent nature of the contacts.

Synthesis of bimetallic nanoparticles based on cobalt and nickel. Effects of their composition and structure on catalytic and magnetic properties

Bimetallic core-shell nanoparticles Co@Ni and Ni@Co and CoNi alloy ones have been prepared via polyol synthesis. Comparison of morphology, magnetic, and catalytic properties of the nanoparticles have revealed that the particles structure rather than the nickel/cobalt ratio determines their catalytic activity in the model reaction of p-nitrophenol reduction into p-aminophenol.

Low-temperature equilibriums in solutions of isocyanide-phosphine complexes of palladium(II) chloride

Abstractcis-[PdCl2(CNR)(PPh3)] [R = Cy, t-Bu, C(Me)2CH2C(Me)3] have been synthesized via the interaction of [(PPh3)ClPd(μ-Cl)2PdCl(PPh3)] with isocyanide in CH2Cl2 at room temperature with 90–98% yield and characterized by means of mass spectrometry as well as 1H, 13C{1H, 31P}, and 31P{1H} NMR spectroscopy. The complexes structure in the solid phase has been elucidated by means of X-ray diffraction analysis. Dynamic processes in the solutions of the complexes in CDCl3 and CD2Cl2 at temperature of–95 to 60°С have been studied by means of 1H and 31P NMR spectroscopy. It has been found that the studied compounds existed exclusively in the cis-[PdCl2(CNR)(PPh3)] form in the solutions. In the case of cis-[PdCl2(CNCy)(PPh3)] in CH2Cl2, the conformational transitions of the equilibrium forms (the transition of the substituent in the cyclohexyl cycle between the equatorial and axial positions) are slowed down, the equatorial conformer prevailing in the solution (2: 1 at–95°С). Quantum-chemical simulation (DFT) has revealed that the standard Gibbs energy of the conformational transition from the axial form of cis-[PdCl2(CNCy)(PPh3)] into the equatorial one in the CH2Cl2 solution at 178 K equals–2.5 kJ/mol, being in agreement with the experimental data.

Synthesis of Platinum(II) Phoshine Isocyanide Complexes and Study of Their Stability in Isomerization and Ligand Disproportionation Reactions

Phosphine isocyanide complexes cis-[PtCl2(CNMes)(P)] with mesitylisocyanide and phoshine ligands were synthesized in yields of 92‒98%. The products were characterized by mass spectrometry, IR and 1H NMR, COSY, NOESY, HSQC, and HMBC spectroscopy, and X-ray diffraction analysis. The solid-state and solution structures of the complexes and their stability in isomerization and ligand disproportionation reactions were studied.

A highly diastereoselective one-pot three-component 1,3-dipolar cycloaddition of cyclopropenes with azomethine ylides generated from 11H-indeno[1,2-b]-quinoxalin-11-ones

A simple and efficient method has been developed for the synthesis of complex compounds with spiro-fused 11H-indeno[1,2-b]quinoxaline and cyclopropa[a]pyrrolizine or azabicyclo[3.1.0]hexane moieties. All the products have been synthesized in good to high yields and excellent diastereoselectivity by one-pot three-component 1,3-dipolar cycloaddition reactions of various derivatives of cyclopropene with azomethine ylides. Azomethine ylides were in situ generated from 11H-indeno[1,2-b]quinoxalin-11-one derivatives and amines, such as N-substituted and N-unsubstituted α-amino acids, benzylamines, and also peptides (dipeptide Gly-Gly and tripeptide Gly-Gly-Gly). To understand the mechanism that allows for azomethine ylide generation followed by 1,3-dipolar cycloaddition, a quantum chemical investigation was performed. The anticancer activity of some of the obtained compounds against the human leukemia K562 cell line was evaluated by flow cytometry in vitro.

Facile selective synthesis of 2-methyl-5-amino-1,2,4-oxadiazolium bromides as further targets for nucleophilic additions

The reaction of aminonitrones R1C(NH2) = N+(Me)O− (R1 = Alk, Ar) with isocyanides R2NC (R2 = Alk, Ar; 1.2 equiv.) and Br2 (1 equiv.) conducted in CHCl3 (RT, 5 min) gives 2-methyl-5-amino-1,2,4-oxadiazolium bromides in good to excellent yields (65–95%; 16 examples). These species are highly electrophilically activated and 5-cyclohexylamino-2-methyl-3-phenyl-1,2,4-oxadiazolium bromide, taken as a model compound for the reactivity study, reacts rapidly under mild conditions with hydroxylamine, hydrazine, or benzamidine, to give 5-cyclohexylamino-3-phenyl-1,2,4-oxadiazole (88%), 5-cyclohexylamino-3-phenyl-1,2,4-triazole (95%), and 2-cyclohexylamino-4,6-diphenyl-1,3,5-triazine (64%), respectively. Treatment of the oxadiazolium salt with excess water provides N-benzoyl-N′-cyclohexylurea (95%).