Alexander N. Boyko

Collapsed Cu(II)-Hydroxamate Metallacrowns

Degradation of a strained, thermodynamically destabilized pentanuclear copper(II) 12-metallacrown-4 complex based on a picoline hydroxamic acid resulted in the formation of the tetranuclear compounds which are the first examples of solely hydroxamate-based Cu(II) metallacrown complexes with a collapse of the metallamacrocyclic cavity.

Acceptor properties of amino groups in aminobenzene crystals: study from the energetic viewpoint

Acceptor properties of the amino groups of aniline and ortho, meta and para-diaminobenzenes in the crystal phase have been studied through the analysis of their crystal structures based on comparison of interaction energies in a crystal. Analysis of pairwise interaction energies allowed recognition of the basic structural motifs (BSMs) and determination of the types of hydrogen bonds which cause the bonding of the molecules within the BSMs and between neighboring ones. The N–H⋯N hydrogen bonds where the nitrogen lone pair is a proton acceptor were shown to be present in all studied crystals and played different roles in crystal packing. The N–H⋯N hydrogen bonds form the building unit and the primary structural motif in two polymorphic modifications of ortho-diaminobenzene. In the crystal of meta-diaminobenzene, the N–H⋯N interactions role is comparable with that of the N–H⋯π hydrogen bonds. Both these interactions form the primary basic structural motifs. Finally, the N–H⋯N hydrogen bonds have a minor role in the crystals of aniline and para-diaminobenzene where these interactions ensure bonding between secondary basic structural motifs. The crystals of the monoclinic and orthorhombic polymorphs of aniline as well as para-diaminobenzene differ from each other by mutual arrangement of the secondary basic structural motifs.

A solution-phase parallel synthesis of alkylated guanidines from thioisocyanates and amines

An efficient solution-phase parallel synthesis of alkylated guanidines from commercial thioisocyanates and amines is described. In the first step, a thioisocyanate reacts with one equivalent of ammonia or a primary or secondary amine to give a thiourea intermediate. The latter is S-alkylated with n-dodecyl bromide resulting in the corresponding thiouronium bromide. Finally, the reaction of the thiouronium salt with a second equivalent of ammonia or a primary amine yields an alkylated guanidine. All three synthetic steps are easily combined in a one-pot high-yielding procedure with a simple work-up. Ca. 250 guanidine derivatives with high structural and functional diversity were synthesized by the developed method. 35 representatives reported in this study were fully characterized.

Influence of substituents on the acceptor properties of the amino groups in the diaminobenzene analogues

The influence on the geometric characteristics and acceptor properties of the amino groups has been studied in substituted diaminobenzenes. Quantum-chemical calculations using different approaches to the modeling of a polarizing environment have shown the most significant influence of the nitro group in the ortho and para positions relative to the amino substituent. The study of the crystal packing of mono- and dinitrodiaminobenzenes has revealed the increasing role of stacking interactions in the crystal structure up to the formation of the building unit. In most cases, stacking interactions compete with the N–H⋯O hydrogen bonds, forming the primary basic structural motifs (BSM) or bonding them. The N–H⋯N hydrogen bonds with the nitrogen lone pair as proton acceptor have been revealed for the meta-amino groups and play a negligible role in crystal packing, bonding the secondary BSM. Surprisingly, the N–H⋯N hydrogen bonds in the crystals of 3-amino-4-nitroaniline form the primary BSM, but they may be considered rather the N–H⋯π interactions.

A Facile Synthesis of Functionalized 1,2,6,7-Tetrahydroimidazo[1,5-c]pyrimidine-3,5-diones

Abstract A Pd-mediated hydrogenation of ethyl 6-azidomethyl-1,2,3,4-tetrahydro-4-R-2-oxo-5-pyrimidinecarboxylates leads to the corresponding ethyl 6-aminomethyl1,2,3,4-tetrahydro-4-R-2-oxo-5-pyrimidinecarboxylates. The latter react with bis(trichloromethyl)carbonate, yielding the title ethyl 1,2,3,5,6,7-hexahydro-7-R-3,5-dioxoimidazo[1,5-c]pyrimidine-8-carboxylates. Supplemental materials are available for this article. Go to the publishers online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT

Tris(2,2′-bipyridine-κ2N,N′)cobalt(III) bis­[bis­(pyridine-2,6-dicarboxyl­ato-κ3O2,N,O6)cobaltate(III)] perchlorate dimethyl­formamide hemisolvate 1.3-hydrate

In the title compound, [Co(C10H8N2)3][Co(C7H3NO4)2]2(ClO4)·0.5C3H7NO·1.3H2O, the CoIII atom in the complex cation is pseudooctahedrally coordinated by six N atoms of three chelating bipyridine ligands. The CoIII atom in the complex anion is coordinated by two pyridine N atoms and four carboxylate O atoms of two doubly deprotonated pyridine-2,6-dicarboxylate ligands in a distorted octahedral geometry. One dimethylformamide solvent molecule and two water molecules are half-occupied and one water molecule is 0.3-occupied. O—H⋯O hydrogen bonds link the water molecules, the perchlorate anions and the complex anions. π–π interactions between the pyridine rings of the complex anions are also observed [centroid–centroid distance = 3.804 (3) Å].

Diaqua-bis-(pyridine-2-carboxyl-ato-κN,O)manganese(II) dimethyl-formamide hemisolvate.

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

Diaquabis(pyridine-2-carboxylato-κ2N,O)manganese(II) dimethylformamide hemisolvate

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

Diaqua­bis­(pyridine-2-carboxyl­ato-κ2N,O)manganese(II) dimethyl­formamide hemisolvate

There are two crystallographically independent complex molecules with very similar geometries in the unit cell of the title compound, [Mn(C6H4NO2)2(H2O)2]·0.5C3H7NO. The central ion is situated in a distorted octahedral environment of two N- and four O-donor atoms from two pyridine-2-carboxylate ligands and two cis-disposed water molecules. The carboxylate ligands are coordinated in a chelate fashion with the formation of two five-membered rings. In the crystal, the complex molecules are connected by O—H⋯O hydrogen bonds between the coordinated water molecules and the uncoordinated carboxylate O atoms, thus forming hydrogen-bonded walls disposed perpendicularly to the bc plane.

Poly[di-μ2-aqua-μ5-(pyridine-2,6-dicarboxyl­ato)-μ3-(pyridine-2,6-dicarboxyl­ato)-cobalt(II)disodium]

In the title compound, [CoNa2(C7H3NO4)2(H2O)2]n, the CoII atom is coordinated by two pyridine N atoms and four carboxylate O atoms from two doubly deprotonated pyridine-2,6-dicarboxylate ligands in a distorted octahedral geometry. One Na+ cation is coordinated by three carboxylate O atoms and two water molecules and the other is coordinated by five carboxylate O atoms and two water molecules in an irregular geometry. The bis(pyridine-2,6-dicarboxylato)cobalt complex units are connected by Na+ cations and bridging water molecules into a three-dimensional coordination network. O—H⋯O hydrogen bonds are formed between the water molecules and the carboxylate O atoms.