Adducts of Rhodium(II) Acetate and Rhodium(II) Pivalate with 1,8-Diazabicyclo[5.4.0]undec-7-ene

In this article, we describe the synthesis of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) adducts of rhodium(II) carboxylate complexes, [Rh2(μ-O2CCR3)4(DBU)2] (R = H (1), Me (2)). The DBU ligand is coordinated to the axial site in both adducts via the imido-nitrogen atom, and single-crystal X-ray diffraction analysis of 1 and 2 revealed structurally similar attributes between the compounds. The Rh–Rh bond distance is 2.4108(3) Å for 1 and 2.4143(2) Å for 2. The Rh–N distance is 2.2681(3) Å for compound 1 and 2.2587(10) Å for compound 2. Compound 1, however, crystallized with solvent molecules in its unit cell, and Hirshfeld surface analysis showed intermolecular C–H···O interactions between oxygen atoms of [Rh2(μ-O2CCH3)4] and the hydrogen of the chloroform solvent among other intermolecular close-contact interactions. The crystal structure of compound 2 was found to be devoid of solvent and showed weak intramolecular C–H···O interactions from the DBU axial ligand to the oxygens of the bridging acetates. Otherwise, Hirshfeld analysis showed that 2 was dominated by H···H interactions. UV-vis spectroscopy of both adducts was also conducted in different solvents to examine shifts attributed to the π*(Rh2) to σ*(Rh2) band.

Conversion of diarylchalcones into 4,5-dihydropyrazole-1-carbothioamides: molecular and supramolecular structures of two precursors and three products

Chalcones of type 4-XC6H4C(O)CH=CHC6H4(OCH2CCH)-4, where X = Cl, Br or MeO, have been converted to the corresponding 4,5-dihydropyrazole-1-carbothioamides using a cyclocondensation reaction with thiosemicarbazide. The chalcones 1-(4-chlorophenyl)-3-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C18H13ClO2, (I), and 1-(4-bromophenyl)-3-[4-(prop-2-ynyloxy)phenyl]prop-2-en-1-one, C18H13BrO2, (II), are isomorphous, and their molecules are linked into sheets by two independent C—H...π(arene) interactions, both involving the same aryl ring with one C—H donor approaching each face. In each of the products (RS)-3-(4-chlorophenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C19H16ClN3OS, (IV), (RS)-3-(4-bromophenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C19H16BrN3OS, (V), and (RS)-3-(4-methoxyphenyl)-5-[4-(prop-2-ynyloxy)phenyl]-4,5-dihydropyrazole-1-carbothioamide, C20H19N3O2S, (VI), the reduced pyrazole ring adopts an envelope conformation with the C atom bearing the 4-prop-2-ynyloxy)phenyl substituent, which occupies the axial site, displaced from the plane of the four ring atoms. Compounds (IV) and (V) are isomorphous and their molecules are linked into chains of edge-fused rings by a combination of N—H...S and C—H...S hydrogen bonds. The molecules of (VI) are linked into sheets by a combination of N—H...S, N—H...N and C—H...π(arene) hydrogen bonds. Comparisons are made with the structures of some related compounds.

The crystal structure of (RS)-7-chloro-2-(2,5-dimethoxyphenyl)-2,3-dihydroquinazolin-4(1H)-one: two hydrogen bonds generate an elegant three-dimensional framework structure

In the title compound, C61H15ClN2O3, the heterocyclic ring adopts an envelope conformation, folded across the N...N line, with the 2,5-dimethoxyphenyl unit occupying a quasi-axial site. There are two N—H...O hydrogen bonds in the structure: one hydrogen bond links molecules related by a 41 screw axis to form a C(6) chain, and the other links inversion-related pairs of molecules to form an R 2 2(8) ring. The ring motif links all of the chains into a continuous three-dimensional framework structure. Comparisons are made with the structures of some related compounds.

Crystal structure of di-μ-chlorido-bis[dichlorido(L-histidinium-κO)cadmium(II)]

In the title compound, [Cd2(C6H9N3O2)2Cl6], the coordination polyhedra around the CdII cations are distorted trigonal bipyramids. Two of the chloride ions (one axial and one equatorial) are bridging to the other metal atom, leading to a Cd...Cd separation of 3.9162 (4) Å. The O atom of the L-histidinium cation lies in an axial site. In the crystal, numerous N—H...Cl, N—H...O, C—H...O and C—H...Cl hydrogen bonds link the molecules into a three-dimensional network. Theoretical calculations and spectroscopic data are available as supporting information.

A versatile synthesis of cyclic dipeptides using the stepwise construction of the piperazine-2,5-dione ring from simple precursors: synthetic sequence and the structure of a representative product, (3RS)-4-(2-allyl-3,5-dimethylphenyl)-1-benzyl-3-phenylpiperazine-2,5-dione

A versatile synthesis of multiply substituted cyclic dipeptides has been designed, based on the stepwise construction of the piperazine-2,5-dione ring using molecular fragments from four different precursor molecules. Starting from substituted 2-allylanilines, reaction with methyl 2-bromo-2-phenylacetate yields the corresponding methyl 2-(2-allylanilino)-2-phenylacetates, which react with haloacetyl chlorides to give methyl 2-[N-(2-allylphenyl)-2-haloacetamido]-2-phenylacetates, which then undergo ring closure with benzylamine to yield the corresponding cyclic dipeptides of type 4-(2-allylphenyl)-1-benzyl-3-phenylpiperazine-2,5-dione. (3RS)-4-(2-Allyl-3,5-dimethylphenyl)-1-benzyl-3-phenylpiperazine-2,5-dione, C28H28N2O2, (IIId), crystallizes with Z′ = 2 in the space group P21/c; the allyl groups in the two independent molecules adopt different conformations and, in one of them, the allyl group is disordered over two sets of atomic sites having occupancies of 0.534 (4) and 0.466 (4). In both molecules, the piperazine-2,5-dione ring adopts a boat conformation, with the 3-phenyl ring in a quasi-axial site. The molecules of (IIId) are linked into a three-dimensional framework structure by a combination of three C—H...O hydrogen bonds and three C—H...π(arene) hydrogen bonds. Comparisons are made with some related structures.

Crystal structure of ebastinium 3,5-dinitrobenzoate

Ebastine, 4-(benzhydryloxy)-1-[4-(4-tert-butylphenyl)-4-oxobutyl]piperidine, reacts with 3,5-dinitrobenzoic acid in methanol solution to give the title 1:1 salt, ebastinium 3,5-dinitrobenzoate, C32H40NO2+·C7H3N2O6−. In the cation, the disubstituted aryl ring exhibits orientational disorder over two sets of atomic sites having occupancies 0.706 (4) and 0.294 (6), with a dihedral angle of 41.2 (5)° between the two orientations: the bulky Ph2CH—O– substituent occupies an axial site on the piperidine ring. The two ions in the selected asymmetric unit are linked by a nearly linear N—H...O hydrogen bond and this, in combination with two C—H...O hydrogen bonds, links the ions into complex sheets.

Six polycyclic pyrimidoazepine derivatives: syntheses, molecular structures and supramolecular assembly

A versatile synthetic method has been developed for the formation of variously substituted polycyclic pyrimidoazepine derivatives, formed by nucleophilic substitution reactions on the corresponding chloro-substituted compounds; the reactions can be promoted either by conventional heating in basic solutions or by microwave heating in solvent-free systems. Thus, (6RS)-6,11-dimethyl-3,5,6,11-tetrahydro-4H-benzo[b]pyrimido[5,4-f]azepin-4-one, C14H15N3O, (I), was isolated from a solution containing (6RS)-4-chloro-8-hydroxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepine and benzene-1,2-diamine; (6RS)-4-butoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-8-ol, C18H23N3O2, (II), was formed by reaction of the corresponding 6-chloro compound with butanol, and (RS)-4-dimethylamino-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-8-ol, C16H20N4O, (III), was formed by reaction of the chloro analogue with alkaline dimethylformamide. (6RS)-N-Benzyl-8-methoxy-6,11-dimethyl-6,11-dihydro-5H-benzo[b]pyrimido[5,4-f]azepin-4-amine, C22H24N4O, (IV), (6RS)-N-benzyl-6-methyl-1,2,6,7-tetrahydropyrimido[5′,4′:6,7]azepino[3,2,1-hi]indol-8-amine, C22H22N4, (V), and (7RS)-N-benzyl-7-methyl-2,3,7,8-tetrahydro-1H-pyrimido[5′,4′:6,7]azepino[3,2,1-ij]quinolin-9-amine, C23H24N4, (VI), were all formed by reaction of the corresponding chloro compounds with benzylamine under microwave irradiation. In each of compounds (I)–(IV) and (VI), the azepine ring adopts a conformation close to the boat form, with the C-methyl group in a quasi-equatorial site, whereas the corresponding ring in (V) adopts a conformation intermediate between the twist-boat and twist-chair forms, with the C-methyl group in a quasi-axial site. No two of the structures of (I)–(VI) exhibit the same range of intermolecular hydrogen bonds: different types of sheet are formed in each of (I), (II), (V) and (VI), and different types of chain in each of (III) and (IV).

Similar molecular constitutions but different conformations and different supramolecular assemblies in two related fused tetracyclic benzo[b]pyrimido[5,4-f]azepine derivatives

A simple and effective two-step approach to tricyclic pyrimidine-fused benzazepines has been adapted to give the tetracyclic analogues. In (RS)-8-chloro-6-methyl-1,2,6,7-tetrahydropyrimido[5′,4′:6,7]azepino[3,2,1-hi]indole, C15H14ClN3, (I), the five-membered ring adopts an envelope conformation, as does the reduced pyridine ring in (RS)-9-chloro-7-methyl-2,3,7,8-tetrahydro-1H-pyrimido[5′,4′:6,7]azepino[3,2,1-ij]quinoline, C16H16ClN3, (II). However, the seven-membered rings in (I) and (II) adopt very different conformations, with the result that the methyl substituent occupies a quasi-axial site in (I) but a quasi-equatorial site in (II). The molecules of (I) are linked by C—H...N hydrogen bonds to formC(5) chains and inversion-related pairs of chains are linked by a π–π stacking interaction. A combination of a C—H...π hydrogen bond and two C—Cl...π interactions links the molecules of (II) into complex sheets. Comparisons are made with some similar fused heterocyclic compounds.

Crystal structures of (1,4,7,10-tetraazacyclododecane-κ4N)bis(tricyanomethanido-κN)nickel and (1,4,7,10-tetraazacyclododecane-κ4N)(tricyanomethanido-κN)copper tricyanomethanide

The structures of two mononuclear transition-metal complexes with tricyanomethanide (tcm−) and 1,4,7,10-tetraazacyclododecane (cyclen) ligands, [Ni(C4N3)2(C8H20N4)], (I), and [Cu(C4N3)(C8H20N4)](C4N3), (II), are reported. In the neutral complex (I), the nickel cation is coordinated by one cyclen ligand and two monodentate N-bound tcm−anions in a distorted octahedral geometry. The tcm−ligands are mutuallycis. The CuIIatom in (II) displays a distorted tetragonal–pyramidal geometry, with the four N-donor atoms of the cyclen ligand in the equatorial plane, and one tcm−anion bound through a single N atom in an axial site, forming a monocation. The second tcm−molecule acts as a counter-ion not directly coordinating to the copper cation. In both (I) and (II), extensive series of N—H...N and C—H...N hydrogen bonds generate three-dimensional network structures.

Crystal structure of (2,4-di-tert-butyl-6-{[(6,6′-dimethyl-2′-oxido-1,1′-biphenyl-2-yl)imino]methyl}phenolato-κ3O,N,O′)bis(propan-2-olato-κO)titanium(IV)

In the mononuclear TiIVtitle complex, [Ti(C29H33NO2)(C3H6O)2], the TiNO4coordination polyhedron comprises an N-atom and two O-atom donors from the dianionic Schiff base ligand and two O-atom donors from monodentate isopropoxide anions. The stereochemistry is distorted trigonal–bipyramidal with the N-donor in an elongated axial site [Ti—N = 2.2540 (17) Å], the O-donors having normal Ti—O bond lengths [1.7937 (14) Å (axial)–1.8690 (14) Å]. In the crystal, C—H...π interactions link molecules into centrosymmetric dimers.