Molecular structure and spectroscopic properties of N-methylmorpholine betaine complex with 4-hydroxybenzoic acid

Crystal structure of the 1:1 complex of N-methylmorpholine betaine (MMB) with 4-hydroxybenzoic acid (4-HBA) has been determined by X-ray diffraction. Crystals are orthorhombic, space group Pna2₁ with a=7.933(2), b=15.336(3), and Z=4, R=0.033. The acid molecule forms two O-H?O hydrogen bonds with two betaine molecules. The COOH group of the acid forms shorter hydrogen bond with betaine (2.587(2) Å), than the hydroxyl group (2.677(2) Å). The carbonyl oxygen atom of the acid also interacts with the methylene hydrogen atom of the betaine through C-H?O hydrogen bond (3.256(2) Å). Thus formed infinite chains parallel to the z axis are connected by other C-H?O hydrogen bonds into layers perpendicular to the x axis. The morpholine ring has a chair conformation with the methyl group in the equatorial position and CH₂COO⁻ group in the axial one. The powder FTIR and Raman spectra and semiempirical calculations of the isolated molecule confirm the structure of the complex investigated. The ¹H and ¹³C spectra indicate that in DMSO-d₆ solution, protons are not transferred from the acid to the betaine molecules.     

Effective synthesis and X-ray investigation of (±)-2<Emphasis Type="Italic">S</Emphasis>-2-(2-chlorophenyl)-3-acetyl-1,3-oxazolidine

The crystal and molecular structure of (±)-2S-2-(2-chlorophenyl)-3-acetyl-1,3-oxazolidine was determined by X-ray diffraction analysis. Orthorhombic crystal with unit cell parameters a = 6.7419(8) Å, b = 10.3797(12) Å, c = 14.9233(18) Å; space group P2₁2₁2₁, Z = 4, ρ _calc = 1.436 g/cm³, composition C₁₁H₁₂ClNO₂. The deviation of the chlorine atom from the mean square plane of the phenyl cycle is ?0.010(5) Å. The five-membered oxazolidine cycle has an envelope conformation, which is typical for this class of compounds; the cycle is rotated at the C-C bond with respect to the phenyl fragment (the dihedral angle is 79.7(1)°). The spatial structure of the C2 chiral center lying in the plane of the 2-chlorophenyl fragment may be described as a distorted tetrahedron with an S configuration of the sp ³ hybridized carbon atom. Analysis of torsion angles and deviation of the nitrogen atom from the surrounding three-angle plane by ?0.017(3) Å allows one to speak about a tendency toward a pyramidal structure for the trisubstituted nitrogen atom. The 3D crystal structure is formed by intermolecular hydrogen bonds of C-H...O type and a strong intermolecular contact of 3.164(3) Å between the chlorine atom and the carbonyl oxygen of the acyl group.     

A Nonempirical Quantum-Chemical Study and Natural Bond Orbital Analysis of C6H5XCY3 Species (X = SO or SO2, Y = H or F)

The potential functions of internal rotation about the C² _sp—S bonds for C₆H₅XCY₃ species (X = SO or SO₂, Y = H or F) have been obtained at the MP2 (full)/6-31+G(d) level of ab initio theory. It is found that the spatial structures with the plane of C² _sp—S—C³ _sp bonds, which is near perpendicular to the benzene ring plane, are the energy-favourable conformations. The values of the rotational barrier about the C² _sp—S bond are equal to (kJ/mole): 21.2 (C₆H₅SOCH₃), 29.0 (C₆H₅SOCF₃), 20.4 (C₆H₅SO₂CH₃), and 28.2 (C₆H₅SO₂CF₃). On the basis of the Natural Bond Orbital (NBO) analysis results, it has been revealed that the double S=O bond is a strongly polarized covalent -bond, whereas -bond electrons practically are localized on the oxygen atom. The S=O bond order for aromatic sulfoxides and sulphones is mainly caused by hyperconjugational interactions according to the LP(O) ^*(S—C_ipso) and LP(O) ^*(S—C _Y ) mechanisms. In sulphones there is also the additional mechanism of hyperconjugational interactions such as LP(O^{1 *}(S—O²) and LP(O²) ^*(S—O¹). With the replacement of one hydrogen atom on the —XCY₃ group, the charge loss of the unsubstituted benzene molecule increases: —SOCH₃ < —SO₂CH₃ < — SOCF₃ < —SO₂CF₃. The substitution of the —CH₃ group for the —CF₃ group weakly influences the charge value on the sulfur atom but effects the acceptor characteristics of the substituent to a greater extent than the variation of the sulfur atom coordination.     

Preparation and crystal structure of hydrated crystalline complex of ciprofloxacin and copper tetrachloride

Synthesis of a complex formed by ciprofloxacin (cfH) and copper(II) chloride is described; its crystal structure is reported and analyzed in comparison to related compounds. The obtained compound (cfH₃)CuCl₄·H₂O (cfH ₃ ²⁺ — double protonated cfH molecule) crystallizes as platelets of P2₁/c symmetry having the unit cell parameters a = 13.491(1) Å, b = 11.0459(7) Å, c = 16.299(1) Å; β = 111.392(7)°. Carbonyl oxygen O(1) is protonated, and hydrogen atom combined with it forms an intramolecular hydrogen bond with carboxylic O(2) oxygen (O(1)?O(2) = 2.642(5) Å). Terminal nitrogen atom N(3) of the piperazinyl group is also protonated, and two its hydrogen atoms participate in hydrogen bonds of N-H?Cl type. The structure also has hydrogen bonds O-H?O, O-H?Cl with the participation of water molecules which occupy hydrophilic channels. Molecular ions cfH ₃ ²⁺ make couples with intrapair π?π interactions.     

C（sp3）-H bond functionalization of oximes derivatives via 1,5-hydrogen atom transfer induced by iminyl radical

Oximes derivatives have been vastly used in organic synthesis. In this review, C（sp³）-H bond functionalization of oximes derivatives via iminyl radical induced 1,5-hydrogen atom transfer was discussed. According to the different type of products, this review was divided into three parts:（1） C（sp³）-H bond functionalization for C-C bond formation.（2） C（sp³）-H bond functionalization for C-N bond formation.（3） C（sp³）-H bond functionalization for C-S, C-F b...     

Self-assembly of diorganotin(IV) 2-{[(E)-1-(2-oxyaryl)alkylidene]amino}acetates: An investigation of structures by X-ray diffraction, solution and solid-state tin NMR, and electrospray ionization MS

The diorganotin(IV) compounds, [Me₂SnL²(OH₂)]₂ (1), [ⁿBu₂SnL²(OH₂)]₂ (2), [ⁿBu₂SnL¹]₃ · 0.5C₃H₆O (3), [ⁿBu₂SnL³]₃ · 0.5C₆H₆ (4) and [Ph₂SnL³]_n · 0.5C₆H₆ (5) (L = carboxylic acid residue, i.e., 2-{[(E)-1-(2-oxyaryl)alkylidene]amino}acetate), were synthesized by treating the appropriate diorganotin(IV) dichloride with the potassium salt of the ligand in anhydrous methanol.The reaction of Ph₂SnL² (L = 2-{[(E)-1-(2-oxyphenyl)ethylidene]amino}acetate) with 1,10-phenanthroline (Phen) yielded a 1:1 adduct of composition, [Ph₂SnL²(Phen)] (6).The crystal structures of 1-6 were determined.The crystal of 1 is composed of centrosymmetric dimers of the basic Me₂SnL²(OH₂) moiety, where the two Sn-centres are linked by two asymmetric Sn-O?Sn bridges involving the carboxylic acid O atom of the ligand and a long Sn?O distance of 3.174(2) Å.The dimers are further linked into columns by hydrogen bonds.The coordination geometry about the Sn atom is a distorted pentagonal bipyramid with the two methyl groups in axial positions.The structure of 2 is similar.The same Sn atom coordination geometry is observed in compound 3, which is a cyclic trinuclear[ⁿBu₂SnL¹]₃ compound. Each Sn atom is coordinated by the phenoxide O atom, one carboxylate O atom and the imino N atom from one ligand and both the exo- and endo-carboxylate O atoms (mean Sn-O(exo): 2.35 Å; Sn-O(endo): 2.96 Å) from an adjacent ligand to form the equatorial plane, while the two butyl groups occupy axial positions. Compound 4 was found to crystallize in two polymorphic forms. The Sn-complex in both forms has a trinuclear [ⁿBu₂SnL³]₃ structural motif similar to that found in 3. In compound 5, distorted trigonal bipyramidal Ph₂SnL³ units are linked into polymeric cis-bridged chains by a weak Sn?O interaction (3.491(2) Å) involving the exocyclic O atom of the tridentate ligand of a neighboring Sn-complex unit. This interaction completes a highly distorted octahedron about the Sn atom, where the weakly coordinated exocyclic O atom and one phenyl group are trans to one another. In contrast, a monomeric distorted pentagonal bipyramidal geometry is found for adduct 6 where the Sn-phenyl groups occupy the axial positions. The solution and solid-state structures are compared by using ¹¹⁹Sn NMR chemical shift data. Compounds 1-6 were also studied using ESI-MS and their positive- and negative-ions mass fragmentation patterns are discussed.     

Dinuclear and polynuclear silver(I) saccharinate complexes with 1,3-diaminopropane and N-methylethylenediamine constructed from Ag?C interactions

New dinuclear and polynuclear Ag(I) complexes with the formula of [Ag₂(sac)₂(pen)₂] (1) and [Ag₂(sac)₂(nmen)]_n (2), (sac = saccharinate, pen = 1,3-diaminopropane, nmen = N-methylethylenediamine) have been synthesized and characterized by IR spectroscopy and thermal (TG/DTG, DTA) analysis. In addition, their structures were determined by single crystal X-ray diffraction technique. In 1, Ag(I) ions are doubly bridged by two pen ligands, besides pen ligands exhibit an interesting coordination mode by binding bridging ligand. Sac ligands connect to silver atom through its imino N atom. Furthermore, each Ag(I) ion exhibits a T-shaped coordination geometry. In 2, Ag(I) coordination environment is again T-shaped, including weak Ag-Ag bonds. The sac exhibits bidentate bringing mode, involving its imino nitrogen and carbonyl oxygen atoms, besides, bridging of Ag(I) centres by sac ligands results in argentophilic contacts. The polymeric units are assembled into two-dimensional networks by hydrogen bonds, C-H?π stacking interactions, weak Ag?C_sac (η²) and Ag?O interactions.     

Crystal structure and conformational analysis of 1-[N-(2-bromophenyl)]naphthaldimine

1-[N-(2-bromophenyl)]naphthaldimine (C₁₇H₁₂NOBr) (1) was synthesised and its crystal structure was determined. The compound 1 is orthorhombic, space group P2₁2₁2₁ with a=12.653(2), b=13.7311(14), Z=4, R=0.032 for 499 reflections I>2σ(I)]. There is an intramolecular hydrogen bond of distance 2.473(3) Å between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformation was calculated as a function of torsion angle θ (C10-C11-N1-C12) varied every 5 degrees. The optimized geometry of the crystal structure corresponding to the non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by hydrogen-hydrogen repulsions between the ortho-hydrogen atoms on the aldehyde rings. Complementary IR, ¹H NMR and UV measurements in solution and in the solid state were carried out.     

Two-dimensional supramolecular assembly of phenylmercury(II) and cadmium(II) complexes with a tridentate thiohydrazone NNS donor ligand: Synthesis,coordination behavior and crystal structure

The reaction of phenylmercury(II) acetate and cadmium(II) acetate with a refluxed solution of diacetylmonoxime and morpholine N-thiohydrazide formed a novel phenylmercury(II) complex, [PhHg(Hdammthiol)] (1) and a cadmium(II) complex, [Cd(Hdammthiol)₂] (2), respectively (where H₂dammthiol is the thiol form of diacetylmonoximemorpholine N-thiohydrazone (Hdammth) formed by the condensation of diacetylmonoxime and morpholine N-thiohydrazide in the presence of phenylmercury(II) and cadmium(II) ions). The complexes were characterised by elemental analyses and spectral data (electronic, infrared and ¹H NMR) and also by X-ray crystal structure analysis. The X-ray crystallography shows that the phenylmercury(II) complex attained a tricoordinated distorted T-shaped structure, while the cadmium(II) complex attained a trapezoidal bipyramidal geometry. The phenylmercury(II) complex forms a two-dimensional sheet via C–H?O and O–H?N hydrogen bonding and also forms a two-dimensional supramolecular dimer, having C–H?π synthons. Intermolecular C–H?O and O–H?O hydrogen bonding of the cadmium(II) complex forms a two-dimensional supramolecular sheet along the bc plane and posses an impressively short intermolecular C(sp³)?O(sp³) contact.     

Ni(0)-promoted activation of Csp2–H and Csp2–O bonds

A dinickel(0)–N₂ complex, stabilized with a rigid acridane-based PNP pincer ligand, was studied for its ability to activate C(sp²)–H and C(sp²)–O bonds. Stabilized by a Ni–μ–N₂–Na⁺ interaction, it activates C–H bonds of unfunctionalized arenes, affording nickel–aryl and nickel–hydride products. Concomitantly, two sodium cations get reduced to Na(0), which was identified and quantified by several methods. Our experimental results, including product analysis and kinetic measurements, strongly suggest that this C(sp²)–H activation does not follow the typical oxidative addition mechanism occurring at a low-valent single metal centre. Instead, via a bimolecular pathway, two powerfully reducing nickel ions cooperatively activate an arene C–H bond and concomitantly reduce two Lewis acidic alkali metals under ambient conditions. As a novel synthetic protocol, nickel(ii)–aryl species were directly synthesized from nickel(ii) precursors in benzene or toluene with excess Na under ambient conditions. Furthermore, when the dinickel(0)–N₂ complex is accessed via reduction of the nickel(ii)–phenyl species, the resulting phenyl anion deprotonates a C–H bond of glyme or 15-crown-5 leading to C–O bond cleavage, which produces vinyl ether. The dinickel(0)–N₂ species then cleaves the C(sp²)–O bond of vinyl ether to produce a nickel(ii)–vinyl complex. These results may provide a new strategy for the activation of C–H and C–O bonds mediated by a low valent nickel ion supported by a structurally rigidified ligand scaffold.

A structurally rigidified nickel(0) complex was found to be capable of cleaving both C(sp²)–H and C(sp²)–O bonds.     

Preparation and study of chiral boron containing amine-cyano(pyrrolyl-1)borane complexes. Preparation of (−)-(S)-α-phenylethylamine-(−)-cyano(pyrrolyl-1)borane and (+)-(R)-α-phenylethylamine-(+)-cyano(pyrrolyl-1)borane

Several amine-cyano(pyrrolyl)borane complexes [A · BH(NC₄H₄)CN] containing a chiral boron atom were prepared from the reactions of sodium cyanohydrodipyrrolylborate-tridioxane¹ [NaBH(NC₄H₄)₂CN · 3C₄H₈O₂] with amine hydrochlorides as well as by base exchange from the appropriate 4-cyanopyridine complex [4-CNC₅H₄N · BH(NC₄H₄)CN]. Amines with an sp² N atom give stable complexes of a wide range of basicity (pK_a = 0.8?9.7), in contrast to the anines with sp³ hybridized N where only the stronger bases (pK_a ? 7.3) are capable of giving stable complexes (mainly secondary and tertiary amines). These compounds undergo hydrolysis in neutral and alkaline media, while in strong acids they give stable boronium ions by protonation at the α-C atom of the pyrrolyl group. The compounds (?)-(S)-α-phenylethylamine-(?)-cyanopyrrolylborane and (+)-(R)-α-phenylethylamine-(+)-cyanopyrrolylborane have been prepared in pure form; in solution they undergo slow epimerization. Treatment of the appropriate complexes with KH has given the chiral boron-containing borates KBH(NC₄H₄)(CN)X (X = imidazolyl-, pyrazolyl-). Dicyanohydropyrrolylborane was obtained from 4-cyanopyridine-cyanopyrrolylborane and NaCN.     

Site-selective amination and/or nitrilation via metal-free C(sp2)–C(sp3) cleavage of benzylic and allylic alcohols

Benzylic/allylic alcohols are converted via site-selective C(sp²)–C(sp³) cleavage to value-added nitrogenous motifs, viz., anilines and/or nitriles as well as N-heterocycles, utilizing commercial hydroxylamine-O-sulfonic acid (HOSA) and Et₃N in an operationally simple, one-pot process. Notably, cyclic benzylic/allylic alcohols undergo bis-functionalization with attendant increases in architectural complexity and step-economy.

Benzylic/allylic alcohols are converted via site-selective C(sp²)–C(sp³) cleavage to value-added nitrogenous motifs, viz., anilines and/or nitriles as well as N-heterocycles, utilizing commercial hydroxylamine-O-sulfonic acid (HOSA) and Et₃N in an operationally simple, one-pot process.     

Neodymium(III) triaquatrihydroxo(1,3-diamino-2-propanoltetraacetato)germanium(IV) hydrate [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>] · H<Subscript>2</Subscript>O: Synthesis and crystal and molecular structure

The heteronuclear germanium(IV) and neodymium(III) complex with 1,3-diamino-2-propanoltetraacetic acid (H₅Hpdta) [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H₂O)₃] · H₂O has been synthesized for the first time and characterized by physicochemical methods (elemental analysis, X-ray powder diffraction, thermogravimetry, IR spectroscopy, X-ray crystallography). The crystals are monoclinic: a = 9.331(3) Å, b= 10.279(4) Å, c = 21.474(7) Å, β = 94.59(3)°, V = 2053.0(12) ų, Z = 4, space group P2₁/n, R1 = 0.0245 for 4060 reflections with I > 2σ(I). The compound is built of complex binuclear molecules [Ge(OH)(μ-HHpdta)(μ-OH)Nd(OH)(H₂O)₃] and water molecules of crystallization. The germanium and neodymium atoms are bridged by the oxygen atom of the hydroxo group (Ge-O, 1.798(2) Å; Nd-O, 2.539(2) Å) and the deprotonated oxygen atom of the isopropanol group of the HHpdta^4? ligand (Fe-O, 1.858(2)Å; Nd-O, 2.420(2) Å) to form a dimeric molecule. Each coordination sphere (of the Ge atom and of the Nd atom) contains one nitrogen atom (Ge-N, 2.096(3) Å; Nd-N, 2.807(2) Å) and two carboxylic oxygen atoms from four acetate branches of the octadentate HHpdta^4? ligand (av. Ge-O, 1.928(2) Å; Nd-O, 2.391(2) Å). The coordination polyhedron of the Ge atom is completed to a distorted octahedron by the oxygen atom of the terminal hydroxo group (Ge-O 1.811(2) Å), and the polyhedron of the Nd atom is completed to a nine-vertex polyhedron by the oxygen atoms of the terminal hydroxo group (Nd-O 2.494(3) Å) and three water molecules (Nd-O, 2.512(3), 2.520(3), and 2.723(3) Å). In the crystal structure, the complex molecules and the water molecules of crystallization are joined by a hydrogen bond system.     

Experimental and theoretical study of N-(2-hydroxyethyl)morpholine betaine

N-(2-hydroxyethyl)morpholine betaine (HEMB) has been characterized by a single crystal X-ray analysis, FTIR spectroscopy and DFT calculations. The crystals are monoclinic, space group P2₁/c with a=10.273(2), b=9.360(2), c=9.447(2) Å and β=104.72(3)Å. Two molecules of HEMB form a centrosymmetric dimer (X2) connected by a pair of hydrogen bonds between the CH₂CH₂OH and COO⁻ groups, with the O?O distance of 2.672(2) Å. The morpholine ring adopts a chair conformation with the CH₂CH₂OH group in the axial and the CH₂COO⁻ group in the equatorial position. The structures of the dimer, B2, and two monomers, B1a and B1b, have been optimized by the B3LYP approach using the 6-31G(d,p) basis set. The computed structure of B2, agrees well with the experimental X2. From two stable monomeric conformers the more favored is B1a, with the intramolecular hydrogen bond with the O-H?O distance of 2.566 Å. The effects of hydrogen bonding and electrostatic interactions on the conformation of the molecules investigated have been discussed. The FTIR spectrum shows a broad absorption in the 3300-2600 cm⁻¹ region, typical of moderate O-H?O hydrogen bonds.     

Complexes of pyridine and quinoline N-oxides with boron trifluoride: the <Superscript>1</Superscript>H NMR study

The formation of complexes of pyridine and quinoline N-oxides with BF₃ was studied by ¹H NMR method. It was shown that the molecular complexes obtained are either individual isomers or a mixture of stereoisomers, whose structures are determined by both electronic and steric properties of substituents in a heterocycle. The type of hybridization (sp3 or sp2) of the O atom of the N-oxide group in the above adducts was assumed to be specified also by the above factors.     

Synthesis, crystal structure, infrared and Raman spectra of Sr5(As2O7)2(AsO3OH)

The new compound Sr₅(As₂O₇)₂(AsO₃OH) was synthesized under hydrothermal conditions. It represents a previously unknown structure type and belongs to a group of a few compounds in the system SrO-As₂O₅-H₂O; (As₂O₇)⁴⁻ besides (AsO₃OH)²⁻ groups have not been described yet. The crystal structure of Sr₅(As₂O₇)₂(AsO₃OH) was determined by single-crystal X-ray diffraction (space group P2₁/n, a=7.146(1), b=7.142(1), , β=93.67(3)°, , Z=4). One of the five symmetrically unique Sr atoms is in a trigonal antiprismatic (Inorg. Chem. 35 (1996) 4708)—coordination, whereas the other Sr atoms adopt the commonly observed (“Collect” data collection software, Delft, The Netherlands, 1999; Methods Enzymol. 276 (1997) 307)—coordination. The position of the hydrogen atom was located in a difference Fourier map and subsequently refined with an isotropic displacement parameter. Worth mentioning is the very short hydrogen bond length O_h-H?O(1) of 2.494(4) Å; it belongs to the shortest known examples where the donor and acceptor atoms are crystallographically different. This hydrogen bond was confirmed by IR spectroscopy. In addition, Raman spectra were collected in order to study the arsenate groups.     

Fragmentation of the metastable molecular ion of methyl lactate: The formation of oxygen-protonated methanol [CH3OH2]+ involving double hydrogen atom transfers

The spontaneous unimolecular dissociation reaction of methyl lactate (1) ionized by electron impact was investigated by a combination of mass-analyzed ion kinetic energy spectrometry and deuterium labeling. The metastable ions 1^+· decompose in a variety of ways: four fragment peaks are observed at m/z 89, 76, 61, and 45, which correspond to the losses of ?H₃, CO, CH₃?O, and ?OOCH₃, respectively. Double hydrogen atom transfer occurs in the third reaction. The source-generated m/z 61 ions decompose into oxygen-protonated methanols at m/z 33 ([CH₃OH ₂ ⁺ ]) by the loss of CO with double hydrogen atom migration. Both hydroxyl and methyne hydrogen atoms in 1 ^+· are present in the resultant protonated methanols.