Ring Centroid Research Articles

Lewis acidity of Si6Cl12 and its role as convenient SiCl2 source.

The free cyclohexasilane Si6Cl12 (1) was obtained in 66% yield from the corresponding Cl(-) diadduct [nBu4N]2[1·2Cl] and AlCl3 in C6H6. The substituted cyclohexasilane 1,1-(Cl3Si)2Si6Cl10 (2), however, cannot be liberated from [nBu4N]2[2·2Cl] under comparable reaction conditions. Instead, a mixture of several products was obtained, from which the oligosilane Si19Cl36 (3) crystallized in low yields. X-ray crystallography revealed 3 to consist of two Si5 rings, bridged by one silicon atom. Compound 1 possesses Lewis acidic sites above and below the ring centroid. Competition experiments reveal that their corresponding acid strengths are comparable to that of BCl3. The reaction of 1 with 6 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Idipp) leads to a complete breakdown of the cyclic scaffold and furnishes the dichlorosilylene adduct Idipp-SiCl2.

Synthesis and structure of nitrile-solvated rare earth metallocene cations [Cp2Ln(NCR)3][BPh4] (Cp = C5Me5, C5H4SiMe3; R = Me, tBu, Ph)

The coordination chemistry of MeCN, tBuCN, and PhCN with the cationic rare earth metallocene complexes [(C5Me5)2Ln][(μ-Ph)2BPh2], 1-Ln (Ln=Y, La, Gd), has been examined to determine how nitrile coordination will affect the metallocene geometry. Crystallographic determination of geometry was possible for [(C5Me5)2Ln(NCMe)3][BPh4] (2-Y, 2-Gd), [(C5Me5)2Y(NCtBu)3][BPh4] (3-Y), and [(C5Me5)2Ln(NCPh)3][BPh4] (4-La, 4-Gd). In each case, only three nitriles are found to coordinate and the metallocenes are bent with (C5Me5 ring centroid)–metal–(C5Me5 ring centroid) angles of 137–140°. The THF adduct, [(C5Me5)2La(NCMe)2(THF)][BPh4], 5-La, was also crystallographically characterized. A similar result was observed with the yttrium metallocene of the trimethylsilyl-containing ligand (C5H4SiMe3)1−: coordination of only three nitriles is found in [(C5H4SiMe3)2Y(NCMe)3][BPh4], 6-Y, which has a 136.8° (C5Me5 ring centroid)–Y–(C5Me5 ring centroid) angle.

Crystal structure of nuarimol.

The title compound [systematic name: (RS)-(2-chloro­phen­yl)(4-fluoro­phen­yl)(pyrimidin-5-yl)methanol], C17H12ClFN2O, is a pyrimidine fungicide. The asymmetric unit comprises two independent mol­ecules, A and B, in which the dihedral angles between the plane of the pyrimidine ring and those of the chloro­phenyl and fluoro­phenyl rings are 71.10 (6) and 70.04 (5)° in mol­ecule A, and 73.24 (5) and 89.30 (5)° in mol­ecule B. In the crystal, O—H⋯N hydrogen bonds link the components into [010] chains of alternating A and B mol­ecules. The chains are cross-linked by C—H⋯F hydrogen bonds and weak C—H⋯π and C—Cl⋯π [Cl⋯ring centroid = 3.7630 (8) Å] inter­actions, generating a three-dimensional network.

Crystal structure of 3-amino-2-propyl-quinazolin-4(3H)-one.

In the title mol­ecule, C11H13N3O, the propyl group is almost perpendicular to the quinazolin-4(3H)-one mean plane, making a dihedral angle of 88.98 (9)°. In the crystal, mol­ecules related by an inversion centre are paired via π–π overlap, indicated by the short distances of 3.616 (5) and 3.619 (5) Å between the centroids of the aromatic rings of neighbouring mol­ecules. Inter­molecular N—H⋯N and N—H⋯O hydrogen bonds form R 6 6(30) rings and C(5) chains, respectively, generating a three-dimensional network. Weak C—H⋯O inter­actions are also observed.

Synthesis and crystal structures of two coordination polymers and a binuclear cadmium(II) complex containing 3- and 4-aminobenzoate ligands.

Due to their wide range of coordination modes and versatile conformations when binding to metal atoms, multicarboxylate ligands are of interest in the design of metal-organic frameworks (MOFs). Three Cd(II) complexes, namely catena-poly[diammonium [[chloridocadmium(II)]-di-μ-chlorido-[chloridocadmium(II)]-bis(μ-3-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N]], {(NH4)[CdCl2(C7H6NO2)]}n, (I), catena-poly[[[aquacadmium(II)]-bis(μ-4-aminobenzoato)-κ(3)N:O,O';κ(3)O,O':N] monohydrate], {[Cd(C7H6NO2)2(H2O)]·H2O}n, (II), and di-μ-acetato-κ(4)O:O'-bis[(4-aminobenzoato-κ(2)O,O')(2,2'-bipyridine-κ(2)N,N')cadmium(II)], [Cd2(CH3COO)2(C7H6NO2)2(C10H8N2)2], (III), with different stuctural forms are reported. Complex (I) has a one-dimensional ladder structure, with strong N-H···O and weak N-H···Cl hydrogen bonds linking the cations and anions in the three-dimensional supramolecular structure. Complex (II) has a one-dimensional chain structure. Extensive O-H···O and N-H···O hydrogen bonds between the anionic ligands and the solvent water molecules and π-π stacking interactions between the centroids of the benzene rings lead to the three-dimensional supramolecular structure. Complex (III) is a binuclear molecule which is extended into a three-dimensional supramolecular structure via strong N-H···O and weak C-H···O hydrogen bonds.

Crystal structure of azimsulfuron.

The title compound {systematic name: 1-(4,6-di­meth­oxy­pyrimidin-2-yl)-3-[1-methyl-4-(2-methyl-2H-tetra­zol-5-yl)pyrazol-5-ylsulfon­yl]urea}, C13H16N10O5S, is a sulfonyl­urea herbicide. In this compound, the dihedral angles between the planes of the central pyrazole and the terminal di­meth­oxy­pyrimidine and tetra­zole rings are 79.10 (8) and 17.21 (16)°, respectively. In the crystal, N—H⋯O hydrogen bonds link adjacent mol­ecules, forming R 2 2(8) inversion dimers. In addition, weak C—H⋯O and C—H⋯N hydrogen bonds and weak π–π inter­actions [ring centroid separation = 3.8255 (12) Å] are present, resulting in a three-dimensional architecture.

1-{[(E)-(4-{[(2Z)-2,3-Di-hydro-1,3-thia-zol-2-yl-idene]sulfamo-yl}phen-yl)iminium-yl]meth-yl}naphthalen-2-olate.

In the title zwitterionic compound, C20H15N3O3S2, the 2-hy­droxy­naphthalene-1-carbaldehyde group A, the anilinic unit B and the 1,3-thia­zol-2(3H)-imine group C are each approximately planar with r.m.s. deviation of 0.0721, 0.0412 and 0.0125 Å, respectively. The dihedral angles between A/B, A/C and B/C are 24.70 (10), 79.97 (7) and 83.14 (6)°, respectively. There is an intra­molecular S(6) motif involving the imine N—H and the naphtho­late O atom. In the crystal, inversion-related mol­ecules form dimers as a result of N—H⋯N and N—H⋯O hydrogen bonds with R 2 2(8) and R 1 2(4) motifs, respectively. Weak π–π inter­actions between the benzene and naphthyl rings of inversion-related mol­ecules have ring centroid–centroid distances of 3.638 (2) and 4.041 (2) Å. A C—H⋯π inter­action occurs between the thia­zol ring and the benzene ring of an adjacent mol­ecule.

Crystal structure of catena-poly[[[tetra-aqua-zinc(II)]-μ-1,4-bis-[4-(1H-imidazol-1-yl)benzo-yl]piperazine] dinitrate monohydrate

In the title polymeric complex, {[Zn(C24H22N6O2)(H2O)4](NO3)2·2H2O}n, the ZnII cation, located about a twofold rotation axis, is coordinated by two imidazole groups and four water mol­ecules in a distorted N2O4 octa­hedral geometry; among the four coordinate water mol­ecules, two are located on the same twofold rotation axis. The 1,4-bis­[4-(1H-imidazol-1-yl)benzo­yl]piperazine] ligand is centro-symmetric, with the centroid of the piperazine ring located on an inversion center, and bridges the ZnII cations, forming polymeric chains propagating along [201]. In the crystal, O—H⋯O and weak C—H⋯O hydrogen bonds link the polymeric chains, nitrate anions and solvent water mol­ecules into a three-dimensional supra­molecular architecture. A short O⋯O contact of 2.823 (13) Å is observed between neighboring nitrate anions.

Crystal structure of catena-poly[[tri-methyl-tin(IV)]-μ-2-(2-nitro-phen-yl)acetato-κ(2) O:O'

In the title one-dimensional coordination polymer, [Sn(CH3)3(C8H6NO4)]n, the SnIV atom is coordinated by three methyl C atoms and two carboxyl­ate O atoms (one symmetry generated), resulting in an almost regular SnC3O2 trigonal pyramid. The C atoms occupy the equatorial sites and the O atoms occupy the axial sites. In the ligand, the dihedral angles between the benzene ring and the pendant acetate and nitro groups are 57.7 (1) and 36.9 (3)°, respectively. The bridging ligand leads to [010] chains in the crystal, with adjacent metal atoms related by a 21 screw axis. A weak π–π inter­action exists between the centroids of symmetry-related benzene rings at a distance of 3.9131 (19) Å.

Crystal structure of chlorfluazuron.

The title compound (systematic name: 1-{3,5-di­chloro-4-[3-chloro-5-(tri­fluoro­meth­yl)pyridin-2-yl­oxy]phen­yl}-3-(2,6-difluoro­benzo­yl)urea), C20H9Cl3F5N3O3, is a benzoyl­phenyl­urea insecticide. The dihedral angles between the planes of the central di­chloro­phenyl and the terminal di­fluoro­phenyl and chloro­pyridyl rings are 79.51 (6) and 78.84 6)°, respectively. In the crystal, pairs of N—H⋯O hydrogen bonds link adjacent mol­ecules, forming R 2 2(8) inversion dimers. In addition, the dimers are linked by short F⋯Cl [3.1060 (16) Å] and Cl⋯Cl [3.2837 (7) Å] contacts, as well as weak inter­molecular π–π inter­actions [ring centroid separation = 3.6100 (11) and 3.7764 (13) Å], resulting in a two-dimensional architecture parallel to (111).

Structural, spectroscopic, and theoretical comparison of traditional vs recently discovered Ln(2+) ions in the [K(2.2.2-cryptand)][(C5H4SiMe3)3Ln] complexes: the variable nature of Dy(2+) and Nd(2+).

The Ln(3+) and Ln(2+) complexes, Cp'3Ln, 1, (Cp' = C5H4SiMe3) and [K(2.2.2-cryptand)][Cp'3Ln], 2, respectively, have been synthesized for the six lanthanides traditionally known in +2 oxidation states, i.e., Ln = Eu, Yb, Sm, Tm, Dy, and Nd, to allow direct structural and spectroscopic comparison with the recently discovered Ln(2+) ions of Ln = Pr, Gd, Tb, Ho, Y, Er, and Lu in 2. 2-La and 2-Ce were also prepared to allow the first comparison of all the lanthanides in the same coordination environment in both +2 and +3 oxidation states. 2-La and 2-Ce show the same unusual structural feature of the recently discovered +2 complexes, that the Ln-(Cp' ring centroid) distances are only about 0.03 Å longer than in the +3 analogs, 1. The Eu, Yb, Sm, Tm, Dy, and Nd complexes were expected to show much larger differences, but this was observed for only four of these traditional six lanthanides. 2-Dy and 2-Nd are like the new nine ions in this tris(cyclopentadienyl) coordination geometry. A DFT-based model explains the results and shows that a 4f (n)5d(1) electron configuration is appropriate not only for the nine recently discovered Ln(2+) ions in 2 but also for Dy(2+) and Nd(2+), which traditionally have 4f (n+1) electron configurations like Eu(2+), Yb(2+), Sm(2+), and Tm(2+). These results indicate that the ground state of a lanthanide ion in a molecule can be changed by the ligand set, a previously unknown option with these metals due to the limited radial extension of the 4f orbitals.

Synthesis and Crystal Structures of Methyl 3,4,5-Trimethoxybenzoate and 1,2-Dihydro-2,2,4-Trimethylquinoline Derivatives

Two 1,2-dihydro-2,2,4-trimethylquinoline derivatives and two methyl 3,4,5-trimethoxybenzoate derivatives have been synthesized and their crystal structure determined by X-ray single crystal diffraction. Both methyl 3,4,5-trimethoxybenzoate derivatives: methyl 2,6-dibromo-3,4,5-trimethoxybenzoate (1) and methyl 3,4,5-trimethoxy-2-nitrobenzoate (2) crystallize in the monoclinic crystal system with a = 17.2605(5) A, b = 8.9082 (3) A, c = 8.9920 (3) A, β = 105.922 (2)°, space group Cc for 1, and a = 20.4898 (4) A, b = 9.7348 (2) A, c = 24.3911 (5) A, β = 99.457 (1)°, space group C2/c for 2. 1,2-Dihydro-8-methoxy-2,2,4-trimethylquinoline (3) crystallizes in the orthorhombic, space group Pna21, with a = 11.3745 (2) A, b = 8.0638 (1) A and c = 12.0019 (2) A, while 6-chloro-1,2-dihydro-2,2,4-trimethylquinoline (4) crystallizes in the monoclinic, space group P21/c, with a = 7.8063 (10) A, b = 17.757 (3) A, c = 7.8675 (10) A and β = 91.559 (8)°. The three-dimensional crystal packing structures of all four compounds are consolidated by a combination of van der Waals forces and weak directional hydrogen bonds, mostly though the overlap of peripheral groups with the centroids of the aromatic rings as the planar aromatic systems appeared to be displaced from each other resulting in the absence of π–π stacking intereactions usually found in the structural stacking of aromatic systems. This report deals with a comparative analysis of the crystal structures and crystal packing of two pairs of closely related molecules (1, 2) and (3, 4).

A new 3D lanthanide metal-organic framework based on fluorescent whitener: Synthesis, structures, and luminescent properties

A new 3D lanthanide metal-organic framework, [Sm(L)(Bpdc)0.5(Phen)]∞ (I) (L = 4,4′-bis(2-sulfonatostyryl)biphenyl; Bpdc = 4,4′-biphenyldicarboxylate; Phen = 1,10-phenanthroline), has been synthesized hydrothermally and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis and single-crystal X-ray diffraction (CIF file CCDC no. 990856). Compound I crystallizes in monoclinic, space group P21/n with a = 13.070(3), b = 21.365(4), c = 14.947(3) A, β = 101.65(3)°, V = 4087.8(15) A3, ρc = 1.572 g/cm3, Z = 4, μ = 1.597 mm−1, F(000) = 1944, and the final R = 0.0573 and wR = 0.1238 for 9304 observed reflections (I > 2σ(I)). It is evident that there is a face-to-face π-π stacking interaction between each L ligand with adjacent Phen groups at a plane-plane distance of 3.482 A. The ring normal and the vector between the ring centroids form an angle of 11.6° up to centroid-centroid distances of 3.555 A. The experimental result shows that compound I exhibits good thermal stability and luminescent property.

Crystal structures and hydrogen bonding in the proton-transfer salts of nicotine with 3,5-di-nitro-salicylic acid and 5-sulfosalicylic acid.

The structures of the 1:1 anhydrous salts of nicotine (NIC) with 3,5-di-nitro-salicylic acid (DNSA) and 5-sulfosalicylic acid (5-SSA), namely (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 2-carb-oxy-4,6-di-nitro-phenolate, C10H15N2 (+)·C7H3N2O7 (-), (I), and (1R,2S)-1-methyl-2-(pyridin-3-yl)-1H-pyrrolidin-1-ium 3-carb-oxy-4-hy-droxy-benzene-sulfonate, C10H15N2 (+)·C7H5O6S(-), (II), are reported. The asymmetric units of both (I) and (II) comprise two independent nicotinium cations (C and D) and either two DNSA or two 5-SSA anions (A and B), respectively. One of the DNSA anions shows a 25% rotational disorder in the benzene ring system. In the crystal of (I), inter-unit pyrrolidinium N-H⋯Npyridine hydrogen bonds generate zigzag NIC cation chains which extend along a, while the DNSA anions are not involved in any formal inter-species hydrogen bonding but instead form π-π-associated stacks which are parallel to the NIC cation chains along a [ring-centroid separation = 3.857 (2) Å]. Weak C-H⋯O inter-actions between chain substructures give an overall three-dimensional structure. In the crystal of (II), A and B anions form independent zigzag chains with C and D cations, respectively, through carb-oxy-lic acid O-H⋯Npyridine hydrogen bonds. These chains, which extend along b, are pseudocentrosymmetrically related and give π-π inter-actions between the benzene rings of anions A and B and the pyridine rings of the NIC cations C and D, respectively [ring centroid separations = 3.6422 (19) and 3.7117 (19) Å]. Also present are weak C-H⋯O hydrogen-bonding inter-actions between the chains, giving an overall three-dimensional structure.

Synthesis and characterization of Ni(II) and Zn(II) complexes of (furan-2-yl)methyl(2-(thiophen-2-yl)ethyl)dithiocarbamate (ftpedtc): X-ray structures of [Zn(ftpedtc)2(py)] and [Zn(ftpedtc)Cl(1,10-phen)

Seven complexes of a new dithiocarbamate ligand (ftpedtc=(furan-2-yl)methyl(2-(thiophen-2-yl)ethyl)dithiocarbamate) namely [Ni(ftpedtc)2] (1), [Ni(ftpedtc)(NCS)(PPh3)] (2), [Ni(ftpedtc)(PPh3)2]ClO4 (3), [Zn(ftpedtc)2] (4), [Zn(ftpedtc)2(py)] (5), [Zn(ftpedtc)2(1,10-phen)] (6) and [Zn(ftpedtc)2(2,2′-bipy] (7) have been prepared. The complexes were characterized by IR, UV–Vis and NMR (1H and 13C) spectroscopy. Single crystal X-ray structural analysis was carried out for complexes 5 and [Zn(ftpedtc)Cl(1,10-phen)] (8). Electronic spectral studies suggest square planar geometry for nickel complexes. The 13C NMR peaks of the group N13CS2 are found in all the cases, at around 205.0ppm, which indicates the bidentate character of the dithiocarbamate ligand. X-ray structures of 5 and 8 show bidentate coordination by dithiocarbamate ligands and a distorted trigonal bipyramidal geometry for zinc, defined by NS4 and ClN2S2 donor sets, respectively. The packing in 8 involves π–π stacking interactions involving the 1,10-phenanthroline ring systems with the distance between ring centroids being 3.587Å.

Monomolecular sheets of propeller-shaped triethyl 4,4',4''-[benzene-1,3,5-triyltris(ethyne-2,1-diyl)]tribenzoate deuterochloroform monosolvate.

The title compound, C39H30O6·CDCl3, has a chemical threefold axis and an approximately planar structure, with an ethoxycarbonyl substituent on each of the terminal benzenes oriented in the same direction, thus forming a propeller-shaped molecule. This molecule is of particular interest in the field of metal-organic frameworks (MOFs), where its hydrolyzed analogue forms MOF structures with high surface areas. The benzene ring which occupies the centre of the molecule forms π-π interactions to the equivalent benzene ring at a perpendicular distance of 3.32 (1) Å. Centrosymmetric dimers formed in this way are interconnected by intermolecular C-H···π interactions with a rather short H···CgA distance of 2.51 Å (CgA is the centroid of the central benzene ring). The molecules are arranged in regular parallel sheets. Within a sheet, molecules are interconnected via C-H···O interactions where all carbonyl O atoms participate in weak hydrogen bonds as hydrogen-bond acceptors. Neighbouring sheets are connected through the above-mentioned π-π and C-H···π interactions.

Crystal structure of the magnesium salt of the herbicide 2,4-D: penta-aqua-[(2,4-di-chloro-phenoxy)acetato-κO]magnesium (2,4-di-chloro-phen-oxy)acetate hemihydrate.

In the crystal structure of the title magnesium salt of the phen-oxy herbicide (2,4-di-chloro-phen-oxy)acetic acid (2,4-D), [Mg(C8H5Cl2O3)(H2O)5](C8H5Cl2O3)·0.5H2O, the discrete cationic MgO6 complex unit comprises a carboxyl-ate O-donor from a monodentate 2,4-D anionic ligand and five water mol-ecules, resulting in a slightly distorted octa-hedral coordination sphere. The free 2,4-D anions are linked to the complex units through duplex water-carboxyl-ate O-H⋯O hydrogen bonds through the coordinating water mol-ecules. In the crystal, inter-unit O-H⋯O hydrogen-bonding inter-actions involving coordinating water mol-ecules as well as the solvent water mol-ecule (occupancy 0.5) with carboxyl-ate O-atom acceptors, give a layered structure lying parallel to (001), in which π-π ligand-cation inter-actions [minimum ring centroid separation = 3.6405 (17) Å] and a short O-H⋯Cl inter-action are also found.

Crystal structure of triclopyr.

In the title compound {systematic name: 2-[(3,5,6-tri­chloro­pyridin-2-yl)­oxy]acetic acid}, the herbicide triclopyr, C7H4Cl3NO3, the asymmetric unit comprises two independent mol­ecules in which the dihedral angles between the mean plane of the carb­oxy­lic acid group and the pyridyl ring plane are 79.3 (6) and 83.8 (5)°. In the crystal, pairs of inter­molecular O—H⋯O hydrogen bonds form dimers through an R 2 2(8) ring motif and are extended into chains along [100] by weak π–π inter­actions [ring centroid separations = 3.799 (4) and 3.810 (4) Å]. In addition, short inter­molecular Cl⋯Cl contacts [3.458 (2) Å] connect the chains, yielding a two-dimensional architecture extending parallel to (020). The crystal studied was found to be non-merohedrally twinned with the minor component being 0.175 (4).

2-(5-Methyl-1,3,4-oxadiazol-2-yl)phenyl acetate

In the title compound, C11H10N2O3, which is a potential bioactive compound, the benzene and oxa­diazole rings are approximately coplanar, with an inter-ring dihedral angle of 4.14 (2)°, while the ester plane is rotated out of the benzene plane [dihedral angle = 82.69 (9)°]. In the crystal, the mol­ecules form layers down the a axis with weak π–π inter­actions between the oxa­diazole and benzene rings [minimum ring centroid separation = 3.7706 (14) Å].

Di-chlorido-(4-{[(quinolin-2-yl)methyl-idene]amino}phenol-κ(2) N,N')mercury(II).

In the mononuclear title complex, [HgCl2(C16H12N2O)], synthesized from the phenolic Schiff base 4-[(quinolin-2-yl­methyl­idene)amino]­phenol (QMAP), the coordination geometry around Hg2+ is distorted tetra­hedral, comprising two Cl atoms [Hg—Cl = 2.3565 (12) and 2.5219 (12) Å] and two N-atom donors from the QMAP ligand, viz. one imine and the other quinoline [Hg—N = 2.392 (2) and 2.237 (2) Å, respectively]. In the crystal, O—H⋯Cl hydrogen bonds generate a chain structure extending along the c-axis direction. Weak C—H⋯Cl and π–π stacking inter­actions [minimum ring centroid separation = 3.641 (3) Å] give an overall layered structure lying parallel to (001).