Di­bromo{N-[2-(di­phenyl­phosphino)­benzyl­idene]-2,6-diiso­propyl­aniline-κ2N,P}nickel

In the title compound, [NiBr₂(C₃₁H₃₂NP)], (I), the second reported example of a nickel–imino­phosphine N,P-chelate in which the Ni atom has tetrahedral coordination, the Ni coordination is distorted as a consequence of the N—Ni—P chelate bite angle of 91.07 (6)° compensated by the Br—­Ni—­Br angle of 126.385 (18)°. In (I) and its analogue, viz. dichloro{[2-(4-isobutyloxazol-2-yl)phenyl]diphenylphos­phine-N,P}nickel(II), the Ni—N and Ni—P distances are greater and the N—Ni—P ligand bite angles smaller than those observed in a series of related complexes with square-planar nickel.     

N1‐(4‐tert‐Butyl­phenyl)‐N2‐hydroxy‐α‐oxo‐α‐phenyl­acet­amidine and N2‐hydroxy‐N1‐(4‐nitro­phenyl)‐α‐oxo‐α‐phenyl­acet­amidine hemihydrate

In the title compounds, C₁₈H₂₀N₂O₂, (I), and C₁₄H₁₁N₃O₄·0.5H₂O, (II), respectively, the oxime groups have an E configuration. In (I), the mol­ecules exist as polymers bound by intermolecular C—H⋯O and O—H⋯N hydrogen bonds around inversion centres. In (II), intermolecular OW—H⋯N, OW—H⋯O and O—H⋯OW interactions stabilize the molecular packing.     

cis‐ and trans‐Dichloro(3,6‐dihydro‐1,2‐oxazine‐N)(dimethyl sulfoxide‐S)‐platinum(II)

Both the cis, (I), and trans, (II), isomers of the title complex, [PtCl₂(C₄H₇NO)(C₂H₆OS)], possess relatively undistorted square‐planar geometries about the Pt atoms. For (I), cisL—Pt—L angles are in the range 88.8 (2)–91.08 (8)°, while trans angles are 178.61 (8) and 179.4 (2)°. For (II), cisL—Pt—L 86.1 (3)–93.7 (1)°, and transL—Pt—L 175.5 (1) and 179.1 (3)°. The di­methyl sulfoxide (dmso) ligand adopts a normal pyramidal geometry in both complexes. In (I), the S=O bond essentially eclipses the adjacent Pt—N bond, while the oxazine ligand in (I) is twisted so as to avoid steric interactions with the adjacent chloride ligand. By contrast, the dmso ligand in (II) is rotated such that the S=O bond is approximately perpendicular to the square plane, while the oxazine ligand is once again twisted out of the plane by a similar amount as in (I). These are the first structural examples of square‐planar platinum(II) complexes containing a 1,2‐oxazine ligand.     

Assembling an isomer grid: the isomorphous 4‐, 3‐ and 2‐fluoro‐N′‐(4‐pyridyl)benzamides

The three title isomers, 4‐, (I), 3‐, (II), and 2‐fluoro‐N′‐(4‐pyridyl)benzamide, (III), all C₁₂H₉FN₂O, crystallize in the P2₁/c space group (No. 14) with similar unit‐cell parameters and are isomorphous and isostructural at the primary hydrogen‐bonding level. An intramolecular C—H...O=C interaction is present in all three isomers [C...O = 2.8681 (17)–2.884 (2) Å and C—H...O117–118°], with an additional N—H...F [N...F = 2.7544 (15) Å] interaction in (III). Intermolecular amide–pyridine N—H...N hydrogen bonds link molecules into one‐dimensional zigzag chains [graph set C(6)] along the [010] direction as the primary hydrogen bond [N...N = 3.022 (2), 3.049 (2) and 3.0213 (17) Å]. These are augmented in (I) by C—H...π(arene) and cyclic C—F...π(arene) contacts about inversion centres, in (II) by C—F...F—C interactions [C...F = 3.037 (2) Å] and weaker C—H...π(arene)/C—H...F contacts, and in (III) by C—H...π(arene) and C=O...O=C interactions, linking the alternating chains into two‐dimensional sheets. Typical amide N—H...O=C hydrogen bonds [as C(4) chains] are not present [N...O = 3.438 (2) Å in (I), 3.562 (2) Å in (II) and 3.7854 (16) Å in (III)]; the C=O group is effectively shielded and only participates in weaker interactions/contacts. This series is unusual as the three isomers are isomorphous (having similar unit‐cell parameters, packing and alignment), but they differ in their interactions and contacts at the secondary level.     

Polymer Structures and Glass Transition: A Molecular Dynamics Simulation Study

Full atomistic molecular dynamics (MD) simulations on five polymers with different chain backbone (C—C, Si—O, and C—O) and different side groups (—H, one —CH₃, and two —CH₃) are performed to study the effects of chain flexibility and side groups on the glass transition of polymers. Molecular dynamics simulations of NPT (constant pressure and constant temperature) dynamics are carried out to obtain specific volume as a function of temperature for polyethylene (PE), poly(propylene) (PP), polyisobutylene (PIB), poly(oxymethylene) (POM), and poly(dimethylsiloxane) (PDMS). The volumetric glass transition temperature has been determined as the temperature marking the discontinuity in slope of the plots of V–T simulation data. Various energy components at different temperatures of the polymers are investigated and their roles played in the glass transition process are analyzed. In order to understand the polymer chain conformations above and below the glass transition temperature, dihedral angle distributions of polymer chains at various temperatures are also studied.     

A new polymorph of 1‐ferrocenyl‐3‐(3‐nitroanilino)propan‐1‐one

Recrystallization of the title compound, [Fe(C₅H₅)(C₁₄H₁₃N₂O₃)], from a mixture of n‐hexane and dichloromethane gave the new polymorph, denoted (I), which crystallizes in the same space group (P) as the previously reported structure, denoted (II). The Fe—C distances in (I) range from 2.015 (3) to 2.048 (2) Å and the average value of the C—C bond lengths in the two cyclopentadienyl (Cp) rings is 1.403 (13) Å. As indicated by the smallest C—Cg1—Cg2—C torsion angle of 1.4° (Cg1 and Cg2 are the centroids of the two Cp rings), the orientation of the Cp rings in (I) is more eclipsed than in the case of (II), for which the value was 15.3°. Despite the pronounced conformational similarity between (I) and (II), the formation of self‐complementary N—H...O hydrogen‐bonded dimers represents the only structural motif common to the two polymorphs. In the extended structure, molecules of (I) utilize C—H...O hydrogen bonds and, unlike (II), an extensive set of intermolecular C—H...π interactions. Fingerprint plots based on Hirshfeld surfaces are used to compare the packing of the two polymorphs.     

Diverse Ring-seco Limonoids from Munronia unifoliolata and Their Biological Activities

Twenty-two new limonoids,mufolinoids A—V(1—22),including six rings A,B-seco limonoids(1—6),twelve ring A-seco limonoids(7—18),four ring-intact limonoids(19—22),together with thirteen known compounds(23—35)were isolated from Munronia unifoliolata.Their structures including absolute configurations were elucidated by combination of NMR,HR-MS,single-crystal X-ray diffraction and calculations of ECD and NMR technologies.Compounds 24,25,33,34 could be significantly reversed the multidrug resistance of MCF-7/doxorubicin(DOX)cells,and the reversal fold(RF)was much higher than that of positive drug Verapamil.Compounds 24,28,and 29 exhibited significant anti-inflammatory activity with the IC50 values in the range of 17.7—39.4μmol/L.Furthermore,compound 29 could markedly inhibit the release of IL-1βby inhibiting the initiation and assembly of NLRP3 inflammasome,which demonstrates the great potential of limonoids as an anti-inflammatory agent.     

Vinyl sulfones

Four neutral vinyl sulfones, two of which are paired with phosphonate groups, are described. The compounds are diisopropyl (2‐phenylethenylsulfonylmethyl)phosphonate, C₁₅H₂₃O₅PS, (I), diisopropyl {[2‐(7‐methoxy‐1,3‐benzodioxol‐5‐yl)ethenylsulfonyl]methylsulfonylmethyl}phosphonate, C₁₈H₂₇O₁₀PS₂, (II), bis(trans‐2‐phenylethenyl) sulfone, C₁₆H₁₄O₂S, (III), and bis(trans‐2‐phenylethenylsulfonyl)methane, C₁₇H₁₆O₄S₂, (IV). Their structures can be considered as highly functionalized mimics of mono‐, di‐ and triphosphates. These phosphate isosteres are currently of interest as agents for enzyme inhibition in both cancer and HIV therapy. All except one of the compounds has Z′ > 1. The lone exception is (IV), a disulfone with twofold crystallographic symmetry. Geometrically, the sulfone functionality is found to be a good mimic for phosphate. The principal effect of the vinyl group is to shorten the S—C(vinyl) distance relative to the S—CH₂ distance by ca 0.05 Å. The S—C—S and S—C—P backbones resemble the P—O—P backbone but are not identical because the S—C and P—C distances are longer than the P—O distance and the S—C—S and S—C—P angles are more acute than the P—O—P angle. No prior crystal structures of comparable compounds have been published.     

cis-Di­chloro­bis­(triethyl­arsine)­platinum(II) and cis-di­chloro­bis­(triethyl­phosphine)­platinum(II)

The crystal structure of cis-[PtCl₂(C₆H₁₅As)₂], (I), is isostructural with a previously reported structure of cis-[PtCl₂(C₆H₁₅P)₂], (II). A new polymorph of (II) is also reported here. Selected geometrical parameters in the arsine complex are Pt—Cl 2.3412 (12) and 2.3498 (13), Pt—As 2.3563 (6) and 2.3630 (6) Å, Cl—Pt—Cl 88.74 (5), As—Pt—As 97.85 (2), and Cl—Pt—As 171.37 (4) and 177.45 (4)°. Corresponding parameters in the phosphine complex are Pt—Cl 2.364 (2) and 2.374 (2), Pt—P 2.264 (2) and 2.262 (2) Å, Cl—Pt—Cl 85.66 (9), P—Pt—P 98.39 (7), and Cl—Pt—P 170.26 (7) and 176.82 (8)°.     

A structural systematic study of three isomers of difluoro‐N‐(4‐pyridyl)benzamide

The isomers 2,3‐, (I), 2,4‐, (II), and 2,5‐difluoro‐N‐(4‐pyridyl)benzamide, (III), all with formula C₁₂H₈F₂N₂O, all exhibit intramolecular C—H...O=C and N—H...F contacts [both with S(6) motifs]. In (I), intermolecular N—H...O=C interactions form one‐dimensional chains along [010] [N...O = 3.0181 (16) Å], with weaker C—H...N interactions linking the chains into sheets parallel to the [001] plane, further linked into pairs via C—H...F contacts about inversion centres; a three‐dimensional herring‐bone network forms via C—H...π(py) (py is pyridyl) interactions. In (II), weak aromatic C—H...N(py) interactions form one‐dimensional zigzag chains along [001]; no other interactions with H...N/O/F < 2.50 Å are present, apart from long N/C—H...O=C and C—H...F contacts. In (III), N—H...N(py) interactions form one‐dimensional zigzag chains [as C(6) chains] along [010] augmented by a myriad of weak C—H...π(arene) and O=C...O=C interactions and C—H...O/N/F contacts. Compound (III) is isomorphous with the parent N‐(4‐pyridyl)benzamide [Noveron, Lah, Del Sesto, Arif, Miller & Stang (2002). J. Am. Chem. Soc. 124 , 6613–6625] and the three 2/3/4‐fluoro‐N‐(4‐pyridyl)benzamides [Donnelly, Gallagher & Lough (2008). Acta Cryst. C 64 , o335–o340]. The study expands our series of fluoro(pyridyl)benzamides and augments our understanding of the competition between strong hydrogen‐bond formation and weaker influences on crystal packing.     

cis‐Bis(3,6‐di­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II) and cis‐bis(3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine‐N)­di­iodo­platinum(II)

The title complexes, [Pt(C₄H₇NO)₂I₂], (I), and [Pt(C₄H₉NO)₂I₂], (II), possess similar square‐planar coordination geometries with modest distortions from ideality. For (I), the cis‐L—Pt—L angles are in the range 87.0 (4)–94.2 (3)°, while the trans angles are 174.4 (3) and 176.4 (3)°. For (II), cis‐L—Pt—L are 86.1 (8)–94.2 (6)° and trans‐L—Pt—L are 174.4 (6) and 177.4 (5)°. One 3,6‐di­hydro‐2H‐1,2‐oxazine ligand in (I) is rotated so that the N—O bond is out of the square plane by approximately 70°, while the N—C bond is only ca 20° out of the plane. The other oxazine ligand is rotated so that the N—C bond is about 80° out of the plane, while the N—O bond is out of the plane by approximately 24°. In (II), the 3,4,5,6‐tetra­hydro‐2H‐1,2‐oxazine ligands are also positioned with one having the N—O bond further out of the plane and the other having the N—C bond positioned in that fashion. Both ligands, however, are rotated approximately 90° compared with their positions in (I). In both complexes, this results in an unsymmetrical distortion of the I—Pt—N bond angles in which one is expanded and the other contracted. These features are compared to those of reported cis‐di­amine­di­iodo­platinum(II) complexes.     

3‐Deoxy‐β‐d‐ribo‐hexopyranose (3‐deoxy‐β‐d‐glucopyranose)

The β‐pyranose form, (III), of 3‐deoxy‐d ‐ribo‐hexose (3‐deoxy‐d ‐glucose), C₆H₁₂O₅, crystallizes from water at 298 K in a slightly distorted ⁴C₁ chair conformation. Structural analyses of (III), β‐d ‐glucopyranose, (IV), and 2‐deoxy‐β‐d ‐arabino‐hexopyranose (2‐deoxy‐β‐d ‐glucopyranose), (V), show significantly different C—O bond torsions involving the anomeric carbon, with the H—C—O—H torsion angle approaching an eclipsed conformation in (III) (−10.9°) compared with 32.8 and 32.5° in (IV) and (V), respectively. Ring carbon deoxygenation significantly affects the endo‐ and exocyclic C—C and C—O bond lengths throughout the pyranose ring, with longer bonds generally observed in the monodeoxygenated species (III) and (V) compared with (IV). These structural changes are attributed to differences in exocyclic C—O bond conformations and/or hydrogen‐bonding patterns superimposed on the direct (intrinsic) effect of monodeoxygenation. The exocyclic hydroxymethyl conformation in (III) (gt) differs from that observed in (IV) and (V) (gg).     

Synthesis,Structure, and Spectroscopic Properties of Copper(II) and Nickel(II) Complexes Containing the 1, 4, 7‐Triisopropyl‐1, 4, 7‐triazacyclononane Ligand

Three new complexes [CuL(N₃)₂] ( 1 ), [CuL(SCN)₂] ( 2 ), and [NiL(SCN)₂] ( 3 ) (L = 1, 4, 7‐triisopropyl‐1, 4, 7‐triazacyclononane, [—NR—C₂H₄—NR—C₂H₄—NR—C₂H₄—], R = i‐Pr) have been synthesized and structurally characterized. The three complexes all crystallize in the monoclinic space group P2₁/n, with the unit cell parameters a = 9.100(5), b = 19.492(11), c = 11.646(6)Å, β = 94.526(9)° for 1 , a = 10.148(3), b = 13.611(5), c = 15.777(6)Å, β = 95.412(6)° for 2 and a = 9.270(7), b = 16.629(14), c = 14.886(12)Å, β = 101.217(15)° for 3 . The central copper(II) and nickel(II) ions are coordinated to five nitrogen atoms, three of which from the L and two from N₃^— or SCN^—, forming a slightly distorted square pyramidal geometry. Moreover, elemental analysis, IR, UV‐vis and ESR spectra of complexes 1 ‐ 3 were also determined.     

Studies on sulfinatodehalogenation: XVII. The sulfinatodehalogenation of primary perfluoroalkyl iodides and bromides by Rongalite

Using acetonitrile or DMF as cosolvent, both perfluoroalkyl iodides such as Cl(CF₂)_nI (n = 4,6,8, la—lc ), CF₃ (CF₂)_n I (n = 5,6,7, ld—lf ), I (CF₂)_n O (CF₂) SO₃ Na(n = 2,4,6, lg—li ) and perfluoroalkyl bromides such as Cl (CF₂)_n Br (n = 4,6, 3a—3b ) and C₇F₁₅ Br (3e) reacted with Rongalite in aqueous solution to give the corresponding sulfinates Cl (CF₂)_n SO₂ Na (n = 4,6,8, 2a—2c ), CF₃-(CF₂)_nSO₂Na (n = 5,6,7, 2d—2f ) and NaO₂S(CF₂)_nO(CF₂)₂SO₃Na (n = 2,4,6, 2g—2i ) in moderate yields. 1 H-perfluoroalkanes were formed as the main products when other solvents such as ethanol. iso-propanol, 1,4-dioxane and morpholine were used.     

Three new phosphoric triamides with a [C(O)NH]P(O)[N(C)(C)]2 skeleton: a database analysis of C—N—C and P—N—C bond angles

In N,N,N′,N′‐tetraethyl‐N′′‐(4‐fluorobenzoyl)phosphoric triamide, C₁₅H₂₅FN₃O₂P, (I), and N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis(4‐methylpiperidin‐1‐yl)phosphoric triamide, C₁₉H₂₈F₂N₃O₂P, (II), the C—N—C angle at each tertiary N atom is significantly smaller than the two P—N—C angles. For the other new structure, N,N′‐dicyclohexyl‐N′′‐(2‐fluorobenzoyl)‐N,N′‐dimethylphosphoric triamide, C₂₁H₃₃FN₃O₂P, (III), one C—N—C angle [117.08 (12)°] has a greater value than the related P—N—C angle [115.59 (9)°] at the same N atom. Furthermore, for most of the analogous structures with a [C(=O)NH]P(=O)[N(C)(C)]₂ skeleton deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388], the C—N—C angle is significantly smaller than the two P—N—C angles; exceptions were found for four structures with the N‐methylcyclohexylamide substituent, similar to (III), one structure with the seven‐membered cyclic amide azepan‐1‐yl substituent and one structure with an N‐methylbenzylamide substituent. The asymmetric units of (I), (II) and (III) contain one molecule, and in the crystal structures, adjacent molecules are linked via pairs of N—H...O=P hydrogen bonds to form dimers.     

Gas-phase pyrolytic reactions. Part 6. [1] Behavior of ethyl (hetero)arylcarboxylate esters in thermal elimination reactions

Rates, Arrhenius parameters, and Hammett substituent constants are obtained for the gas-phase thermal elimination of ethyl benzoate (1) and ethyl 2—thienyl— (2), 3—thienyl— (3), 2—furyl— (4), 3—furyl— (5), 4—pyridyl— (6), 3—pyridyl— (7), and 2—pyridylcarboxylate (8) esters. The log A/s⁻¹ and the E_a/kJ mol⁻¹ values of these esters averaged 13.60 and 216.3, respectively. The present results are compared with data previously reported for the corresponding isopropyl and t-butyl analogues, and the findings are rationalized in terms of a plausible transition state for the elimination pathway. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 289–293, 1997.     

Two isomers of Pd2(S2NC7H4)4

The dichloromethane solvates of the isomers tetrakis(μ‐1,3‐benzothiazole‐2‐thiolato)‐κ⁴N:S;κ⁴S:N‐dipalladium(II)(Pd—Pd), (I), and tetrakis(μ‐1,3‐benzothiazole‐2‐thiolato)‐κ⁶N:S;κ²S:N‐dipalladium(II)(Pd—Pd), (II), both [Pd₂(C₇H₄NS₂)₄]·CH₂Cl₂, have been synthesized in the presence of (o‐isopropylphenyl)diphenylphosphane and (o‐methylphenyl)diphenylphosphane. Both isomers form a lantern‐type structure, where isomer (I) displays a regular and symmetric coordination and isomer (II) an asymmetric and distorted structure. In (I), sitting on an centre of inversion, two 1,3‐benzothiazole‐2‐thiolate units are bonded by a Pd—N bond to one Pd atom and by a Pd—S bond to the other Pd atom, and the other two benzothiazolethiolate units are bonded to the same Pd atoms by, respectively, a Pd—S and a Pd—N bond. In (II), three benzothiazolethiolate units are bonded by a Pd—N bond to one Pd atom and by a Pd—S bond to the other Pd atom, and the fourth benzothiazolethiolate unit is bonded to the same Pd atoms by, respectively, a Pd—S bond and a Pd—N bond.     

Active Chemical Constituents from Sauropus androgynus

This paper describes the chemical investigation on BuOH-soluble EtOH extract from the aerial part of Sauropus androgynus. This study led to the characterization of six bioactive ingredients including three nucleosides—adenosine (1), 5′-deoxy-5′-methylsulphinyl-adenosine ( 2 ), and uridine ( 3 ), two flavonol dioside — 3-O-β-D-glucosyl-7-O-α-L-rhamnosyl-kaempferol ( 4 ), 3-O-β-D-glucosyl-(1→6)-β-D-glucosyl-kaempferol ( 5 ), and one rare flavonol trioside — 3-O-β-D-glucosyl-(1→6)-β-D-glucosyl-7-O-α-L-rhamno-syl-kaempferol ( 6 ). Their structures were determined on the basis of spectral analysis.     

Supramolecular hydrogen‐bonding patterns in two cocrystals of the N(7)–H tautomeric form of N6‐benzoyladenine: N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (1/1) and N6‐benzoyladenine–DL‐tartaric acid (1/1)

Two novel cocrystals of the N(7)—H tautomeric form of N⁶‐benzoyladenine (BA), namely N⁶‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C₁₂H₉N₅O·C₆H₅NO₃, (I), and N⁶‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C₁₂H₉N₅O·C₄H₆O₆, (II), are reported. In both cocrystals, the N⁶‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R₂²(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R₂²(4)]. Both crystal structures are further stabilized by π–π stacking interactions.     

NMR experiments on acetals—XXV: Conformational energy for the chair-twist interconversion of the 1,3-dioxane system

Trans-4-t-Bu-6-R-1,3-dioxanes (R = Me, Prⁱ and cyclohexyl) show temperature-dependent values for ²J(H—2) and ³J(H—4(6), H—5) in their PMR spectra. This is the result of the presence of twist-boat conformations. With the aid of typical limit-values of ²J(H—2) for the chair and twist forms, the amount of flexible conformations were determined as a function of temperature (Table 2), allowing the determination of the enthalpy change for chair-twist interconversion in 1,3-dioxane itself (6·2 ± 0·3 kcal/mole). Typical values for ²J(H—2) were obtained from a study of low temperature spectra and from appropriate model compounds of which 4-(1′-adamantyl)-6-t-Bu-1,3-dioxane served as the model for a genuine twist form with a twofold axis through C-2/C-5.