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.     

Room-temperature monoclinic and low-temperature triclinic phase-transition structures of meso-octa­methyl­calix­[4]­pyrrole–di­methyl sulfoxide (1/1)

Crystals of the title complex, C₂₈H₃₆N₄·C₂H₆OS, undergo a phase transition between room temperature and 198 K, as determined by X-ray diffraction techniques. A monoclinic form is observed at room temperature, while a triclinic modification is found at 198 K, with Z′ changing from 1 to 2. Differential scanning calorimetry (DSC) of the calix­pyrrole–di­methyl sulfoxide complex revealed a series of phase changes between 273 and 243 K. The transition from the room-temperature monoclinic form to the low-temperature triclinic form is reversible, as determined by changes in the cell dimensions from remeasuring selected reflections at room temperature and at temperatures below 223 K. The uncomplexed calix­[4]­pyrrole mol­ecule shows no phase changes occurring between room temperature and 233 K, the low-temperature limit of the DSC.     

trans-Bis(2-amino­pyridine-N)bis(O,O′-diiso­propyl di­thio­phosphato-S,S′)nickel(II)

In the title compound, [Ni(C₆H₁₄O₂PS₂)₂(C₅H₆N₂)₂], the coordination around the Ni atom, which lies on a crystallographic centre of symmetry, is octahedral with the S atoms from the di­thio­phosphate ligands occupying the equatorial positions, while the axial positions are occupied by the ring N atoms of the 2-amino­pyridine ligands. The mol­ecules form layers in the bc plane which are stacked in the direction of the a axis.     

The 143 and 300 K polymorphs of hexa­methyl­enetetraminium 2,4-di­nitro­phenolate monohydrate

The title compound, 3,5,7-tri­aza-1-azoniatri­cyclo­[3.3.1.1^3,7]­decane 2,4-di­nitro­phenolate monohydrate, C₆H₁₃N₄⁺·C₆H₃N₂O₅⁻·H₂O, the 1:1 hydrate adduct of hexa­methyl­enetetr­amine (HMT) and 2,4-di­nitro­phenol, undergoes a temperature phase transition. In the room-temperature phase, the adduct crystallizes in the monoclinic P2₁/m space group, whereas in the low-temperature phase, the adduct crystallizes in the triclinic P space group. This phase transition is reversible, with the transition temperature at 273 K, and the phase transition is governed by hydrogen bonds and weak interactions. In both these temperature-dependent polymorphs, the crystal structure is alternately layered with sheets of hexa­methyl­enetetr­amine and sheets of di­nitro­phenol stacked along the c axis. The hexa­methyl­enetetr­amine and di­nitro­phenol moieties are linked by intermolecular hydrogen bonds. The water mol­ecule in the adduct plays an important role, forming O—H⋯O hydrogen bonds which, together with C—H⋯O hydrogen bonds, bridge the adducts into molecular ribbons. Extra hydrogen bonds and weak interactions exist for the low-temperature polymorph and these interconnect the molecular ribbons into a three-dimensional packing structure. Also in these two temperature-dependent polymorphs, di­nitro­phenol acts as a hydrogen-bond acceptor and HMT acts as a hydrogen-bond donor.     

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)°.     

Bis(O,O′-diiso­propyl di­thio­phosphato-S,S′)(1,10-phenanthroline-N,N′)metal(II) complexes with cadmium(II) and iron(II)

The two title compounds, [M(C₆H₁₄O₂PS₂)₂(C₁₂H₈N₂)], where M = Cd^II and Fe^II, are isomorphous. Each compound has a crystallographic twofold axis of symmetry through the metal atom and the 1,10-phenanthroline mol­ecule. The central metal atom is coordinated to four S atoms from the two dithiophos­phate groups and two N atoms from the 1,10-phenanthroline ligand. The environment of the metal atom is a distorted octahedron.     

A 1:1:1 chloro­form/tetra­hydro­furan solvate of p-tert-butyl­tetra­homo­dioxa­calix­[4]­arene

The title compound, 7,13,21,27-tetra-tert-butyl-3,17-di­oxa­penta­cyclo­[23.3.1.1^5,9.1^11,15.1^9,23]ditriaconta-1(29),­5,­7,­9(30),11(31),­12,­14,­19(32),­20,­22,­25,­27-do­deca­ene-29,­30,­31,­32-tetraol, crystallizes as a solvate with one mol­ecule of chloro­form and one mol­ecule of tetra­hydro­furan, C₄₆H₆₀O₆·CHCl₃·C₄H₈O. The calixarene assumes a cone-like conformation stabilized by intramolecular hydrogen bonds involving both phenolic and ether O atoms. The two solvent mol­ecules are located in each of the two half-cone cavities of the calixarene.     

Sodium thio­phenolate N,N,N′,N′-tetra­methyl­ethyl­enedi­amine

The title compound, Na⁺·C₆H₅S⁻·C₆H₁₆N₂, forms lipophilically wrapped infinite sodium chains along the a axis. Each sodium cation is coordinated by three thio­phenolate S atoms and two N centres of one tetra­methyl­ethyl­enedi­amine molecule.     

catena-Poly[[trans-di­chloro­copper(II)]-μ-1,4,7,10,13,16-hexa­thia­cyclo­octa­decane-S1:S10]

In the title complex, [CuCl₂(C₁₂H₂₄S₆)]_n, the CuCl₂ unit and the ligand lie on and about inversion centres, respectively. The coordination geometry at Cu^II is a tetragonally elongated octahedron with the equatorial positions occupied by two chlorides, Cu—Cl 2.2786 (12) Å, and two S donors, Cu—S 2.3710 (13) Å. The apical positions of the octahedron are defined by two S donors at distances of 2.8261 (14) Å from the metal. The macrocyclic ligand adopts a very puckered and distorted conformation. Eight of the 18 torsion angles are less than 90° and all S-donors are oriented exo to the ring.     

1-Methyl­indole-3-carbox­aldehyde oxime derivatives

1-Methyl­indole-3-carbox­aldehyde oxime, C₁₀H₁₀N₂O, (I),and (E)-5-methoxy-1-methyl­indole-3-carbox­aldehyde oxime, C₁₁H₁₂N₂O₂, (II), were ex­amined structurally to ascertain the geometry of the hydroxy­imino function relative to the indole core. Oxime (I) exhibits cis geometry and there are two mol­ecules in the asymmetric unit. In contrast, oxime (II) exhibits trans geometry and has four mol­ecules in the asymmetric unit, with the geometry of the 5-methoxy group in one mol­ecule differing from that in the other three. Both crystal structures are maintained by hydrogen bonding with no π-stacking of the indole moiety present.     

Thermochemistry of ammonium based ionic liquids: Tetra-alkyl ammonium nitrates – Experiments and computations

In this work data of the molar enthalpies of formation of the ionic liquids [R₄N][NO₃] were measured by means of combustion calorimetry. The thermal behavior of [R₄N][NO₃] was studied using differential scanning calorimetry. First-principles calculations of the enthalpy of formation in the gaseous phase have been performed for the ionic species using the G3(MP2) theory. Enthalpies of formation of aqueous tetra-alkyl ammonium ions ${\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{°}$ ([R₄N]⁺_(aq)) derived in this work are useful for prediction thermochemical properties of the ammonium based ionic liquids.     

Di­chloro­bis(4-methyl­pentan-2-onato-C4,O)­tin(IV) and bis(4-methyl­pentan-2-onato-C4,O)(2-thio­xo-1,3-di­thiole-4,5-di­thiol­ato-S,S′)­tin(IV) at 150 K

The structures of the ketotins determined here, [SnCl₂(C₆H₁₁O)₂] and [Sn(C₃S₅)(C₆H₁₁O)₂], respectively, along with that previously reported for [MeC(O)CH₂CMe₂]₂SnI₂, are compared with the structures of the analogous estertins [MeOC(O)CH₂CH₂]₂SnX₂. Pairwise comparison of the mean ketotin [estertin] Sn—X and Sn—O distances as Sn—X 2.4422 (4) [2.4054 (7) Å], 2.4970 (4) [2.471 (2) Å] and 2.8463 (4) [2.7788 (8) Å] and Sn—O 2.4926 (12) [2.528 (1) Å], 2.6110 (11) [2.629 (7) Å] and 2.435 (3) [2.525 (4) Å] (for X = Cl, S and I, respectively) clearly demonstrates the superior donor ability of the ketotin O atom in chelate formation.     

Phenyl­phosphinic acid

The crystal structure of the title compound, C₆H₇O₂P, shows continuous hydrogen-bonding chains in the x direction, with a P—O⋯O=P distance of 2.513 (3) Å.     

Di­methyl (1R,8R)-1,11,11-tri­methyl-2,3-di­aza­tri­cyclo­[6.2.1.02,6]­undeca-3,5-diene-4,5-di­carboxyl­ate,a chiral mol­ecule with an approximate centrosymmetric crystal structure

The crystal structure of the title compound, C₁₆H₂₂N₂O₄, has two independent chiral mol­ecules related by a pseudo-inversion centre. 14 of the 22 non-H atoms have a centrosymmetric counterpart within a tolerance of 0.17 Å. A search of the Cambridge Structural Database [Spring 2000; Allen & Kennard (1993). Chem. Des. Autom. News, 8 , 1, 31–37] shows at least 10% of the crystal structures reported in the literature with space group P2₁ and Z = 4 to be chiral compounds with a pseudo-P2₁/c packing.     

Tri­carbonyl­[1,1′,1′′-ethyl­idyne­tris­(pyrazole-κN2)]­rhenium(I) bromide and tri­carbonyl­[methyl­idyne­tris­(pyrazole-κN2)]­rhenium(I) iodide ethanol hemisolvate

The two title compounds, [Re(C₁₀H₁₀N₆)(CO)₃]Br and [Re(C₁₁H₁₂N₆)(CO)₃]I·0.5C₂H₆O, have slightly distorted octahedral geometries about the rhenium centers. The distortions result from the constraints of the η³-coordinated tris­(pyrazol-1-yl)­methane ligands in each case which reduce the N—Re—N bond angles well below the preferred value of 90° for facially disposed ligands at a six-coordinate metal center.     

5,6-Bis(2-pyridyl)-2,3-pyrazine­dicarbo­nitrile

The crystal structure of the title compound, C₁₆H₈N₆, contains two independent mol­ecules with no significant difference in their structures. The pyrazine ring makes dihedral angles of 36.7 (2) and 36.5 (3)° with the two pyridine rings in one mol­ecule, and 43.1 (2) and 38.4 (1)° in the other. The dihedral angles between the two pyridine rings are 58.2 (2) and 56.0 (2)°, respectively. The favoured orientation of the pyridine rings is such that their N atoms face each other.     

Alkali metal and ammonium cation–arene interactions with tetraphenylborate anion

Sodium, potassium, rubidium, caesium, ammonium and tetramethylammonium tetraphenylborates were studied by both positive and negative ion electrospray mass spectrometry. An affinity order of Cs⁺ > Rb⁺ > K⁺ ～ Na⁺ was obtained. The results obtained were compared with both calculations and solid-state structures, where available. The previously reported high affinity of caesium for tetraphenylborate concluded from NMR experiments was confirmed for the gas phase. The affinity does not appear to result from steric effects and a cation–pi interaction seems likely. In the positive ion mode, a unique acetonitrile complex of NaBPh₄ was observed.