Showing papers on "Tetrahedral molecular geometry published in 2000"

Synthesis, Structure, and Electroluminescence of BR2q (R = Et, Ph, 2-Naphthyl and q = 8-Hydroxyquinolato)

Abstract: Three 8-hydroxyquinolato (q) boron compounds B(C2H5)2q (1), BPh2q (2), and B(2-naph)2q (3) have been synthesized by the reaction of 8-hydroxyquinoline with an appropriate BR3 compound. Compounds 1−3 have a tetrahedral geometry as demonstrated by the structure of 1 determined by a single-crystal X-ray diffraction analysis. Compounds 1−3 emit a green-blue color at λmax = 495−500 nm when irradiated by UV light. The electroluminescent (EL) properties of 2 and 3 were examined by fabricating EL devices using 2 and 3 as the light-emitting layer, respectively. The devices of 2 produce a yellow-green light with broad emission spectra, attributed to the formation of an exciplex of 2 with the N,N‘-di-1-naphthyl-N,N‘-diphenylbenzidine (NPB) in the hole transport layer while the intrinsic EL emission of compound 3 was observed. Both 2 and 3 were found to be good electron transport materials in EL devices.

Syntheses, structures, and fluxionality of blue luminescent zinc(II) complexes: Zn(2,2',2"-tpa)Cl2, Zn(2,2',2"-tpa)2(O2CCF3)2, and Zn(2,2',3"-tpa)4(O2CCF3)2 (tpa = tripyridylamine).

Abstract: Three novel Zn(II) complexes containing either 2,2‘,2‘ ‘-tripyridylamine (2,2‘,2‘ ‘-tpa) or 2,2‘,3‘ ‘-tripyridylamine (2,2‘,3‘ ‘-tpa) have been synthesized and structurally characterized. Compound 1, Zn(2,2‘,2‘ ‘-tpa)Cl2, has a tetrahedral geometry while compounds 2, Zn(2,2‘,2‘ ‘-tpa)2(O2CCF3)2, and 3, Zn(2,2‘,3‘ ‘-tpa)4(O2CCF3)2, have an octahedral geometry. The 2,2‘,2‘ ‘-tpa ligand in 1 and 2 functions as a bidentate ligand, chelating to the zinc center, while the 2,2‘ ‘,3‘ ‘-tpa ligand in 3 functions as a terminal ligand, binding to the zinc center through the 3-pyridyl nitrogen atom. All three compounds emit a blue color in solution and in the solid state. The emission maxima for the three compounds in solution are at λ = 422, 426, and 432 nm, respectively. The blue luminescence of the complexes is due to a π* → π transition of the tpa ligand as established by an ab initio calculation on the free ligand 2,2‘,2‘ ‘-tpa and complex 1. Compounds 1 and 2 are fluxional in solution owing to an exchange proce...

Spectroscopic and Electronic Structural Studies of Blue Copper Model Complexes. 1. Perturbation of the Thiolate−Cu Bond

Abstract: A tris(pyrazolyl)hydroborate triphenylmethylthiolate Cu(II) model complex (1) that reproduces structural and spectroscopic features of active sites of blue Cu proteins is characterized using low-temperature absorption, magnetic circular dichroism (MCD), X-ray absorption (XAS), and resonance Raman (rR) spectroscopies combined with DFT calculations to define its electronic structure. The electronic structure of 1 is further related to the oxidized Cu site in plastocyanin. The key spectral differences relative to plastocyanin include an increase in the intensity of the S pπ → Cu CT band and a decrease in the absorption intensity at ∼450 nm. The energies of d → d transitions in 1 decrease relative to plastocyanin, which reflects the more tetrahedral geometry of 1. S K-edge XAS measurements demonstrate a more covalent thiolate interaction in the HOMO of 1 (52% S p) than in plastocyanin (38% S p). The effects of the high thiolate covalency on the absorption and Raman spectral features for 1 are evaluated. Addit...

Influence of ligand backbones and counter ions on structures of helical silver(I) complexes with di-Schiff bases derived from phthalaldehydes and diamine

Abstract: Five silver(I) complexes of Schiff bases, [Ag2L2][ClO4]21, [Ag2L2][PF6]2·H2O 2, [Ag2L2][NO3]23, 1∞[(AgL′)(dnb)(H2O)0.25] (dnb = 3,5-dinitrobenzoate) 4 and 1∞[(AgL′)(NO3)] 5 were synthesized, where L and L′ are derived from the [1 + 2] condensation of 2-(aminoethylamino)ethanol with isophthalaldehyde or terephthalaldehyde. Complexes 1, 2, 4 and 5 have been structurally characterised by X-ray crystallography, which shows that the cations in 1 and 2 have similar double helical structures, and 4 has a single-stranded helical structure. However, complex 5 exhibits a one-dimensional staircase-like structure. Each Ag atom in 1, 2 and 4 adopts a highly distorted tetrahedral geometry, while that in 5 features a T-shaped geometry. In solution, 1–3 have virtually identical 1H NMR spectra, similar FAB mass spectra and electrochemical properties.

Structural influence of hydrophobic core residues on metal binding and specificity in carbonic anhydrase II.

Abstract: Aromatic residues in the hydrophobic core of human carbonic anhydrase II (CAII) influence metal ion binding in the active site. Residues F93, F95, and W97 are contained in a beta-strand that also contains two zinc ligands, H94 and H96. The aromatic amino acids contribute to the high zinc affinity and slow zinc dissociation rate constant of CAII [Hunt, J. A., and Fierke, C. A. (1997) J. Biol. Chem. 272, 20364-20372]. Substitution of these aromatic amino acids with smaller side chains enhances Cu(2+) affinity while decreasing Co(2+) and Zn(2+) affinity [Hunt, J. A., Mahiuddin, A., & Fierke, C. A. (1999) Biochemistry 38, 9054-9062]. Here, X-ray crystal structures of zinc-bound F93I/F95M/W97V and F93S/F95L/W97M CAIIs reveal the introduction of new cavities in the hydrophobic core, compensatory movements of surrounding side chains, and the incorporation of buried water molecules; nevertheless, the enzyme maintains tetrahedral zinc coordination geometry. However, a conformational change of direct metal ligand H94 as well as indirect (i.e., "second-shell") ligand Q92 accompanies metal release in both F93I/F95M/W97V and F93S/F95L/W97M CAIIs, thereby eliminating preorientation of the histidine ligands with tetrahedral geometry in the apoenzyme. Only one cobalt-bound variant, F93I/F95M/W97V CAII, maintains tetrahedral metal coordination geometry; F93S/F95L/W97M CAII binds Co(2+) with trigonal bipyramidal coordination geometry due to the addition of azide anion to the metal coordination polyhedron. The copper-bound variants exhibit either square pyramidal or trigonal bipyramidal metal coordination geometry due to the addition of a second solvent molecule to the metal coordination polyhedron. The key finding of this work is that aromatic core residues serve as anchors that help to preorient direct and second-shell ligands to optimize zinc binding geometry and destabilize alternative geometries. These geometrical constraints are likely a main determinant of the enhanced zinc/copper specificity of CAII as compared to small molecule chelators.

Redox and catalytic chemistry of Ti in titanosilicate molecular sieves: an EPR investigation

Abstract: An EPR study of Ti3+ in titanosilicate molecular sieves, TS-1, TiMCM-41, ETS-10 and ETS-4 is reported. Ti4+ is reduced to Ti3+ by dry hydrogen above 673 K. Ti ions in TS-1 and TiMCM-41 are located in tetragonally elongated Td and those of ETS-10 and ETS-4 in a tetragonally compressed Oh geometric positions. Reduction at 873 K revealed the presence of two non-equivalent Ti3+ sites in TS-1 and TiMCM-41. Ti4+ ions in a tetrahedral geometry are more difficult to reduce than in an octahedral symmetry. The effects of cation exchange and Pt impregnation, on the geometry and reducibility of titanium in ETS-10, are also examined. Interaction of a tetrahedrally coordinated Ti3+ with O2 or H2O2 results in a diamagnetic titanium(IV) hydroperoxo species. Under the same conditions, an octahedrally coordinated Ti3+ forms a paramagnetic titanium(IV) superoxo species. The higher catalytic activity of TS-1 and TiMCM-41 in selective oxidation reactions is probably a consequence of the formation of the hydroperoxy species on their surface during the catalytic reaction. The presence of Pt in the vicinity of Ti enables the use of H2 and O2 (instead of H2O2) to generate the active hydroperoxy site. The absence of formation of titanium hydroperoxy species in ETS-4 and ETS-10 is the cause of their inactivity in selective oxidation reactions.

Copper(II), nickel(II), cobalt(II) and oxovanadium(IV) complexes of substituted β-hydroxyiminoanilides

Abstract: Complexes of the general formula, ML2 [M = CuII, NiII, CoII and OVIV; L = 1,2,3,5,6,7,8,8a-octahydro-3-hydroxyimino-N-(4-X-phenyl)-l-phenyl-5-(phenylmethylene)-2-naphthalenecarboxamide (X = H, Me, OMe, Cl)] have been prepared and characterized on the basis of elemental analysis, magnetic moments and i.r., e.p.r. and electronic spectra. These metal complexes contain the N4 chromophore with the ligand coordinating through nitrogens of the azomethine and deprotonated anilide functions. C.v. measurements indicate that the copper(II) complexes are quasi-reversible in acetonitrile solution. Square planar and square pyramidal structures are assigned respectively to the copper(II) and oxovanadium(IV) complexes, whereas tetrahedral geometry is assigned to the nickel(II) and cobalt(II) complexes. Deprotonated anilide nitrogen is involved in coordination and the presence of an electron-donating group para to the anilide function decreases the ΔE values of the d–d transitions while the value is found to increase when electron-withdrawing groups are substituted. Line spacing in the e.p.r. spectra of the copper(II) and oxovanadium(IV) complexes increases when methyl group is para to the anilide group, and decreases when this group is replaced by methoxy or chloro. The ν(C–N) of the anilide group and the ν(C-N) of the azomethine function of the oxime metal complexes are metal-sensitive and the blue shift for the above stretching frequencies follows the order: copper(II) > oxovanadium(IV) > nickel(II) ≈ cobalt(II).

Unprecedented Stabilization of Cobalt(II) in a Tetrahedral S2O2 Environment: The Use of a Redox-Noninnocent Ligand†

Abstract: The reaction of Zn(II) and Co(II) with thiosalicylic acid, o-HSC6H4COOH, and its methyl ester has led to the following complexes: [Zn(SC6H4COO)] (1), (NEt4)Na[Zn(SC6H4COO)2].H2O (2), (NEt4)2Na[Co(SC6H4COO)3].2H2O (3), (NEt4)3Na3[(Co(SC6H4COO)3)2].6MeOH (4), [Zn(SC6H4COOMe)2] (5), and [Co(SC6H4COOMe)n], n = 2 (6), 3 (7). These ligands have not allowed stabilization of Co(II) in a sulfur-oxygen coordination environment. The structures of complexes 2-4 and 7 have been determined crystallographically. Those of 2-4 show significant similarities such as the behavior of the -SC6H4COO- anion as chelating ligand and the involvement of sodium ions as a structural element. Thus, the structure of the [Na(Zn(SC6H4COO)2)(H2O)]- anion in complex 2 can be described as infinite chains of consecutive [Zn(SC6H4COO)2]2- metalloligands linked by [Na(H2O)]+ centers, that of the [Na(Co(SC6H4COO)3(H2O)2)]2(4-) anion in 3 as a centrosymmetric tetranuclear Co2Na2 dimer with a (CoIII(S[symbol: see text]O)3)Na(mu-H2O)2Na(CoIII(S[symbol: see text]O)3) core, and that of the pentanuclear [Na3(Co(SC6H4COO)3)2(MeOH)6]3- anion in 4 as two dinuclear [(CoIII(S[symbol: see text]O)3)Na(MeOH)3] fragments linked to a central sodium ion, which appears to be the first structurally characterized example of a NaS6 site. The use of the o-HSC6H4COOMe ligand allowed the synthesis of [Co(SC6H4COOMe)2] (6) but not its full structural characterization. Instead, [Co(SC6H4COOMe)3] (7) was obtained and structurally characterized. It consists of mononuclear molecules containing an octahedral CoIIIS3O3 core. The selection of 2,2-diphenyl-2-mercaptoacetic acid as ligand with reductive properties has afforded the first mononuclear complex containing a CoIIS2O2 core and thus an unprecedented model for Co(II)-substituted metalloproteins containing tetrahedral MS2O2 active sites. The synthesis and full structural characterization of the isostructural complexes (NEt4)2[Zn(Ph2C(S)COO)2] (8) and (NEt4)2[Co(Ph2C(S)COO)2] (9) show that they consist of discrete [M(Ph2C(S)COO)2]2- anions, with a distorted tetrahedral coordination about the metal. In addition, the stability conferred by the ligand on the CoIIS2O2 core has allowed its characterization in solution by paramagnetic 1D and 2D 1H NMR studies. The longitudinal relaxation times of the hyperfine-shifted resonances and NOESY spectra have led to the assignment of all resonances of the cobalt complex and confirmed that it maintains its tetrahedral geometry in solution. Magnetic measurements (2-300 K) for complex 9 and 9.2H2O are in good agreement with distorted tetrahedral and octahedral environments, respectively.

Structure and Thermal Reactivity of a Novel Pd(0) Metalloenediyne

Abstract: We report the X-ray diffraction structure and thermal reactivity of the metalloenediyne compound bis(1,2-bis(diphenylphosphinoethynyl)benzene)palladium(0) (Pd(dppeb)2, 1). The structure of 1 features a tetrahedral Pd(0) center with four phosphorus atoms from two chelating ligands. The PPdP bond angles nearly match the idealized 109.5° geometry expected for a d10 metal center in a tetrahedral ligand field. The tetrahedral geometry of the metal center forces the alkyne termini separation of the enediyne ligand to a distance of 3.47 A, which results in a thermally stable compound at room temperature. However, at 115 °C 1 exhibits solvent-dependent reactivity. In o-fluorotoluene, 1 decomposes via ligand dissociation, while in o-dichlorobenzene, carbon−halide bond activation of solvent occurs leading to the oxidative addition product trans-Pd((2-chlorophenyl)diphenylphosphine)2Cl2 and free (2-chlorophenyl)diphenylphosphine. The thermal reactivity of 1 is markedly more endothermic (44 kcal/mol) than that of the...

A supramolecular analog of cyclohexane sustained by aromatic C–H···π interactions between ferrocene moieties: molecular packing of ferrocene-containing thiosemicarbazato metal complexes

Abstract: Novel supramolecular cyclohexane-like structures, [NiL2] (1) and [ZnL2] (2) (HL=acetylferrocenyl thiosemicarbazone), have been constructed by self-assembly of ferrocene moieties ia aromatic C–H···π interactions. The nickel(II) atom in 1 is coordinated in a distorted square-planar cis configuration with two ferrocene-containing ligands positioned on the same side. One of the ferrocene moieties interacts with symmetry-related species to form a supramolecular arrangement that is topologically equivalent to cyclohexane, but in which edge-to-face C–H···π interactions between ferrocene moieties serve the same structural functions as the C–C bonds in cyclohexane. The zinc(II) atom in 2 is coordinated in a tetrahedral geometry with two equivalent Zn–S and Zn–N bonds. Each ferrocene moiety interacts with symmetry-related species using C–H···π interactions to form a two-dimensional cyclohexane-like network. Powder X-ray diffraction analyses of complexes 1 and 2, together with the palladium(II) complex [PdL2] (3), copper(II) complex [CuL2] (4), and cobalt(II) complex [CoL2] (5) reveal that the supramolecular cyclohexane-like aggregation is robust enough to be exchanged from one network to another. All the results indicate that although C–H···π interactions have energies only in the 2–20 kJ mol−1 range, these interactions are directional enough in combination that the orientation of molecules in the solid can be predicted with a reasonable degree of accuracy.

Equilibrium and solution structural study of the interaction of tri- and tetra-dentate polyimidazole ligands with transition metal ions

Abstract: Copper(II) and zinc(II) complexes of two polyimidazole derivatives, 4-(imidazol-4-ylmethyl)-2-(imidazol-2-ylmethyl)imidazole (TRIM) and bis[4-(imidazol-4-ylmethyl)-imidazol-2-yl]methane (TIM), containing three and four methylene-linked imidazole rings as donor groups, have been studied by potentiometry, UV–VIS, EPR and NMR spectroscopic methods. The data revealed that both ligands form extremely stable and varied complexes with zinc(II) and copper(II). In equimolar solutions of the metal ions and TRIM, two and three imidazole co-ordinated MAH and MA species were formed. The complex Zn(TRIM) probably has tetrahedral geometry. The formation of bis-complexes has also been detected with the ligand in excess. The data revealed 6N and 5N co-ordinated central ions in ZnA2 and CuA2, respectively. In MA complexes of TIM, the ligand is co-ordinated to the metal ions via all the four imidazole units. Formation of bis-complexes has only been found in the zinc(II) containing system. Ternary systems of zinc(II)–TRIM and –TIM have also been studied with L-cysteine as a second ligand. The potentiometric and NMR results established the formation of ternary complexes with different protonation states in relatively high amount, in spite of the high stability of the parent complexes.

A 1:2 complex of mercury(II) chloride with 1,3-imidazole-2-thione.

Abstract: The Hg atom in the title monomeric complex, di­chloro­bis(3-imidazolium-2-thiol­ato-S)­mercury(II), [HgCl2(C3H4N2S)2], is four-coordinate having an irregular tetrahedral geometry composed of two Cl atoms [Hg—Cl 2.622 (2) and 2.663 (2) A] and two thione S atoms [Hg—S 2.445 (2) and 2.462 (2) A]. The monodentate thione ligand adopts a zwitterionic form and exists as the 3-imidazolium-2-thiol­ate ion. The bond angle S1—Hg—S2 of 130.87 (8)° has the greatest deviation from ideal tetrahedral geometry. Intermolecular hydrogen bonds between two of the four N—H groups and one of the Cl atoms [3.232 (8) and 3.238 (7) A] stabilize the crystal structure, while the other two N—H groups contribute through the formation of N—H⋯Cl intramolecular hydrogen bonds with the other Cl atom [3.121 (7) and 3.188 (7) A].

Synthesis and Structural Characterization of Tin(IV) N-nitroso-N-phenylhydroxylaminato Complexes: Crystal Structures of Sn(O2N2Ph)4, Ph2Sn(O2N2Ph)2 and [Me2Sn(O2N2Ph)2]2

Abstract: Reaction of cupferron [NH4L, L = PhN(O)NO–] with tin(IV), diphenyltin(IV) and dimethyltin(IV) halides yields the cupferronato complexes SnL4 (1), Ph2SnL2 (2) and [Me2SnL2]2 (3). All were characterized by FT-IR, FT-Raman, NMR (1H, 13C and 119Sn) spectroscopic methods and X-ray structural analysis. An almost ideal, very rare dodecahedral geometry is found in the structure of 1. The hexacoordinated tin center exhibits a bicapped tetrahedral geometry in complex 2. The tin centers are heptacoordinated in a pentagonal bipyramidal geometry in the dimeric complex 3. These complexes incorporate five-membered SnO2N2 and four-membered Sn2O2 inorganic rings. Vibrational spectral data are consistent with the structures determined. The 119Sn NMR spectra indicate that in solution 1 retains its octacoordinated nature; in compound 2 the tin atom is hexacoordinated, while in 3 the tin atom is pentacoordinated.

Complexes of Nickel(II) with 1,2-DI(imino-47′-antipyrinyl)Ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Abstract: Nickel(II) complexes of the Schiff bases 1,2-di(imino-4′-antipyrinyl)ethane (GA) and 4-N-(4′-antipyrylmethylidene)aminoantipyrine (AA) having the compositions [Ni(GA)]X2 and [Ni(AA)2]X2 (where X - ClO4, NO3, Cl, Br or I) have been prepared and characterized by elemental analyses, electrical conductance in non-aqueous solvents, infrared and electronic spectra as well as magnetic susceptibility measurements. GA acts as a neutral tetradentate ligand coordinating through both carbonyl oxygens and both azomethine nitrogens while AA acts as a neutral bidentate ligand coordinating through one of the carbonyl oxygens and the azomethine nitrogen. In all these complexes both the anions are not coordinated resulting in a square planar geometry around the Ni(II) ion in complexes of GA and a tetrahedral geometry in complexes of AA.

Crystal structures of nitronium tetranitratogallate and its reversible solid-state phase transition mediated by nonmerohedral twinning

Abstract: Single-crystal X-ray crystallographic analyses of [NO2][Ga(NO3)4] reveal that it undergoes a reversible phase transition without any apparent damage to the crystal during repeated temperature cyclings. The room-temperature, noncentrosymmetric, body-centered tetragonal (I 4), polymorph 1 (a = 9.2774(3) A, c = 6.1149(2) A, Z = 2) consists of well-separated nitronium and tetranitratogallate ions. The [Ga(NO3)4]- units exhibit a slightly squashed tetrahedral geometry in which all of the ligands are monodentate. Below approximately 250 K, distortions lower the symmetry to the chiral, body-centered monoclinic nonstandard space group I2. Both components (2a: a = 9.5857(2) A, b = 5.9399(1) A, c = 8.9759(2) A, β = 90.409(1)°, Z = 2. 2b: a = 9.5898(2) A, b = 5.9376(1) A, c = 8.9784(1) A, β = 90.420(1)°, Z = 2) of the nonmerohedrally twinned structure are independently refined and found to be enantiomeric with nearly identical distance and angle parameters. As in the high-temperature polymorph, the cations and an...

The structure and stability of Sb4H+ clusters: The importance of nonclassical structures

Abstract: The structure and relative stabilities of the different Sb4H+ clusters were investigated by means of high level ab initio calculations. For this purpose we have developed a split valence and an extended basis set for the treatment of Sb-containing compounds to be used with different effective core potentials available in the literature. The split-valence basis set reported seems to reproduce nicely the geometries and vibrational frequencies of different Sb-containing compounds, provided that electron correlation effects are included at the MP2 level. When the extended basis set is used, within the framework of the G2(ECP) theory, the atomization enthalpies of antimony derivatives are reproduced within ±3 kcal/mol. A systematic study of the Sb4H+ potential energy surface (PES) using these basis sets, showed that the global minimum is the result of the side protonation of the Sb4 tetrahedral molecule. In this species the hydrogen is covalently attached to two Sb atoms through the formation of a three-center...

Quantum Chemical Studies of Reactions of the Cyclic Disulfides with the Zinc Finger Domains in the HIV-1 Nucleocapsid Protein (NCp7)

Abstract: By using quantum chemistry methods, including ab initio Hartree−Fock (HF), as well as the Density Functional Theory approach employing B3LYP approximation, the reaction profiles of three cyclic disulfide species with model zinc finger domains in the HIV-1 nucleocapsid protein (NCp7) have been analyzed. It is shown that the disulfide molecules can act as efficient agents destroying the tetrahedral coordination sphere of the zinc finger domains. The consequence of the reaction is a break of one of the Zn−S bonds and removal of the corresponding molecular thiolate group from the domain by forming a new S−S bond between sulfur atoms from the withdrawing fragment and of the electrophilic agent. As a result of this process the zinc-containing site transforms from the initial tetrahedral geometry to a planar geometry configuration. This transformation further facilitates destruction of the metal binding site. The calculations explicitly show correlations between redox potentials of the electrophilic agents, thei...

Three sulfur-containing diborane(4) compounds

Abstract: The preparation and structures of three diborane(4) compounds are described. The compound B2(3,4-S2C4H2-1-S)2 [2,2′-bi(1,3,5,2-tri­thia­borapentalene), C8H4B2S6] is planar and lies at a crystallographic inversion centre. The amine adducts [B2(C3S5)2(NHMe2)2] [2,2′-bis­(di­methyl­amino)-2,2′-bi(1,3,4,6,2-tetra­thia­borapentalene-5-thione), C10H14B2N2S10] and [B2(1,2-S2C2H4)2(NHMe2)2]·0.33CH2Cl2 [1,2-bis­(di-methylamino)-1,1:2,2-bis(dimethylenedithioxy)diborane(4) di­chloro­methane solvate, C8H22B2N2S4·0.33CH2Cl2] contain di­methyl­amine ligands bound to each boron in an anti conformation about the B—B bond, with tetrahedral geometry at the B atoms. The crystal structures display a number of S⋯S interactions, which appear to dictate the packing arrangements.

Bis(thiosemicarbazide-S,N)zinc(II) dinitrate.

Abstract: In the title compound, [Zn(CH5N3S)2](NO3)2, the zinc(II) ion is located on the twofold axis and chelated by two thiosemicarbazide ligands with Zn—S and Zn—N distances of 2.0904 (17) and 2.2672 (6) A, respectively. Thus the central zinc(II) is four-coordinated and in a distorted tetrahedral geometry. The inter- and intramolecular hydrogen bonds formed between thiosemicarbazide ligands and nitrate anions assemble the molecules into a one-dimensional chain.

Two mixed-metal carboxylate-base adducts

Abstract: The crystal structures of hexa-μ-propionato-1:2κ6O:O′;1:3κ6O:O′-di­quinoline-2κN,3κN-calcium(II)­dizinc(II), [Ca­Zn2(C3H5O2)6(C9H7N)2], and hexa-μ-pivalato-1:2κ6O:O′;1:3κ6O:O′-di­quinoline-2κN,3κN-calcium(II)­dicobalt(II), [Ca­Co2(C5H9O2)6(C9H7N)2], are described. Both contain a linear array of one CaII ion and two MII (M = Zn, Co) ions connected by two sets of three carboxyl­ate ligands in syn–syn bridging modes. The distorted tetrahedral geometry around the MII ion is completed by a quinoline N atom. The central CaII ion occupies a crystallographic inversion centre and is octahedrally coordinated by six carboxyl O atoms in each structure. The ZnII⋯CaII and CoII⋯CaII distances are 3.8504 (9) and 3.7929 (5) A, respectively.

Tris[(pentafluorophenyl)trimethyl­silylamido](tetrahydrofuran)­samarium(III)

Abstract: In the title complex, [Sm(C9H9F5NSi)3(C4H8O)], the Sm metal center is coordinated in a highly distorted tetrahedral geometry by the three N atoms of the amido ligands and by the O atom of the tetra­hydro­furan ligand. Principal bond lengths include: Sm—N 2.299 (4), 2.339 (4) and 2.366 (4) A, and Sm—O 2.446 (3) A, close Sm⋯F contacts of 2.536 (3) and 2.556 (3) A, and an `agostic' Sm⋯C interaction of 3.154 (4) A.

Compositional disorder in trans‐[RhBr0.26Cl0.74H(PMe3)4][B(1,2‐O2C6Br4)]·CH2Cl2

Abstract: The structure of trans-(bromo/­chloro)­hy­drido­tetra­kis­(tri-me­thyl­phos­phine)­rhod­ium(III) bis­(tetra­bromo­pyro­catechol-ato-O,O′)­borate dichloromethane solvate, [RhCl0·74Br0·26H-(C3­H9­P)4]­(C12­BBr8­O4)·­CH2Cl2, is reported. The RhIII com­plex shows bromine/chlorine compositional disorder with a trans arrangement of the hydride and halide ligands. The anion has approximate D2d symmetry, with a central spiro-B atom distorted from regular tetrahedral geometry by the small chelating O—B—O angles.

Spectroscopic study of phosphine selenide complexes of Au(I) and X-ray structure of [(cyclohexyl)3PSeAuBr]

Abstract: The X-ray structure determination of the complex, [(cyclohexyl)3PSe-AuBr], revealed a triclinic space group P-1, with a = 9.7654(7), b = 10.9441(9), c = 11.2064(9) A, α = 117.076(6)°, β = 99.076(6)° γ = 95.417(6)°, V = 1034.07(14) A3 and Z = 2. The Au(I) atom in this complex has a linear coordination with Se1 atom at 2.3776(9) A on one side and Br1 at 2.3843(9) A at the trans position making the Se1-Au1-Br1 angle of 177.97(4)°. The P1 atom in the phosphine has tetrahedral geometry. All three cyclohexyl groups are in their usual boat conformation. The phosphorus atom of the triphenylphosphine is approximately perpendicular to the Se1—Au1—Br1 linkage with P1—Se1—Au1 angle of 99.19(6)°. The Δδ in the 31P NMR of the free ligands and their corresponding L—Se—Au—Br (L—Se = trialkyl/arylphosphine selenides) complexes, and the changes in the P—Se bond frequencies in the FTIR upon complexation, are indicative of the bonding of the ligand to Au(I) through selenium. There is a strong corelation between the chemical shifts of the 31P NMR and the C—P—C angle in the phosphines.

(4,6-Dimercapto-1,3,5-triazine-2-thiol­ato-S2)­tris­(tri­phenyl­phosphine-P)gold(I) di­methyl­form­amide solvate

Abstract: In the title compound, [Au(C3H2N3S3)(C18H15P)3]·C3H7NO, the AuI atom has a distorted tetrahedral geometry consisting of one uncoordinated di­methyl­form­amide mol­ecule, one tri­thio­cyanurate ligand and three PPh3 ligands. The S—Au distance is 2.909 (2) A, and the P—Au distances fall in the range 2.400 (14)–2.4074 (13) A. The S—Au—P angles are 92.81 (6), 99.17 (6) and 104.21 (5)°, and the P—Au—P angles are 114.46 (5), 119.04 (5) and 119.66 (5)°.