Novel multi-chalcogen ring systems with three different chalcogen atoms: synthesis,structure and redox property of five-membered trichalcogenaheterocycles

The molecular structure of novel five-membered trichalcogenaheterocycles with three different chalcogen atoms, sulfur, selenium and tellurium, has been determined by crystallographic studies.     

Polyhedral members of the Mg2nP2m family derived from dimeric magnesium trialkylsilylphosphandiide

The magnesiation of tri(tert-butyl)silylphosphane in THF yields tetrameric (tetrahydrofuran-O)magnesium tri(tert-butyl)silylphosphandiide 1. The central moiety is a slightly distorted Mg4P4 cube with tetracoordinate magnesium and phosphorus atoms. The reaction of dibutylmagnesium with H2PSitBu3 in toluene gives tetramagnesium tetrakis[mu-tri(tert-butyl)silylphosphanide] bis[mu 4-tri(tert-butyl)silylphosphandiide] 2. The central fragment is a Mg4P2 octahedron with the phosphorus atoms in a trans position. The Mg...Mg edges are bridged by the phosphanide substituents. Crystallographic data of 1: C68H148Mg4O5P4Si4, monoclinic, P2(1)/c, a = 13.454(1) A, b = 26.123(1) A, c = 24.539(2) A, beta = 96.53(1) degrees, Z = 4; crystallographic data of 2: C72H166Mg4P6Si6, monoclinic, P2(1)/n, a = 13.951(1) A, b = 14.269(1) A, c = 24.209(2) A, beta = 102.415(1) degrees, Z = 2.     

Image contrast analysis of STM images of self-assembled dioctadecyl chalcogenides on graphite at the liquid-solid interface.

The structures of self-assembled monolayers of dioctadecyl selenide (CH3(CH2)17)2Se and dioctadecyl telluride (CH3(CH2)17)2Te, as well as dioctadecyl ether (CH3(CH2)17)2O and dioctadecyl sulfide (CH3(CH2)17)2S, on graphite at the liquid-solid interface were systematically investigated by scanning tunneling microscopy (STM). Both dioctadecyl selenide and telluride formed monolayer structures in which the tilt angle between the molecular axis of the alkyl chain and the lamellae axis was 90 degrees , while dioctadecyl ether assembled with a tilt angle of 60 degrees . Dioctadecyl sulfide was found to make two different self-assembled structures having tilt angles of 60 and 90 degrees . When selenide was embedded in ether compounds in mixed self-assembled monolayers, the alkyl chains of the selenide became blurred, implying that the alkyl chains in the monolayers were unstable. This is in contrast with the structure of co-adsorbed monolayers of the ether and sulfide compounds, where the images of all alkyl chains had high spatial resolution. For the co-adsorbed monolayers, the image contrast of chalcogen atoms was normalized compared with that of alkyl chains of the ether compound in the same image frame. The normalized image contrast was found to be independent of the measurement conditions involving tip shapes, having the following trend, Te>Se>S>C>O. The difference in the normalized image contrast among chalcogen atoms are discussed based on fundamental parameters like polarizability and atomic radii.     

Catalytic adaptive recognition of thiol (SH) and selenol (SeH) groups toward synthesis of functionalized vinyl monomers

An unprecedented sustainable procedure was developed to produce functionalized vinyl monomers H(2)C═C(R)(FG) starting from a mixture of sulfur and selenium compounds as a functional group donor (FG = S or Se). The reaction serves as a model for efficient utilization of natural resources of sulfur feedstock in oil and technological sources of sulfur/selenium. The catalytic system is reported with amazing ability to recognize SH/SeH groups in the mixture and selectively incorporate them into valuable organic products via wastes-free atom-economic reaction with alkynes (HC≡CR). Formation of catalyst active site and the mechanism of the catalytic reaction were revealed by joint experimental and theoretical study. The difference in reactivity of μ(1)- and μ(2)-type chalcogen atoms attached to the metal was established and was shown to play the key role in the action of palladium catalyst. An approach to solve a challenging problem of dynamically changed reaction mixture was demonstrated using adaptive tuning of the catalyst. The origins of the adaptive tuning effect were investigated at molecular level and were found to be governed by the nature of metal-chalcogen bond.     

Generation of metal phosphinites by the reaction of Se-alkyl phosphinoselenoates with organometallics and its application to the synthesis of optically active organophosphorus compounds

Reaction of Se-Alkyl phosphinoselenoates with organometallics resulted in a selective attack on the selenium atom. Sequential treatment of optically active Se-benzyl t-butylphenylphosphinoselenoate with PhLi and then with electrophiles, such as alkyl halides, an α,β-unsaturated ester, and chalcogen atoms gave optically active phosphorus compounds in 5–91% yields and in high optical yields, with retention of configuration at the phosphorus atom, along with a quantitative yield of benzyl phenyl selenide.     

Synthesis and structural characterization of Sm(II) and Yb(II) complexes containing sterically demanding, chelating secondary phosphide ligands

Metathesis between [(Me3Si)2CH)(C6H4-2-OMe)P]K and SmI2(THF)2 in THF yields [([Me3Si]2CH)(C6H4-2-OMe)P)2Sm(DME)(THF)] (1), after recrystallization. A similar reaction between [(Me3Si)2CH)(C6H3-2-OMe-3-Me)P]K and SmI2(THF)2 yields [([Me3Si]2CH)(C6H3-2-OMe-3-Me)P)2Sm(DME)].Et2O (2), while reaction between [(Me3Si)2CH)(C6H4-2-CH2NMe2)P]K and either SmI2(THF)2 or YbI2 yields the five-coordinate complex [([Me3Si]2CH)(C6H4-2-CH2NMe2)P)2Sm(THF)] (3) or the solvent-free complex [([Me3Si]2CH)(C6H4-2-CH2NMe2)P)2Yb] (4), respectively. X-ray crystallography shows that complex 2 adopts a distorted cis octahedral geometry, while complex 1 adopts a distorted pentagonal bipyramidal geometry (1, triclinic, P1, a = 11.0625(9) A, b = 15.924(6) A, c = 17.2104(14) A, alpha = 72.327(2) degrees, beta = 83.934(2) degrees, gamma = 79.556(2) degrees, Z = 2; 2, monoclinic, P2(1), a = 13.176(4) A, b = 13.080(4) A, c = 14.546(4) A, beta = 95.363(6) degrees, Z = 2). Complex 3 crystallizes as monomers with a square pyramidal geometry at Sm and exhibits short contacts between Sm and the ipso-carbon atoms of the ligands (3, monoclinic, C2/c, a = 14.9880(17) A, b = 13.0528(15) A, c = 24.330(3) A, beta = 104.507(2) degrees, Z = 4). Whereas preliminary X-ray crystallographic data for 4 indicate a monomeric structure in the solid state, variable-temperature 1H, 13C(1H), 31P(1H), and 171Yb NMR spectroscopies suggest that 4 undergoes an unusual dynamic process in solution, which is ascribed to a monomer-dimer equilibrium in which exchange of the bridging and terminal phosphide groups may be frozen out at low temperature.     

Reactions of diiminopyridine ligands with chalcogen halides

The reactions of the chalcogen halides (Ch = S, Se, Te) with a series of diiminopyridine (DIMPY) ligands were explored. It was determined through these studies that varying both the substitution on the α-carbon and the chalcogen halide reagent afforded different products. If methyl groups were present on the α-carbon, reactivity was observed through the eneamine tautomer to yield N,N',C-bound neutral chalcogen complexes. In the cases where H and C(6)H(5) groups were in the same position, N,N',N″-chelated chalcogen cations or dications were produced. Many of the reactions resulted in complex mixtures postulated to occur by the release of halogen decomposing the product or, for reactions with the CH(3) substituted ligand, uncontrollable reactivity with the eneamine tautomer. This is the first report of reactions of sulfur and selenium halides with the ubiquitous diiminopyridine ligands and only the second example for a tellurium halide.     

Solvothermal synthesis and structure of a new selenium-rich selenophosphate K(3)PSe(4).2Se(6)

The compound K(3)PSe(4).2Se(6) was synthesized at 110 degrees C via solventothermal techniques from binary starting materials and Se in acetonitrile. The compound crystallizes in the space group Fd macro 3 of the cubic system with eight formula units in a cell with a dimension of a = 16.415(2) A at T = 193 K. The structure contains an unusual intermixing of ionic and uncharged species. The selenophosphate tetrahedral trianions PSe(4)(3-) are surrounded by potassium cations; other potassium cations in the structure are coordinated to 12 selenium atoms from four Se(6) rings in a tetrahedral arrangement. There are no short contacts between adjacent selenium rings. Heating the same reaction mixture to 160 degrees C results in the formation of only needles of trigonal selenium.     

Coordination chemistry of Group 12 metals with phosphorodiselenoates: syntheses, structures and VT 31P NMR study of monomer-dimer exchange equilibrium

The reactions of diselenophosphates, [dsep, (RO)2PSe2-; R = Et, (n)Pr and (i)Pr] with cadmium(II) and mercury(II) perchlorates in a 2 : 1 molar ratio formed compounds of stoichiometry M[Se2P(OR)2]2{M = Cd, R = Et (1), (n)Pr (2), (i)Pr (3); Hg, Et(4), (n)Pr (5), (i)Pr (6)}, and with zinc(II) perchlorates, chalcogen centered tetranuclear clusters, [Zn4(micro4-E){Se2P(OR)2}6]{E = Se, R = Et (7), (n)Pr (8), (i)Pr (9); E = O, R = Et (10), (n)Pr (11), (i)Pr (12)} were formed. All these complexes have been characterized with the help of analytical data, X-ray crystallography (1, 3, 6, 10, 11 and 12), and FAB-mass spectrometry (7-12). Compound 1 is a linear double-chain polymer, in which each pair of Cd atoms is bridged by two dsep ligands; the mercury 6 polymer has a helical chain structure, in which two Hg atoms are bridged by one dsep ligand, and the other ligand chelates the Hg atom. The chelating dsep ligands lie on either side of the helical chain. Compound 3 exists as a dimer in which two cadmium atoms are connected by two bridging dsep ligands, and each cadmium atom is further chelated by a dsep ligand. The metal atoms in 1, 3 and 6 are each coordinated by four selenium atoms in a distorted tetrahedral geometry. Clusters 10-12 have tetrahedral array of zinc atoms with an oxygen atom in the center with edge-bridging dsep ligands. Positive FAB-mass spectra support the formation of selenium-centered clusters,7-9, of which the cluster 8 was structurally confirmed earlier. The solution state behavior of compounds 1-12 has been studied by using multinuclear NMR spectroscopy. Dimer 3 in CD2Cl2 showed monomer-dimer exchange equilibrium in the temperature range 20 to -90 degrees C and the free energy of activation is calculated from the coalescence temperature as DeltaG++(223 K)= 38.5 kJ mol(-1). Polymer undergoes depolymerization in CDCl3 and exhibits monomer-dimer exchange equilibrium in the temperature range 20 to -60 degrees C.     

New tetradentate N,N,N,N-chelating α-diimine ligands and their corresponding zinc and nickel complexes: synthesis, characterisation and testing as olefin polymerisation catalysts

A series of zinc complexes of the general formula {[ZnCl(ArN=C(An)-C(An)=NAr)](+)}(2)[Zn(2)Cl(6)](2-) (where Ar = 2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl 2a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)phenyl 2b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl 2c; An = acenaphthene backbone) were prepared by the condensation of acenaphthenequinone with the corresponding o-triazolyl-substituted anilines (2-(1-benzyl-1H-1,2,3-triazol-4-yl)aniline 1a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)aniline 1b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline 1c) which were formed by the copper(I)-catalyzed Huisgen[3+2] dipolar cycloaddition between 2-ethynylaniline and the corresponding azides in high yields, using anhydrous ZnCl(2) as the metal template, in boiling glacial acetic acid. Zinc complexes of the type [ZnCl(ArN=C(An)-C(An)=NAr)](+)[ZnCl(3)(NCCH(3))](-) (4a-c) were synthesized by crystallisation of the corresponding complexes 2a-c in acetonitrile, at -20 °C. After removal of zinc dichloride from complexes 2a-c by the addition of potassium oxalate, in dichloromethane, the tetradentate N,N,N,N-chelating α-diimine ligands of the type ArN=C(An)-C(An)=NAr (5a-c) were obtained. The new ligand precursors and zinc complexes were characterised by elemental analysis, (1)H and (13)C{(1)H} NMR spectroscopy, two-dimensional NMR spectroscopy, and X-ray diffraction. Reaction of the ligand precursors 5a-c with [NiBr(2)(DME)], in dichloromethane, gave nickel complexes of the type [NiBr(2)(ArN=C(An)-C(An)=NAr)] (6a-c). The results of single crystal X-ray diffraction characterisation and magnetic susceptibility measurements demonstrated that nickel complexes 6a-c possess octahedral geometries around the nickel atoms with variable configurations, the Br atoms of which can be ionized when dissolved in methanol. In preliminary catalytic tests, complexes 6a-c revealed to be active as catalysts for the polymerisation of norbornene and styrene, when activated by cocatalyst MAO. The characterisation of the polymers by (1)H and (13)C{(1)H} NMR spectroscopy, gel permeation chromatography/size-exclusion chromatography (GPC/SEC) revealed that these polymers were formed by a coordination addition mechanism.     

New antitumor-active azole-bridged dinuclear platinum(II) complexes: synthesis, characterization, crystal structures, and cytotoxic studies

Three new derivatives of the cytotoxic azole-bridged dinuclear platinum(II) complex [(cis-Pt(NH3)2)2(mu-OH)(mu-pz)][NO3]2 (1) have been prepared and structurally characterized. Their formulas are [(cis-Pt(NH3)2)2(mu-OH)(mu-1,2,3-ta)][NO3]2 (2) (1,2,3-ta = 1,2,3-triazolate), [(Pt(R,R-dach))(mu-OH)(mu-pz)(Pt(S,S- dach))][NO3]2 (3) (dach = 1,2-diaminocyclohexane, pz = pyrazolate), and [(Pt(R,R-dach))(mu-1,2,3- ta)2(Pt(S,S-dach))][NO3]2 (4). The compounds were characterized by 1H, 13C, and 195Pt NMR spectroscopy, and elemental analysis, and their crystal structures were determined. Relevant data for 2: triclinic, space group P1, a = 8.5225(15) A, b = 9.1977(18) A, c = 9.9771(7) A, alpha = 66.988(10) degrees, beta = 75.423(9) degrees, gamma = 67.321(13) degrees, Z = 2. 3: orthorhombic, space group Pca2(1), a = 17.7653(3) A, b = 12.4076(3) A, c = 10.7091(3) A, Z = 4. 4: orthorhombic, space group Pbca, a = 13.8944(1) A, b = 17.8668(1) A, c = 20.7647(2) A, Z = 8. In the crystal structures of 2, and 3, the intramolecular distances between the two Pt atoms are 3.4411(6) and 3.4873(5) A, and the dihedral angles between the platinum coordination planes are 14.1(3) and 9.3(4) degrees, respectively. In 2, an intramolecular hydrogen bond is observed between N9 of the ammine ligand and the noncoordinated nitrogen atom (N3) of the triazole ring (N9...N3: 2.962(10) A). 4 has a boat-form structure, and the two coordination planes cross at 83.64(10) degrees. A cytotoxicity assay of these dinuclear platinum(II) compounds on human tumor cell lines was performed. In most of the cell lines, 1 and 2 showed much higher cytotoxicity than those of cisplatin. On the other hand, 3 was found to be moderately active, and 4 was found only marginally cytotoxic. Implications of these findings are discussed in the context of a structure-activity relationship.     

Spirodienone route for the stereoselective methylene functionalization of p-tert-butylcalix[4]arene.

A new method for the regio- and stereoselective functionalization of two distal methylene groups of p-tert-butylcalixarene (1a) is described. Reaction of the meso bis(spirodienone) calixarene derivative 2a with bromine afforded the tetrabrominated product 3a derived from exo 1,4-additions of bromine to the diene subunits. A phase-transfer-catalyzed reaction of 3a with aqueous NaOH/CH2Cl2 yielded the exo bis(epoxide) calixarene derivative 4. Heating 3a in a vacuum eliminated two molecules of HBr and afforded a product (5b) that retained the C(i) symmetry of the starting material. X-ray analysis indicated that the calixarene derivative 5b possesses two exocyclic double bonds of E configuration. Calixarene 5b undergoes reaction with nucleophiles at the exocyclic double bonds, with concomitant bond shifts and expulsion of the bromine atoms. Selective trans monodeuteration of two methylene groups of 1 was achieved by reaction of 5b with NaBD4 followed by aromatization of the labeled spirodienol derivative. Reaction of 5b with RONa/ROH (R = Me, Et) afforded the methylene-substituted bis(spirodienone) derivatives 9a and 9b possessing two trans alkoxy groups. X-ray crystallography of 9b indicated that the two trans substituents are located at pseudoequatorial positions of the methylene groups. LiAlH4 reduction of the substituted bis(spirodienone) derivatives afforded calix[4]arenes incorporating trans alkoxy groups at two distal methylene positions.     

Self-assembly of chemically linked rod-disc mesogenic liquid crystals

A series of new molecular discs (RDn, here n is the number of carbon atoms between the rod and disc mesogens) was synthesized via the chemical attachment of six cyanobiphenyl calamitic (rod) mesogens (R) linked to the triphenyl discotic (disc) mesogen (D) with a series of six alkyl chain linkages (n = 6-12). In this study, phase structures, transitions, and liquid crystalline (LC) behavior of the RD12 compound with 12 carbon atoms in each alkyl chain linkage between the rod and disc mesogens were investigated. Differential scanning calorimetry, polarized light microscopy, wide-angle X-ray diffraction (WAXD), and selected area electron diffraction (SAED) allowed us to identify three ordered phases below the isotropization temperature: nematic (N) LC and K1 and K2 crystalline phases. On the basis of the structural results obtained via 2D WAXD experiments on oriented samples and SAED experiments on single crystals, the K1 crystalline unit cell was determined to be triclinic with the dimensions of a = 1.36 nm, b = 1.45 nm, c = 2.11 nm, alpha = 85 degrees, beta = 100 degrees, and gamma = 50 degrees. The K2 phase was metastable with respect to the K1 phase. It also possessed a triclinic unit cell with a = 1.40 nm, b = 1.51 nm, c = 1.92 nm, alpha = 87 degrees, beta = 117 degrees, and gamma = 62 degrees. Molecular packing models for the crystalline phases were proposed on the basis of the diffraction results. In the whole range of ordered structures, it was found that RD12 molecular discs are intercalated. Both triphenyl discotic mesogens and cyanobiphenyl calamitic mesogens are completely interdigitated.     

Square Planar (SP-4) and Octahedral (OC-6) Complexes of Platinum(II) and -(IV) with Predetermined Chirality at the Metal Center

cis-Bis-homoleptic platinum(II) complexes, with predetermined helical chirality at the metal center, can be obtained by using strongly sterically interacting ligands. With this aim, two new ligands, (8R,10R)-2-(2'-thienyl)-4,5-pinenopyridine, th4,5ppy (2), and (8R,10R)-2-(2'-thienyl)-5,6-pinenopyridine, th5,6ppy (4), were synthesized and coordinated to platinum. The structures of the resulting complexes, Pt(th4,5ppy)(2) (5) and Pt(th5,6ppy)(2) (6), were determined by X-ray diffraction, and it was found that they both crystallize with a Delta-cis configuration. Thermal oxidative additions (TOA) of alkyl halides were performed with both complexes leading, in the case of 5, to a mixture of isomers and, in the case of 6, to isomerically pure products. The predetermination of chirality at the metal center is therefore preserved in the octahedral (OC-6) platinum(IV) complexes. Crystals of Pt(th4,5ppy)(2) (5) are orthorhombic, of space group P2(1)2(1)2(1), with a = 12.973(1) ?, b = 13.619(2) ?, c = 17.665(2) ?, alpha = beta = gamma = 90 degrees, and Z = 4. Final R = 0.0268 and R(w) = 0.0424 for 3101 observed reflections. Crystals of Pt(th5,6ppy)(2) (6) are hexagonal, of space group P6(1), with a = 11.5465(4) ?, b = 11.5465(4) ?, c = 35.356(3) ?, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 6. Final R = 0.0424 and R(w) = 0.0845 for 2660 observed reflections. Neither molecule possesses a crystallographic C(2) symmetry.     

Benzo[2,1-c:3,4-c']bis(1,2,3-thiaselenazole) (BSe) and its charge trasfer chemistry. Crystal and electronic structure of [BSe]3[ClO4]2

The S-Se-N-based heterocycle benzo[2,1-c:3,4-c']bis(1,2,3-thiaselenazole) (BSe) can be prepared by the condensation of 1,4-diaminobenzene-2,3-dithiol with selenium tetrachloride. Crystals of this compound are not isomorphous with the related benzo[2,1-c:3,4-c']bis(1,2,3-dithiazole) (BT); a structure is adopted that allows for more extensive intermolecular Se- - -Se contacts. Electro-oxidation of BSe in the presence of [n-Bu4N][ClO4] affords metallic green needles of the charge transfer salt [BSe]3[ClO4]2, which exhibit a pressed pellet conductivity sigma(RT) = 10(-1) S cm(-1). The crystal structure of [BSe]3[ClO4]2 consists of slipped pi-stacks based on the triple-decker closed shell [BSe]3(2+) building block. The packing is analogous to that found for the charge transfer salt [BT]3[FSO3]2, for which sigma(RT) = 10(-2) S cm(-1). Extended Hückel band structure calculations on these two (sulfur- and selenium-based) 3:2 salts reveal more extensive intermolecular interactions in the selenium compound. As a result, the latter has a more two-dimensional electronic structure. Crystal data for Se2S2N2C6H2, a = 4.103(2) A, b = 12.159(2) A, c = 16.171(2) A, orthorhombic, Pbnm, Z = 4. Crystal data for Se6S6N6C18H6Cl2O4, a =17.00(1) A, b = 18.36(1) A, c = 10.679(4) A, 110.27(3), monoclinic, C2/c, Z = 4.     

Mercury(I) molybdates and tungstates: Hg2WO4 and two modifications of Hg2MoO4

The high-temperature (beta-) modification of Hg2MoO4 was prepared by solid-state reaction of HgO with MoO2 at 400 degrees C. Well-crystallized samples of the low-temperature (alpha-) modification of Hg2MoO4 and isotypic Hg2WO4 were obtained by hydrothermal recrystallization of the microcrystalline powders at 180 degrees C. The crystal structures of these transparent yellow compounds were determined by single-crystal X-ray diffractometry. beta-Hg2MoO4: P2(1)/c, Z = 4, a = 511.31(6) pm, b = 901.83(7) pm, c = 1086.0(1) pm, beta = 101.01(3) degrees. alpha-Hg2MoO4 and Hg2WO4: C2/c, Z = 4, a = 873.52(6) and 873.0(1) pm, b = 1155.19(7) and 1147.6(3) pm, c = 493.05(3) and 493.24(6) pm, beta = 115.196(5) degrees and 114.86(1) degrees, respectively. In beta-Hg2MoO4 the molybdenum atoms are tetrahedrally coordinated by oxygen atoms and the MoO4 tetrahedra are linked via Hg2 dumb-bells, thus forming infinite zigzag chains. The low-temperature (alpha-)modification of Hg2MoO4 contains MoO6 octahedra, which are linked via common edges to form zigzag chains, which are further linked via Hg2 dumb-bells, resulting in puckered two-dimensionally infinite sheets. Bonding between adjacent sheets is achieved only via weak (secondary) Hg-O bonds of 254.8 pm, while the strong Hg-O bonds of the nearly linear O-Hg-Hg-O groups within the sheets have a length of 214.8 pm. The Hg-Hg bond lengths are practically the same in the three compounds with 252.3(1), 253.49(7), and 253.3(1) pm in beta-Hg2MoO4, alpha-Hg2MoO4, and Hg2WO4, respectively. The average Mo-O distances within the MoO4 tetrahedra and the MoO6 octahedra are 176.2, and 196.5 pm, respectively. The structural chemistry of these compounds is discussed together with that of previously reported mercury I and II molybdates and tungstates.     

Synthesis and X-ray Powder Structures of Two Lamellar Copper Arylenebis(phosphonates)

Reaction of copper salts with 1,4-phenylenebis(phosphonic acid) yielded a conventional layered compound, Cu(2)[(O(3)PC(6)H(4)PO(3))(H(2)O)(2)], while a similar reaction with 4,4'-biphenylenebis(phosphonic acid) resulted in a new lamellar structure with composition Cu[HO(3)P(C(6)H(4))(2)PO(3)H]. The structures of these compounds were solved ab initio by using X-ray powder diffraction data. The crystals of the phenylenebis(phosphonate) compound are monoclinic, space group C2/c, with a = 18.8892(4) ?, b = 7.6222(2) ?, c = 7.4641(2) ?, beta = 90.402(2) degrees, and Z = 4. The layer structure in this case is similar to that in copper phenylphosphonate, Cu[O(3)PC(6)H(5)]. The metal atoms display a distorted square pyramidal geometry where four of the coordination sites are occupied by the phosphonate oxygens. The remaining site is filled by an oxygen atom of the water molecule. Adjacent metal-O(3)PC layers are covalently pillared by the phenyl group of the phosphonates to create a 3-dimensional structure. Cu[HO(3)P(C(6)H(4))(2)PO(3)H] is triclinic, space group P&onemacr;, with a = 4.856(2) ?, b = 14.225(5) ?, c = 4.788(2) ?, alpha = 97.85(1) degrees, beta = 110.14(1) degrees, gamma = 89.38(1) degrees, and Z = 1. The structure in this case, ideally consists of linear chains of copper atoms. The copper atoms are bridged by centrosymmetrically related phosphonate groups utilizing two of their oxygen atoms. This binding mode leads to square planar geometry for the copper atoms. The third oxygen atom of the phosphonate is protonated and is involved in linking adjacent linear chains through hydrogen bonds. At the same time, these hydroxyl oxygens interact weakly (Cu-O = 3.14 ?) with the copper atoms of the adjacent chain. Considering these long Cu-O interactions, the geometry of the copper atom may be described as distorted square bipyramidal. As in the phenylphosphonate structure, the biphenyl groups covalently link the Cu-O(3)PC networks in the perpendicular direction.     

Synthesis, Characterization, and Bonding of Two New Heteropolychalcogenides: alpha-CsCu(S(x)()Se(4-x)) and CsCu(S(x)()Se(6-x))

The Cs-Cu-Q (Q = S, Se) system has been investigated using copper metal, cesium chloride, and alkali-metal polychalcogenide salts under mild hydrothermal reaction conditions. Heteropolychalcogenide salts and mixtures of known polysulfide and polyselenide salts have been used as reagents. The reaction products contain the alpha-CsCuQ(4) and CsCuQ(6) structures. The alpha-CsCuQ(4) phase exhibits a smooth transition in lattice parameters from the pure sulfur to the pure selenium phases, based on Vegard's law. The CsCuQ(6) phase has been prepared as the pure sulfur analog and a selenium rich analog. The single-crystal structures of the disordered compounds alpha-CsCuS(2)Se(2) (P2(1)2(1)2(1), Z = 4, a = 5.439(1) ?, b = 8.878(2) ?, c = 13.762(4) ?) and CsCuS(1.6)Se(4.4) (P&onemacr;, Z = 2, a = 11.253(4) ?, b = 11.585(2) ?, c = 7.211(2) ?, alpha = 92.93 degrees, beta = 100.94 degrees, gamma = 74.51 degrees ) have been solved using a correlated-site occupancy model. These disordered structures display a polychalcogenide geometry in which the sulfur atoms prefer positions that are bound to copper. The optical absorption spectra of these materials have been investigated. The optical band gap varies as a function of the sulfur-selenium ratio. Extended Hückel crystal orbital calculations have been performed to investigate the electronic structure and bonding in these compounds in an attempt to explain the site distribution of sulfur and selenium.     

Stepwise construction of manganese-chromium carbonyl chalcogenide complexes: synthesis, electrochemical properties, and computational studies

When trigonal-bipyramidal clusters, [PPN][E(2)Mn(3)(CO)(9)] (E = S, Se), were treated with Cr(CO)(6) and PPNCl in a molar ratio of 1:1:2 or 1:2:2 in 4 M KOH/MeCN/MeOH solutions, mono-Cr(CO)(5)-incorporated HE(2)Mn(3)-complexes [PPN](2)[HE(2)Mn(3)Cr(CO)(14)] (E = S, [PPN](2)[1a]; Se, [PPN](2)[1b]), respectively, were formed. X-ray crystallographic analysis showed that 1a and 1b were isostructural and each displayed an E(2)Mn(3) square-pyramidal core with one of the two basal E atoms externally coordinated with one Cr(CO)(5) group and one Mn-Mn bond bridged by one hydrogen atom. However, when the TMBA(+) salts for [E(2)Mn(3)(CO)(9)](-) were mixed with Cr(CO)(6) in a molar ratio of 1:1 in 4 M KOH/MeOH solutions and refluxed at 60 °C, mono-Cr(CO)(3)-incorporated E(2)Mn(3)Cr octahedral clusters [TMBA](3)[E(2)Mn(3)Cr(CO)(12)] (E = S, [TMBA](3)[2a]; Se, [TMBA](3)[2b]), respectively, were obtained. Clusters 2a and 2b were isostructural, and each consisted of an octahedral E(2)Mn(3)Cr core, in which each Mn-Mn or Mn-Cr bond of the Mn(3)Cr plane was semibridged by one carbonyl ligand. Clusters 1a and 1b (with [TMBA] salts) underwent metal core closure to form octahedral clusters 2a and 2b upon treatment with KOH/MeOH at 60 °C. In addition, 1a and 1b were found to undergo cluster expansion to form di-Cr(CO)(5)-incorporated HE(2)Mn(3)-clusters [HE(2)Mn(3)Cr(2)(CO)(19)](2-) (E = S, 3a; Se, 3b), respectively, upon the addition of 1 or 2 equiv of Cr(CO)(6) heated in refluxing CH(2)Cl(2). Clusters 3a and 3b were structurally related to clusters 1a and 1b, but with the other bare E atom (E = S, 3a; Se, 3b) further externally coordinated with one Cr(CO)(5) group. The nature, cluster transformation, and electrochemical properties of the mixed manganese-chromium carbonyl sulfides and selenides were systematically discussed in terms of the chalcogen elements, the introduced chromium carbonyl group, and the metal skeleton with the aid of molecular calculations at the BP86 level of the density functional theory.     

Assessment of the intramolecular C–H⋯X (X=F,Cl, Br) hydrogen bonding of 1,4-diphenyl-1,2,3-triazoles

The intramolecular six-membered C–H?X (X=F, Cl, Br) hydrogen bonding motif of halogen-substituted 1,4-diphenyl-1,2,3-triazole compounds has been assessed. Twelve triazole derivatives have been designed and prepared, which bear fluorine, chlorine or bromine atoms on the ortho- and/or para-positions of the benzene rings. ¹H NMR, X-ray crystallography, and DFT calculation investigations revealed that the ortho-fluorine, chlorine, and bromine atoms of the benzene ring on the C-4 of the triazole unit all can form six-membered C–H?X hydrogen bonding. In contrast, only fluorine forms similar, relatively stable intramolecular hydrogen bonding on the N-1 side of the triazole unit.