Bimetallic Complexes with Bridging Dithiaalkane Ligands: Preparation and Kinetic Study

Reactions of M(CO)₅THF, which was generated photochemically from M(CO)₆ in THF, with (CH₃)₃CS(CH₂)_nSC(CH₃)₃ (=SS; n=5, 6; M=W, Cr) at room temperature afforded exclusively the bimetallic complexes (CO)₅MSSM(CO)₅. These new complexes with dithiaalkane bridging ligands have been characterized by IR and ¹H NMR spectroscopies and elemental analysis. Kinetic studies of ligand-exchange reactions in these complexes in chlorobenzene (=CB) solutions employing tri(iso-propyl)phosphite (=L) as an incoming nucleophile indicated that the bridging ligand SS is replaced by L to afford finally (CO)₅MP(O-i-Pr)₃ as the sole reaction product. The kinetic data have also confirmed that replacement of SS by L under pseudo-first-order reaction conditions is dissociative and proceeds via a mechanism which involves initial M-S bond breaking followed by other steps. First order rate constants and activation parameters for these reactions have been determined.     

Influence of alkyl substituents in 1,3-diethyl-2-thiobarbituric acid on the coordination environment in M(H2O)2(1,3-diethyl-2-thiobarbiturate)2 M = Ca2+, Sr2+

Two new isostructural complexes, [Ca(H₂O)₂(μ₂-Detba-O,O′)₂]_n (1) and [Sr(H₂O)₂(μ₂-Detba-O,O′)₂]_n (2) (HDetba = 1,3-diethyl-2-thiobarbituric acid), were synthesized and characterized by single-crystal and powder X-ray diffraction analysis, TG-DSC, FT-IR, and emission spectroscopy. The single-crystal X-ray diffraction data revealed that 1 and 2 are polymeric where M²⁺ (M = Ca, Sr) is a six-coordinate octahedral binding four Detba^? ions and two water molecules. The octahedra are linked through bridging Detba^? ions forming a 2-D layer. Two intermolecular hydrogen bonds O–H…S in the crystal form a 3-D net. The comparison of M(Detba)₂ and M(Htba)₂ (H₂tba = 2-thiobarbituric acid) structures showed that the coordination number of metals in M(Detba)₂ does not exceed six and there are no π–π interactions, unlike compounds with Htba^?; Detba^? ions are only bridges in HDetba coordination compounds. Thermal decomposition of 1 and 2 includes dehydration, which mainly ends at 200 °C, and organic ligand oxidation at 300–350 °C with a release of CO₂, SO₂, H₂O, NH₃, and isocyanate. Upon excitation at 220 nm, 1 and 2 exhibit an intense emission maximum at 557 nm.     

Preparation and characterization of four polymeric metal complexes based on the flexible ligand 1H-1,2,4-triazole-1-propionic acid in different conformations

Three 2-D layered coordination polymers with (4,4) topology, {[Cu(trzp)₂(H₂O)]·1.18H₂O} _n (1), {[Co(trzp)₂(H₂O)₂]·2H₂O} _n (2), and {[Cd(trzp)₂(H₂O)]·2H₂O} _n (3), have been synthesized with the flexible, bifunctional ligand 1H-1,2,4-triazole-1-propionate (trzp^?) as a two-connected bridge. In addition, a complicated 3-D MOF [Ag₃(trzp)₂(NO₃)] _n (4) has been obtained with the help of Ag?Ag interactions and trzp^? as a four-connected linker. Htrzp and 1–4 have been characterized by single-crystal X-ray diffraction, elemental analysis, and infrared spectroscopy. The structural analysis showed that Htrzp has a gauche conformation in the solid state. However, both gauche and trans conformers of trzp^? are observed in the crystals of 1; only one conformer of trzp^? exists in the other three compounds (trans conformation in 2 and 3, and gauche conformation in 4). The thermal behaviors of 1–4 have been examined by thermal gravimetric analysis under nitrogen, which revealed that metal cyanide salts M(CN) _n (M?=?Cu(II), Co(II), Cd(II), and Ag(I), n?=?1 or 2) may be an intermediate pyrolytic decomposition product of the corresponding compounds.     

Thermal behaviour of new N,N-dimethylbiguanide complexes having selective and effective antibacterial activity

The complexes of the type M(HDMBG)₂(CH₃COO)₂·nH₂O ((1) M:Mn, n=1.5; (2) M:Ni, n=0; (3) M:Cu, n=2; (4) M:Zn, n=2; DMBG: N,N-dimethylbiguanide) present in vitro antimicrobial activity. The thermal analysis has evidenced the thermal intervals of stability and also the thermodynamics effects that accompany them. The different nature of the ligands generates a different thermal behaviour for the complexes. The thermal transformations are complex processes according to TG and DTG curves including dehydration, oxidative condensation of –C=N– units as well as thermolysis processes. The final products of decomposition are the most stable metal oxides.     

THE CRYSTAL STRUCTURES OF TWO IMINO-1,2,4- DITHIAZOLES FORMED BY THERMAL DECOMPOSITION OF 5-(DIALKYLAMINO)-3-(SUBSTITUTED IMINO)-1,2,4-DITHIAZOLES

Abstract

The thermal decomposition products of two substituted imino-1,2,4-dithiazoles have been studied by single crystal x-ray analysis. Both products crystallize in space group P2^1/c with four molecules per unit cell. The first product, obtained from 5-(dimethylamino)-3-(methylimino)-1,2,4-dithiazole has cell dimensions of a=9.922(8) Å, b=12.052(11) Å, c=13.358(12) Å and β=104.9(1)°. The molecule is made up of two planar segments related by an extremely large twist (?154°) about a C?N double bond. The results from this study have also contributed further information in the area of nonbonded interactions between ring and thione sulfur atoms. The second product, from 5-(dimethylamino)-3(phenylimino)-1,2,4-dithiazole was shown to be an ordered 1:1 complex of the starting material and one of its isomers. The cell dimensions are a=12.420(6) Å, b=8.840(9) Å, c=22.276(22) Å and β= 112.2(1)°. The different molecules are linked by an inter molecular NH… N hydrogen bond.     

Energy dependence of rearrangements of an N-terminal protecting group in tandem mass spectrometry of protonated tripeptides containing C-terminal arginine

The types and intensities of tandem mass spectrometric products of side-chain interactions were investigated with a hybrid tandem instrument. Positive-ion unimolecular decomposition and collisionally activated decomposition studies were conducted on the [M + H]⁺ ions of two N-benzyloxycarbonyl (Cbz or Z)-protected tripeptides, Cbz-Gly-Leu-Arg-NH₂ and Cbz-Gly-Pro-Arg-NH₂. The loss of benzyl alcohol (108 u) and the formation of other significant product ions and their dependence on collision energy and gas pressure suggest reaction between both ends of the molecule. Replacement of leucine with proline at the second position in the tripeptide produces a very intense [M + H ? 108]⁺ ion and fewer lower mass fragment ions in the tandem mass spectra for Cbz-Gly-Pro-Arg-NH₂ than in those for Cbz-Gly-Leu-Arg-NH₂.     

甲酸及联吡啶配体构筑的三维网状镍（Ⅱ）/钴（Ⅱ）配位聚合物的合成及晶体结构

通过水热法合成两个新的混配的配位聚合物[M（bipy）（Metha）₂]_n·nH₂O（M=Ni,1;Co,2;bipy=4,4’-联吡啶;Metha=甲酸）,并对配合物进行了元素分析、红外光谱和X-射线单晶衍射测定。结果表明,2个配合物为单斜晶系,C2/c空间群。配合物1和2具有相似的三维网状结构。配体Metha以2种不同的类型与M²⁺离子配位,一种是Metha中的2个氧原子作为桥联配位原子,连接着由bipy作为双基配体连接2个不同的金属离子构成的链,另一个Metha中的羧基氧只有1个氧原子与金属离子配位,使配合物构成三维结构。     

Syntheses,crystal structures,and properties of two molecular double-supporting polyoxotungstates

Two molecular double-supporting polyoxotungstates [SiW₁₂O₄₀{M(phen)₂H₂O}₂] · nH₂O (phen = 1,10′-phenanthroline, M = Mn 1, n = 2; M = Co 2, n = 3) were synthesized hydrothermally and characterized by elemental analyses, IR, TG, and X-ray single-crystal diffraction. The variable-temperature magnetic susceptibilities were measured at 2–300 K. The double-supporting polyoxotungstate molecule consists of a Keggin-type dodecatungstosilicate anion and a pair of transition metal complex fragments which are covalently linked to opposite sides of the Keggin anion. The transition metal ion locates in the center of a distorted octahedron. Multiple H-bonding interactions are observed between the coordinated waters of the transition metal complex fragments and terminal oxygen atoms of Keggin units and also between the bridging oxygen atoms of Keggin units and the lattice waters, which creates one-dimensional chains or two-dimensional layers. Between the layers or chains there are weak CH···O hydrogen bonding interactions and van der Waals forces. The molecular double-supporting polyoxotungstosilicate begins to decompose at ca. 500 °C. The variable-temperature magnetic behavior of 1 shows weak antiferromagnetic characteristics with a small value of θ = −0.289 K.     

Syntheses,structural characteristics,and antimicrobial activities of new organotin(IV) 3-(4-bromophenyl)-2-ethylacrylates

New organotin(IV) carboxylates, [n-Bu₂SnL₂] (1), [Et₂SnL₂] (2), [Me₂SnL₂] (3), [n-Oct₂SnL₂] (4), [n-Bu₃SnL] _n (5), [Me₃SnL] _n (6), and [Ph₃SnL] _n (7), where L?=?3-(4-bromophenyl)-2-ethylacrylate, were synthesized and characterized by elemental analysis, FT-IR, and multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn). Spectroscopic studies confirm coordination of L to the organotin moiety via COO group. Single-crystal X-ray analysis reveals bridging mode of coordination in 6. Packing diagram established a supramolecular cage-like structure for 6 due to Sn–O interactions (3.287?Å). Subsequent antimicrobial activities proved them to be active biologically.     

Organic cluster ions from continuous-flow fast atom bombardment

Cluster ions from fast atom bombardment of liquid alcohols and nitriles were examined using a continuous-flow technique. Protonated molecular M_nH⁺ species are the dominant cluster ions observed in molecules of formula M. The abundances of the M_nH⁺ cluster ions decrease monotonically with increasing n, and within a homologous series the M_nH⁺ abundance diminishes more rapidly for higher molecular mass compounds. Reaction products (ROH)_n(H₂O)H⁺ and (ROH)_n(ROR)H⁺ are observed also in the case of alcohols, and the ion abundances decrease with increasing n. Radiation damage yields fragment ions and ionic alkyl reaction products which are captured in solvent clusters. Semi-empirical molecular orbital methods were used to examine the energetics of cluster ion formation and decomposition pathways. Metastable decomposition processes exhibit only evaporative loss of monomers, with the probability of loss increasing sharply with n. The evaporative ensemble model of Klots was used to predict the cluster size-dependent trends of metastable dissociation processes observed for alcohol and nitrile cluster ions.     

Evidence of quasi-intramolecular redox reactions during thermal decomposition of ammonium hydroxodisulfitoferriate(III), (NH4)2[Fe(OH)(SO3)2]·H2O

Synthesis of ammonium hydroxodisulfitoferriate(III), (diammonium catena-{bis(μ ²-sulfito-κO,κO)-μ ²-hydroxo-κ²O}ferrate(III) monohydrate) (NH₄)₂[Fe(OH)(SO₃)₂]·H₂O (compound 1) and its thermal behavior is reported. The compound is stable in air. Its thermal decomposition proceeds without the expected quasi-intramolecular oxidation of sulfite ion with ferric ions. The disproportionation reaction of the ammonium sulfite, formed from the evolved NH₃, SO₂ and H₂O in the main decomposition stage of 1, results in the formation of ammonium sulfate and ammonium sulfide. The ammonium sulfide is unstable at the decomposition temperature of 1 (150 °C) and transforms into NH₃ and H₂S which immediately forms elementary sulfur by reaction with SO₂. The formation and decomposition of other intermediate compounds like (NH₄)₂S_nO_x (n = 2, x = 3 and n = 3, x = 6) results in the same decomposition products (S, SO₂ and NH₃). Two basic iron sulfates, formed in different ratios during synthesizing experiments performed under N₂ or in the presence of air, have been detected as solid intermediates which contain ammonium ions. The final decomposition product was proved to be α-Fe₂O₃ (mineral name hematite).

     

Synthesis and crystal structures of two new zigzag versus helical coordination polymers based on diphenic acid

Two new coordination polymers, [Mn(dpa)(2,2′-bipy)] _n (1) and [Ni(dpa)(2,2′-bipy)] _n (2) (H₂dpa = 3,4′-biphenyl-dicarboxylic acid, 2,2′-bipy = bipyridine), have been synthesized and structurally characterized by elemental analysis, IR, and X-ray diffraction. Single-crystal X-ray analyses revealed that 3,4′-diphenic acid acts as a bridging ligand, exhibiting rich coordination modes to link metal ions: μ ₂–η ¹: η ¹, μ ₁–η ¹: η ¹, and μ ₁ –η ¹: η ⁰. Compound 1 demonstrates a 1-D zigzag chain. Compound 2 is a 1-D helical chain. In 1 and 2, there exist intermolecular π–π stacking interactions and non-covalent interactions responsible for the stabilization of the supramolecular structure. In 1, the Mn(II) chains exhibit a weak antiferromagnetic interaction.     

Metal–π Interactions Dominate in the Solid‐State Structures of Molecular Heterobimetallic Alkali‐Metal–Europium(II) Aryloxo Complexes

Treatment of Eu metal, 2,6‐diphenylphenol (HOdpp), and MOdpp (M=Na, K) at elevated temperature in the presence of mercury afforded heterobimetallic complexes which were structurally characterized after crystallization from toluene. The structures of [MEu(Odpp)₃]?nPhMe (M=Na, n=1, 1 ; K, n=2.5, 2 ) consist solely of bridging aryloxide ligands and feature extensive π‐Ph–metal interactions. Rather than a heterobimetallic species, treatment of Eu metal and HOdpp with LiOdpp under similar conditions afforded a number of products, including a mixed‐valent europium complex, [Eu₂(Odpp)₃][Eu(Odpp)₄]?4 PhMe ( 3 ). The structural framework of the [Eu₂(Odpp)₃]⁺ cation of 3 is similar to that of the molecular heterobimetallics 1 and 2 , including the presence of π‐Ph–Eu interactions. The reluctance of the reaction to provide a Eu/Li heterobimetallic complex was exemplified by the simultaneous crystallization of [Eu₂(Odpp)₄]?PhMe ( 6 ) and the homoleptic cubane [Li₄(Odpp)₄]?2 C₆H₁₄ ( 5 ) from toluene/hexane.     

Ring and Cluster Structures of {Li[C(NtBu)2(HNtBu)]}2·(THF) and {Li2[C(NtBu)3]}2, Containing the Novel Anions [C(NtBu)2(HNtBu)]−- and [C(NtBu)3]2−

The reaction of tert.-butyl carbodiimide with one equivalent of LiNH^tBu in tetrahydrofuran at-78 °C produces {Li[C(N^tBu)₂(HN^tBu)]}₂-(THF) (1), which is an eight-membered Li₂C₂N₄ ring; the deprotonation of (1) with two equivalents of n-BuLi in tetrahydrofuran at -78 °C and recrystallisation of the product from n-pentane yielded the unsolvated dimer {Li₂[C(N^tBu)₃]}₂ (2), which adopts the structure of a distorted hexagonal prism.     

Thermal behaviour of some new complexes with bismacrocyclic ligands as potential biological active species

Novel complexes of type [M₂LCl₄]·nH₂O ((1) M:Ni, n = 5; (2) M:Cu, n = 0 and (3) M:Zn, n = 2; L: ligand resulted from 1,2-phenylenediamine, 3,6-diazaoctane-1,8-diamine and formaldehyde template condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. Processes as water or hydrochloric acid elimination as well as oxidative degradation of the organic ligand were observed. Complexes display a different thermal behaviour as result of dissimilar chemical interaction of metal ions with chloride anions. The final product of decomposition was metal(II) oxide as powder X-ray diffraction indicated.     

Copper(I) bromide complexes of two 15-memberd O2S2-macrocycles with different sulfur-to-sulfur separations: dimer and one-dimensional coordination polymer

Abstract

A comparative study on the exo-coordination-based networking of 15-membered O₂S₂-macrocycle isomers (L¹ and L²) induced by interdonor distances is reported. In copper(I) bromide complexation, the isomer L¹ incorporating a shorter sulfur-to-sulfur separation yielded a discrete dimer complex [(μ-Cu₂Br₂)(L¹)₂] (1) in which two macrocycles are bridged by a Cu₂Br₂ square cluster. While, the reaction of copper(I) bromide with the isomer L² incorporating a longer sulfur-to-sulfur separation afforded a double-stranded one-dimensional (1D) coordination polymer {[(μ₄-Cu₂Br₂)(L²)₂]·CH₂Cl₂}_n (2) as a kinetic product which converted to [(μ₄-Cu₂Br₂)(L²)₂]_n (3) with different 1D connectivity pattern as a thermodynamic product. The results indicate as examples of programmed self-assembly that the proposed interdonor distances and the ligand isomerism play decisive roles cooperatively in the topologies of the supramolecular products via different coordination modes.     

Structure and properties of μ<Subscript>2</Subscript>-<Emphasis Type="Italic">S</Emphasis>-[bis(benzenethiolato)tetranitrosyldiiron] in solution

Dinuclear iron tetranitrosyl complex with the composition [Fe₂(SPh)₂(NO)₄] (1) was synthesized and its single crystals and polycrystals were studied by X-ray diffraction, IR spectroscopy, and elemental analysis. The decomposition products of complex 1 were investigated by electrochemical method and mass spectrometry. The mass spectrum of a solution of complex 1 shows two groups of ions: the primary decomposition products of 1 in solution (the complex ions [Fe(SPh)(NO)₂(NO₂)]⁻, [Fe(SPh)₂(NO)]⁻, and [Fe(SPh)₂(NO)₂]⁻) and a series of the ions [FeO₂ + n(NO)]⁻ and [FeO₃ + n(NO)]⁻ (n = 0–4), which are formed in secondary reactions. The structures of the complexes, which were formed through the Fe-NO bond dissociation and the replacement of the NO ligand by aqua and oxygen ligands in complex 1, and the structure of the complex [FeO₃]⁻ were studied by quantum chemical modeling.     

甲酸及联吡啶配体构筑的三维网状镍(Ⅱ)/钴(Ⅱ)配位聚合物的合成及晶体结构(英文)

通过水热法合成两个混配的配位聚合物[M(bipy)(Metha)2]n·nH2O(M=Ni,1;Co,2;bipy=4,4′-联吡啶;Metha=甲酸),并对配合物进行了元素分析、红外光谱和X-射线单晶衍射测定。结果表明,2个配合物为单斜晶系,C2/c空间群。配合物1和2具有相似的三维网状结构。配体Metha以2种不同的类型与M2+离子配位,一种是Metha中的2个氧原子作为桥联配位原子,连接着由bipy作为双基配体连接2个不同的金属离子构成的链,另一个Metha中的羧基氧只有1个氧原子与金属离子配位,使配合物构成三维结构。     

Bridging function mediated intermetallic coupling in diruthenium- bis (bipyridine) complexes

The interactions of potentially dinucleating bridging functionalities (I–VI) with the ruthenium-bis(bypyridine) precursor [Ru^II(bpy)₂(EtOH)₂]²⁺have been explored. The bridging functionsI,II andVI directly result in the expected dinuclear complexes of the type [(bpy)₂Ru^IILⁿRu^II(bpy)₂]^z+ (1,2,7 and 8) (n = 0,z =4 andn = -2,z = 2). The bridging ligandIII undergoes N-N or N-C bond cleavage reaction on coordination to the Ru^II(bpy)₂ core which eventually yields a mononuclear complex of the type [(bpy)₂Ru^II(L)]⁺,3, where L =^-OC₆H₃(R)C(R′)=N-H. However, the electrogenerated mononuclear ruthenium(III) congener, 3⁺in acetonitrile dimerises to [(bpy)₂Ru^III {^-OC₆H₃(R)C(R′)=N-N=(R′)C(R)C₆H₃O^-}Ru^III(bpy)₂]⁴⁺ (4). In the presence of a slight amount of water content in the acetonitrile solvent the dimeric species (4) reduces back to the starting ruthenium(II) monomer (3). The preformed bridging ligandIV undergoes multiple transformations on coordination to the Ru(bpy)₂ core, such as hydrolysis of the imine groups ofIV followed by intermolecular head-to-tail oxidative coupling of the resultant amino phenol moieties, which in turn results in a new class of dimeric complex of the type [(bpy)₂Ru^{II -}OC₆H₄-N=C₆H₃(=NH)O^-Ru^II(bpy)₂]²⁺ (5). In5, the bridging ligand comprises of twoN,O chelating binding sites each formally in the semiquinone level and there is ap-benzoquinonediimine bridge between the metal centres. In complex6, the preformed bridging ligand, 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2-dihydro-1,2,4,5-tetrazine, H₂L (V) undergoes oxidative dehydrogenation to aromatic tetrazine based bridging unit, 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine, L. The detailed spectroelectrochemical aspects of the complexes have been studied in order to understand the role of the bridging units towards the intermetallic electronic coupling in the dinuclear complexes.