Oxazolone copper(I) complexes inspired by the methanobactin active site

Two oxazolone-derived potential ligands with enethioether substituents have been synthesized that differ by the terminal thioether moiety (S-Et in L¹, S-C₆H₄(OMe)-2 in L²). Both L¹ and L² behave as bidentate {NS} chelate ligands to form stable complexes with copper(I) triflate that crystallize as dimeric complexes [L₂Cu₂(OTf)₂] (4 and 5) featuring a central {Cu₂S₂} diamond core with distinctly different Cu-S bonds. L¹ as well as 4 and 5 have been characterized by single crystal X-ray diffraction. NMR spectroscopy including ¹H and ¹⁹F DOSY experiments reveals that 4 and 5 dissociate into monomeric species [LCu(OTf)] (4′ and 5′) in CDCl₃ solutions. 4′ and 5′ retain the {NS} binding motif of the oxazolone-derived ligands, but are in slow equilibrium with their {OS} isomers 4″ and 5″ that result from E/Z isomerization of the exocyclic enethioether double bond.     

Group 3 complexes incorporating (furyl)-substituted disilazide ligands

A series of mono- and bis-amide scandium and yttrium compounds incorporating the furyl-substituted disilazide ligand, [N{SiMe₂R}₂]⁻ {i} (where R = 2-methylfuryl) have been synthesized. The compounds Sc{i}Cl₂ (1), Sc{i}(CH₂SiMe₃)₂ (2) and Sc{i}(OAr)₂ (3) were made from suitable scandium starting materials employing either a salt metathesis protocol with Li{i} or via protonolysis of Sc-C bonds by the neutral amine H{i}. The thermally unstable bis-alkyl yttrium compound, ‘Y{i}(CH₂SiMe₃)₂^’ was isolated as the bis-THF adduct (4) and the bis-aryloxide Y{i}(OAr)₂ (5) was synthesized by elimination of LiOAr from Y(OAr)₃. The bis-amide complex Y{i}₂Cl (6) and conversion to a rare example of an yttrium benzyl compound Y{i}₂(CH₂Ph) (7) are described. The yttrium cation, [Y{i}₂]⁺, was synthesized by benzyl abstraction from 7 using B(C₆F₅)₃. Structural characterization of representative examples show variation in the coordination modes for amide ligand {i}, differing primarily in the number of furyl groups that coordinate to the metal, with examples in which zero, one or two M-O_furyl bonds are present. Preliminary investigation in two areas of catalysis are presented.     

Nickel promoted C-H, C-C and C-O bond activation in solution

Reaction of NiI₂ with the PCP-ligand {1-Et-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (1) results in selective activation of the strong sp²-sp³ aryl-ethyl bond to afford the aryl-nickel complex [Ni{2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (2), whereas reaction of NiI₂ with {1,3,5-(CH₃)₃-2,6-(CH₂PⁱPr₂)₂-C₆H} (4) leads to the formation of the benzylic complex [Ni{1-CH₂-2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (5) by selective C-H bond activation. Thermolysis of 5 results in formation of [Ni{2,6-(CH₂PⁱPr₂)₂-3,5-(CH₃)₂-C₆H}I] (6) by activation of the sp²-sp³ C-C bond. The identity of the new 16-electron complexes 2 and 6 was confirmed by reaction of NiI₂ with {1,3-(CH₂PⁱPr₂)₂-C₆H₄} (3) and {1,3-(CH₃)₂-4,6-(CH₂PⁱPr₂)₂-C₆H₂} (7), respectively, lacking the aryl-alkyl groups between the “phosphines arms” (alkyl=ethyl, methyl). Complexes 2 and 5 have been fully characterized by X-ray analysis. Nickel-based activation of an unstrained C-O single bond was observed as well. Reaction of the aryl-methoxy bisphosphine {1-OMe-2,6-(CH₂PⁱPr₂)₂-C₆H₃} (8) with NiI₂ results in the formation of the phenoxy complex [Ni{1-O-2,6-(CH₂PⁱPr₂)₂-C₆H₃}I] (9) by selective sp³-sp³ C-O bond activation.     

Stereosensitive formation and interconversion of sulfur-bridged cobalt(III)-mercury(II) polynuclear complexes with d- and/or l-penicillaminates

The reaction of trans(N)-[Co(d-pen)₂]⁻ (pen = penicillaminate) with HgCl₂ or HgBr₂ in the molar ratios of 1:1 gave the sulfur-bridged heterodinuclear complex, [HgX(OH₂){Co(d-pen)₂}] (X = Cl (1a) or Br (1b)). A similar reaction in the ratio of 2:1 produced the trinuclear complex, [Hg{Co(d-pen)₂}₂] (1c). The enantiomers of 1a and 1c, [HgCl(OH₂){Co(l-pen)₂}] (1a′) and [Hg{Co(l-pen)₂}₂] (1c′), were also obtained by using trans(N)-[Co(l-pen)₂]⁻ instead of trans(N)-[Co(d-pen)₂]⁻. Further, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 1:1 resulted in the formation of [HgCl(OH₂){Co(d-pen)(l-pen)}] (2a). During the formations of the above six complexes, 1a, 1b, 1c, 1a′, 1c′, and 2a, the octahedral Co(III) units retain their configurations. On the other hand, the reaction of cis · cis · cis-[Co(d-pen)(l-pen)]⁻ with HgCl₂ in the molar ratio of 2:1 gave not [Hg{Co(d-pen)(l-pen}₂] but [Hg{Co(d-pen)₂}{Co(l-pen)₂}] (2c), accompanied by the ligand-exchange on the terminal Co(III) units. The X-ray crystal structural analyses show that the central Hg(II) atom in 1c takes a considerably distorted tetrahedral geometry, whereas that in 2c is of an ideal tetrahedron. The interconversion between the complexes is also examined. The electronic absorption, CD, and NMR spectral behavior of the complexes is discussed in relation to the crystal structures of 1c and 2c.     

Platinum(II) and palladium(II) complexes with (N,N') and (C,N,N')- ligands derived from pyrazole as anticancer and antimalarial agents: synthesis, characterization and in vitro activities

The study of the reactivity of three 1-(2-dimethylaminoethyl)-1H-pyrazole derivatives of general formula [1-(CH₂)₂NMe₂}-3,5-R₂-pzol] {where pzol represents pyrazole and RH (1a), Me (1b) or Ph (1c)} with [MCl₂(DMSO)₂] (MPt or Pd) under different experimental conditions allowed us to isolate and characterize cis-[M{κ²-N,N′-{[1-(CH₂)₂NMe₂}-3,5-R₂-pzol])}Cl₂] {MMPtPt (2a-2c) or Pd (3a-3c)} and two cyclometallated complexes [M{κ³-C,N,N′-{[1-(CH₂)₂NMe₂}-3-(C₅H₄)-5-Ph-pzol])}Cl] {MPt(II) (4c) or Pd(II) (5c)}. Compounds 4c and 5c arise from the orthometallation of the 3-phenyl ring of ligand 1c. Complex 2a has been further characterized by X-ray crystallography. Ligands and complexes were evaluated for their in vitro antimalarial against Plasmodium falciparum and cytotoxic activities against lung (A549) and breast (MDA MB231 and MCF7) cancer cellular lines. Complexes 2a-2c and 5c exhibited only moderate antimalarial activities against two P. falciparum strains (3D7 and W2). Interestingly, cytotoxicity assays revealed that the platinacycle 4c exhibits a higher toxicity than cisplatin in the three human cell lines and that the complex 2a presents a remarkable cytotoxicity and selectivity in lung (IC₅₀ = 3 μM) versus breast cancer cell lines (IC₅₀ > 20 μM). Thus, complexes 2c and 4c appear to be promising leads, creating a novel family of anticancer agents. Electrophoretic DNA migration studies in presence of the synthesized compounds have been performed, in order to get further insights into their mechanism of action.     

1,3-Dipolar cycloaddition to the FeSC fragment 20. Preparation and properties of carbonyliron complexes of di-thiooxamide. Reactivity of the mononuclear (di-thiooxamide)Fe(CO)3 towards dimethyl acetylenedicarboxylate

Reaction of Fe₂(CO)₉ at room temperature in THF with the di-thiooxamides (L), SC{N(R,R′)}C{(R,R′)N}S [R=Me, R′-R′=(CH₂)₂ (a); R=H, R′=ⁱPr (b); R=H, R′=iPr (c), R=H, R′=benzyl (d); R=H, R′=H (e)], results for ligands a-d initially in the formation of the mononuclear σ-S, σ-S′ chelate complexes Fe(CO)₃(L) (7a-d), which could be isolated in case of 7a and 7d. Under the reaction conditions, complexes 7a-d react further with [Fe(CO)₄] fragments to give three types of Fe₂(CO)₆(L) complexes (8a-d) in high yields, depending on the di-thiooxamide ligand used together with traces of the known complex S₂Fe₃(CO)₉ (14). The molecular structures of these complexes have been established by the single crystal X-ray diffraction determinations of 8a, 8b and 8d. In the reaction with ligand e the corresponding complex 7e was not detected and the well-known complexes 14 and S₂Fe₃(CO)₉ (15) were isolated in low yield. In situ prepared 7a reacts in a slow reaction with 1 equiv. of dimethyl acetylene dicarboxylate in a 1,3-dipolar cycloaddition reaction to give the stable initial ferra [2.2.1] bicyclic complex 10a in 60% yield. In complex 10a an additional Fe(CO)₄ fragment is coordinated to the sulfido sulfur atom of the cycloadded FeSC fragment. When a toluene solution of 10a is heated to 50 °C it loses two terminal CO ligands to give the binuclear FeFe bonded complex 11a in almost quantitative yield. The molecular structures of 10a and 11a have been confirmed by single crystal X-ray diffraction. Reaction of 7d at room temperature with 2 equiv. of dimethyl acetylene dicarboxylate results in the mononuclear complex 12d in 5% yield. The molecular structure of 12b has been established by single crystal X-ray diffraction and comprises a tetra dentate ligand with two ferra-sulpha cyclobutene, and a ferra-disulpha cyclopentene moiety. When the reaction is performed at 60 °C a low yield of 2,3,4,5-thiophene tetramethyl tertracarboxylate is obtained besides complex 12d.     

New ruthenium(II) precursors with the tetradentate sulfur macrocycles tetrathiacyclododecane ([12]aneS4) and tetrathiacyclohexadecane ([16]aneS4) for the construction of metal-mediated supramolecular assemblies

The preparation and structural characterization of several new Ru(II) complexes in which four coordination positions are occupied by the sulfur atoms of a macrocycle, either 1,4,7,10-tetrathiacyclododecane ([12]aneS4) or 1,5,9,13-tetrathiacyclohexadecane ([16]aneS4), and the two others by relatively labile ligands (Cl⁻, , H₂O, dmso-S), are described:cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a), cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b), cis-[Ru([16]aneS4)Cl₂] (4), and trans-[Ru([16]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (5).The complexes of the larger [16]aneS4 macrocycle have a flexible coordination geometry, either cis or trans, that makes them unsuited for being used as precursors in metal-driven self-assembly processes.On the contrary, the [12]aneS4 complexes cis-[Ru([12]aneS4)(dmso-S)Cl]Cl (1) and, above all, its chlorido free derivatives cis-[Ru([12]aneS4)(dmso-S)(H₂O)](CF₃SO₃)₂ (2a) and cis-[Ru([12]aneS4)(dmso-S)(ONO₂)](NO₃) (2b) are potential precursors of the geometrically stable 90° bis-acceptor fragment cis-[Ru([12]aneS4)]²⁺.Preliminary results of their reactivity towards the linear linker pyrazine (pyz) showed that the nature of the isolated product depends on that of the counter-anion.When treated with pyz 2b afforded the dinuclear complex [{Ru([12]aneS4)(ONO₂)}₂(μ-pyz)](NO₃)₂ (8), while 2a gave the molecular triangle [{cis-Ru([12]aneS4)(μ-pyz)}₃](CF₃SO₃)₆ (9), both in low yields.The X-ray structures of compounds 2a, 2b, 4, 5, [{Ru([12]aneS4)Cl}₂(μ-pyz)]Cl₂ (7), 9, and of the sandwich complex[Ru([12]aneS3-S)₂](CF₃SO₃)₂ (3), in which only three sulfur atoms of each macrocycle are bound to ruthenium, are also described.     

Synthesis, crystal structures and luminescent properties of manganese and zinc complexes with in situ ligand formation of 3-amino-4-(5-tetrazolyl)-1H-pyrazole

Three metal-organic frameworks, [Mn(HL)(N₃)] (1), [Mn(HL)Cl(H₂O)] (2) and [Zn₂(L)₂(H₂O)] (3) where H₂L = 3-amino-4-(5-tetrazolyl)-1H-pyrazole, have been yielded through in situ hydrothermal reactions of manganese(II) or zinc(II) salts, NaN₃ and 3-amino-4-cyano-1H-pyrazole (HACP). The crystal structure analysis reveals that 1-3 have different dense 3D frameworks with Schläfli symbols of {3·4²·5²·6}{3²·4³·5⁴·6⁶} for 1 which is an unprecedented (4,6)-connected framework, {4·12²}2{4²·12⁴} for 2 which is a typical sqc519 structure, and {4²·6}2{4⁴·6²·8⁸·10} for 3 which is a typical ant/anatase structure, respectively. The ligand takes three different coordination modes in 1-3 as 3- or 4-connector. In addition, the photoluminescence of complex 3 was studied in solid state at room temperature, together with its thermal analysis.     

Synthesis and structures of zinc complexes with new binucleating ligands containing alkoxide bridges, and their activities in the hydrolysis of tris(p-nitrophenyl)phosphate

Four new binucleating ligands featuring a hydroxytrimethylene linker between two coordination sites (1,3-bis{N-[3-(dimethylamino)propyl]-N-methylamino}propan-2-ol, HL¹; 1,3-bis{N-[2-(dimethylamino)ethyl]-N-methylamino}propan-2-ol, HL²; 1,3-bis[bis(2-methoxyethyl)amino]propan-2-ol, HL³; and 1-bis[(2-methoxyethyl)amino]-3-{N-[2-(dimethylamino)ethyl]-N-methylamino}propan-2-ol, HL⁴) were synthesized, along with the corresponding zinc complexes. The structures of three dinuclear zinc complexes ([Zn₂L¹(μ-CH₃COO)₂]BPh₄ (1), [Zn₂L³(μ-CH₃COO)₂]BPh₄ (3), and [Zn₂L⁴(μ-CH₃COO)(CH₃COO)(EtOH)]BPh₄ (4)) and a tetranuclear zinc complex ({[Zn₂L²(μ-CH₃COO)]₂(μ-OH)₂}(BPh₄)₂ (2)) were revealed by X-ray crystallography. Hydrolysis of tris(p-nitrophenyl)phosphate (TNP) by these zinc complexes in an acetonitrile solution containing 5% Tris buffer (pH 8.0) at 30 °C was investigated spectrophotometrically and by ³¹P NMR. Although zinc complexes 1, 3, and 4 did not show hydrolysis activity, the tetranuclear zinc complex 2, containing μ-hydroxo bridges, was capable of hydrolyzing TNP. This suggests that the hydroxide moiety in the complex may have an important role in the hydrolysis reaction.     

One-dimensional Zn(II) oligo(phenyleneethynylene)dicarboxylate coordination polymers: Synthesis, crystal structures, thermal and photoluminescent properties

The rigid, π-conjugated dicarboxylic acid 1,4-bis-[2-(4-carboxyphenyl)ethynyl]-2,5-dihexylbenzene {HO₂C[PEP(hexyl)₂EP]CO₂H} has been used to synthesise the new crystalline coordination polymers {Zn(O₂C[PEP(hexyl)₂EP]CO₂)(DMF)₂} (1) and {Zn(O₂C[PEP(hexyl)₂EP]CO₂)(DEF)₂} (2) in N,N-dimethylformamide (DMF) and N,N-diethylformamide (DEF), respectively, under mild conditions. Single-crystal X-ray crystallography revealed that 1 and 2 are isostructural and consist of uncharged zigzag coordination chains in which [Zn(formamide)₂]²⁺ fragments are bridged by (O₂C[PEP(hexyl)₂EP]CO₂)²⁻ ligands. The zigzag chains possess different intra-chain Zn?Zn?Zn angles due to the different volumes of the coordinating formamide molecules and subtle differences in the hydrophobic inter-chain interactions. Upon heating 1 and 2 to 200 °C, removal of the coordinating formamide molecules occurs, yielding the formamide-free compounds 1-DMF and 2-DEF of composition {Zn(O₂C[PEP(hexyl)₂EP]CO₂)}. According to powder X-ray diffraction and FT-IR spectroscopy studies, these materials are not crystalline but still possess partial ordering of intact, yet modified coordination chains in a structural arrangement which appears to be related to the respective parent compounds. Compounds 1, 2, 1-DMF and 2-DEF exhibit blue photoluminescence. The emission maxima of 1-DMF and 2-DEF are red-shifted by ca. 25 nm with respect to λ_max of 1 and 2, respectively.     

Synthesis of new palladium(II) compounds with several bidentate nitrogen-donor ligands: Structural analyses by H and C{H} NMR spectroscopy and crystal structures

The reaction of [PdCl₂(CH₃CN)₂] with N-alkylaminopyrazole (NN′) ligands, 1-[2-(ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[2-(ⁱpropylamino)ethyl]-3,5-dimethylpyrazole (deai), and 1-[2-(^tbutylamino)ethyl]-3,5-dimethylpyrazole (deat), affords a series of square planar Pd(II) complexes [PdCl₂(NN′)] (NN′ = deae (1), deai (2) and deat (3)). The solid-state structures of complexes 1 and 3 were determined by single crystal X-ray diffraction studies. The NN′ ligands are coordinated through the N_pz and N_amine atoms to the metal atom, which completes its coordination with two chlorine atoms in a cis disposition. These palladium(II) compounds were characterised by elemental analyses, conductivity measurements, IR, ¹H and ¹³C{¹H} NMR spectroscopies. The NMR studies of the complexes prove the rigid conformation of the ligands when they are complexed.     

Syntheses and structures of two copper-molybdate complexes: The 3-D [Cu(4,4′-bpy)(MoO4)] and 1-D [Cu2(HDABCO)2(H2Mo8O27)] · 4H2O

Hydrothermal reaction of molybdenum oxide and copper(II) source in the presence of 4,4′-bipyridine (4,4′-bpy) afforded three-dimensional covalent framework [Cu^II(4,4′-bpy)(MoO₄)] (1), while reaction with 1,4-diazoniabicyclo[2,2,2]octane (DABCO) in place of 4,4′-bpy and addition of metal molybdenum resulted in one-dimensional chain-like compound . The copper in 1 is divalent and approximately shows trigonal bipyramidal geometry, while in 2 is monovalent and approximately shows T-shaped geometry. The structure of 1 has a three-dimensional pillar-layered framework constructed from bimetallic {CuMoO₄} layers bridged by bifunctional ligand 4,4′-bpy. Interestingly, the {CuMoO₄} layer in 1 consists of 16-membered {Cu₄Mo₄O₈} rings and 8-membered {Cu₂Mo₂O₄} rings, different from other reported {CuMoO₄} layers. The structure of 2 consists a one-dimensional chain that is attached by peripheral {Cu(HDABCO)}²⁺ units. The chain is constructed from octamolybdates through common corners.     

An unsaturated half-sandwich ruthenium(II) complex containing a dithioimidodiphosphinate ligand

Treatment of [Cp*RuCl₂]_x (Cp* = η⁵-C₅Me₅) with K[N(Ph₂PS)₂] afforded [Cp*Ru{N(Ph₂PS)₂}Cl] (1). Reduction of 1 with Li[BEt₃H] gave the 16-electron half-sandwich Ru(II) complex [Cp*Ru{N(Ph₂PS)₂}] (2). Complexes 1 and 2 have been characterized by X-ray crystallography. The Ru-Cp*(centroid) and average Ru-S distances in 1 are 1.827 and 2.3833(5) Å, respectively. The corresponding bond distances in 2 are 1.739 and 2.379(1) Å. Treatment of 2 with 2-electron ligands L afforded the adducts [Cp*Ru{N(Ph₂PS)₂}L] (L = CO (3), 2,6-Me₂C₆H₄NC (4), MeCO₂CCCO₂Me (5)). Oxidation of 2 with tetramethylthiuram disulfide gave the Ru(IV) complex [Cp*Ru{S₂CNMe₂}₂][N(Ph₂PS)₂] (6). The Ru-Cp*(centroid) and average Ru-S distances in 6 are 1.897 and 2.387(1) Å, respectively.     

Syntheses and characterization of novel sterically demanding amido ligand derivatives and their alkali metal ion complexes, crystal structures of [SiH2Mes2], [NH(SiHMes2)2] and [Na{N(SiHMes2)2}(OEt2)]

Three bulky silanes, [SiH₂Mes₂] (1), [SiHMeMes₂] (2), SiHMes₃ (3), two novel amines, [NH(SiHMes₂)₂] (4), NH₂(SiMeMes₂) (5), and three novel alkali metal ion complexes, [Na{N(SiHMes₂)₂}(OEt₂)] (6), Li{N(SiHMes₂)₂} (7), K{N(SiHMes₂)₂} (8), have been synthesized and characterized by multinuclear NMR and mass spectroscopy. The structures of compounds 1, 4 and 6 have been determined by X-ray crystallography. The spectroscopy and structural results are discussed.     

Synthesis of new platinum(II) compounds with several bidentate and tridentate nitrogen-donor ligands. Structural analyses by H, C{H} and Pt{H} NMR spectroscopy and X-ray crystal structure

The reaction of the N-alkylaminopyrazole (NN′) ligands 1-[2-(ethylamino)ethyl]-3,5-dimethylpyrazole (deae), 1-[2-(tert-butylamino)ethyl]-3,5-dimethylpyrazole (deat), or (NN′N) ligands bis[(3,5-dimethylpyrazolyl)methyl]ethylamine (bdmae) and bis[(3,5-dimethylpyrazolyl)ethyl]ethylamine (ddae) with [PtCl₂(CH₃CN)₂] affords a series of square-planar Pt(II) complexes with formula [PtCl₂(NN′)] (NN′ = deae (1); deat (2)), [PtCl₂(bdmae)] (3), or [PtCl(ddae)]Cl (4). Treatment of complex 4 in the presence of AgBF₄ in CH₂Cl₂/methanol (3:1) gives [PtCl(ddae)](BF₄) (5). These Pt(II) complexes have been characterised by elemental analyses, conductivity measurements and IR, ¹H, ¹³C{¹H}, and ¹⁹⁵Pt{¹H} NMR spectroscopies. The ¹H NMR spectroscopic studies of the complexes prove the rigid conformation of the ligands when they are complexed. The solid-state structure of complex 1 was determined by single crystal X-ray diffraction methods. The deae ligand is coordinated through the N_pz and N_amino atoms to the metallic centre, which completes its coordination with two chlorine atoms in cis disposition.     

Zinc(II) tweezers containing artificial peptides mimicking the active site of phosphotriesterase: The catalyzed hydrolysis of the toxic organophosphate parathion

Two new ligand-containing histidine based on N,N′,N″-tris(N-benzyl-l-histidinyl)tri(2-aminoethyl)amine, L¹, namely N,N′,N″-tris[(1S)-2-methoxy-2-oxy-1-(1-benzylimidazol-4-ylmethyl)]nitrilotriacetamide L² and N,N′,N″-tris{N-benzyl-N-[N-benzyl-N-(N-benzyl-l-histidinyl)-l-histidinyl]-l-histidinyl}tri(2-aminoethyl)amine L³ were prepared. Zinc(II) binding studies by these ligand systems were analyzed by means of potentiometric and ¹H NMR titrations in aqueous methanol (33 % v/v). Subsequently their zinc(II) complexes [L¹Zn(H₂O)](ClO₄)₂·HClO₄ (1), [L²Zn(OH₂)](ClO₄)₂·H₂O (2), and ([L³Zn₃(H₂O)₃](ClO₄)₆·3HClO₄·5H₂O (3), respectively were synthesized and characterized. The reactivity of the trinuclear complex (3) toward the hydrolysis of the toxic organophosphate parathion was investigated and compared with that of the mononuclear reference complex (1). From the pH dependence of the apparent rate constants, and the deprotonation constant (pK_a) of the coordinated water molecules in (1), the active species were confirmed to be {[HL¹Zn(OH)]²⁺/[L¹Zn(H₂O)]²⁺} at pH 8.5. The trizinc complex (3) effects hydrolysis of parathion, with three times rate enhancement over the mononuclear (1), indicating that cooperative action of the three zinc centers is limited.     

Syntheses and structures of Group 12 metal thioacetate anions, [M(SC{O}Me)nCl4−n] (n=3 and 4) and [Cd2Cl2(SC{O}Me)4]

We have utilized the possibility of altering the ratio of reactants to result in tetrahedral anions, [M(SC{O}Me)_nCl_4−n]²⁻ (n=3, 4) and [Cd₂Cl₂(SC{O}Me)₄]²⁻. Complexes of the formula [Ph₄P]₂[M(SC{O}Me)₄] (M=Zn(II) (1), Cd(II) (2) or Hg(II) (3)) were synthesized by the reaction of thioacetate ligand with the metal salts and Ph₄PCl in 4:1:2 molar ratio in suitable solvents. The geometry of Zn(II) in 1 is nearly tetrahedral and the distortion in tetrahedron increases in the order of 1<2<3 as observed from the SMS angles in the crystal structures. The tendency of monoanionic complexes [Ph₄P][M(SC{O}Me)₃] to react with 1 mole equivalent of Ph₄PCl resulted in complexes of the type [Ph₄P]₂[M(SC{O}Me)₃Cl] (M=Cd(II) (4) or Hg(II) (5)). In the structures of 4 and 5, three sulfur atoms and one chloride atom occupy the corners of the tetrahedron around the metal centers. However, in a 4:2:2 or 2:1:2 molar reaction of Me{O}CS⁻ with CdCl₂ and Ph₄PCl in aqueous medium resulted in a chloro bridged dimer, [Ph₄P]₂[Cd₂(μ-Cl)₂(SC{O}Me)₄] (6) as determined by X-ray crystallography.     

Hydrothermal synthesis of copper complexes of 4′-pyridyl terpyridine: From discrete monomer to zigzag chain polymer

Seven copper complexes [Cu(L1)I₂] (1), [Cu₂(L1)₂I₂]₂[Cu₂(μ-I)₂I₂] (2), [Cu(L2)I₂] (3), [Cu₂(L2)(μ-I)I(PPh₃)] (4), [Cu₄(L2)₂(μ-I)₂I₂] (5), {[Cu(L2)I]₂[Cu₂(μ-I)₂I₂]}_n (6) and [Cu₂(L2)(μ-I)₂]_n (7) have been prepared by reactions of ligands: 4′-(2-pyridyl)-2,2′:6′,2″-terpyridine (L1) and 4′-(3-pyridyl)-2,2′:6′,2″-terpyridine (L2) with CuI in hydrothermal conditions, respectively. By alternating the oxidations states of the metal centers, increasing stoichiometric metal/ligand ratio and introducing a second ligand, the compounds, were successfully developed from mononuclear (1 and 3) to multinuclear (2, 4 and 5) and polymers (6 and 7). The synthesis of these compounds may provide an approach for the construction of coordination compounds of 4′-pyridyl terpyridine with different nuclearity.     

Intramolecular ether oxygen coordination in the zinc complexes with dipicolylamine (DPA)-derived ligands

The ether oxygen coordination to the zinc center in the complexes with dipicolylamine (DPA)-derived ligands, N-(2-methoxyethyl)-N,N-bis(2-pyridylmethyl)amine (L), N-(3-methoxypropyl)-N,N-bis(2-pyridylmethyl)amine (L′), and N-{3-(2-pyridylmethyloxy)propyl}-N,N-bis(2-pyridylmethyl)amine (L^Py) has been discussed. Upon chelation of the oxygen atom, L forms a five-membered chelate ring with respect to the 2-aminoethyl ether moiety whereas L′ forms a six-membered chelate in 3-aminopropyl ether unit. This difference was highlighted by the crystal structures of ZnCl₂ complexes, in which [Zn(L)Cl₂] (1) exhibited ether oxygen coordination but [Zn(L′)Cl₂] (2) had the ether oxygen non-coordinated. The terminal pyridyl group of L^Py facilitates the ether oxygen atom coordination via a metal binding from the basal plane trans to the aliphatic nitrogen.     

Metallosupramolecular silver complexes with ligands of 4,4′-di(2-pyridyl-4-pyrimidinyl) disulfide and 4,4′-di(3-pyridyl-4-pyrimidinyl) disulfide: Syntheses, structures and luminescent properties

Reaction of 4,4′-di(3-pyridyl-4-pyrimidinyl) disulfide (3-PPDS) with AgNO₃ leads to a unique 2D extended structure {[Ag(3-PPDS)(NO₃)]}_n (1) based on [Ag₂(3-PPDS)₂] macrocycle units, of which 1D inorganic [Ag(NO₃)]_n helical chains are generated. By contrast, definite Ag-S bonding interactions associated with the disulfide function have been established in {[Ag(2-PPDS)]ClO₄}_n (2), which is assembled of 4,4′-di(2-pyridyl-4-pyrimidinyl) disulfide (2-PPDS) with AgClO₄. Solid state luminescent properties of complexes 1 and 2 are also examined.