Novel octahedral nickel(II) dithiocarbamates with bi- or tetradentate N-donor ligands: X-ray structures of [Ni(Bzppzdtc)(phen)2]ClO4 · CHCl3 and [Ni(Bz2dtc)2(cyclam)]

A series of novel octahedral nickel(II) dithiocarbamate complexes involving bidentate nitrogen-donor ligands (phen = 1,10-phenanthroline, bpy = 2,2′-bipyridine) or a tetradentate ligand (cyclam = 1,4,8,11-tetraazacycloteradecane) of the composition [Ni(BzMetdtc)(phen)₂]ClO₄ (1), [Ni(Pe₂dtc)(phen)₂]ClO₄ (2), [Ni(Bzppzdtc)(phen)₂]ClO₄ · CHCl₃ (3), [Ni(Bzppzdtc)(phen)₂](SCN) (4), [Ni(BzMetdtc)(bpy)₂]ClO₄ · 2H₂O (5), [Ni(Pe₂dtc)(cyclam)]ClO₄ (6), [Ni(BzMetdtc)₂(cyclam)] (7), [Ni(Bz₂dtc)₂(cyclam)] (8) and [Ni(Bz₂dtc)₂(phen)] (9) (BzMetdtc = N,N-benzyl-methyldithiocarbamate(1-) anion, Pe₂dtc = N,N-dipentyldithiocarbamate(1-) anion, Bz₂dtc = N,N-dibenzyldithiocarbamate(1-) anion, Bzppzdtc = 4-benzylpiperazinedithiocarbamate(1-) anion), have been synthesized. Spectroscopic (electronic and infrared), magnetic moment and molar conductivity data, and thermal behaviour of the complexes are discussed. Single crystal X-ray analysis of 3 and 8 confirmed a distorted octahedral arrangement in the vicinity of the nickel atom with a N₄S₂ donor set. They represent the first X-ray structures of such type complexes. The catalytic influence of complexes 2, 3, 6, and 7 on graphite oxidation was studied and discussed.     

Syntheses, structures and ligand conformations of Cu(II), Co(II) and Ag(I) complexes containing the phosphinic amide ligands

The syntheses, structures and ligand conformations of the complexes trans-Cu(L1)₂(ClO₄)₂, (L1 = N-(2-pyrimidinyl)-P,P-diphenyl-phosphinic amide), 1, [trans-Co(L1)₂(CH₃OH)₂](ClO₄)₂·O(C₂H₅)₂, 2, [trans-Co(L2)₂(H₂O)₂](ClO₄)₂·2CH₃OH, (L2 = N-(2-pyridinyl)-P,P-diphenyl-phosphinic amide), 3, [cis-Co(L2)₂(NO₃)](NO₃), 4, and [Ag(L3)(NO₃)(CH₃CN)]_∞, (L3 = N-(6-methyl-2-pyridinyl)-P,P-diphenyl-phosphinic amide), 5, are reported. The L1 and L2 ligands in the monomeric complexes 1-4 chelate the metal centers through the pyrimidyl/pyridyl nitrogen atoms and the phosphinic amide oxygen atoms, whereas the L3 ligands in complex 5 bridge the metal centers, forming a 1-D zigzag chain. The chelating L2 ligands in complexes 3 and 4 adopt cis conformations and the bridging L3 ligand in complex 5 adopts a trans conformation, respectively.     

Synthesis and structures of nickel(II) and copper(II) compounds of 5,5,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradecane and the 13-ethyl-5,5,7-trimethyl-homologue

Reduction by NaBH₄ of the imine functions of (5,7,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradec-4-ene)-nickel(II) and -copper(II), and of their 13-ethyl-5,7,7-trimethyl-homologues, yield the nitro-substituted cyclic tetraamine cations (5,5,7,13-tetramethyl-13-nitro-1,4,8,11-tetraazacyclotetradecane)-nickel(II) and -copper(II), [M(neh)]²⁺, and (13-ethyl-5,5,7-trimethyl-homologues, [M(nph)]²⁺, respectively. The nickel(II) cations form square–planar, singlet ground, state salts with poorly coordinating anions and octahedral, triplet ground state, compounds with additional ligands, trans-β-[Ni(neh)A₂], A⁻ = Cl⁻, NCS⁻ and trans-β-[Ni(neh)A₂](ClO₄)₂, X = NH₃, MeCN, all with nitrogen configuration III, 1R,4R,8S,11S = β. With oxalate the chain-polymeric compound catena-trans-β-[Ni(neh)(μ-C₂O₄)]_n · 3n(H₂O) is formed. Folded macrocycle compounds cis-α-[Ni(neh)(C₅H₇O₂)]ClO₄ and cis-α-[{Ni(neh)}₂(C₂O₄)](ClO₄)₂ are formed with the chelates acetylacetonate and oxalate, with configuration 1R,4R,8R,11R = α. These react with HClO₄ to form metastable α-[Ni(neh)](ClO₄)₂ with retention of configuration. The copper(II) cations form crimson salts with poorly coordinating anions and compounds of the type β-[Cu(neh)A]ClO₄ of varying shades of blue with coordinating anions. Structures of singlet ground state square–planar nickel(II) compounds β-[Ni(neh)](ClO₄)₂ · H₂O, β-[Ni(neh)](ClO₄)₂, β-[Ni(neh)]₂[ZnCl₃(OH₂)]₂[ZnCl₄] · H₂O and α-[Ni(neh)](ClO₄)₂, the triplet ground state chain-polymeric compound catena-trans-β-[Ni(neh)(μ-C₂O₄)]_n · 3n(H₂O) and of square–pyramidal β-[Cu(nph)Cl]ClO₄ are reported.     

Complexes derived from the general copper(II)/maleamic acid/N,N′,N′′-chelate reaction systems: Synthetic,reactivity, structural and spectroscopic studies

The synthetic investigation of the Cu^II/maleamate(−1) ion (HL⁻)/N,N′,N′′-chelate general reaction system has allowed access to compounds [Cu₂(HL)₂(bppy)₂](ClO₄)₂·H₂O (1·H₂O), [Cu(HL)(bppy)(ClO₄)] (2) and [Cu(HL)(terpy)(H₂O)](ClO₄) (4) (bppy = 2,6-bis(pyrazol-1-yl)pyridine, terpy = 2,2′;6′,2′′-terpyridine). In the absence of externally added hydroxides, compound [Cu₂(L′)₂(bppy)₂](ClO₄)₂ (3) was obtained from MeOH solutions; L′⁻ is the monomethyl maleate(−1) ligand which is formed in situ via the Cu^II-assisted HL⁻ → L′⁻ transformation. In the case of tptz-containing (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) reaction systems, the Cu^II-assisted hydrolysis of tptz to pyridine-2-carboxamide (L1) afforded complex [Cu(L1)₂(NO₃)₂] (5). The crystal structures of 1–5 are stabilized by intermolecular hydrogen bonding and π–π stacking interactions. Characteristic IR bands of the complexes are discussed in terms of the known structures and the coordination modes of the ligands.     

Copper(II) complexes with 1,2,4-triazolo[1,5-a] pyrimidine and its 5,7-dimethyl derivative

Several Cu(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidine (tp) and its 5,7-dimethyl derivative (dmtp) have been isolated and structurally characterized. Five of them are mononuclear and contain 1,10-phenanthroline (phen) or ethylenediamine (en) as auxiliary ligands, their formula being [Cu(H₂O)(phen)(tp)₂](ClO₄)₂ · H₂O, [Cu(H₂O)(phen)(dmtp)₂](ClO₄)₂, [Cu(NO₃)(H₂O)(phen)(tp)](NO₃), [Cu(H₂O)₂(en)(tp)₂](ClO₄)₂ and [Cu(H₂O)₂(en)(dmtp)₂](ClO₄)₂. In all these compounds the tp or dmtp ligand is monodentately coordinated via the nitrogen atom in position 3. The auxiliary ligand influences the coordination number, which is five when this ligand is phen and six when it is en whereas the number of triazolopyrimidine ligands linked to the metal seems to be influenced by the nature of the counteranion. A dinuclear compound with tp has also been isolated, its formula being [Cu₂(OH)(H₂O)_2.5(tp)₅](ClO₄)₃·(H₂O)_1.5, with both metal atoms linked by an hydroxydo group and by a tp bridging ligand, coordinated to one of the copper atoms via N3 and to the other via N4. This compound has several unusual features among the metal complexes with triazolopyrimidine derivatives: the presence of two different kinds of bridging moieties, the coexistence of bridging and terminal ligands and the formation of a N3–N4 bridge for a Cu(II) dinuclear compound for a derivative without exocyclic oxygen atoms.     

N,N′-Bis(aryl)pyridine-2,6-dicarboxamide complexes of ruthenium: Synthesis,structure and redox properties

Reaction of five N,N′-bis(aryl)pyridine-2,6-dicarboxamides (H₂L-R, where H₂ denotes the two acidic protons and R (R = OCH₃, CH₃, H, Cl and NO₂) the para substituent in the aryl fragment) with [Ru(trpy)Cl₃](trpy = 2,2′,2″-terpyridine) in refluxing ethanol in the presence of a base (NEt₃) affords a group of complexes of the type [Ru^II(trpy)(L-R)], each of which contains an amide ligand coordinated to the metal center as a dianionic tridentate N,N,N-donor along with a terpyridine ligand. Structure of the [Ru^II(trpy)(L-Cl)] complex has been determined by X-ray crystallography. All the Ru(II) complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. Cyclic voltammetry on the [Ru^II(trpy)(L-R)] complexes shows a Ru(II)–Ru(III) oxidation within 0.16–0.33 V versus SCE. An oxidation of the coordinated amide ligand is also observed within 0.94–1.33 V versus SCE and a reduction of coordinated terpyridine ligand within −1.10 to −1.15 V versus SCE. Constant potential coulometric oxidation of the [Ru^II(trpy)(L-R)] complexes produces the corresponding [Ru^III(trpy)(L-R)]⁺ complexes, which have been isolated as the perchlorate salts. Structure of the [Ru^III(trpy)(L-CH₃)]ClO₄ complex has been determined by X-ray crystallography. All the Ru(III) complexes are one-electron paramagnetic, and show anisotropic ESR spectra at 77 K and intense LMCT transitions in the visible region. A weak ligand-field band has also been shown by all the [Ru^III(trpy)(L-R)]ClO₄ complexes near 1600 nm.     

pH-dependent self-assembly of copper(II) complexes with a new imidazole-containing polyamine ligand: Synthesis,structure and magnetic property

Four copper(II) complexes were synthesized by reactions of new imidazole-containing polyamine ligand N¹-(2-aminoethyl)-N¹-(1H-imidazol-4-ylmethyl)-ethane-1,2-diamine (HL) with Cu(ClO₄)₂ · 6H₂O under different pH and their structures were characterized by X-ray crystallography. Interestingly, the complexes have diverse structures from protonated ligand [H₃(HL)][CuCl₄] · Cl (1), dinuclear [Cu₂(HL)₂Cl](ClO₄)₃ · H₂O (2), one-dimensional chain polynuclear {[Cu(L)](ClO₄)}_n (3) to cyclic-tetranuclear [Cu₄(L)₄](ClO₄)₄ · 3CH₃CN (4) coordination compounds by varying reaction pH from acidic to basic. The results indicate that the reaction pH has great impact on the formation and structure of the complexes. The magnetic measurements show that there are antiferromagnetic interactions between the Cu(II) centers with g = 2.09, J = −39.0 cm⁻¹ and g = 2.17, J = −36.8 cm⁻¹ for 3 and 4, respectively.     

Syntheses,crystal structures,and properties of Ni(II) and Co(III) complexes derived from tripod polypyridine ligands containing N7 or N6 donor set atoms

New complexes [Ni^II(pbpaen)](ClO₄)₂ (1) and [Co^III(pbpaen)](ClO₄)₃ (2) (pbpaen = N′-(pyridin-2-ylmethyl)-N,N-bis {2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine) have been synthesized and characterized by IR and UV–Vis spectroscopies. An X-ray structure of the nickel(II) complex shows that [Ni(pbpaen)](ClO₄)₂ (1) crystallizes in the monoclinic space group P2_1/c. The cation [Ni(pbpaen)]²⁺ is pseudo-octahedral with one of the three pyridyl nitrogen atom uncoordinated. The crystal lattice of this complex is stabilized by intra and intermolecular hydrogen bonding systems, giving one-dimensional sheets like arrays. All attempts to obtain nickel or cobalt complexes with protonated forms of the ligand resulted in isolation of only [Co^III(bpaen)](ClO₄)₃ (3) compound in which the tripod pbpaen ligand has lost one of the three pyridylmethyl groups, procuring then bpaen ligand {bpaen = N,N-bis{2-[(pyridin-2-ylmethyl)amino]ethyl}ethane-1,2-diamine}. The X-ray crystal structure reveals that the compound 3 crystallizes in the orthorhombic space group Pna2 with the Co³⁺ ion having a distorted-octahedral environment. These two ligands with strong-field N donor stabilise the +3 oxidation state of the Co center.     

Metal-assisted transformation of N-benzoyldithiocarbazate to 5-phenyl-1,3,4-oxadiazole-2-thiol in the presence of ethylenediamine,and its first row transition metal complexes

The reaction of metal complexes of the type [M(HL)Cl] or [M(HL)₂] [where M = Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) and H₂L = N-benzoyldithiocarbazate] with an excess of ethylenediamine (en) in CHCl₃–MeOH medium leads to ring closure by desulfurisation to yield unique mixed-ligand complexes 1–4, [Cu(en)₂](pot)₂(pot = 5-phenyl-1,3,4-oxadiazole-2-thiol), [M(en)₂(pot)₂] [M = Ni(II), Mn(II)] and [Zn(en)(pot)₂]. The metal complexes have been characterized by various physicochemical methods. The molecular structure of [Cu(en)₂](pot)₂ has been determined by a single crystal X-ray diffraction study. In the centrosymmetric unit of [Cu(en)₂](pot)_2, the metal ion has a square planar arrangement of four symmetry related N-atoms of two en groups and is ionically bonded to two pot anions. Weak interaction studies on the complex reveal the presence of a hydrogen-bonded network in the molecule involving non-coordinating donor atoms of the pot anion with en resulting in the formation of an extended three-dimensional network. The arrangement of the [Cu(en)₂]²⁺ units, at a dihedral angle of 49.43° to pot⁻, provides a network of intermingled chains leading to a π–π stacked 3-dimensional framework.     

Synthesis,characterization and superoxide dismutase activity of some octahedral nickel(II) complexes

Four new mixed ligand nickel(II) complexes viz., [Ni(tren)(phen)](ClO₄)₂ (1), [Ni(tren)(bipy)](ClO₄)₂ (2), [Ni(SAA)(PMDT)] · 2H₂O (3) and [Ni(SAA)(TPTZ)] (4) (tren = tris(2-aminoethylamine), phen = 1,10-phenanthroline, bipy = 2,2′-bipyridine, SAA = salicylidene anthranilic acid, PMDT = N,N,N′,N″,N″-pentamethyldiethylenetriamine, TPTZ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine) have been synthesized and characterized by means of elemental analysis, spectroscopic, magnetic susceptibility and cyclic voltammetric measurements. Single crystal X-ray analysis of [Ni(tren)(phen)](ClO₄)₂ (1) and [Ni(SAA)(PMDT)] · 2H₂O (3) has revealed the presence of a distorted octahedral geometry. Superoxide dismutase activity of these complexes has also been measured.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Syntheses,crystal structures and magnetic properties of three new binuclear Ni(II) complexes derived from tripodal tetradentate (N4) ligands

Three new binuclear Ni(II) complexes [{Ni(L_22py)Cl}₂](ClO₄)₂ (1), [{Ni(L_23py)Cl}₂](ClO₄)₂ (2), and [{Ni(L_33py)Cl}₂](ClO₄)₂ (3), {L_22py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,2-diaminoethane, L_23py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,3-diaminopropane, L_33py = N-(2-pyridylmethyl)-N-(3-aminopropyl)-1,3-diaminopropane} have been synthesized. Single crystal X-ray structure analysis showed that in each complex two distorted octahedral Ni(II) ions are bridged asymmetrically by a pair of chloride anions. Variable temperature magnetic susceptibility measurements of 1 and 3 revealed dominant ferromagnetic exchange interactions.     

The synthesis and structure of trans-di(cyano-κ)-(trans-6,13-dimethyl-6,13-bis(propionylamido)-1,4,8,11-tetraazacyclotetradecane-κ)cobalt(III) perchlorate dihydrate

trans-Di(cyano-κ¹)-(trans-6,13-dimethyl-6,13-bis(propionylamido)-1,4,8,11-tetraazacyclotetradecane-κ⁴)cobalt(III) perchlorate dihydrate, trans-[Co(C₁₈H₃₈N₆O₂)(CN)₂)]ClO₄ · 2H₂O, is formed by reaction of trans-[Co(diam)(CN)₂]ClO₄ · 2H₂O (diam = trans-6,13-diamino-6,13-dimethyl-1,4,8,11-tetraazacyclotetradecane) with propionic anhydride in DMF. The centrosymmetrical cation has the azamacrocycle in planar coordination by the four secondary amine nitrogen atoms of the azamacrocycle, with Co–N = 1.979(2) and 1.968(2) Å and with trans cyano groups with Co–C = 1.920(2) Å. The propionylamido substituents are axially oriented, with the terminal methyl group disordered over two sites.     

Preparation and characterisation of mononuclear Pd(II) complexes with 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) ligand: Spectroscopy studies and crystal structure of trans-[Pd(SCN)2(bddo)]

Mononuclear palladium(II) complexes containing a pyrazole-thioether ligand, with general formula trans-[Pd(X)₂(bddo)] (X = CN⁻ (1), SCN⁻ (2) or N₃⁻ (3); bddo = 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane), have been prepared. Similar reactivity carried out with pyridine or triphenylphosphine has been assayed. When pyridine is used, a mixture of [Pd(bddo)(py)₂](BF₄)₂ ([4](BF₄)₂) and [Pd(bddo)](BF₄)₂ is obtained. When triphenylphosphine is used, only [Pd(bddo)](BF₄)₂ is obtained. The complexes have been characterised by elemental analyses, conductivity measurements, IR and NMR spectroscopies. X-ray crystal structure of trans-[Pd(SCN)₂(bddo)] (2) is presented. In this complex the metal atom is coordinated by the two azine nitrogen atoms of the pyrazole rings and two SCN⁻ anions in trans disposition.     

Cationic (fluoromesityl)palladium(II) complexes

Halide abstraction from [Pd(μ-Cl)(Fmes)(NCMe)]₂ (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) with TlBF₄ in CH₂Cl₂/MeCN gives [Pd(Fmes)(NCMe)₃]BF₄, which reacts with monodentate ligands to give the monosubstituted products trans-[Pd(Fmes)L(NCMe)₂]BF₄ (L = PPh₃, P(o-Tol)₃, 3,5-lut, 2,4-lut, 2,6-lut; lut = dimethylpyridine), the disubstituted products trans-[Pd(Fmes)(NCMe)(PPh₃)₂]BF₄, cis-[Pd(Fmes)(3,5-lut)₂(NCMe)]BF₄, or the trisubstituted products [Pd(Fmes)L₃]BF₄ (L = CN^tBu, PHPh₂, 3,5-lut, 2,4-lut). Similar reactions using bidentate chelating ligands give [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda, dppe, OPPhPy₂-N,N′, (OH)(CH₃)CPy₂-N,N′). The complexes trans-[Pd(Fmes)L₂(NCMe)]BF₄ (L = PPh₃, tht) (tht = tetrahydrothiophene) and [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda) were obtained by halide extraction with TlBF₄ in CH₂Cl₂/MeCN from the corresponding neutral halogeno complexes trans-[Pd(Fmes)ClL₂] or [Pd(Fmes)Cl(L-L)]. The aqua complex trans-[Pd(Fmes)(OH₂)(tht)₂]BF₄ was isolated from the corresponding acetonitrile complex. Overall, the experimental results on these substitution reactions involving bulky ligands suggest that thermodynamic and kinetic steric effects can prevail affording products or intermediates different from those expected on purely electronic considerations. Thus,water, whether added on purpose or adventitious in the solvent, frequently replaces in part other better donor ligands, suggesting that the smaller congestion with water compensates for the smaller M-OH₂ bond energy.     

Strictly heterodinuclear compounds containing U and Cu or Ni ions

Treatment of [M(H₂Lⁱ)] with UCl₄ in pyridine led to the formation of the dinuclear complexes [MLⁱ(py)UCl₂(py)₂] and/or [Hpy][MLⁱ(py)UCl₃] [Lⁱ = N,N′-bis(3-hydroxysalicylidene)-R, R = 1,2-phenylenediamine (i = 1), R = trans-1,2-cyclohexanediamine (i = 2), R = 2-amino-benzylamine (i = 3), R = 1,3-propanediamine (i = 4), R = 2,2-dimethyl-1,3-propanediamine (i = 5); M = Cu or Ni]. The crystal structures show that the 3d and 5f ions occupy, respectively, the N₂O₂ and O₄ cavities of the Schiff base ligand, the U⁴⁺ ion adopting a dodecahedral or pentagonal bipyramidal configuration in the neutral and anionic complexes, respectively.     

Hetero-metallic frameworks of [Pd(CN)4] and Cu(II) with triamines: A rare example of a tetracyanometallate bridged 2D coordination polymer

Four cyano bridged Cu(II)–Pd(II) heterometallic complexes, [Cu(dpt)Pd(CN)₄]_n (1), {[Cu₂(medpt)₂Pd(CN)₄](ClO₄)₂ · 3H₂O}_n (2), {[Cu₂(dien)₂Pd(CN)₄](ClO₄)₂ · 2CH₃OH}_n (3) and {[Cu₂(iPrdien)₂Pd(CN)₄](ClO₄)₂ · 2H₂O}_n (4) [dpt = 3,3′-iminobispropylamine; medpt = 3,3′-diamino-N-methyldipropylamine; dien = diethylenetriamine and iprdien = N′-isopropyldiethylenetriamine] have been synthesized and characterized by single crystal X-ray diffraction analysis, magnetic measurement and thermal study. Complexes 1, 2 and 3 are 1D coordination polymers, while 4 presents a 2D network. In 1, the cis-directed cyanide ligands of [Pd(CN)₄]²⁻ anions link two Cu(dpt) units to form a neutral coordination polymer, whereas in 2, 3 and 4, all the cyanide groups of [Pd(CN)₄]²⁻ take part in bonding with four adjacent Cu(II) ions, resulting in cationic coordination polymers counterbalanced by perchlorate anions. The structures are compared with those of analogous [Ni(CN)₄]²⁻ derivatives. The magnetic behavior shows antiferromagnetic interactions in all the complexes.     

Synthesis,characterization and antimicrobial activity of Ni(II) and Zn(II) complexes with N′,N′-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide. Crystal structures of two highly solvated bimetallic complexes of Ni(II)

The bimetallic [Ni₂(H₂L2)₂](ClO₄)₄ (1), [Ni₂(HL2)(H₂L2)](ClO₄)₃ (2) and [Zn₂(H₂L2)₂](BF₄)₄ (3) complexes (H₂L2 = N′,N′²-bis[(1E)-1-(2-pyridyl)ethylidene]propanedihydrazide) were synthesized and characterized. The structure of complexes (1) and (2) was established by X-ray analysis. NMR spectroscopy was used for the characterization of complex (3). The complexes (1) and (2) were obtained from the same synthetic reaction and two crystal types of these complexes have been isolated during the fractional crystallization process.     

Synthesis and coordination chemistry of new tetradentate N2S2 donor Schiff-base ligand ca2-dapte: Mononuclear and dinuclear copper(I) complexes [Cu(ca2dapte)]ClO4 and [{Cu(PPh3)(X)}2(ca2dapte)] (X = I and Br)

A mononuclear copper(I) complex, [Cu(ca₂dapte)]ClO₄ (1), and two dinuclear copper(I) complexes, [{Cu(PPh₃)(X)}₂(ca₂dapte)] (X = I (2) and Br (3)), of a new tetradentate N₂S₂ donor Schiff-base ligand ca₂dapte have been prepared (ca₂dapte = N,N′-bis(trans-cinnamaldehyde)-1,2-di(o-iminophenylthio)ethane). These compounds have been characterized by elemental analyses (CHN), FT-IR, UV–Vis and ¹H NMR spectroscopy. The crystal structures of these copper(I) complexes have been determined by single-crystal X-ray diffraction. The coordination geometry around Cu(I) centers in these complexes is a distorted tetrahedron. The ca₂dapte is coordinated to Cu(I) as a tetradentate ligand in 1, while it acts as a bis-bidentate bridging ligand in 2 and 3.