Homo- and heteropolynuclear platinum complexes stabilized by dimethylpyrazolato and alkynyl bridging ligands: synthesis, structures, and luminescence

This work describes the synthesis of cis-[Pt(C[triple bond]CPh)2(Hdmpz)2] (1) and its use as a precursor for the preparation of homo- and heteropolynuclear complexes. Double deprotonation of compound 1 with readily available M(I) (M = Cu, Ag, Au) or M(II) (M = Pd, Pt) species affords the discrete hexanuclear clusters [{PtM2(mu-C[triple bond]CPh)2(mu-dmpz)(2)}(2)] [M = Cu (2), Ag (3), Au (4)], in which both "Pt(C[triple bond]CPh)2(dmpz)(2)" fragments are connected by four d(10) metal centers, and are stabilized by alkynyl and dimethylpyrazolate bridging ligands, or the trinuclear complexes [Pt(mu-C[triple bond]CPh)2(mu-dmpz)(2){M(C/\P)}2] (M = Pd (5), Pt (6); C/\P = CH(2)-C(6)H(4)-P(o-tolyl)2-kappaC,P), respectively. The X-ray structures of complexes 1-4 and 6 are reported. The X-ray structure of the platinum-copper derivative 2 shows that all copper centers exhibit similar local geometry being linearly coordinated to a nitrogen atom and eta(2) to one alkynyl fragment. However in the related platinum-silver (3) and platinum-gold (4) derivatives the silver and gold atoms present three different coordination environments. The complexes have been studied by absorption and emission spectroscopy. The hexanuclear complexes exhibit bright luminescence in the solid state and in fluid solution (except 4 in the solid state at 298 K). Dual long-lived emission is observed, being clearly resolved in low-temperature rigid media. The low-energy emission is ascribed to MLM'CT Pt(d)/pi(C[triple bond]CPh)-->Pt(p(z))/M'(sp)/pi*(C[triple bond]CPh) modified by metal-metal interactions whereas the high-energy emission is tentatively attributed to an emissive state derived from dimethylpyrazolate-to-metal (d(10)) LM'CT transitions pi(dmpz)-->M'(d(10)).     

Two new [Ni(tren)2]2+ complexes: [Ni(tren)2]Cl2 and [Ni(tren)2]WS4

Both title compounds, bis­[tris(2‐amino­ethyl)­amine]­nickel(II) dichloride, [Ni(tren)₂]Cl₂, (I), and bis­[tris(2‐amino­ethyl)­amine]­nickel(II) tetra­thio­tungstate, [Ni(tren)₂]WS₄, (II), contain the [Ni(tren)₂]²⁺ cation [tren is tris(2‐amino­ethyl)­amine, C₆H₁₈N₄]. The tren mol­ecule acts as a tridentate ligand around the central Ni atom, with the remaining primary amine group not bound to the central atom. In (I), Ni²⁺ is located on a centre of inversion surrounded by one crystallographically independent tren mol­ecule. In the [Ni(tren)₂]²⁺ cation of (II), the Ni atom is bound to two crystallographically independent tren mol­ecules. The Ni atoms in the [Ni(tren)₂]²⁺ complexes are in a distorted octahedral environment consisting of six N atoms from the chelating tren mol­ecules. The counter‐ions are chloride anions in (I) and the tetrahedral [WS₄]^2? anion in (II). Hydro­gen bonding is observed in both compounds.     

Metal complexes with macrocyclic ligands. Part XIX. Synthesis and Cu2+-complexes of a series of 12-, 14- and 16-membered cis- and trans-N2S2-macrocycles

A series of 12-, 14-, and 16-membered N₂S₂-macrocycles ( 9–11 and 19–21 ) with cis and trans-arrangement of the heteroatoms have been synthesized by high-dilution cyclization and subsequent reduction of the amides with B₂H₆. With these ligands the corresponding Cu²⁺-complexes were prepared and their UV/VIS spectra, their electrochemistry and their EPR properties have been studied. Generally three absorption bands at 270–320 nm, 330–370 nm and 530–620 nm can be observed in aqueous solution and these have been assigned to the N→Cu²⁺ and S→Cu²⁺ charge-transfer bands and to the d-d* transition, respectively. The cyclic voltammetry in CH₃CN shows in all cases a reversible or quasi-reversible Cu²⁺/Cu⁺-transition at potentials of 10–480 mV against SHE. The values of g_‖ and A_‖ obtained from EPR spectra indicate that the geometry of the Cu²⁺-complex of the 14-membered cis-N₂S₂-macrocycle is less distorted than that of the other complexes.     

Synthesis,structure and bioactivity of Ni2+ and Cu2+ acylhydrazone complexes

Two acylhydrazone complexes, bis{6‐methyl‐N′‐[1‐(pyrazin‐2‐yl‐κN¹)ethylidene]nicotinohydrazidato‐κ²N′,O}nickel(II), [Ni(C₁₃H₁₂N₅O)₂], (I), and di‐μ‐azido‐κ⁴N¹:N¹‐bis({6‐methyl‐N′‐[1‐(pyrazin‐2‐yl‐κN¹)ethylidene]nicotinohydrazidato‐κ²N′,O}nickel(II)), [Cu₂(C₁₃H₁₂N₅O)₂(N₃)₂], (II), derived from 6‐methyl‐N′‐[1‐(pyrazin‐2‐yl)ethylidene]nicotinohydrazide (HL) and azide salts, have been synthesized. HL acts as an N,N′,O‐tridentate ligand in both complexes. Complex (I) crystallizes in the orthorhombic space group Pbcn and has a mononuclear structure, the azide co‐ligand is not involved in crystallization and the Ni²⁺ centre lies in a distorted {N₄O₂} octahedral coordination environment. Complex (II) crystallizes in the triclinic space group P and is a centrosymmetric binuclear complex with a crystallographically independent Cu²⁺ centre coordinating to three donor atoms from the deprotonated L^? ligand and to two N atoms belonging to two bridging azide anions. The two‐ and one‐dimensional supramolecular structures are constructed by hydrogen‐bonding interactions in (I) and (II), respectively. The in vitro urease inhibitory evaluation revealed that complex (II) showed a better inhibitory activity, with the IC₅₀ value being 1.32±0.4 µM. Both complexes can effectively bind to bovine serum albumin (BSA) by 1:1 binding, which was assessed via tryptophan emission–quenching measurements. The bioactivities of the two complexes towards jack bean urease were also studied by molecular docking. The effects of the metal ions and the coordination environments in the two complexes on in vitro urease inhibitory activity are preliminarily discussed.     

Synthesis and structure of chloronitroacetamide complexes with Cu2+ and Ni2+ ions

Conclusions Stable complexes of chloronitroacetamide with Cu²⁺ and Ni²⁺ ions were synthesized. The molecular structure of bis(chloronitroacetamidato) tetramminecopper(II) was determined by x-ray diffraction structural analysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 214–216, January, 1987.     

Metal complexes with macrocyclic ligands. Part XXV. One-step synthesis of mono-N-substituted azamacrocycles with a carboxylic group in the side-chain and their complexes with Cu2+ and Ni2+

Mono-N-substituted azamacrocycles 2 – 7 , containing a carboxyalkyl or carboxyaryl side-chain, are obtained by reacting a five-fold excess of the macrocycle with 1 equiv. of a suitable halogenocarboxylic acid in alkaline aqueous EtOH. For halogenocarboxylic acids, which easily lactonize under alkaline conditions, a variant with the corresponding ester or nitrile as alkylating agent is also described. The salient point of this synthesis lies in the use of an excess of the macrocycle over the alkylating agent, thus reducing the amount of polyalkylation to a minimum, and in the easy separation of the excess of unreacted educt from the aminocarboxylic acid. These new ligands form Ni²⁺ and Cu²⁺ complexes, the spectral properties of which have been studied. In the case of the Cu²⁺ complexes with ligand 2 , 3 , and 6 , a pH-dependent color change is observed. This is explained with an equilibrium between a species, in which the carboxylate group is bound to the metal, and one, in which it is protonated and non-coordinated. In the case of the Ni²⁺ complexes with the same ligands, only the species with a coordinated carboxylate was observed. In the Cu²⁺ and Ni²⁺ complexes with ligands 4 and 5 , however, the carboxylate group does not coordinate at all, because of the length or the special structure of the chain.     

Metal complexes with macrocyclic ligands. XVI. Spectrophotometric and thermodynamic studies of solvents and unidentate ligands interaction with the pentacoordinate Co2+-, Ni2+- and Cu2+-complexes of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane

The interaction of solvents and of unidentate ligands such as N, SCN^?, OCN^? and OH^? with the Co²⁺-, Ni²⁺ and Cu²⁺-complexes of 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (TMC) have been studied by Spectrophotometric and calorimetric techniques. The spectra in different solvents (Table 2) show that the Ni²⁺- and probably also the Cu²⁺-complex with TMC exist as square planar or pentacoordinate species or as a mixture of both, depending on the donor properties of the solvent. The [Co(TMC)]²⁺-complex is pentacoordinate in all the solvents studied. Ternary complexes [M(TMC)X]ⁿ⁺ are also formed by the unidentate ligands X = N, OCN^?, OH^?, F^? and NH₃ and their stability constants have been determined. Interesting is the high selectivity of [Ni(TMC)]²⁺ towards the addition of a further donor (Table 3). Only small ligands such as those listed above form stable adducts, whereas the larger ones such as imidazole or pyridine do not. This is a consequence of the special structure of the complex and of the trans-I-(RSRS)- conformation of the ligand in these complexes. Since the four methyl groups are all on the side of the macrocycle to which the additional unidentate ligand binds, steric interaction between the four methyl groups and the larger ligands prevents the formation of the adducts. The calorimetric measurements show that the stability of the complexes [M(TMC)X]ⁿ⁺ is due to both an enthalpic and entropic contribution which differ in their magnitude (Table 4). This indicates that several antagonistic factors are important in determining the overall stability.     

Metal complexes with macrocyclic ligands. Part XXII. Synthesis two of bis-tetraaza-macrocycles and study of the structures,electrochemistry, VIS and EPR spectra of their binuclear Cu2+ and Ni2+ complexes

The two bis-macrocycles 4 and 5 in which the tetraaza units are separated by a chain of different length, have been synthesized using 1,4,7-tritosyl-1,4,7,11-tetraazacyclotetradecane as starting compound and bifunctional alkylating agents. The bis-macrocycles give binuclear complexes with Ni²⁺ and Cu²⁺, the properties of which have been studied to obtain information about the interaction of the two subunits as a function of the distance. The VIS spectra of the Ni²⁺ and Cu²⁺ complexes indicate that both metal ions are in a square-planar geometry as expected from the results of the analogous complexes with 1,4,7,11-tetraazacyclotetradecane 7 . Cyclic voltammetry and differential pulse polarography of the binuclear Ni²⁺complexes in CH₃CN show a single two-electron step for ligand 5 , whereas two distinct one-electron redox processes can be observed for ligand 4 , indicating that the two metal ions interact with each other when the chain length is shorter. Similarly, the EPR studies of frozen solutions of the binuclear Cu²⁺ complexes clearly show that a magnetic dipolar interaction between the two paramagnetic centers exists, and that the strength of it depends upon the length of the bridge. Finally, from the X-ray structures of the binuclear Ni²⁺ complexes with 4 and 5 , it is seen that the two rings are kept apart as far as possible, the distances between the two metal ions determined in the solid correlate well with the observations in solution.     

Synthesis,characterization, and antioxidant activities of three Cu(II) complexes with Schiff-base ligands

Cu(II) complexes of three bis(pyrrol-2-yl-methyleneamine) ligands were synthesized and characterized by elemental analyses, mass spectra, and IR spectra. X-ray diffraction analysis shows that [CuL³]₂ is a dinuclear complex with an extremely distorted square-planar geometry. Furthermore, the antioxidant activities of the compounds have been investigated. The electrochemical properties of the Cu(II) complexes have also been studied by cyclic voltammetry. The Cu(II) complexes show similar superoxide dismutase (SOD) activity compared with that of the native Cu, Zn-SOD.     

Metal complexes with macrocyclic ligands. XIII. The complexation of Cu2+ with triazacycloalkanes

The potentiometric study of the complexation of Cu²⁺ with 1,4,7-triazacyclononane ( 1 ), 1,4,8-triazacyclodecane ( 2 ) 1,5,9-triazacyclododecane ( 3 ) has shown that CuL, CuL₂ and (CuLOH)₂ are the main species present in solution. Their stabilities (Table 1) and their absorption spectra (Table 2) indicate facial coordination of the cyclic triamines in a distorted octahedral geometry. The formation and dissociation kinetics have been measured by stopped-flow techniques. The formation in acetate buffer can be described by the reaction of Cu²⁺ and CuAcO⁺ with the monoprotonated species of the ligand. The bimolecular rate constants for these complexations (Table 3) decrease when the ring size increases. In contrast the dissociation induced by acid is only little affected by the ring size. Thus for these complexes the rate of formation and not that of the dissociation determines the overall stability.     

Binding of Ni2+ and Cu2+ ions to peptides with a Cys-His motif

Waglerin I is a 22 amino acid snake venom toxin. Its three fragments (GGKPDLRPCHP-NH2, PCHYIPRPKPR-NH2, PCHPPCHYIPR-NH2), due to the presence of two Cys and His residues, are potentially very attractive ligands for transition metal ions. The main aim of this work was to establish the impact of these two adjacent residues on Ni2+ ion binding, especially because this kind of motif is very common in nature, and the study of low molecular weight models could be helpful in understanding larger systems. In this work waglerin fragments and their N-protected analogues were studied with Ni2+ (and Cu2+ for peptides with disulfide bridges) ions using combined potentiometric and spectroscopic measurements (UV-Vis, CD, EPR and NMR). In all peptides, except PCHPPCHYIPR-NH2 with a disulfide bridge, the Cys-His motif was found to be crucial for the coordination of Ni2+ ions. In the case of the N-unprotected analogues, the N-terminal amino group participates in the coordination as well.     

The effects of auxiliary ligands on the synthesis,crystal structures and properties of three complexes with a substituted pyridazine ligand

Abstract  Three new complexes, [Co(L)₂(SCN)₂] (1), [Co₂(L)₄(μ-N₃)₂](ClO₄)₂(H₂O)_1.5 (2), and [Ni(L)₃](ClO₄)₂(CH₃OH)₂ (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Single crystal X-ray analyses show that all three complexes crystallize in the monoclinic crystal system. In complex (1), the Co(II) atom is in a distorted octahedral environment consisting of four nitrogen atoms from two ligands and two nitrogen atoms of SCN⁻, which is further extended into a 1D chain by intermolecular hydrogen bonds. Two Co(II) atoms in complex (2) are linked by two azide anions in a μ-1,1 mode to make a binuclear structure. Without any auxiliary ligand, the Ni(II) atom in complex (3) adopts a distorted octahedral geometry involving six nitrogen atoms from three ligands. The electronic absorption spectra of the title compounds are discussed as well. The effects of auxiliary ligands on the structures and properties of the title complexes have been studied and discussed. Graphical Abstract  Three new complexes, [Co(L)₂(SCN)₂] (1), [Co₂(L)₄(μ-N₃)₂](ClO₄)(H₂O)_1.5 (2) and [Ni(L)₃](ClO₄)₂(CH₃OH)₂ (3), have been synthesized and structurally characterized, where L is 3-(3′,5′-dimethyl-pyrazole)-6-Cl-pyridazine. Complexes (1) and (3) are mononuclear compounds, which are different from the binuclear complex (2). Auxiliary ligands are the main reasons that results in the different structures of the title complexes and their different fungicidal activities. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

CO2 Fixation by Cu2+ and Zn2+ complexes of a terpyridinophane aza receptor. Crystal structures of Cu2+ complexes, pH-metric, spectroscopic, and electrochemical studies

The synthesis of the terpyridinophane-type polyamine 2,6,9,12,16-pentaaza[17]-(5,5' ')-cyclo-(2,2':6',2' ')-terpyridinophane heptahydrobromide tetrahydrate (L.7HBr.4H2O) is described. L presents six protonation constants with values in the range 9.21-3.27 logarithmic units. L interacts with Cu2+ and Zn2+ forming in both cases, neutral, protonated, and hydroxylated mono- and binuclear complexes whose constants have been calculated by potentiometry in 0.15 M NaClO4 at 298.1 K. The crystal structures of the compounds [Cu(HL-carb)(H2O)](ClO4)3.2H2O (1) and [Cu2(H2L)(CO3)]2(ClO4)8.9H2O (2) have been solved by X-ray diffraction. In 1, the metal center presents square pyramidal geometry. The base of the pyramid is formed by the three nitrogen atoms of pyridine and one oxygen atom of a CO2 group which is forming a carbamate bond with the central nitrogen atom of the polyamine chain. The axial position is occupied by a water molecule. In 2, one Cu2+ is bound by the three pyridine nitrogens and the other one by the three central nitrogen atoms of the polyamine chain. The square planar coordination geometry is completed by a carbonate group taken up from the atmosphere that behaves as a bridging mu,mu'-ligand between the two centers. The pH-metric titrations on the ternary Cu2+-L-carbonate and Zn2+-L-carbonate systems show the extensive formation of adduct species which above pH 6 are formed quantitatively in solution. The stoichiometries of the main species formed in solution at pH = 6.8 agree with those found in the crystalline compounds. CO2 uptake by the Zn2+ and Cu2+ 1:1 complexes in aqueous solution has also been followed by recording the variations in the band at ca. 300 nm. The formation of the Zn2+ carbamate moiety has been evidenced by 13C NMR and ESI spectroscopy.     

Kinetic studies of the on/off reaction of the amino group in the side chain of Cu(II), Ni(II), and Co(II) complexes with 14-membered tetraazamacrocycles

The kinetics of the on/off reaction of the amino group in the side chain of tetraazamacrocyclic Cu2+, Ni2+ and Co2+ complexes has been measured. The rate law k(obs)=k(0)+k(H)[H+]+k(OH)/[H+], the sum of the forward and reverse reaction, gives rise to u-shaped pH dependences from which the three rate constants can be determined. k(H) describes the proton assisted dissociation of the amino group bound to the metal ion and is roughly correlated to the equilibrium constant of the reaction. k(OH) is determined by the protonation constant of the free amino group and the rate constant describing the binding of the amino group to the metal ion. k(0) is composed of the rate constant for the opening of the chelate ring without proton assistance and the rate for the reactivity of the ammonium group in the formation of the chelate ring. Our results show that the rates of the opening and closing of the chelate ring are very little dependent on the nature of the metal ion.     

Gas phase ion thermochemistry of tetraaza complexes such as cyclamM2+ with H2O, CH3OH, NH3, and other ligands, where M2+ = Mn2+, Ni2+, Cu2+, and Zn2+

Tetraaza complexes with M(2+) were produced in the gas phase by Electrospray (ESI) of solutions containing salts of M(2+)dinitrates and a tetraaza compound such as cyclam. The complex CyclM(2+) formed in solution and transferred to the gas phase via ESI was introduced into a reaction chamber containing known partial pressures of a ligand L. Equilibria between CyclM(2+) and L establish CyclML(n)(2+) = CyclML(n-1)(2+) + L and the equilibrium constants K(n,n-1) are determined with a mass spectrometer. Determinations at different temperatures lead to not only the DeltaG(0)(n,n-1) values but also the DeltaH(0)(n,n-1) and DeltaS(0)(n,n-1) values. Data for n = 1, 2, and 3 were obtained for L = H(2)O and CH(3)OH. The DeltaG(0)(1,0), DeltaH(0)(1,0) as well as DeltaG(0)(2,1), DeltaH(0)(2,1) values, when M(2+) = Mn(2+) and Zn(2+), were larger than those for Ni(2+) and Cu(2+). The ligand field theory and the Irvine-Williams series predict a reverse order, i.e., stronger bonding with Ni(2+) and Cu(2+) for simple ligand reactions with M(2+). An examination of the differences of the reactions in solution and gas phase provides a rationale for the observed reverse order for the CyclM(2+) + L reactions. Differences between gas phase and solution are found also when M(2+) = Cu(2+), but the tetraaza macrocycle is changed from, 12-ane to 14-ane to 15-ane. The strongest bonding in solution is with the 14-ane while in the gas phase it is with the 15-ane. Bond free energies, DeltaG(0)(1,0), for CyclCu(2+) with L = H(2)O, CH(3)OH, NH(3), C(2)H(5)OH, C(3)H(7)OH, (C(2)H(5))(2)O, and CH(3)COCH(3), are found to increase in the above order. The order and magnitude of the DeltaG(0)(1,0) values is close to DeltaG(0)(1,0) values observed with potassium K(+) and the same ligands. These results show that the cyclam in CyclCu(2+) leads to an extensive shielding of the +2 charge of Cu(2+). Ligands with gas phase basicities that are relatively high, lead to deprotonation of CyclM(2+). The deprotonation varies with the nature of M(2+) and provides information on the extent of electron transfer from the N atoms of the cyclam, to the M(2+) ions.     

Metal complexes with macrocyclic ligands,XVII. Synthesis of two key intermediates for the preparation of mono-N-functionalized tetraazamacrocycles and their metal complexes

With a modification of the cyclization procedure of Richman & Atkins [8] the two macrocycles 1,4,7-tritosyl-11-benzyl-1,4,7,11-tetraazacyclotetradecane ( 8 ) and 1,7,11-tritosyl-4-trityl-1,4,7,11-tetraazacyclotetradecane ( 15 ) were prepared. After selective cleavage of the benzyl and trityl group, respectively, one obtains the two key products 1,4,7-tritosyl-11-benzyl-1,4,7,11-tetraazacyclotetradecane ( 9 ) and 1,7,11-tritosyl-4-trityl-1,4,7,11-tetraazacyclotetradecane ( 16 ) which have three N-atoms protected by tosyl groups and one accessible for further reactions. To test some of the possibilities we have alkylated 9 and 16 with iodoacetamide, 1-tosyl-aziridine and acrylonitrile. After detosylation with HBr in glacial acetic acid in the presence of phenol mono-N-functionalized tetraazamacrocycles were thus obtained. The advantage of this synthesis is that the cyclization which is the most difficult step of the whole procedure, has to be done only once, regardless of the nature of the pendant arm. In addition a large number of derivatives can be prepared by varying the alkylation component. With Ni²⁺, Cu²⁺ and Zn²⁺ metal complexes of these new ligands were prepared and their IR. and VIS. spectra studied. In the case of the carbamoyl derivatives 12, 14 and 18 the Cu²⁺-complexes exist in two forms. Whereas at low pH the carboxamide group of the pendant arm is probably not bound to the metal ion, at high pH after deprotonation it coordinates in one of the axial positions.     

Novel complexes of Co2+, Ni2+, and Cu2+ with N-(phosphonomethyl)aminosuccinic acid

Complexes of Co²⁺, Ni²⁺, and Cu²⁺ with N-(phosphonomethyl)aminosuccinic acid (H₄PMAS) of general formula Na₂MPMAS·nH₂O [M=Co(II), Ni(II), Cu(II), n—number of water molecules] were synthesized. Based on interpretation of diffusion reflectance spectroscopy, structure of all complexes is based on distorted octahedral. Analysis of IR spectra of Co(II), Ni(II), and Cu(II) N-(phosphonomethyl)aminosuccinates demonstrated that metal ions are coordinated to the ligand through nitrogen atom of the imino group, oxygen atoms of the α- and β-carboxyl groups as well as oxygen atom of the phosphonic group of the H₄PMAS. We demonstrated that thermal stability of complexes increases in sequence Cu(II) < Ni(II) < Co(II), obviously as a result of change over from the dimeric to polymeric character of the initial complex. Complete decomposition of ligand occurs at these temperatures and is accompanied by release of H₂O, CO₂, and NO₂. The final products of thermal decomposition of the complexes are mixtures of oxides and phosphates of respective metals.     

Electronic, cyclic voltammetry, IR and EPR spectral studies of copper(II) complexes with 12-membered N4, N2O2 and N2S2 donor macrocyclic ligands

A new series of copper(II) complexes have been synthesized with macrocyclic ligands having three different donating atoms in the macrocyclic ring. It has been shown that the stereochemistry of complexes is dependent on the coordinated anions. These complexes are characterized by various physicochemical techniques, viz. elemental analysis, molar conductance, magnetic susceptibility measurements, IR, electronic, 1H NMR and EPR spectral studies. Cyclic voltammetric behavior of the complexes has also been discussed. The observed anisotropic g-values indicate that the chloro and acetato complexes are six-coordinate tetragonal. Whereas the sulfato and nitrato complexes are found to have five-coordinate square-pyramidal and four-coordinate square-planar geometry, respectively.     

含Cu咪唑桥联异多核配合物的合成、表征及ESR研究

用具有低自旋d^6构型的[(NH3)5MIm]^2^+, [(en)2Co(Im)2]^+(M=Co, Rh; Im^-为咪唑基)为配体与配位未饱和的含Cu单核配合物作用, 定向合成了八种新的咪唑桥联含Cu异双核、异三核和异五核配合物。对它们进行了元素分析、差热失重分析、摩尔电导测定及反射光谱研究, 确证了配合物的组成及分子中咪唑桥的存在, 通过对各配合物的ESR谱测定, 得到了它们的自旋Hamilton参数和键参数, 讨论了配合物的成键性质。