Dichloro­[(1E,1′E)‐1,1′‐(pyridine‐2,6‐diyl)diethanone bis­(O‐methyl­oxime)‐κ3N1,N2,N6]copper(II)

In the title compound, [CuCl₂(C₁₁H₁₅N₃O₂)], the Cu^II ion is five‐coordinated in a strongly distorted trigonal–bipyramidal arrangement, with the two methyl­oxime N atoms located in the apical positions, and the pyridine N and the Cl atoms located in the basal plane. The two axial Cu—N distances are almost equal (mean 2.098 Å) and are substantially longer than the equatorial Cu—N bond [1.9757 (15) Å]. It is observed that the N(oxime)—M—N(pyridine) bond angle for five‐membered chelate rings of 2,6‐diacetyl­pyridine dioxime complexes is inversely related to the magnitude of the M—N(pyridine) bond. The structure is stabilized by intra‐ and inter­molecular C—H⋯Cl hydrogen bonds which involve the methyl H atoms, except for one of the two acetyl­methyl groups.     

1-Bis(carboxymethyl)amino-butandion-2,3-dioxim als ambifunktioneller Ligand in Komplexen der 3d-Elemente

1-Bis(carboxymethyl)amino-butanedione-2,3-dioxime as an Ambifunctional Ligand in Complexes of 3d Elements In acid solution 1-bis(carboxymethyl)amino-butanedione-2,3-dioxime H₄A affords octahedral 1,1 complexes M^II(H₂A)(H₂O)_x (M^II = Cu, Ni, Co) coordinating as a tetradentate ligand by the imino diacetic acid group and the oxime group in 2-position. At 4.5 < pH < 8 Ni(H₂A)(H₂O)_x and Cu(H₂A)(H₂O)_x are deprotonated, in addition to Ni(HA)^? the binuclear chelate [Ni₂(HA)₂]^2? is formed. In solution containing a surplus of ligand H₄A also the planar chelate [Ni(HA)₂]^4? with the donor set N₄ can be detected. The transition from [Ni(HA)]^? to [Ni(HA)₂]^4? is connected with a change of the coordination sphere (imino diacetic acid group → dioxime group) and the cis-trans isomerization of at least one oxime group. Protonation and stability constants are given and the properties of solid complexes are described.     

Die massenspektrometrische Fragmentierung von NiII-Chelaten mit O-, N-, S-, Se-Donoratomen

Mass Spectrometric Fragmentation of Ni^II Chelates with O-, N-, S-, Se-Donor Atoms The mass spectra of 6Ni^II chelates having the same substituents but different donor atoms (sequence of ligand atoms ? C(X)? NH? C(Y)? ; X, Y = O, S, Se, NH; see formula (1)) are discussed. The fragmentation pattern of the (thio)benzoyl(thio, seleno)ureas are characterized by the abstraction of S or Se atoms. The appearence of small neutral molecules seems to be typical for the fragmentation of all complexes. The mass spectrum of the Ni^II chelate having a NiS₂Se₂ coordination sphere shows no molecular ion peak. The contents of molecular ions in the total ion stream correlates with the stability of the complexes.     

Magnetic properties of transition metal complexes with 2,2′-bipyridin-5-yl t-butyl nitroxide

Complexes [Mn^II(5bpno)₃(ClO₄)₂], [Mn^II(5bpno)(CH₃OH)₂Cl₂], [Cu^II(5bpno)₂(ClO₄)₂], and [Cu^II(5bpno)Cl₂] were prepared, where 5bpno stands for 2,2′-bipyridin-5-yl t-butyl nitroxide. X-ray crystallographic analysis clarified that the Cu ion in [Cu(5bpno)₂(ClO₄)₂] was tetra-coordinate with four nitrogen atoms forming two chelate rings. Magnetic measurements revealed the presence of ferromagnetic couplings in the Mn complexes, whereas the Cu complexes showed antiferromagnetic couplings. Magnetic exchange couplings between the metal and radical spins through the intervening pyridine ring can be explained in terms of the spin-polarization mechanism.     

Bis(2‐pyridyl­methanol)­bis­(saccharinato)­zinc(II) and ‐cadmium(II) at 120 K: three‐dimensional structures containing both N‐and O‐coordinated ambi­dentate saccharinate ligands

The title complexes [M(sac)₂(mpy)₂] [sac is saccharinate (C₇H₄NO₃S) and mpy is 2‐pyridyl­methanol (C₆H₇NO)], with M = Zn^II and Cd^II, are isostructural and consist of neutral mol­ecules. The Zn^II or Cd^II cations are octahedrally coordinated by the two neutral mpy and two anionic sac ligands. The mpy ligand acts as a bidentate donor through the amine N and hydroxyl O atoms. The sac ligands exhibit an ambidentate coordination behaviour; one is N‐coordinated and the other is O‐coordinated within the same coordination octahedron. The crystal packing is determined by C—H?O‐type hydrogen bonding, as well as by weak py–py and sac–sac aromatic π–π‐stacking interactions.     

On the nature of the chemical bond in heterobimetallic palladium(II) complexes with divalent 3<Emphasis Type="Italic">d</Emphasis> metals

The complex Pd(μ-OOCMe)₄Cu(OH₂) · 2Pd₃(μ-OOCMe)₆ was synthesized and characterized by X-ray crystallography. In the heterometallic moiety of this complex, the Pd^II and Cu^II atoms are at an extraordinary short distance (2.521(3) Å). DFT quantum-chemical calculations of the geometric and electronic structure of a series of heterobinuclear paddlewheel complexes Pd^IIM^II(μ-OOCMe)₄L (M = Zn^II, Ni^II, Cu^II, Co^II, Fe^II; L = OH₂ and NCH) and their formate analogues Pd^IIM^II(μ-OOCH)₄L (M = Zn^II, Ni^II, Fe^II) showed that the extraordinary short Pd?M distance in all these complexes is caused only by the tightening effect of carboxylate bridges rather than by the metal-metal bond. The direct Pd-M interaction becomes possible only after removal of electrons from the antibonding orbitals and formation of oxidized complexes of the [Pd^III(μ-OOCMe)₄Ni^III]²⁺ type.     

(Acetonitrile){2,6‐bis[1‐(2,4,6‐trimethylphenylimino)ethyl]pyridine}dichloridoruthenium(II) dichloromethane solvate

In the title compound, [RuCl₂(C₂H₃N)(C₂₇H₃₁N₃)]·CH₂Cl₂, the Ru^II ion is six‐coordinated in a distorted octahedral arrangement, with the two Cl atoms located in the apical positions, and the pyridine (py) N atom, the two imino N atoms and the acetonitrile N atom located in the basal plane. The two equatorial Ru—N_imino distances are almost equal (mean 2.087 Å) and are substantially longer than the equatorial Ru—N_py bond [1.921 (4) Å]. It is observed that the N_imino—M—N_py angle for the five‐membered chelate rings of pyridine‐2,6‐diimine complexes is inversely related to the magnitude of the M—N_py bond. The title structure is stabilized by intra‐ and intermolecular C—H...Cl hydrogen bonds, as well as by van der Waals interactions.     

ELECTRONIC STRUCTURE OF CYANO-BRIDGED DINUCLEAR IRON COMPLEXES

Abstract

A series of complexes of formula [(NC)₅Fe^II—NC—Fe^II(CN)₄L]^n?, with L = H₂O, pyridine, isonicotinamide and 4-cyanopyridine were prepared in aqueous solution by substitution of the corresponding [Fe^II(CN)₅L]^n? ions into [Fe^II(CN)₅H₂O]^3?. The mixed valent (II, III) and fully oxidized (III, III) complexes were also obtained. The (II, II) complexes were moderately stable toward dissociation into the mononuclear species, but the mixed-valent ions were properly characterized by UV-vis-NIR spectroscopy and electrochemistry. Distinctive intervalence (IV) bands were assigned in the NIR region, with the energy being dependent on the binding properties of L; the IV band energy also correlated with the redox potential at the [NC—Fe(CN)₄L] fragment. By application of the Hush model, a valence-trapped situation was found for the [(NC)₅Fe^III—NC—Fe^II(CN)₄L]^n? ions. The class II behavior shows, however, a value of H _ab, the electronic coupling factor, of ca. 1600cm^?1, indicating a moderate-to-strong communication between the metal centers.     

Poly[[tetraaqua(μ7‐pyridine‐2,3,5,6‐tetracarboxylato)dicadmium(II)] monohydrate]

The title compound, {[Cd₂(C₉HNO₈)(H₂O)₄]·H₂O}_n, consists of two crystallographically independent Cd^II cations, one tetrabasic pyridine‐2,3,5,6‐tetracarboxylate (pdtc) anion, four coordinated water molecules and one solvent water molecule. The Cd^II cations have distorted square‐antiprismatic (one pyridine N, six carboxylate O and one water O atom) and octahedral (three carboxylate O and three water O atoms) coordination environments. Each pdtc ligand employs its pyridine and carboxylate groups to chelate and bridge seven Cd^II cations. The square‐antiprismatic coordinated Cd^II cations are linked by pdtc ligands into a lamellar framework structure, while the octahedral coordinated Cd^II cations are bridged by the μ₂‐carboxylate O atoms and the pdtc ligands into a chain network that further joins neighbouring lamellae into a three‐dimensional porous network. The cavities are filled with solvent water molecules that are linked to the host through complex hydrogen bonding.     

Zur Addition von Übergangsmetallhalogeniden an Acetylacetonate zweiwertiger Metallionen

Addition of Transition Metal Dihalides to Acetylacetonates of Divalent Metal Ions Transition metal dihalides ^aM^IIX₂ (FeCl₂, CoCl₂ NiBr₂ etc.) are added by the chelates M^II(acac)₂ under formation of binuclear complexes (THF)₂M^II(acac)₂(^aM^IIX₂). The octahedral and the tetrahedral centre of these compounds are connected by tridentate oxygen atoms of the two acetylacetonato ligands which are simultaneously included in four-membered rings (M^IIOM^II). The addition is combined with a deformation of the octahedral centre, as a prerequisite of a closest package of the atoms within the M^IIOM^II-ring. In the trinuclear complex (THF)₂Ni(acac)₂(HgCl₂)₂ III the interaction between the three coordination centres is weak. No structural change of the octahedral centre (THF)₂Ni(acac)₂ is found, but the HgCl₂-groups diverge slightly from linearity (Cl? Hg? Cl 171.1°). No binuclear complexes with a central ion of the oxidation state III in the octahedral centre were obtained. One reason is the lowered donor strength of the bidentate Lewis base function of the octahedral centre [(THF)₂Mⁿ⁺(acac)₂]^n-2 with M⁺³ as a centralatom. Reacting systems with di- and trivalent ions prefer ionic complexes, as it is shown by the formation of [(THF)₂V(acac)₂][(THF)CoCl₃] IV from VCl₃ and Co(acac)₂. The crystal structures of (THF)₂Co(acac)₂CoCl₂ II and [(THF)₂V(acac)₂][(THF)CoCl₃] IV were determined by x-ray diffraction. II : orthorhombic-primitive; space group P2₁2₁2₁, Z = 4; a = 967.4(2), b = 1453.4(3), c = 1715.9(4) pm; R = 0.049 for 3084 observed reflections. IV : triclinic; space group P1, Nr. 2; Z = 2; a = 871,5(2), b = 930,6(3), c = 1865,6(6) pm; α = 101,70(2), b? = 92,45(2), γ = 91,06(2)°; R = 0,060 für 4221 observed reflections.     

Complexing behaviour of aromatic thioamides (ArCSNHCOR). Transition metal complexes of N-carboethoxy-4-chlorobenzene- and N-carboethoxy-4-bromobenzene thioamide ligands

N-Carboethoxy-4-chlorobenzene thioamide (Hcct or HL) and N-carboethoxy-4-bromobenzene thioamide (Hcbt or HL) react with bivalent (Ni, Co, Cu, Ru, Pd and Pt), trivalent (Ru and Rh) and tetravalent (Pt) transition metal ions to give [M^II(L)₂], [Ru^III(L)₃], [Rh^III(L)(HL)Cl₂] and [Pt(L)₂Cl₂] complexes, respectively. In the presence of pyridine, Co^II and Ni^II salts react with the ligands (HL) to give [M^II(L)₂Py] (M = Co and Ni) complexes. Soft metal ions abstract sulphur from the ligands to yield the corresponding sulphide, together with oxygenated forms of the ligands. All the metal complexes have been characterised by chemical analyses, conductivity, spectroscopic and magnetic measurements.     

Redox properties of cobalt(II) complexes with isoindoline-based ligands

Cobalt bis-(N-arylimino)isoindolinates undergo electrostatic interactions with DNA or react with alkyl hydroperoxides to form ketones and alcohols. Redox behavior of the metal center should affect such reactivities; therefore, six neutral Co^II(L)₂ complexes with L = bis-(N-arylimino)isoindolinates have been synthesized to elucidate the effect of the aryl substituents on the redox potential of the metal center. Redox properties of various M^II(L)₂ complexes (M = Mn, Fe, Co, Ni) are compared. Moreover, data are presented on the dismutation rates of superoxide radical anion (a knowingly sensitive reagent on the redox properties of the metal center) in the presence of the various Co^II(L)₂ complexes among identical conditions.     

Synthesis and electrochemical study of 3- and 4-(2-pyridyl)-1,3-benzothiazole complexes with transition metals (CoII, NiII, and CuII). Molecular structure of bis{(4-(2-pyridyl)-1,3-benzothiazole)copper(ii)} tetraacetate

A series of the M(L)Cl₂ · nH₂O and {M(L)}₂(OAc)₄ complexes (M = Ni^II, Co^II, and Cu^II; L is 3- and 4-(2-pyridyl)-1,3-benzothiazole) were synthesized by the reaction of L with MX₂ · nH₂O (X = Cl, OAc) in ethanol. The molecular and crystal structures of the CuL₂(OAc)₄ binuclear complex (L is 4-(2-pyridyl)benzothiazole) were determined by X-ray diffraction analysis. The copper atoms have a distorted tetragonal bipyramidal environment and are coordinated to the nitrogen atom of the pyridine moiety of the ligand and to two oxygen atoms of the bridging acetate ligands. The Cu-Cu distance is 2.6129(9) Å. The electrochemical behavior of the synthesized ligands and complexes was studied using the cyclic voltammetry and rotating disk electrode techniques in DMF solutions (0.1 M Bu₄NClO₄). The primary reduction of all the complexes under study is directed to the metal.     

Control of Redox Potential by Deprotonation of Coordinated 1H‐Imidazole in Complexes of 2‐(1H‐Imidazol‐2‐yl)pyridine

Complexes [ML₃]²⁺ of the bidentate ligand 2‐(1H‐imidazol‐2‐yl)pyridine were prepared with iron(II), cobalt(II), and ruthenium(II). The electronic spectra suggest the ligand to be a weaker σ‐donor and π‐acceptor than the closely related 2,2′‐bipyridine. The complexes are readily deprotonated by addition of base, and the effect of the deprotonation is to lower the M^III/M^II redox potential by roughly 900 mV. This is roughly 75% of the drop observed for related complexes of 2,6‐di‐1H‐imidazol‐2‐ylpyridine, and suggests the effect to be largely coulombic in origin.     

(Acetonitrile){2,6‐bis­[1‐(2‐ethyl‐6‐methyl­phenyl­imino)­ethyl]­pyridine}­dichloro­ruthenium(II) dichloro­methane hemisolvate: a chain of edge‐fused R66(24) rings

In the title compound, [RuCl₂(C₂H₃N)(C₂₇H₃₁N₃)]·0.5CH₂Cl₂, the Ru^II ion is six‐coordinated in a distorted octa­hedral arrangement, with the two Cl atoms located in the apical positions, and the pyridine (py) N atom, the two imino N atoms and the acetonitrile N atom located in the basal plane. The dichloromethane solvent mol­ecule lies on a twofold axis. The two equatorial Ru—N_imino distances are almost equal (mean 2.089 Å) and are substantially longer than the equatorial Ru—N_py bond [1.914 (4) Å]. It is observed that the N_imino—M—N_py bond angle for the five‐membered chelate rings of pyridine‐2,6‐diimine complexes is inversely related to the magnitude of the M—N_py bond. The title structure is stabilized by intra‐ and inter­molecular C—H⋯Cl hydrogen bonds. The inter­molecular hydrogen bonds form an R₆⁶(24) ring and a chain of edge‐fused rings running parallel to the [001] direction.     

Jahn-Teller-Verzerrungen von Übergangsmetallionen in tetraedrischer Koordination – die Strukturen von Cat[MII(NCS)4] (MII: Co,Ni, Cu) und von Spinellmischkristallen MIICr2O4(MII: Zn?Ni,Zn?Cu,Cu?Ni)

Jahn-Teller Distortions of Transition Metal Ions in Tetrahedral Coordination — The Structures of Cat[M^II(NCS)₄]^II (M^II: Co, Ni, Cu) and of Mixed Crystals M^IICr₂O₄(M^II: Zn? Ni, Zn? Cu, Cu? Ni) of the Spinel Type The structure determination of compounds Cat[M^II(NCS)₄] with Cat = p-xylylenebis(triphenylphosphonium)²⁺ and M^II = Co, Ni, Cu [space group P2₁/n, Z = 4] yielded pseudotetrahedral M^IIN₄-polyhedra, which are distorted by packing forces and vibronic coupling effects of the Jahn-Teller type. Spinel mixed crystals with M^II = Zn? Ni, Zn? Cu, Ni? Cu in the tetrahedral sites exhibit phase transition to tetragonal and o-rhombic structures, induced by cooperative Jahn-Teller interactions. The distortion symmetries of the M^IIN₄ and M^IIO₄ tetrahedra are analysed on the basis of the respective electronic groundstate and the possible Jahn-Teller active vibrational modes.     

Ligandenaustauschreaktionen am Bis(1,3-diselenol-2-selon-4,5-diselenolato)-kupferat(II) ([Cu(dsis)2]2−) mit Kupfer(II)-Vier- und Fünfringchelaten geminaler und vicinaler ungesättigter Dichalkogenoliganden. Eine EPR-Untersuchung

Ligand Exchange on Bis(1,3-diselenole-2-selone-4,5-diselenolato)cuprate(II) ([Cu(dsis)₂]^2?) with Cu^II Four and Five Ring Bis-chelates Containing Unsaturated Vicinal and Geminal Dichalcogeno Ligands. An EPR Study Ligand exchange reactions (“chelate metathesis”) of bis(1,3-diselenole-2-selone-4,5-diselenolato)cuprate(II), ([Cu(dsis)₂]^2?, with other Cu^II four- or five-ring chelates of unsaturated dichalcogeno ligands are reported. The small solubility of salts of the title complex in common solvents like acetone or chloroform requires pyridine. Mixed-ligand complexes could be detected for all combinations of two starting complexes studied by means of their g_o and a_o^Cu (EPR) parameters. Due to the coordinating properties of pyridine and electronic reasons commonly used linear dependences of the g value from the composition of the first coordination sphere (“additivity rules”) are not applicable.     

Flat vs. Folded Chelate Rings in cis‐PtIIa2 (a = NH3, a2 = en,a2 = 2, 2′‐bpy) Complexes of Twofold Substituted Diazine Ligands

Acid‐base and ligating properties of three bis(substituted)pyrazine (pz) and pyrimidine (pym) ligands (pyrazine‐2, 5‐dicarboxylic acid, 2, 5‐pzdcH2, 2, 3‐bis(pyridine‐2‐yl)pyrazine, 2, 3‐bppz, pyrimidine‐4, 6‐dicarboxylic acid, 4, 6‐pmdcH₂) toward cis‐Pt^IIa₂ (a = NH₃, a₂ = en, a₂ = 2, 2′‐bpy) have been studied. Combinations of pz‐N/pym‐N with donor atoms of the substituents lead to 5‐membered platinum chelates, but exclusive N, N‐coordination through the pyridyl substituents of 2, 3‐bppz can lead to a 7‐membered platinum chelate with a characteristic L‐shape of the resulting cation. It is observed for Pt^II(2, 2′‐bpy), yet not for Pt^II(en), and is a consequence of differences in sterical interactions between the 2, 3‐bppz ligand and the coligands of Pt^II.     

(2,6‐Bis{1‐[4‐(dimethylamino)phenylimino]ethyl}pyridine)dichlorido(triphenylphosphine‐κP)ruthenium(II): a zigzag chain of fused centrosymmetric R22(12) rings

The title compound, [RuCl₂(C₂₅H₂₉N₅)(C₁₈H₁₅P)], a transfer hydrogenation catalyst, is supported by an N,N′,N′′‐tridentate pyridine‐bridged ligand and triphenylphosphine. The Ru^II centre is six‐coordinated in a distorted octahedral arrangement, with the two Cl atoms located in the axial positions, and the pyridine (py) N atom, the two imino N atoms and the triphenylphosphine P atom located in the equatorial plane. The two equatorial Ru—N_imino distances (mean 2.093 Å) are substantially longer than the equatorial Ru—N_py bond [1.954 (4) Å]. It is observed that the N_imino—M—N_py bond angle for the five‐membered chelate rings of 2,6‐bis(imino)pyridine‐based complexes is inversely related to the magnitude of the M—N_py bond. The title structure is stabilized by intra‐ and intermolecular C—H...Cl hydrogen bonds, as well as by intramolecular π–π stacking interactions between the aromatic rings belonging to the triphenylphosphine ligand and the dimethylaminophenyl fragment. The intermolecular hydrogen bonds form an R₂²(12) ring and a zigzag chain of fused centrosymmetric rings running parallel to the [100] direction.     

(2,2′‐Biquinoline‐κ2N,N′)dichloropalladium(II), ‐copper(II) and ‐zinc(II)

In the three title complexes, namely (2,2′‐biquinoline‐κ²N,N′)dichloro­palladium(II), [PdCl₂(C₁₈H₁₂N₂)], (I), and the corresponding copper(II), [CuCl₂(C₁₈H₁₂N₂)], (II), and zinc(II) complexes, [ZnCl₂(C₁₈H₁₂N₂)], (III), each metal atom is four‐coordinate and bonded by two N atoms of a 2,2′‐biquinoline molecule and two Cl atoms. The Pd^II atom has a distorted cis‐square‐planar coordination geometry, whereas the Cu^II and Zn^II atoms both have a distorted tetra­hedral geometry. The dihedral angles between the N—M—N and Cl—M—Cl planes are 14.53 (13), 65.42 (15) and 85.19 (9)° for (I), (II) and (III), respectively. The structure of (II) has twofold imposed symmetry.