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.     

Preparation and properties of palladium(II) and rhodium(I) complexes containing bidentate phosphine sulphide and selenide ligands

Summary The synthesis and properties of cationic complexes of general formula [ML₂{CH₂(Ph₂PE)₂}]BF₄, where M = Pd^II and Rh^II, L₂ = ³-MeC₃H₄, {P(O)(OR)₂}₂H (R = Me, Et), COD, (CO)₂, (CO)PPh₃ and E = S, Se are described. The methylene proton of the coordinated phosphine sulphide or selenide ligands react with strong bases as BuLi in n-hexane or NaH in THF, to give neutral complexes of the type [ML₂{CH(Ph₂PE)₂}], where M = Pd^II, Rh^I; L₂ = ³-MeC₃H₄, COD and E = S, Se. The complexes have been characterized by elemental analyses, molar conductivities, i.r., ¹H n.m.r. and ³¹P{¹H} n.m.r. spectroscopy.     

The coordination chemistry ofN,N′-ethylenebis(2-acetylpyridine imine) andN,N′-ethylenebis(2-benzoylpyridine imine); two potentially tetradentate ligands containing four nitrogen atoms

Summary New complexes of the general formulae [ML_A(H₂O)₂]-Cl₂ (M=Ni or Cu), [ML_AX₂] (M=Co or Cu; X=Cl or Br), [NiL_ABr₂]·H₂O, [ML_A] [MCl₄] (M=Pd or Pt), [NiL_B(H₂O)₂]Cl₂·2H₂O, [ML_BCl₂] (M=Co, Ni, Cu, Pd or Pt; X=Cl or Br) and [ML_B] [MCl₄] (M=Pd or Pt), where L_A=N,N-ethylenebis(2-acetylpyridine imine) and L_B=N, N-ethylenebis(2-benzoylpyridine imine), have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, t.g./d.t.g. methods, magnetic susceptibilities and spectroscopic (i.r., far-i.r., ligand field,¹Hn.m.r.) studies. Monomeric pseudo-octahedral stereochemistries for the Co^II, Ni^II and Cu^II complexes andcis square planar structures for the compounds [ML_BX₂] (M=Pd or Pt; X=Cl or Br) are assigned in the solid state. The molecules L_A and L_B behave as tetradentate chelate ligands in the Co^II, Ni^II, Cu^II and Magnus-type Pd^II and Pt^II complexes, bonding through both the pyridine and methine nitrogen atoms. A bidentateN-methine coordination of the Schiff base L_B is assigned in the [ML_BX₂] complexes (M=Pd or Pt; X=Cl or Br). The anomalous magnetic moment values of the Co^II complexes are discussed.     

Magnetochemical Complexity of Hexa‐ and Heptanuclear Wheel Complexes of Late‐3d Ions Supported by N,O‐Donor Pyridyl–Methanolate Ligands

The scaffold geometries, stability and magnetic features of the (pyridine‐2‐yl)methanolate (L) supported wheel‐shaped transition‐metal complexes with compositions [M₆L₁₂] ( 1 ), [Na?(ML₂)₆]⁺ ( 2 ), and [M′?(ML₂)₆]²⁺ ( 3 ), in which M=Co^II, Ni^II, Cu^II, and Zn^II were investigated with density functional theory (DFT). The goals of this study are manifold: 1) To advance understanding of the magnetism in the synthesized compounds [Na?(ML₂)₆]⁺ and [M′?(ML₂)₆]²⁺ that were described in Angew. Chem. Int. Ed.­ 2010 , 49, 4443 ( I ‐{Na?Ni₆}, I ‐{Ni′?Ni₆}) and Dalton Trans.­ 2011 , 40, 10526 ( II ‐{Na?Co₆}, II ‐{Co′?Co₆}); 2) To disclose how the structural, electronic, and magnetic characteristics of 1 , 2 , and 3 change upon varying M^II from d⁷ (Co²⁺) to d¹⁰ (Zn²⁺); 3) To estimate the influence of the Na⁺ and M′²⁺ ions (X^Q+) occupying the central voids of 2 and 3 on the external and internal magnetic coupling interactions in these spin structures; 4) To assess the relative structural and electrochemical stabilities of 1 , 2 , and 3 . In particular, we focus here on the net spin polarization, the determination of the strength and the sign of the exchange coupling energies, the rationalization of the nature of the magnetic coupling, and the ground‐state structures of 1 , 2 , and 3 . Our study combines the broken symmetry DFT approach and the model Hamiltonian methodology implemented in the computational framework CONDON 2.0 for the modeling of molecular spin structures, to interpret magnetic susceptibility measurements of I ‐{Na?Ni₆} and I ‐{Ni′?Ni₆}. We illustrate that whereas the structures, stability and magnetism of 1 , 2 , and 3 are indeed influenced by the nature of 3d transition‐metals in the {M₆} rims, the X^Q+ ions in the inner cavities of 2 and 3 impact these properties to an even larger degree. As exemplified by I ‐{Ni′?Ni₆}, such heptanuclear complexes exhibit ground‐state multiplets that cannot be described by simplistic model of spin‐up and spin‐down metal centers. Furthermore, we assess how future low‐temperature susceptibility measurements at high magnetic fields can augment the investigation of compound 3 with M=Co, Ni.     

Astatistical aspects of the stabilities of ternary complexes of cobalt(II), nickel(II), copper(II) and zinc(II) involving aminopolycarboxylic acids as primary ligands and salicylaldoxime as a secondary ligand

Summary Stability constants of binary (ML, ML₂) and ternary (MAL) complexes, where M=Co^II, Ni^II, Cu^II and Zn^II; A-iminodiacetic acid (ida),N-methyliminodiacetic acid (Me-ida), anthranilatediacetic acid (ada), nitrilotriacetic acid (nta); LH₂=salicylaldoxime have been determined at 25° C at 0.1M KNO₃ ionic strength by the Irving-Rossotti technique. K _MAL ^MA is always lower than K _ML ^M and KMI ₂ ^ML . In the ternary systems studied, the K _MAL ^ML values lie in the sequence: K _M(ida)L ^M(ida) >K _M(Me-ida)L ^M(Me-ida) >K _M(nta)L ^M(nta) >K _M(ada)L ^M(ada) . For Cu^II, the K _Cu(nta)L ^Cu(nta) and K _Cu(ada)L ^Cu(ada) values are significantly reduced compared to all other primary ligands. For different primary ligands, the K _MAL ^MA sequence is reversed compared to K _MA ^M , but for A=ada and nta their relative positions remain unaltered in both binary and ternary systems. The results have been explained in the light of different astatistical factors such as electrostatic effects, steric hindrance, change of electronegativity of the central metal and stereochemical factors.     

Metal chelates of thiazole-2-ylthiourea

Summary The formation constants of 1-phenyl-3-thiazole-2-ylthiourea complexes with some bivalent metal ions (Cu^II, Ni^II, Zn^II and Mn^II) have been determined in 75% EtOH–H₂O. Complexes of Cu^II, Ni^II, Zn^II, Hg^II and Pd^II have been isolated and characterized by conductance, i.r., electronic spectra and magnetic measurements. The ligand forms ML complexes with Cu^II and Hg^II and ML₂ with Ni^II, Zn^II and Pd^II, where L is the uninegatively charged bidentate ligand and binds through the ring nitrogen and thiocarbonyl sulphur atoms.     

Structural and Oxidation State Alternatives in Platinum and Palladium Complexes of a Redox-Active Amidinato Ligand

Reaction of [Pt(DMSO)₂Cl₂] or [Pd(MeCN)₂Cl₂] with the electron-rich LH=N,N’-bis(4-dimethylaminophenyl)ethanimidamide yielded mononuclear [PtL₂] ( 1 ) but dinuclear [Pd₂L₄] ( 2 ), a paddle-wheel complex. The neutral compounds were characterized through experiments (crystal structures, electrochemistry, UV-vis-NIR spectroscopy, magnetic resonance) and TD-DFT calculations as metal(II) species with noninnocent ligands L⁻. The reversibly accessible cations [PtL₂]⁺ and [Pd₂L₄]⁺ were also studied, the latter as [Pd₂L₄][B{3,5-(CF₃)₂C₆H₃}₄] single crystals. Experimental and computational investigations were directed at the elucidation of the electronic structures, establishing the correct oxidation states within the alternatives [Pt^II(L⁻)₂] or [Pt^.(L )₂], [Pt^II(L^0.5−)₂]⁺ or [Pt^III(L⁻)₂]⁺, [(Pd^II)₂(μ-L⁻)₄] or [(Pd^1.5)₂(μ-L^0.75−)₄], and [(Pd^2.5)₂(μ-L⁻)₄]⁺ or [(Pd^II)₂(μ-L^0.75−)₄]⁺. In each case, the first alternative was shown to be most appropriate. Remarkable results include the preference of platinum for mononuclear planar [PtL₂] with an N-Pt-N bite angle of 62.8(2)° in contrast to [Pd₂L₄], and the dimetal (Pd₂⁴⁺→Pd₂⁵⁺) instead of ligand (L⁻→L ) oxidation of the dinuclear palladium compound.     

Electrochemical synthesis and magnetic studies of neutral transition metal imidazolates and pyrazolates

Summary The single-step electrochemical synthesis of neutral transition metal complexes of imidazole, pyrazole and their derivatives has been achieved at ambient temperature. The metal was oxidized in an Me₂CO solution of the diazole to yield complexes of the general formula: [M(Iz)₂] (where M = Co, Ni, Cu, Zn; Iz = imidazolate); [M(MeIz)₂] (where M = Co, Ni, Cu, Zn; MeIz = 4-methylimidazolate); [M(PrⁱIz)₂] (where M = Co, Ni, Cu, Zn; PrⁱIz = 2-isopropylimidazolate); [M(pyIz)_n] (where M = Co^III, Cu^II, Zn^II; pyIz = 2-(2-pyridyl)imidazolate); [M(Pz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; Pz = pyrazolate); [M(ClPz)_n] and [M(IPz)_n] (where M = Co^III, Ni^II, Cu^II, Zn^II; ClPz = 4-chloropyrazolate; IPz = 4-iodopyrazolate); [M(Me₂Pz)_n] (where M = Co^II, Cu^I, Zn^II; Me₂Pz = 3,5-dimethylpyrazolate) and [M(BrMe₂Pz)_n] (where M = Co^II, Ni^II, Cu^I, Zn^II; BrMe₂Pz = 3,5-dimethyl-4-bromopyrazolate). Vibrational spectra verified the presence of the anionic diazole and electronic spectra confirmed the stereochemistry about the metal centre. Variable temperature (360-90 K) magnetic measurements of the cobalt and copper chelates revealed strong antiferromagnetic interaction between the metal ions in the lattice. Data for the copper complexes were fitted to a Heisenberg (S= ) model for an infinite one-dimensional linear chain, yielding best fit values of J=–62––65cm^–1 andg = 2.02–2.18. Data for the cobalt complexes were fitted to an Ising (S= ) model with J=–4.62––11.7cm^–1 andg = 2.06–2.49.     

[M3V18O42(H2O)12(XO4)]⋅24 H2O (M=Fe,Co; X=V,S): Metal Oxide Based Framework Materials Composed of Polyoxovanadate Clusters

New framework materials composed of well-defined vanadium oxide clusters were prepared by low-temperature reactions and characterized by X-ray crystal structure analysis. The structures of these solids contain {V₁₈O₄₂} cages linked into two interpenetrating three-dimensional networks by bridging {M(H₂O)₄} groups (M=Fe^II, Co^II; see picture).     

Potentiometric determination of the formation constants for complexes of 3,2′,2″-triaminopropyldiethylamine with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II)

The tripodal tetraamine ligand N{(CH₂)₃NH₂}{(CH₂)₂NH₂}₂ (pee), has been investigated as an asymmetrical tetraamine chelating agent for Co^II, Ni^II, Cu^II, Zn^II and Cd^II. The protonation constants for this ligand and the formation constants for its complexes have been determined potentiometrically in 0.1 M KCl at 25 °C. The successive protonation constants (log K _n ) are: 10.22, 9.51, 8.78 and 1.60 (n = 1–4). One complex with formula M(pee)²⁺ (M = Co, Ni, Cu, Zn and Cd) is common to all five metal ions and the formation constant (log _ML) is: 12.15, 14.17, 16.55, 13.35 or 9.74, respectively. In addition to the simple complexes, Co^II, Cu^II and Zn^II also give hydroxo complexes, and Cu^II and Ni^II give complexes with monoprotonated pee. [Zn(pee)](ClO₄)₂ and [Cd(pee)Cl](ClO₄) complexes were isolated and are believed to have tetrahedral and trigonal-bipyramidal structures, respectively.     

New complexes of iron(III), cobalt(II), nickel(II) and copper(II) with 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol

Summary Fe^III, Co^II, Ni^II and Cu^II complexes of a new Schiff base, 2-phenyl-1,2,3-triazole-4-carboxalidene-2-aminophenol (PTCAP), have been synthesized and characterized by elemental analyses, molar conductance and magnetic susceptibility measurements, and by u.v.-vis., i.r. and e.p.r. spectral observations. The studies indicate an octahedral structure for the complexes with the general formula [ML₂] (M = Co^II, Ni^II or Cu^II.; L = PTCAP) or [M′(OH)L₂] (M′ = Fe^III). The i.r. spectra suggest that the ligand acts as a tridentate (NNO) donor towards Co^II, Ni^II and Cu^II, and, in the Fe^III complex, one of the two ligand molecules acts as a bidentate (NO) donor and the other as a tridentate donor. The M?ssbauer spectrum of the Fe^III complex suggests the presence of a spin equilibrium at room temperature. Cyclic voltammograms are also recorded for the Cu^II and Fe^III complexes.     

Macrocyclic complexes of transition metals with divalent polyaza units

A new series of 14–16-membered hexaazamacrocyclic complexes [ML¹X₂] and [ML²X₂] (M = Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃) have been synthesized by template condensation of phenylenediamine, primary diamines and formaldehyde solution 35% in MeOH and have been characterized by i.r., 1H-n.m.r., e.p.r., and u.v. spectroscopy as well as by magnetic susceptibility and conductivity measurements. An octahedral geometry has been suggested for all the complexes.     

Programmable Self‐Assembly of Heterometallic Palladium(II)–Copper(II) 1D Grid‐Chain using Dinuclear Palladium(II) Corners with Pyrazole–Carboxylic Acid Ligands

A novel heterometallic diPd^II–diCu^II grid‐chain, {[(bpy)₄Pd₄Cu₂L₄](NO₃)₄}_n ( 2 ; bpy=2,2′‐bipyridine), was synthesized through a programmable self‐assembly approach from the molecular corners [(bpy)₂Pd₂(HL)(L)](NO₃) ( 1 ) as linkers with Cu^II nitrate by using the bifunctional H₂L ligand featuring primary (pyrazole) and secondary (benzoic acid) groups. Structural analysis revealed that 1D structure 2 consists of one [Cu₂(O₂CPh)₄]_n unit as a bridge and two [(bpy)₂Pd₂L₂]_n corners. Additionally, the catalytic effect of the heterometallic synergy on the Suzuki coupling reaction by using 2 was further explored.     

Tetraoxotetraamide macrocyclic complexes

A new class of 16- and 17-membered tetraamide macrocyclic complexes, [ML¹X₂] and [ML²X₂] [M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; X = NO₃ or Cl], have been prepared by the template reaction of anthranilic acid, 1,2-diaminoethane or 1,3-diaminopropane and succinic acid in 2:1:1 molar ratio. The stoichiometries and coordination modes of the complexes have been deduced from physicochemical and spectroscopic measurements. This revised version was published online in June 2006 with corrections to the Cover Date.     

Incorporation of peptide bonds in the synthesis of polyazamacrocyclic complexes

Summary A new series of 15- and 16-membered dioxotetraamine macrocyclic complexes, [ML¹X₂] and [ML²X₂] (M = Mn^II, Co^II, Ni^II, Cu^II or Zn^II; X = Cl or NO₃), respectively, were prepared by reacting o-aminobenzoic acid, diaminoethane or 1,3-diaminopropane with 2,4-pentanedione in the presence of metal ions. The complexes were identified by analytical data, i.r., ¹H-n.m.r., e.p.r. and u.v.-vis. spectroscopies, and by conductivity and magnetic moment measurements. They exhibit an octahedral geometry leaving the peptide oxygen uncoordinated. They are air stable and insoluble in water and most organic solvents, but soluble in DMSO and DMF. The low conductivity suggests that the complexes are non-ionic.     

Nickel(II) and Iron(II) coordination compounds with octahydrotriborate(1–) anion [ML<Subscript>3</Subscript>]{B<Subscript>3</Subscript>H<Subscript>8</Subscript>}<Subscript>2</Subscript> (M = Fe<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>; L = bipy,phen)

Methods of synthesis have been developed for new types of promising precursors of metal borides, coordination compounds [ML₃]B{₃H₈{₂ (M = Fe²⁺, Ni²⁺; L = bipy, phen), using modified procedures of synthesis of octahydrotriborate anion. Compounds [Ni(bipy)₃]B{₃H₈}₂, [Ni (phen)₃]B{₃H₈}₂ and [Fe(phen)₃]B{₃H₈}₂ were prepared and characterized by single-crystal X-ray diffraction.     

Darstellung und spektroskopische Charakterisierung von Kupfer(II)- und Nickel(II)-tricyanmethanid-Komplexen mit Imidazol-Derivaten – Kristallstruktur von [Cu{C(CN)3}2(2-meiz)2]

Synthesis and Spectroscopic Characterization of Copper(II) and Nickel(II) Tricyanomethanide Complexes with Imidazoles – Crystal Structure of [Cu{C(CN)₃}₂(2-meiz)₂] The copper(II) and nickel(II) tricyanomethanide complexes with imidazoles of the type [Cu{C(CN)₃}₂L₄], [L = 2- or 4-methylimidazole (meiz)] and [M{C(CN)₃}₂L₂] [M = Cu, L = imidazole (iz), 2- or 4-meiz; M = Ni, L = iz, 2- or 4-meiz] were prepared and characterized by electronic, infrared, and – some of them – by ESR spectroscopy. The structure [Cu{C(CN)₃}₂(2-meiz)₂], solved by X-ray crystallographic analysis, shows a two-dimensional network with unsymmetric C(CN)₃-bridges between the Cu^II atoms. Polymeric structures with bridging C(CN)₃-groups were identified by means of spectroscopic methods also for the other [M{C(CN)₃}₂L₂] complexes. On the other hand, for the complexes [M{C(CN)₃}₂L₄] follow molecular structures, in which monodentate C(CN)₃ ligands are present. All compounds under investigation show a tetragonal-bipyramidal geometry with various degree of tetragonal distortion.     

Cobalt(III), copper(II), and nickel(II) complexes of 1-thia-4,7-diazacyclononane-S-oxide

Summary The title complexes [ML₂]ⁿ⁺=Co^III, Cu^II, Ni^II; L=1-thia-4,7-diazacyclononane-S-oxide) have been prepared and characterized spectroscopically. The sulphoxide group is coordinated through the oxygen atom and the complexes have atrans-O,O geometry. The nickel(II) complex of bis(2-amino-ethyl)sulphoxide has also been studied.     

Synthesis and Structure of Different-Metal Different-Ligand Germanium(IV) and Cobalt(II) or Copper(II) Complexes with 1-Hydroxyethylidenediphosphonic Acid and 1,10-Phenanthroline

Different-metal different-ligand complexes [{Co(Phen)₃}₂{Co(Phen)(H₂O)₄}₂][{Ge(μ-OH)(μ- Hedp)}₆Cl₂] (I), [{Cu(Phen)₂(H₂O)}₂(HPhen)₂][Ge(μ-OH)(μ-Hedp)]₆ · 20H₂O (II) (H₄Hedp = 1-hydroxyethylidenediphosphonic acid, Phen = 1,10-phenanthroline) were synthesized and studied by X-ray diffraction. According to X-ray diffraction data (CIF files CCDC nos. 1573112 (I), 1573113 (II)), compounds I and II are cation–anion type complexes in which the anions are represented by {[Ge(μ-OH)(μ-Hedp)]⁶}^6– and, in the case of I, two additional Cl^– ions, while the cations are [Co(Phen)₃]²⁺, [Co(Phen)(H₂O)₄]²⁺ in I and [Cu(Phen)₂(H₂O)]²⁺, HPhen⁺ in II. In the crystals of compounds I and II, the cations, anions, and water molecules are combined by numerous intermolecular hydrogen bonds, giving rise to a 3D network.     

Astatistical aspects of the stabilities of ternary complexes of cobalt(II), nickel(II), copper(II) and zinc(II) involving aminopolycarboxylic acids and heteroaromaticN-bases as primary ligands and acetohydroxamic acid as a secondary ligand

Summary Stability constants of binary (ML, ML₂) and ternary (MAL) complexes [M=Co^II, Ni^II, Cu^II or Zn^II; A=iminodiacetic acid (ida),N-methyliminodiacetic acid (Me-ida), anthranilatediacetic acid (ada), nitrilotriacetic acid (nta), 2,2-bipyridine (bipy), orthophenanthroline (o-phen); HL =acetohydroxamic acid] have been determined at 25°C at an ionic strength of 0.1M KNO₃ by the Iriving Rossotti technique. In the case of aminopolycarboxylic acids as primary ligands, there is always a lowering of K _MAL ^MA from K _ML ^M and K ₂ ^ML while in the case of heteroaromaticN-bases as primary ligands, the values of K _MAL ^MA are very close to those of K _ML ^M . In the ternary systems studied, the values of K _MAL ^MA are in the sequence, K _M(o-phen) ^M(o-phen) >K _M(bipy)L ^M(bipy) K _M(ida)L ^M(ida) >K _M(Me-ida)L ^M(Me-ida) >K _M(nta)L ^M(nta) >K _M(ada)L ^M(ada) , while in the case of Cu^II, the values of M _M(nta)L ^M(nta) and K _M(ada)L ^M(ada) are drastically reduced compared to all other primary ligands. For aminopolycarboxylic acids, the sequence of K _MAL ^MA is opposite to those of K _MA ^M and K _MAL ^M though in the sequence of K _MA ^M , K _MAL ^M and K _MAL ^MA for A=ada and nta their relative positions are unaltered. The obtained results are explained in the light of different astatistical factors such as electrostatic effects, steric hindrance, change of effective positive charge on the central metal depending upon the -basic and -acidic character of the primary ligands.