Metallkomplexe mit biologisch wichtigen Liganden. CLXVI Metallkomplexe mit Ferrocenylmethyl‐L‐cysteinat und 1,1′‐Ferrocenylbis‐(methyl‐L‐cysteinat) als Liganden

Metal Complexes of Biologically Important Ligands. CLXVI Metal Complexes with Ferrocenylmethylcysteinate and 1,1′‐Ferrocenylbis‐(methylcysteinate) as Ligands A series of complexes of transition metal ions ( Cr³⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ ) and of lanthanide ions ( La³⁺, Nd³⁺, Gd³⁺, Dy³⁺, Lu³⁺ ) with the anions of ferrocenylmethyl‐L‐cysteine [(C₅H₅)Fe(C₅H₄CH(R)SCH₂CH(NH₃⁺)CO₂^?] (L¹) and with the dianions of 1,1′‐ferrocenylbis(methyl‐L‐cysteine) [Fe(C₅H₄CH(R)SCH₂CH(NH₃⁺) CO₂^?)₂] (R = H, Me, Ph) (L²) as N,O,S‐donors were prepared. With the monocysteine ferrocene derivative L¹ as ligands complexes [M^IIL¹₂] or [Cr^IIIL¹₂]Cl type complexes are formed whereas the bis(cysteine) ligand L² yields insoluble complexes of type [ML²]_n, presumably as coordination polymers. The magnetic moments of [Mn^IIL²]_n, [Pr^IIIL²]_n(OH)_n and [Dy^IIIL²]_n(OH)_n exhibit “normal” paramagnetism.     

Synthesis, Spectral and Thermal Analyses of Novel Bi- and Polyhomonuclear Complexes of Pyrimidine Bisazo-dianil Derivatives

Seven new bi‐ and polyhomonuclear transition metal complexes with three polyhydroxlated bisazodianil ligands were synthesized and characterized. The ligands were derived from condensation of 6‐(5‐formyl‐2‐hydroxyphenylazo)‐2,4‐dihydroxypyrimidine with aliphatic diamines (H₈L¹, H₈L² and H₆L³). The data of elemental and thermal analyses, molar conductance measurement, IR, electronic and ESR spectra as well as magnetic moment measurements support the formation of [L¹Co₇Cl₆(H₂O)₁₀]·22H₂O ( 1 ), [H₂L²Mn₆Cl₆(H₂O)₈]·3H₂O·2EtOH ( 3 ), [L²Co₈Cl₈(H₂O)₁₂]·24H₂O ( 4 ), [H₄L³Co₂Cl₂(H₂O)₂]·8H₂O·2EtOH ( 6 ) with a tetrahedral geometry and [H₂L¹Ni₅Cl₄(H₂O)₁₆]·19H₂O·EtOH ( 2 ), [L²Ni₈Cl₈(H₂O)₂₈]·8H₂O·EtOH ( 5 ) with an octahedral geometry while [H₆L³Cu₃(H₂O)₇]Cl₃·10H₂O ( 7 ) has a distorted tetrahedral arrangement. The mode of bonding between the metal ions and the ligand molecules is determined and the metal‐metal interaction was studied. The activation thermo‐kinetic parameters for the thermal decomposition steps of the complexes E*, ΔH*, ΔS*, and ΔG* were calculated.     

[Ni(cod)2][Al(ORF)4], a Source for Naked Nickel(I) Chemistry

The straightforward synthesis of the cationic, purely organometallic Ni^I salt [Ni(cod)₂]⁺[Al(OR^F)₄]⁻ was realized through a reaction between [Ni(cod)₂] and Ag[Al(OR^F)₄] (cod=1,5‐cyclooctadiene). Crystal‐structure analysis and EPR, XANES, and cyclic voltammetry studies confirmed the presence of a homoleptic Ni^I olefin complex. Weak interactions between the metal center, the ligands, and the anion provide a good starting material for further cationic Ni^I complexes.     

Revisit of trinickel metal string complexes [Ni3L4X2] (L = dipyridylamido,diazaphenoxazine; X = NCS,CN) for quantum transport

Metal string complexes contain a linear metal‐atom chain in which the metal centers are coordinated by four equatorial and two axial ligands. With a variety of transition‐metal elements and ligands, the structural framework drives the flourishing of molecular design and properties. The one‐dimensional configuration makes the compounds suitable for the studies of quantum transport across molecular junctions. In this study, we report the conductance measurements and transmission spectra of three trinickel metal strings, [Ni₃(dpa)₄(NCS)₂] ( 1 ), [Ni₃(dzp)₄(NCS)₂] ( 2 ), and [Ni₃(dpa)₄(CN)₂] ( 3 ) (Hdpa = dipyridylamine, Hdzp, diazaphenoxazine) in which 1 is a prototypical compound, dzp of 2 represents an equatorial ligand more rigid than dpa of 1 , and ─CN is an axial ligand with a ligand‐field effect stronger than ─NCS of 1 . Measurement results of molecular junctions for 1 , 2 , and 3 are 2.69, 3.24, and 17.4 MΩ, respectively. The highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps calculated by density functional theory in the gas phase for 1 , 2 , and 3 are about 2.65, 2.34, and 3.85 eV, respectively. Zero‐bias transmission spectra of 1 – 3 show that transmission peaks lie just above E_Fermi (the Fermi energy of the gold electrode), suggesting LUMO‐dominant transport pathways. The transmission peaks at E_Fermi are associated with LUMO+2 found in the gas phase. LUMOs in the free space are located at nearly 1 eV below E_Fermi. The shift of molecular orbitals from their isolated form and the alignment of LUMO+2 with the electrode Fermi level manifest the importance and significant of the electrodes' self‐energy on electron transport.     

A mass spectrometry and DFT study of pyrithione complexes with transition metals in the gas phase

2‐Mercaptopyridine N ‐oxide (pyrithione, PTOH) along with several transition metal ions forms coordination compounds displaying notable biological activities. Gas‐phase complexes formed between pyrithione and manganese (II), cobalt (II), nickel (II), copper (II), and zinc (II) were investigated by infusion in the electrospray source of a quadrupole‐time of flight mass spectrometer. Remarkably, positive ion mode spectra displayed the singly charged metal adduct ion [C₁₀H₈MN₂O₂S₂]²⁺ ([M(PTO)₂]^+• or [M(DPTO)]^+•), where DPTO is dipyrithione, 2,2′‐dithiobis(pyridine N ‐oxide), among the most abundant peaks, implying a change in the oxidation state of whether the metal ion or the ligands. In addition, doubly charged ions were recognized as metal adduct ions containing DPTO ligands, [M(DPTO)_n]²⁺. Generation of [M(PTO)₂]^+• / [M(DPTO)]^+• could be traced by CID of [M(DPTO)₂]²⁺, by observation of the sequential losses of a charged (PTO⁺) and a radical (PTO^•) deprotonated pyrithione ligand. The fragmentation pathways of [M(PTO)₂]^+• / [M(DPTO)]^+• were compared among the different metal ions, and some common features were noticed. Density functional theory (DFT) calculations were employed to study the structures of the observed adduct ions, and especially, to decide in the adduct ion [M(PTO)₂]^+• / [M(DPTO)]^+• whether the ligands are 2 deprotonated pyrithiones or a single dipyrithione as well as the oxidation state of the metal ion in the complex. Characterization of gas‐phase pyrithione metal ion complexes becomes important, especially taking into account the presence of a redox‐active ligand in the complexes, because redox state changes that produce new species can have a marked effect on the overall toxicological/biological response elicited by the metal system.     

Synthesis,Structure, and Cyclic Voltammetric Property of Metal String Complex [Ni3(dpa)4(ClO4)(Cl)]·CH2Cl2

The metal string complex [Ni₃(dpa)₄(ClO₄)(Cl)] · CH₂Cl₂ ( 1 ) [dpa = bis(2‐pyridyl)amine] with different axial ligands was synthesized and characterized by elemental analysis, IR, UV/Vis, and fluorescence spectroscopy and TG analysis. The molecular structure was determined by single‐crystal X‐ray analysis and its electrochemical properties were investigated. This metal string complex is the first example with different axial ligands, and in its structure a different structural packing relative to the metal string complex [Ni₃(dpa)₄(Cl)₂] ( 2 ) with two axial chloride ligands is generated. The intense C–H ··· π interactions observed for 1 provide additional stability. The axial mono‐substitution of Cl^– by ClO₄^– in 1 relative to 2 results in one obviously short Ni–Ni distance and a higher stability towards oxidation.     

Mono-Sulfonated Derivatives of Triphenylphosphine, [NH4]TPPMS and M(TPPMS)2 (TPPMS = P(Ph)2(m-C6H4SO− 3); M = Mn2+, Fe2+, Co2+ and Ni2+). Crystal Structure Determinations for [NH4][TPPMS]·½H2O, [Fe(H2O)5(TPPMS)]TPPMS, [Co(H2O)5TPPMS]TPPMS and [Ni(H2O)6](TPPMS)4·H2O

Preparation of the ammonium salt of TPPMS, [NH₄]TPPMS, TPPMS = PPh₂(m-C₆H₄SO^? ₃), greatly enhances water solubility and provides an efficient route to other metal complexes of TPPMS, M(TPPMS)₂ M = Mn²⁺, Co²⁺, Fe²⁺ and Ni²⁺. For Co²⁺ and Fe²⁺ the metal has an octahedral ligand environment with five water molecules and one TPPMS coordinated through the sulfonate oxygen; the second TPPMS is not coordinated. For Ni²⁺ the octahedral coordination sphere is composed of water molecules and the TPPMS ligands are not coordinated. Structures are fully reported for [NH₄]TPPMS·½H₂O and [Fe(H₂O)₅(TPPMS)]TPPMS and partially reported for [Co(H₂O)₅TPPMS]TPPMS and [Ni(H₂O)₆]TPPMS₂·H₂O. All of the structures show hydrophobic regions consisting of aromatic rings and hydrophilic regions with hydrogen-bonding interactions.     

[2+2+2] Cycloisomerisation of Aromatic Cyanodiynes in the Synthesis of Pyridohelicenes and Their Analogues

We have developed a methodology for the synthesis of pyridohelicenes and their analogues based on the Ni⁰‐, Co^I‐ or Rh^I‐mediated intramolecular [2+2+2] cycloisomerisation of cyanodiynes. It allows for folding the linear precursors into the corresponding helical backbones comprising the newly formed pyridine unit in their central part. Along with racemic pyrido[n]helicenes (n=5,6,7) and their derivatives, both enantio‐ and diastereomerically pure pyrido[n]helicene‐like molecules (n=5,6) were prepared by employing the chiral substrate‐controlled cyclisation of the corresponding enantiopure cyanodiynes.     

Solvent‐Dependent Self‐Assembly Behaviour and Speciation Control of Pd6L8 Metallo‐supramolecular Cages

The C₃‐symmetric chiral propylated host‐type ligands (±)‐tris(isonicotinoyl)‐tris(propyl)‐cyclotricatechylene ( L1 ) and (±)‐tris(4‐pyridyl‐4‐benzoxy)‐tris(propyl)‐cyclotricatechylene ( L2 ) self‐assemble with Pd^II into [Pd₆L₈]¹²⁺ metallo‐cages that resemble a stella octangula. The self‐assembly of the [Pd₆( L1 )₈]¹²⁺ cage is solvent‐dependent; broad NMR resonances and a disordered crystal structure indicate no chiral self‐sorting of the ligand enantiomers in DMSO solution, but sharp NMR resonances occur in MeCN or MeNO₂. The [Pd₆( L1 )₈]¹²⁺ cage is observed to be less favourable in the presence of additional ligand, than is its counterpart, where L=(±)‐tris(isonicotinoyl)cyclotriguaiacylene ( L1 a ). The stoichiometry of reactant mixtures and chemical triggers can be used to control formation of mixtures of homoleptic or heteroleptic [Pd₆L₈]¹²⁺ metallo‐cages where L= L1 and L1 a .     

Tuning the Chirality of Block Copolymers: From Twisted Morphologies to Nanospheres by Self‐Assembly

New advances into the chirality effect in the self‐assembly of block copolymers (BCPs) have been achieved by tuning the helicity of the chiral‐core‐forming blocks. The chiral BCPs {[N?P(R)‐O₂C₂₀H₁₂]_200?x[N?P(OC₅H₄N)₂]_x}‐b‐ [N?PMePh]₅₀ ((R)‐O₂C₂₀H₁₂=(R)‐1,1′‐binaphthyl‐2,2′‐dioxy, OC₅H₄N=4‐pyridinoxy (OPy); x=10, 30, 60, 100 for 3 a – d , respectively), in which the [N?P(OPy)₂] units are randomly distributed within the chiral block, have been synthesised. The chiroptical properties of the BCPs ([α]_D vs. T and CD) demonstrated that the helicity of the BCP chains may be simply controlled by the relative proportion of the chiral and achiral (i.e., [N?P(R)‐O₂C₂₀H₁₂] and [N?P(OPy)₂], respectively) units. Thus, although 3 a only contained only 5 % [N?P(OPy)₂] units and exhibited a preferential helical sense, 3 d with 50 % of this unit adopted non‐preferred helical conformations. This gradual variation of the helicity allowed us to examine the chirality effect on the self‐assembly of chiral and helical BCPs (i.e., 3 a – c ) and chiral but non‐helical BCPs (i.e., 3 d ). The very significant influence of the helicity on the self‐assembly of these materials resulted in a variety of morphologies that extend from helical nanostructures to pearl‐necklace aggregates and nanospheres (i.e., 3 b and 3 d , respectively). We also demonstrate that the presence of pyridine moieties in BCPs 3 a – d allows specific decoration with gold nanoparticles.     

Reactions of (imidazol-2-ylidene)silver(I) chlorides with group 4 metal containing Lewis acids

The reactivity of the monomeric N-heterocyclic carbene silver(I) complexes, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene-silver(I) chloride ([Ag(IMes)Cl], 1) and 1,3-bis-(4-bromo-2,6-dimethylphenyl)imidazol-2-ylidene-silver(I) chloride ([Ag(IMes^Br)Cl], 2), toward the group 4 metal containing Lewis acids, TiCl₄ and (η⁵-C₅H₅)ZrCl₃, in dichloromethane was investigated. Instead of the expected transfer of the N-heterocyclic carbene to the Lewis acidic metal centers with accompanying precipitation of AgCl, chloride transfer occurred leading to the formation of the salts, [Ag(IMes)₂]⁺[(TiCl₃)₂(μ₂-Cl)₃]⁻ (3) and [Ag(IMes^Br)₂]⁺[{(η⁵-C₅H₅)ZrCl}₂(μ₂-Cl)₃]⁻ (4). The structure of the [Ag(IMes^Br)₂]⁺ cation in 4 is significantly distorted in the solid state by interactions between the para-Br atoms of the IMes^Br ligands and chloride ligands of the anions.     

Rational Construction of Polymeric Cadmium(II) Benzimidazole for Transition Metal Ion Exchange

A 1D double‐helical coordination polymer {[Cd(pbbm)₂]₂(ClO₄)₄(H₂O)₂}_n ( 1 ) was successfully constructed by the reaction of Cd(ClO₄)₂ · 6H₂O with 1,1′‐(1,5‐pentanediyl)bis‐1H‐benzimidazole (pbbm). Interestingly, polymer 1 exhibits highly selective capacity for the ionic exchange of Zn²⁺ and Cu²⁺ over Co²⁺ and Ni²⁺ ions in the crystalline solid state when the crystals of 1 are immersed in the aqueous solutions of the perchlorate salts of Cu²⁺, Zn²⁺, Co²⁺, and Ni²⁺ ions, respectively, which indicates that central Cd^II ion exchange might be considered as being dominated by the coordination ability of metal ions to free functional groups, ionic radii of exchanged metal ions, and the solution concentration of adsorbed metal salts. The parent material‐ and ion‐exchange‐induced products are identified by FT‐IR spectroscopy, PXRD patterns as well as SEM and EDS measurements. In addition, the thermal stability of 1 was also investigated.     

Synthesis, characterization and liquid–liquid extraction properties of new methoxyaminobiphenylglyoxime derivatives and their complexes with some transition metals

In this study, three new aminobiphenylglyoximes, [L¹H₂] N-(2-methoxy)aminobiphenylglyoxime, [L²H₂] N-(3-methoxy)aminobiphenylglyoxime and L[³H₂] N-(4-methoxy)aminobiphenylglyoxime have been synthesized by the reaction of (E,E)-4′-biphenylchloroglyoxime with 2-Methoxyaniline, 3-Methoxyaniline and 4-Methoxyaniline in absolute ethanol. The preparation Ni^II, Co^II and Cu^II complexes of these ligands are described. The ligands and their complexes were characterized by elemental analyses, IR, mass, H¹ and ¹³C NMR spectra, thermogravimetric analyses (t.g.a) and magnetic susceptibility measurements. Ligands complexing properties were studied by the liquid–liquid extraction of selected alkali (Li⁺, Na⁺, K⁺, Cs⁺) and transition metals (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺). It has been observed that all ligands show a high affinity to Cu²⁺ ions, whereas almost no affinity to alkali metals. The extraction equilibrium constants (K _ex) for complexes of ligands with Cu²⁺ metal picrates between dichloromethane and water have been determined at 25°C.     

Trinuclear Double Helicates of Iron(II) and Nickel(II): Self-assembly and resolution into helical enantiomers

The synthesis of the linear tris[terpyridine] 1 with three tridentate binding sites is described. The reaction with metal ions of octahedral coordination geometry, such as Fe^II or Ni^II, leads to the self-assembly of trinuclear complexes [M₃( 1 )₂]⁶⁺, which display properties in agreement with a double helical structure. The trinuclear iron (II) helicate has been resolved into its enantiomers.     

Dimorphic Modification of the Trinuclear Nickel(II) Complex [Ni3(NCS)6(pdz)6]: Synthesis,Crystal Structure,Thermal, Magnetic and Spectroscopic Properties

Reaction of nickel(II) thiocyanate and pyridazine (pdz) as organic spacer ligand leads to the formation of the ligand‐rich 1:2 (1:2 = metal to ligand ratio) trinuclear nickel(II) complex of composition [Ni₃(NCS)₆(pdz)₆]. Depending on the reaction solvent, different polymorphic modifications are obtained: Reaction in acetonitrile leads to the formation of the new modification 1I and reaction in ethanol leads to the formation of modification 1II reported recently. In their crystal structures discrete [Ni₃(NCS)₆(pdz)₆] units are found, in which each of the Ni²⁺ cations exhibits a NiN₆ distorted octahedral arrangement. The central Ni²⁺ cation is coordinated by four bridging pdz ligands and two thiocyanato anions in trans positions. Both thiocyanato anions exhibit the end‐on bridging mode. The peripheral Ni²⁺ cations are bridged by one thiocyanato anion and by two pdz ligands with the central Ni²⁺ cation. Further they are coordinated by two terminal N‐bonded thiocyanato anions and one terminal N‐bonded pdz ligand. The structure of 1I was determined by X‐ray single crystal structure investigation and emphasized by infrared spectroscopy. Magnetic measurements revealed a quasi Curie behavior with net ferromagnetic interactions for 1I and net antiferromagnetic interactions for 1II . Solvent‐mediated conversion experiments clearly show that modification 1I represents the thermodynamic most stable form at room temperature and that modification 1II is metastable. On thermal decomposition, both modification transform quantitatively in a new ligand‐deficient intermediate. Elemental analysis revealed a 3:4 compound of composition [Ni₃(NCS)₆(pdz)₄]. A structure model supported by IR spectroscopic investigations was assumed, in which three coordination modes of the thiocyanato anion exist, resulting in a 2D polymeric network.     

Synthesis and study of the structure of new 3d-metal coordination compounds with substituted 2-amino-4(5H)-ketothiophens

A series of new 3d-metal complexes based on 2-amino-3-(1-methylbenzimidazol-2-yl)-4(5H)-ketothiophen (HL¹) and 2-amino-3-(2-benzothiazolyl)-4(5H)-ketothiophen (HL²) were synthesized. Compounds of the general formulas [ML₂] and [M(HL¹)₂Cl₂] (where M = Co²⁺, Ni²⁺, Zn²⁺, Cu²⁺) were prepared by the reaction of the above mentioned ligands with the corresponding acetate (for [ML₂]) or chloride (for [M(HL¹)₂Cl₂]) salts in a methanol or a methanol–chloroform medium. The choice of the anion in the initial metal salt, as well as the selection of the ligand, is crucial for obtaining coordination compounds with a neutral or deprotonated form of the 2-amino-4(5H)-ketothiophens. Thus, in contrast to HL¹, complexes with the neutral form of HL² cannot be obtained under the same conditions. All the complexes were studied by spectroscopic methods and X-ray crystallography (for [CuL¹₂] · H₂O). The coordination polyhedron of the copper atom is formed by four nitrogen atoms from two ligand anions and the geometry of the coordination sphere is intermediate between tetrahedral and square-planar.     

Redox non-innocence of thioether crowns: spectroelectrochemistry and electronic structure of formal nickel(III) complexes of aza-thioether macrocycles

The Ni^II complexes [Ni([9]aneNS₂‐CH₃)₂]²⁺ ([9]aneNS₂‐CH₃=N‐methyl‐1‐aza‐4,7‐dithiacyclononane), [Ni(bis[9]aneNS₂‐C₂H₄)]²⁺ (bis[9]aneNS₂‐C₂H₄=1,2‐bis‐(1‐aza‐4,7‐dithiacyclononylethane) and [Ni([9]aneS₃)₂]²⁺ ([9]aneS₃=1,4,7‐trithiacyclononane) have been prepared and can be electrochemically and chemically oxidized to give the formal Ni^III products, which have been characterized by X‐ray crystallography, UV/Vis and multi‐frequency EPR spectroscopy. The single‐crystal X‐ray structure of [Ni^III([9]aneNS₂‐CH₃)₂](ClO₄)₆?(H₅O₂)₃ reveals an octahedral co‐ordination at the Ni centre, while the crystal structure of [Ni^III(bis[9]aneNS₂‐C₂H₄)](ClO₄)₆?(H₃O)₃? 3H₂O exhibits a more distorted co‐ordination. In the homoleptic analogue, [Ni^III([9]aneS₃)₂](ClO₄)₃, structurally characterized at 30 K, the Ni? S distances [2.249(6), 2.251(5) and 2.437(2) Å] are consistent with a Jahn–Teller distorted octahedral stereochemistry. [Ni([9]aneNS₂‐CH₃)₂](PF₆)₂ shows a one‐electron oxidation process in MeCN (0.2 M NBu₄PF₆, 293 K) at E_1/2=+1.10 V versus Fc⁺/Fc assigned to a formal Ni^III/Ni^II couple. [Ni(bis[9]aneNS₂‐C₂H₄)](PF₆)₂ exhibits a one‐electron oxidation process at E_1/2=+0.98 V and a reduction process at E_1/2=?1.25 V assigned to Ni^II/Ni^III and Ni^II/Ni^I couples, respectively. The multi‐frequency X‐, L‐, S‐, K‐band EPR spectra of the 3+ cations and their 86.2 % ⁶¹Ni‐enriched analogues were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6 %, 42.8 % and 37.2 % Ni character in [Ni([9]aneNS₂‐CH₃)₂]³⁺, [Ni(bis[9]aneNS₂‐C₂H₄)]³⁺ and [Ni([9]aneS₃)₂]³⁺, respectively, consistent with DFT calculations, and reflecting delocalisation of charge onto the S‐thioether centres. EPR spectra for [⁶¹Ni([9]aneS₃)₂]³⁺ are consistent with a dynamic Jahn–Teller distortion in this compound.     

Efficient Synthesis and Properties of Single‐Crystalline [SnTe4]4− Salts

Single‐crystalline K⁺, Rb⁺, and Cs⁺ salts of the ortho‐tellurostannate anion have been prepared by a very efficient fusing/extraction/evaporation method. The resulting compounds with the general composition [A₄(H₂O)_n][SnTe₄] can be transferred into mixed H₂O/en solvates by solving the hydrates in 1,2‐diaminoethane (en) and ensuing layering by toluene. A mixed Rb⁺/Ba²⁺ salt results from a partial cation exchange of the Rb⁺ hydrate phase in solution. All hydrates react to polytellurides when exposed to air and represent useful starting materials for the synthesis of transition metal complexes with [SnTe₄]^4? groups as binary main group elemental ligands. [K₄(H₂O)_0.5][SnTe₄] ( 1 ), [Rb₄(H₂O)₂][SnTe₄] ( 2 ), [Cs₄(H₂O)₂][SnTe₄] ( 3 ), [K₄(H₂O)(en)][SnTe₄] ( 4 ), [Rb₄(H₂O)_0.67(en)_0.33][SnTe₄] ( 5 ), [Cs₄(H₂O)_0.5(en)_0.5][SnTe₄] ( 6 ), and [Rb₂Ba(H₂O)₁₁][SnTe₄] ( 7 ) were characterized by means of X‐ray diffractometry and optical absorption spectroscopy.     

Reactivity of [Ni(cod)2][Al(ORF)4] towards Small Molecules and Elements

To provide a better understanding of the recently published pure metalorganic Ni^I species, [Ni(cod)₂][Al(OR^F)₄] ( 1 ) [cod = 1,5‐cyclooctadiene, R^F = C(CF₃)₃], further characterizations were performed and analyzed. Thus, the solvation of 1 in THF was examined by EPR, surprisingly disclosing the initiation of a disproportionation reaction to [Ni^II(THF)₆][Al(OR^F)₄]₂ ( 3 ) and Ni⁰. Further studies concerning the ability of 1 to activate small molecules exhibit the formation of a remarkable [Ni₃S₂(cod)₃]²⁺ cluster ( 5 ) in an oxidation reaction with S₈, while EPR measurements of the resulting product in a reaction with oxygen indicate a possible coordination of O₂. Single crystal X‐ray structures as well as spectroscopic analyses of 3 and 5 are described.     

A mononuclear complex and a cubane cluster from the initial use of 2-(hydroxymethyl)pyridine in nickel(II) carboxylate chemistry

The reactions of 2-(hydromethyl)pyridine, hmpH, with Ni(O₂CMe)₂·4H₂O in H₂O, in the absence of counterions, have been investigated. The synthetic study has led to the two new complexes [Ni(O₂CMe)₂(hmpH)₂] (1) and [Ni₄(O₂CMe)₄(hmp)₄(H₂O)₂] (2). Complex 1 can also be transformed into 2 by reacting with an excess of NaOH in H₂O. The structures of 1 and 2·2.25H₂O·0.5(1,4-dioxane) have been solved by single-crystal, X-ray crystallography. The octahedral Ni^II center in centrosymmetric 1 is coordinated by two 1.10 (Harris notation) MeCO₂⁻ groups and two N,O-chelating (1.11) hpmH ligands. The tetranuclear cluster molecule of 2·2.25H₂O·0.5(1,4-dioxane) possesses a distorted cubane {Ni₄(μ₃-OR′)₄}⁴⁺ core [R′ = (2-pyridyl)CH₂–] with the Ni^II ions and the oxygen atoms from the 3.31 hmp⁻ ligands occupying alternate vertices of the cube. Two 2.11 MeCO₂⁻ groups cap two opposite faces of the cube, while two 1.10 MeCO₂⁻ ions and two aqua ligands complete the octahedral coordination sphere of the metal centers. Characteristic IR bands for the two complexes are discussed in terms of the nature of bonding and the structures of the two complexes. The variable-temperature magnetic properties of 2 have been modeled with two J values, and reveal antiferromagnetic exchange interactions between the four Ni^II ions to give a diamagnetic ground state.