Unusual Magneto-Structural Features of the Halo-Substituted Materials [FeIII(5-X-salMeen)2]Y: a Cooperative [HS-HS]↔[HS-LS] Spin Transition

X-ray structures of the halo-substituted complexes [Fe^III(5-X-salMeen)₂]ClO₄ (X=F, Cl, Br, I) [salMeen=N-methyl-N-(2-aminoethyl)salicylaldiminate]at RT have revealed the presence of two discrete HS complex cations in the crystallographic asymmetric unit with two perchlorate counter ions linking them by N−H_amine⋅⋅⋅O_perchlorate interactions. At 90 K, the two complex cations are distinctly HS and LS, a rare crystallographic observation of this coexistence in the Fe^III-salRen (R=alkyl) spin-crossover (SCO) system. At both temperatures, crystal packing shows dimerization through C−H_imine⋅⋅⋅O_phenolate interactions, a key feature for SCO cooperativity. Moreover, there are noncovalent contacts between the complex cations through type-II halogen-halogen bonds, which are novel in this system. The magnetic profiles and Mössbauer spectra concur with the structural analyses and reveal 50 % SCO of the type [HS-HS]↔[HS-LS] with a broad plateau. In contrast, [Fe^III(5-Cl-salMeen)₂]BPh₄⋅2MeOH is LS and exhibits a temperature-dependent crystallographic phase transition, exemplifying the influence of lattice solvents and counter ions on SCO.     

Spin-crossover in cobalt(II) compounds containing terpyridine and its derivatives

In this review article we discuss the unique and novel magnetic properties for the cobalt(II) compounds with a variety of terpy derivatives including substituents at the 4-position. These are also compared with the unsubstituted terpy cobalt(II) complex. Since the first SCO cobalt(II) complex with terpy ligand was reported, this system has been widely studied. SCO cobalt(II) complexes possessing terpy or OH-terpy ligand reveal incomplete or gradual SCO behavior. The pyterpy-appended cobalt(II) complex shows SCO depending on the guest molecules involved. Cobalt(II) complexes with long-alkylated terpy ligands, [Co(Cn-terpy)₂](BF₄)₂ (n = 16, 14 and 12) have been synthesized and some were characterized by single crystal X-ray analysis. Furthermore, variable-temperature magnetic susceptibility indicated that the non-solvated compounds [Co(Cn-terpy)₂](BF₄)₂ (n = 16, 14 and 12) exhibit “reverse spin transition” phenomenon with wide thermal hysteresis around room temperature. In addition, the solvated compound [Co(C12-terpy)₂](BF₄)₂·EtOH·0.5H₂O shows “re-entrant SCO” behavior. The long alkyl chains in SCO cobalt(II) complexes can lead to novel physical properties resulting from a synergetic effect between SCO and response of the flexibility toward external stimuli.     

A novel two‐dimensional cobalt(II) complex composed of one‐dimensional twisted pair‐like chains: poly[[tetraaquabis(μ3‐pyridine‐2,5‐dicarboxylato‐κ4N,O2:O5:O5′)dicobalt(II)] dihydrate]

A novel neutral polymer, {[Co₂(C₇H₃NO₄)₂(H₂O)₄]·2H₂O}_n, was hydrothermally synthesized using pyridine‐2,5‐dicarboxylate (2,5‐PDC²⁻) as the organic linker. It features a two‐dimensional layer structure constructed from one‐dimensional {[Co(2,5‐PDC)₂]²⁻}_n chains interlinked by [Co(H₂O)₄]⁺ units. The two Co^II cations occupy special positions, sitting on inversion centres. Each 2,5‐PDC²⁻ anion chelates to one Co^II cation via the pyridine N atom and an O atom of the adjacent carboxylate group, and links to two other Co^II cations in a bridging mode via the O atoms of the other carboxylate group. In this way, the 2,5‐PDC²⁻ ligand connects three neighbouring Co^II centres to form a two‐dimensional network. The two‐dimensional undulating layers are linked by extensive hydrogen bonds to form a three‐dimensional supramolecular structure, with the uncoordinated solvent molecules occupying the interlamellar region.     

Organosulfonate-Modulated Spin-Crossover Behavior in Three Halogen-Functionalized Cobalt(II) Complexes

We present here the syntheses, crystal structures, and spin crossover (SCO) properties of a series of halogen-functionalized cobalt(II) complexes, [Co(Brphtpy)₂](OTf)₂ ⋅ DMF ⋅ 2H₂O ( 1 ), [Co(Brphtpy)₂](HBS)₂ ⋅ H₂O ( 2 ), [Co(Brphtpy)₂](MQ)₂ ⋅ 2MeCN ⋅ 3H₂O ( 3 ) ( Brphtpy =4′–(4-Bromophenyl)–2,2′:6′,2′′-terpyridine; OTf⁻=trifluoromethanesulfonate; HBS⁻=hydroxybenzenesulfonate dihydrate; MQ⁻=methyl orange). Variable-temperature single-crystal X-ray analyses revealed mononuclear compounds of 1 – 3 consisted of [Co(Brphtpy)₂]²⁺ SCO active units and organosulfonate anions and no structural phase transformation happened in measured high-low temperature. The packing structures of these complexes were tuned by varying organosulfonates. However, no notable supramolecular interactions can be found, in turn leading to gradual, incomplete, and non-hysteretic SCO behaviors. Interestingly, the SCO behaviors of these three complexes were significantly modified after the removal of lattice solvents. Combined structural and magnetic investigations revealed the non-cooperative supramolecular packing structures, guest internal pressure, and the small structural distortions of the SCO units should be responsible for the worse SCO properties of 1 – 3 . The foregoing results show that to achieve high-performance Co²⁺ SCO, both the weak interactions, internal pressure, and structural distortion should be considered during the design and construction of SCO complexes.     

Kalium-μ-dithio-bis(pentacyanokobaltat(III)) und Kalium-μ-diseleno-bis(pentacyanokobaltat(III))

Potassium-μ-dithio-bis(pentacyanocobaltate(III)) and Potassium-μ-diseleno-bis(pentacyanocobaltate(III)) The oxidation of [Co(CN)₅]^3? by sulfur or selenium leads to the complexes [Co₂S₂(CN)₁₀]^6? and [Co₂Se₂(CN)₁₀]^6?, respectively, which have been isolated as potassium salts K₆[Co₂S₂(CN)₁₀] · 4 H₂O and K₆[Co₂Se₂(CN)₁₀] · 5 H₂O. The μ-dithio complex has also been formed from [Co(CN)₅]^3? with polysulfide, from [CoOH(CN)₅]^3? with H₂S + O₂ and from [Co₂O₂(CN)₁₀]^6? with H₂S. As shown by their vibrational spectra the new complexes contain bridges Co? S? S? Co and Co? Se? Se? Co, respectively.     

Cyano‐bridged extended heteronuclear supramolecular architectures with hexacyano­cobalt(III) as building blocks

The cyano‐bridged heteronuclear coordination polymer poly[tris[(5,12‐dimethyl‐7,14‐diphenyl‐1,4,8,11‐tetraazacyclo­tetra­deca‐4,11‐diene)copper(II)]‐hexa‐μ‐cyano‐bis[tricyano­cobalt(III)] di­methyl­formamide solvate trihydrate], {[Cu₃Co₂(CN)₁₂(C₂₄H₃₂N₄)₃]·C₃H₇NO·3H₂O}_n, was synthesized by the assembly reaction of [CuL]²⁺ (L is 5,12‐dimethyl‐7,14‐di­phenyl‐1,4,8,11‐tetraazacyclotetradeca‐4,11‐diene) and [Co(CN)₆]³⁻ in a dimethyl­formamide–water solution. The structure consists of neutral cyano‐bridged Cu₃Co₂ units with the unique Co atom in a general position and all three Cu atoms on independent inversion centres. Each [Co(CN)₆]³⁻ ion connects three Cu^II ions via three cyano groups to form a novel cyano‐bridged two‐dimensional stair‐shaped‐layer structure. The water and dimethyl­formamide molecules are situated in the inter‐fragment spaces.     

Hexaaquacobalt(II) and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate

The title complexes, hexaaquacobalt(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Co(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (I), and hexaaquanickel(II) bis(μ‐pyridine‐2,6‐dicarboxylato)bis[(pyridine‐2,6‐dicarboxylato)bismuthate(III)] dihydrate, [Ni(H₂O)₆][Bi₂(C₇H₄NO₄)₄]·2H₂O, (II), are isomorphous and crystallize in the triclinic space group P. The transition metal ions are located on the inversion centre and adopt slightly distorted MO₆ (M = Co or Ni) octahedral geometries. Two [Bi(pydc)₂]⁻ units (pydc is pyridine‐2,6‐dicarboxylate) are linked via bridging carboxylate groups into centrosymmetric [Bi₂(pydc)₄]²⁻ dianions. The crystal packing reveals that the [M(H₂O)₆]²⁺ cations, [Bi₂(pydc)₄]²⁻ anions and solvent water molecules form multiple hydrogen bonds to generate a supramolecular three‐dimensional network. The formation of secondary Bi...O bonds between adjacent [Bi₂(pydc)₄]²⁻ dimers provides an additional supramolecular synthon that directs and facilitates the crystal packing of both (I) and (II).     

μ-Peroxodicobalt(III) complexes containing aromatic ligands

A series of new μ-peroxodicobalt(III) complexes have been prepared and characterized. Studies of the chemical and physical properties of these complexes were carried out using IR, electronic and NMR spectroscopy along with conductivity, magnetic susceptibility and thermogravimetric measurements. The complexes [Co₂(dpk·dien)₂ (dpk·H₂O)O₂] (ClO₄)₄·H₂O, [Co₂(dpk)₄(py)₂O₂](ClO₄)₄·4H₂O, [Co₂(dpk·H₂O₄(py)₂O₂] (ClO₄)₄, and [Co₂(dpk)₂(terpy)₂O₂](ClO₄)₄ were prepared by bubbling oxygen through a solution containing Co(NO₃)₂, NaClO₄, and the appropriate ligand mixture. Electronic spectral studies are consistent with the formulation as binuclear peroxo complexes. Thermogravimetric studies reveal the stoichiometric loss of O₂ and H₂O below 100°C. The auxiliary ligands, pyridine (py), diethylenetriamine (dien) and terpyridine (terpy) are lost at higher temperatures. Molar conductance of these complexes is indicative of a 4:1 electrolyte while magnetic susceptibility measurements indicate the diamagnetic character of the above four complexes. Three additional complexes of Co(II) containing di-2-pyridyl ketone (dpk) and terpy were prepared to compare spectral changes upon oxygenation.     

Trigonal Prismatic Coordination of Discrete Rare Earth Ions,Enforced by the Polyoxotungstate [P4W27O99(H2O)]16–

A family of solution-stable polyanions [Na⊂{Ln^III(H₂O)}{W^VIO(H₂O)}P^V₄W^VI₂₆O₉₈]¹²⁻ (Ln=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) represent the first examples of polyoxometalates comprising a single lanthanide(III) or yttrium(III) ion in a rare trigonal prismatic O₆ environment. Their synthesis exploits the reactivity of the organophosphonate-functionalized precursor [P₄W₂₄O₉₂(C₆H₅P^VO)₂]¹⁶⁻ with heterometal ions and yields hydrated potassium or mixed lithium/potassium salts of composition K_xLn_yH_12–x–y[Na⊂{Ln(H₂O)}{WO(H₂O)}P₄W₂₆O₉₈]⋅nH₂O⋅mLiCl (x=8.5–11; y=0–2; n=24–34; m=0–1.5). The Dy, Ho, Er and Yb derivatives are characterized by slow magnetization relaxation.     

Complexes of NS and NSO donor ligands. Nickel(II), copper(II) and cobalt(II) complexes of glyoxal bis(morpholineN-thiohydrazone) and diacetyl bis(morpholineN-thiohydrazone)

Summary Reactions of glyoxal bis(morpholineN-thiohydrazone), H₂gbmth, with NiCl₂·6H₂O, Ni(OAc)₂·4H₂O, Ni(acac)₂· H₂O, CuCl₂·2H₂O, Cu(OAc)₂·H₂O, Cu(acac)₂, CoCl₂· 6H₂O, Co(OAc)₂·4H₂O and Co(acac)₂·2H₂O yield complexes of the type [M(gbmth)], [M=Ni^II, Cu^II or Co^II]. Diacetyl reacts with morpholineN-thiohydrazide in the presence of nickel salts to yield [Ni^II(dbmth)], [Ni^II(dmth)(OAc)]H₂O and [Ni^II(Hdmth)(NH₃)Cl₂] involving N₂S₂ and NSO donor ligands. Copper and cobalt complexes of N₂S₂ and NSO donor ligands with compositions [Cu^II(dbmth)], [Co^II(dbmth)]·4H₂O and [Co^II(H₂dbmth)]Cl₂, have been isolated. The compounds have been characterised by elemental analyses, magnetic moments, molar conductance values and spectroscopic (electronic and infrared) data.     

Coordination Behavior of a D‐Penicillaminato Aurate(I) Metalloligand Toward Coblat(III) Centers

Treatment of (NH₄)[Au(D‐Hpen‐S)₂](D‐H₂pen = D‐penicillamine) with CoCl₂·6H₂O in an acetate buffer solution, followed by air oxidation, gave neutral Au^ICo^III and anionic Au^I₃Co^III₂ polynuclear complexes, [Au₃Co₃(D‐pen‐N,O,S)₆]([ 1 ]) and [Au₃Co₂(D‐pen‐N,S)₆]^3? ([ 2 ]^3?), which were separated by anion‐exchange column chromatography. Complexes [ 1 ] and [ 2 ]^3? each formed a single isomer, and their structures were determined by single‐crystal X‐ray crystallography. In [ 1 ], each of three [Au(D‐pen‐S)₂]^3?metalloligands coordinates to two Co^III ions in a bis‐tridentate‐N,O,S mode to form a cyclic Au^I₃Co^III₃ hexanuclear structure, in which three [Co(D‐pen‐N,O,S)₂]^? octahedral units and six bridging S atoms adopt trans(O) geometrical and R chiral configurations, respectively. In [ 2 ]^3?, each of three [Au(D‐pen‐S)₂]^3? metalloligands coordinates to two Co^III ions in a bis‐bidentate‐N,S mode to form a Au^I₃Co^III₂ pentanuclear structure, in which two [Co(D‐pen‐N,S)₃]^3? units and six bridging S atoms adopt ∧ and R chiral configurations, respectively.     

An Extremely Porous Hydrogen‐Bonded Framework Composed of d‐Penicillaminato CoIII2AuI3 Complex Anions and Aqua Cobalt(II) Cations: Formation and Stepwise Structural Transformation

A unique example of a hydrogen‐bonded ionic solid with a porosity of 80 %, [Co(H₂O)₆]₃[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 1 ; d ‐H₂pen=d ‐penicillamine), composed of [Co(H₂O)₆]²⁺ cations and [Co₂Au₃(d ‐pen‐N,S)₆]^3? anions, is reported. Solid 1 was kinetically produced and was then transformed stepwise into two more thermodynamically stable solids with lower porosities, [Co(H₂O)₄][Co(H₂O)₆]₂[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 2 ) and [Co(H₂O)₄]₃[Co₂Au₃(d ‐pen‐N,S)₆]₂ ( 3 ), through the coordination of the free carboxylate groups in [Co₂Au₃(d ‐pen‐N,S)₆]^3? to Co^II centers. Solids 1 – 3 were structurally characterized, and the selective adsorption of small molecules into their pores was investigated.     

Four-step spin-crossover in an oxamide-decorated metal-organic framework

Spin-crossover（SCO） complexes with multiple spin states are promising candidates for high-order magnetic storage and multiple switches. Here, by employing the N,N’-4-dipyridyloxalamide（dpo） ligand, we synthesize two Hofmann-type metal-organic frameworks（MOFs） [Fe（dpo）{Ag（CN）₂}₂]·3DMF（1） and [Fe（dpo）{Ag（CN）₂}₂]·0.5Me CN·2DEF（2）, which exhibit guest dependent four-step SCO behaviors with the sequences of LS → ～LS_2/3HS_1/3→ LS_1/2...     

The kinetics of oxidation of N(2-hydroxyethyl)ethylenediaminetriacetatocobaltate(II) by peroxodisulfate ion in aqueous acidic solutions

Summary Peroxodisulfate ion readily oxidises Co^II-YOH [YOH =N(2-hydroxyethyl)ethylenediaminetriacetate] with the formation of an intermediate complex. The kinetics of the electron-transfer step follow the rate law: Rate = 2k_HK_H[H⁺][S₂O₈]²-[Co^II-YOH]/(1 + K_H[H⁺]) where [S₂O₈]^2– is the total peroxodisulfate concentration, k_H is the rate constant for the electron-transfer process, and K_H is the pre-equilibrium protonation constant. Activation parameters have been evaluated. The intermediate, which was identified spectrophotometrically, slowly rearranges to the quinquedentate species Co(YOH)(H₂O). The rate of this rearangement has also been measured.     

Guest-Dependent Pressure-Induced Spin Crossover in FeII4[MIV(CN)8]2 (M=Mo,W) Cluster-Based Material Showing Persistent Solvent-Driven Structural Transformations

Discrete molecular species that can perform certain functions in response to multiple external stimuli constitute a special class of multifunctional molecular materials called smart molecules. Herein, cyanido-bridged coordination clusters {[Fe^II(2-pyrpy)₂]₄[M^IV(CN)₈]₂} ⋅ 4 MeOH ⋅ 6 H₂O (M=Mo ( 1 solv ), M=W ( 2 solv ) and 2-pyrpy=2-(1-pyrazolyl)pyridine are presented, which show persistent solvent driven single-crystal-to-single-crystal transformations upon sorption/desorption of water and methanol molecules. Three full desolvation–resolvation cycles with the concomitant change of the host molecules do not damage the single crystals. More importantly, the Fe₄M₂ molecules constitute a unique example where the presence of the guests directly affects the pressure-induced thermal spin crossover (SCO) phenomenon occurring at the Fe^II centres. The hydrated phases show a partial SCO with approximately two out-of-four Fe^II centres undergoing a gradual thermal SCO at 1 GPa, while in the anhydrous form the pressure-induced SCO effect is almost quenched with only 15 % of the Fe^II centres undergoing high-spin to low-spin transition at 1 GPa.     

Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated RuIII(bpy)33+ Oxidant

The cobalt substituted polyoxotungstate [Co₆(H₂O)₂(α-B-PW₉O₃₄)₂(PW₆O₂₆)]¹⁷⁻ ( Co6 ) displays fast electron transfer (ET) kinetics to photogenerated Ru^III(bpy)₃³⁺, 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II) −OH ₂ and Co6(II) −OH, respectively, whose speciation in aqueous solution is associated to a pK_a of 7.6), and generates a Co(III)−OH moiety ( Co6(III) −OH), as proven by transient absorption spectroscopy; (ii) at pH>pK_a, the Co6(II) −OH→Ru^III(bpy)₃³⁺ ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH <pK_a, the process involves Co6(II) − OH₂ → Co6(III)−OH transformation and proceeds via a multiple-site, concerted proton electron transfer (CPET) where water assists the transfer of the proton, as proven by the absence of effect of buffer base concentrations on the rate of the ET and by a H/D kinetic isotope in a range of 1.2–1.4. The reactivity of water is ascribed to its organization on the surface of the polyanionic scaffold through hydrogen bond networking involving the Co(II)−OH₂ group.     

Experimental and Theoretical Study of the Features of Zinc(II) and Cadmium(II) Complexation with the Substituted closo-Hydridoborate Anion [2-B10H9(OH)]2−

Herein, we studied the experimental and theoretical foundations of the process of zinc(II) and cadmium(II) complexation with 2-hydroxido-nonahydrido-closo-decaborate(2−) anion [2-B₁₀H₉(OH)]²⁻ in the presence of azaheterocyclic ligands L (L=2,2′-bipyridyl (bipy), 1,10-phenanthroline (phen), and 2,2′-bipyridylamine (bpa)), which can be used as model system for obtaining complexes with the required composition and structure. The first examples of mixed-ligand Zn(II) and Cd(II) complexes with [2-B₁₀H₉(OH)]²⁻ coordinated by the metal atom were isolated selectively. The structures of zinc(II) complexes [Zn(bipy)₂(2-B₁₀H₉(OH)-κ²H¹,O)] ⋅ 2CH₃CN ( 1 ⋅ 2CH₃CN) and [Zn(phen)₂(2-B₁₀H₉(OH)-κ²H⁹,O)] ⋅ 2CH₃CN ( 2 ⋅ 2CH₃CN), as well as two cadmium(II) bond isomers [Cd(bipy)₂(2-B₁₀H₉(OH)-κ²H¹,O)] ( 4 a ) and [Cd(bipy)₂(2-B₁₀H₉(OH)-κ²H⁹,H¹⁰)] ( 4 b ) bound into a dimeric pair in the complex [Cd(bipy)₂(2-B₁₀H₉(OH))] ( 4 ), and cadmium(II) complex [Cd(bpa)₂(2-B₁₀H₉(OH)-κ²H⁷,H¹⁰)] ( 7 ) were solved by single-crystal X-ray diffraction (XRD). Density functional theory (DFT) calculations show that for cadmium(II) the formation of both multicenter BH−Cd−HB and BO(H)−Cd−HB bonds is equally probable. The affinity of zinc(II) for oxygen leads to preferential formation of complexes via BO(H)−Zn−HB bonds than BH−Zn−HB bonds. The M−B(H) bonding was found to be presumably electrostatic in nature, which could be the reason of topological isomerism of zinc(II) and cadmium(II) decaborates.     

Two new cobalt(II) fumarates and a redetermination of tetraaquacobalt(II) fumarate monohydrate

Poly[triaqua‐μ₄‐fumarato‐cobalt(II)], [Co(C₄H₂O₄)(H₂O)₃]_n, (I), contains two symmetry‐independent octahedrally coordinated Co²⁺ ions, both on inversion centers. One Co²⁺ ion is coordinated by two water molecules and four fumarate dianions, whereas the other Co²⁺ ion is surrounded by four water molecules and two fumarate dianions. Each fumarate dianion is bonded to three Co²⁺ ions, leading to a two‐dimensional structure. The fumarate dianions are nonplanar; the angle between the planes of the two carboxylate groups is 54.9 (2)°. The cobalt(II) fumarate layers are connected by hydrogen bonding into a three‐dimensional network. Compound (I) is not isostructural with calcium(II) fumarate trihydrate [Gupta et al. (1972). Acta Cryst. B 28 , 135–139]. In poly[μ₄‐fumarato‐dimethanolcobalt(II)], [Co(C₄H₂O₄)(CH₄O)₂]_n, (II), the Co²⁺ ions are octahedrally coordinated by four fumarate dianions and two methanol molecules, leading to a three‐dimensional structure. The fumarate group is planar. The Co²⁺ ions and the fumarate dianions both lie on inversion centers. Additionally, the one‐dimensional structure of catena‐poly[[[tetraaquacobalt(II)]‐μ₂‐fumarato] monohydrate], {[Co(C₄H₂O₄)(H₂O)₄]·H₂O}_n, (III), was redetermined at a higher resolution, and the space group C2/c was confirmed.     

Synthesis of Functionalized Heteroleptic Germylene Alkoxides

N-coordinated Ge(II) alkoxides L¹(tBuO)Ge ( 1 ), L²(tBuO)Ge ( 2 ) and [L²(OtBu)Ge ⋅ BH₃] ( 4 ) were prepared. Effect of either chelating ligands L¹ and L² or Ge→B interaction on strength of the Ge−OtBu bond was studied by insertion reaction of PhNCO. As a result, the Ge(II) carbamate L²{[(tBuO)OC](Ph)N}Ge ( 3 ) was isolated. Alcoholysis exchange reactions of 1 and 2 with substituted phenols were studied to find an easy synthetic protocol for a synthesis of functionalized Ge(II) alkoxides. Reactions yielded Ge(II) alkoxides L^1,2(2-Br−C₆H₄O)Ge ( 5 for L¹, 8 for L²), L^1,2(2-MeNH−C₆H₄O)Ge ( 6 for L¹, 9 for L²), L^1,2(2-Ph₂P−C₆H₄O)Ge ( 7 for L¹, 10 for L²), L²(2-Br-3-OH−C₆H₃O)Ge ( 11 ) and L²(2-NC₅H₄O)Ge ( 12 ) containing the additional polar groups Y (Y=Br, MeNH, PPh₂, OH or N). Finally, phosphane decorated Ge(II) alkoxides 7 and 10 were tested as suitable ligands in reactions with (COD)W(CO)₄ and BH₃. As a consequence, new complexes [(κ²- 7 )W(CO)₄] ( 13 ) and [L¹(2-Ph₂P ⋅ {BH₃}-C₆H₄O)Ge ⋅ {BH₃}] ( 14 ) were isolated. All compounds were characterized by NMR and IR spectroscopy, and compounds 3 , 4 , 9 and 11 were additionally characterized by X-ray diffraction analysis.     

tris-(Benzimidazol-2-yl-methyl)-amine as a Versatile Building Block in Ru(II) Polypyridyl Chemistry

Summary.  tris-(Benzimidazol-2-yl-methyl)-amine, H₃ ntb, was prepared and used in the synthesis of dinuclear Ru(II) polypyridyl and polynuclear Ru(II)–Co(III) complexes of the type [Ru₂(H₂ ntb) (bpy)₄]³⁺, [Ru₂(Hntb)(phen)₄]²⁺, [(Ru₂(H₂ ntb)(bpy)₄)₂Co(en)₂]⁹⁺, and [(Ru₂(Hntb)(phen)₄)₂ Co(en)₂]⁷⁺ (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, en = 1,2-diaminoethane). The complexes were characterized by elemental analysis as well as spectroscopic and redox data. The luminescent properties of the complexes were also studied. The complexes showed significant antitumour and anti-HIV activities. Received May 9, 2001. Accepted (revised) June 7, 2001