Communication of metal ions in the dinuclear ruthenium complexes containing 4,4′-bipyridine, 1,4-diisocyanobenzene, and pyrazine bridging ligands: Synthesis, characterization and structure determination

Reaction of [Ru(2,2′-bipyridine)(2,2′:6′,2″-terpyridine)Cl]PF₆ (abbreviated to [Ru(bipy)(terpy)Cl]PF₆) with 0.5 equiv of the bidentate ligand L produces the dinuclear complexes [{Ru(bipy)(terpy)}₂(μ-L)](PF₆)₄ (L = 4,4′-bipyridine 1, 1,4-diisocyanobenzene 2 and pyrazine 3) in moderate yields. Treating [Ru(bipy)(terpy)Cl]PF₆ with equal molar of 1,4-diisocyanobenzene affords [Ru(bipy)(terpy)(CNC₆H₄NC)](PF₆)₂ (2a). These new complexes have been characterized by mass, NMR, and UV-Vis spectroscopy, and the structures of 1-3 determined by an X-ray diffraction study. Cyclic voltammetric studies suggest that metal communication between the two ruthenium ions increases from 1 to 2 to 3.     

Synthesis, characterization, interaction with DNA and cytotoxicity in vitro of dinuclear Pd(II) and Pt(II) complexes dibridged by 2,2'-azanediyldibenzoic acid

The dinuclear complexes [Pd₂(L)₂(bipy)₂] (1), [Pd₂(L)₂(phen)₂] (2), [Pt₂(L)₂(bipy)₂] (3) and [Pt₂(L)₂(phen)₂] (4), where bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline and L = 2,2′-azanediyldibenzoic dianion) dibridged by H₂L ligands have been synthesized and characterized. The binding of the complexes with fish sperm DNA (FS-DNA) were investigated by fluorescence spectroscopy. The results indicate that the four complexes bound to DNA with different binding affinity, in the order complex 4 > complex 3 > complex 2 > complex 1, and the complex 3 binds to DNA in both coordination and intercalative mode. Gel electrophoresis assay demonstrates the ability of the complexes to cleave the pBR 322 plasmid DNA. The cytotoxic activity of the complexes was tested against four different cancer cell lines. The four complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate.     

Syntheses, spectroscopic properties and crystal structures of two organoruthenium (II) complexes of bipyridines: [{Cp*Ru(2,2′-bipy)}2(μ-Cl)][PF6] and [{(η-p-cymene)Ru}2(μ-OH)2(4,4′-bipy)]2[BF4]4

Interaction of [Cp*RuCl(μ-Cl)]₂ with 2,2′-bipyridine (2,2′-bipy) in the presence of Na[PF₆] gave a chloride bridging dinuclear complex [{Cp*Ru(2,2′-bipy)}₂(μ-Cl)][PF₆] (1). In the crystal structure, the cation [{Cp*Ru(2,2′-bipy)}₂(μ-Cl)]⁺ contains a bent Ru-Cl-Ru linkage with an angle of 141.87(12)°. The tris(μ-hydroxo)diruthenium complex [{(η⁶-p-cymene)Ru}₂(μ-OH)₃][BF₄] in acetone solution was treated by 4,4′-bipyridine (4,4′-bipy) to give a hydroxo-bridged tetranuclear complex [{(η⁶-p-cymene)Ru}₂(μ-OH)₂(μ-4,4′-bipy)]₂[BF₄]₄ (2). Complex 2 consists of four (η⁶-p-cymene)Ru moieties connected by two 4,4′-bipy and four hydroxo-bridging groups, forming a novel metallomacrocycle with alternating hydroxyl and 4,4′-bipy bridges between the ruthenium atoms. Spectroscopic properties along with electrochemistry of two organoruthenium (II) complexes 1 and 2 are reported.     

Cobalt(II) and nickel(II) coordination polymers constructed from P,P′-diphenylmethylenediphosphinic acid (H2pcp) and 4,4′-bipyridine (bipy): Structural isomerism in [Co(pcp)(bipy)0.5(H2O)2]

The P,P′diphenylmethylenediphosphinic acid (H₂pcp) reacts with Co(ClO₄)₂ · 6H₂O and 4,4′-bipyridine to give a mixture of two polymeric isomers of formula [Co(pcp)(bipy)_0.5(H₂O)₂], {red (1) and pink (2)} and the new violet hybrid [Co(Hpcp)₂] (3). The pure red and violet species have been obtained by the reaction of H₂pcp with Co(CH₃COO)₂ · 4H₂O and bipy or with Co(ClO₄)₂ · 6H₂O, respectively. The analogous reaction of Ni(CH₃COO)₂ · 4H₂O or Ni(ClO₄)₂ · 6H₂O with H₂pcp and bipy affords only the [Ni(pcp)(bipy)_0.5(H₂O)₂] species (4). The two cobalt isomers present different structural arrangements. Whereas the red isomer (1) shows an undulated 2D layered structure, the pink one (2) forms an infinite monodimensional strand. Both the architectures extend to higher dimensions through hydrogen bonding interactions. The nickel derivative is isomorphous with the red cobalt isomer. The violet [Co(Hpcp)₂] (3), which is isomorphous with the complexes of the reported series [M(Hpcp)₂], M = Ca(II), Mg(II), presents a monodimensional polymeric structure. Compounds 1 and 4 show a very similar thermal behaviour, the two water molecules being lost in the temperature range 25-150 and 160-320 °C, respectively. Temperature dependent X-ray powder diffractometry (TDXD) has been performed on compound 1 in order to follow the structural transformations that occur during the heating process.     

Synthesis, properties and crystal structures of new binuclear lead(II) complexes based on phenyl, naphthyl-containing fluorine β-diketones and substituted 2,2′-bipyridines

Four lead(II) complexes with substituted 2,2′-bipyridine adducts and β-diketonates ligands, [Pb(5,5′-dm-2,2′-bpy)(tfpb)₂]₂1, [Pb(4,4′-dmo-2,2′-bpy)(tfpb)₂]₂2, [Pb(4,4′-dm-2,2′-bpy)(tfnb)₂]₂3 and [Pb(5,5′-dm-2,2′-bpy)(tfnb)₂]₂4, (“4,4′-dm-2,2′-bpy”, “5,5′-dm-2,2′-bpy”, “4,4′-dmo-2,2′-bpy”, “Htfpb” and “Htfnb” are the abbreviations of 4,4′-dimethyl-2,2′-bipyridine, 5,5′-dimethyl-2,2′-bipyridine, 4,4′-dimethoxy-2,2′-bipyridine, 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, respectively) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy and also studied by thermal and electrochemical as well as X-ray crystallography. The supramolecular features in these complexes are guided/controlled by weak directional intramolecular interactions.     

Formation and structural chemistry of the unusual cyanide-bridged dinuclear species [Ru2(NN)2(CN)7] (NN = 2,2′-bipyridine or 1,10-phenanthroline)

Crystallisation of simple cyanoruthenate complex anions [Ru(NN)(CN)₄]²⁻ (NN = 2,2′-bipyridine or 1,10-phenanthroline) in the presence of Lewis-acidic cations such as Ln(III) or guanidinium cations results, in addition to the expected [Ru(NN)(CN)₄]²⁻ salts, in the formation of small amounts of salts of the dinuclear species [Ru₂(NN)₂(CN)₇]³⁻. These cyanide-bridged anions have arisen from the combination of two monomer units [Ru(NN)(CN)₄]²⁻ following the loss of one cyanide, presumably as HCN. The crystal structures of [Nd(H₂O)_5.5][Ru₂(bipy)₂(CN)₇] · 11H₂O and [Pr(H₂O)₆][Ru₂(phen)₂(CN)₇] · 9H₂O show that the cyanoruthenate anions form Ru-CN-Ln bridges to the Ln(III) cations, resulting in infinite coordination polymers consisting of fused Ru₂Ln₂(μ-CN)₄ squares and Ru₄Ln₂(μ-CN)₆ hexagons, which alternate to form a one-dimensional chain. In [CH₆N₃]₃[Ru₂(bipy)₂(CN)₇] · 2H₂O in contrast the discrete complex anions are involved in an extensive network of hydrogen-bonding involving terminal cyanide ligands, water molecules, and guanidinium cations. In the [Ru₂(NN)₂(CN)₇]³⁻ anions themselves the two NN ligands are approximately eclipsed, lying on the same side of the central Ru-CN-Ru axis, such that their peripheries are in close contact. Consequently, when NN = 4,4′-^tBu₂-2,2′-bipyridine the steric bulk of the t-butyl groups prevents the formation of the dinuclear anions, and the only product is the simple salt of the monomer, [CH₆N₃]₂[Ru(^tBu₂bipy)(CN)₄] · 2H₂O. We demonstrated by electrospray mass spectrometry that the dinuclear by-product [Ru₂(phen)₂(CN)₇]³⁻ could be formed in significant amounts during the synthesis of monomeric [Ru(phen)(CN)₄]²⁻ if the reaction time was too long or the medium too acidic. In the solid state the luminescence properties of [Ru₂(bipy)₂(CN)₇]³⁻ (as its guanidinium salt) are comparable to those of monomeric [Ru(bipy)(CN)₄]²⁻, with a ³MLCT emission at 581 nm.     

A new moisture-sensitive metal-coordination solids {[Cd(C4O4)(bipy)(H2O)2] · 3H2O}∞ (bipy=4,4-bipyridine)

A new mixed-ligands metal-coordination polymer, [Cd(C₄O₄)(bipy)(H₂O)₂] (1), (bipy=4,4^′-bipyridine), was synthesized under hydrothermal condition and characterized by X-ray diffraction method. A three-dimensional interpenetrating network with one-dimensional channels intercalating water molecules undergoes a reversible hydration-dehydration process upon a cooling-heating cycles associated with distinct color change and structural variation.     

Structures and magnetic property studies of four copper(II) and nickel(II) supramolecular complexes derived from diphenic acid constructed by C-H?π and π-π interactions

Four one-dimensional metal-organic polymers derived from diphenic acid (H₂dpa) were synthesized in the presence of auxiliary ligands, [Cu(dpa)CH₃OH](1), [Ni(dpa)CH₃OH] (2), [Cu(bipy)₂(Hdpa)₂(H₂O)₂] (3) and [Ni(bipy)₂(Hdpa)₂(H₂O)₂] (4) (bipy = 4, 4′-bipyridine). The dinuclear paddle-wheel second building units (SBUs) constructed by four dpa²⁻ ligands in complexes 1 and 2 are linked by dpa²⁻ into double chains, which are connected by C-H?π interactions forming a two-dimensional rhombic porous structure. In complexes 3 and 4, the metal ions are connected by bipy ligands, and the grid-like network was formed with the π-π interactions between the adjacent phenyl rings of Hdpa⁻. For 1 and 2, there are strong antiferromagnetic interactions within Cu-Cu and Ni-Ni dimers. It is also strong antiferromagnetic interactions between the dimmers of Cu₂ in 1, while it is weaker of those of Ni₂ in 2. Weaker antiferromagnetic interactions exist among Cu-Cu and Ni-Ni in 3 and 4, in which bipy is the effective coupling media. Thermally gravimetric analyses and differential thermal analyses indicate that the four complexes are all thermal stable.     

Synthesis, characterization and properties of series coordination polymers constructed from a biphenyl dicarboxylate and nitrogen-containing mixed ligands

A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H₂dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co₂(dpa)₂(4,4′-bpy)₂(H₂O)]_n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]_n (2) and discrete complexes [Co₂(dpa)₂(2,2′-bpy)₂(H₂O)₂] (3), [Co₃(dpa)₃(1,10′-phen)₆(H₂O)₂] (4), [Cd(dpa)(1,10′-phen)₂][(H₂dpa)₂(H₂O)₂] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.     

A systematic study on the thermal decomposition reactions of coordination polymers based on metal(II) selenocyanates and 4,4′-bipyridine: Directed synthesis of a μ-1,3 bridging selenocyanate

Reaction of manganese(II), iron(II), cobalt(II) and nickel(II) selenocyanate with 4,4′-bipyridine (bipy) in water at room temperature leads to the formation of the ligand-rich 1:2 hydrates [{M(bipy)(NCSe)₂(H₂O)₂}·bipy]_n (bipy = 4,4′-bipyridine) with M = Mn (1-Mn), Fe (1-Fe), Co (1-Co) and Ni (1-Ni). In their crystal structures, the metal cations are coordinated by two terminally N-bonded selenocyanato anions, two water molecules, and two bridging bipy ligands in an octahedral coordination mode. These building blocks are connected into linear M-bipy-M chains, which are further linked by hydrogen bonds between the water molecules and non-coordinated bipy ligands into layers. On heating these precursor compounds, they decompose into ligand-rich 1:2 anhydrates [M(NCSe)₂(bipy)₂]_n with M = Mn (2-Mn), Fe (2-Fe), Co (2-Co) and Ni (2-Ni). After water removal the coordination spheres of the metal cations are completed by N-coordination of the bipy ligand which formerly was involved in OH···N hydrogen bonding. On further heating, the manganese(II) compound loses half of its bipy ligands leading to a new ligand-deficient 1:1 intermediate [Mn(NCSe)₂(bipy)]_n (3-Mn) with μ-1,3-bridging selenocyanato anions. In contrast, all other compounds decompose without the formation of ligand-deficient intermediates. These structural changes are accompanied with a dramatic change in their magnetic properties: Whereas all ligand-rich 1:2 compounds 1-M and 2-M (M = metal) show only Curie-Weiss paramagnetism, in the ligand-deficient 1:1 intermediate 3-Mn an antiferromagnetic long-range ordering at T_N = 10.5 K is found. The thermal and magnetic properties are qualitatively compared with those of the related ligand-rich and ligand-deficient selenocyanato and thiocyanato compounds based on bipy, pyrazine and pyrimidine as ligand.     

Synthesis, crystal structures, and characterization of three coordination compounds constructed from 4-sulfophthalic acid ligand

Three new coordination compounds with 4-sulfophthalic acid (H₃SPA) ligand, namely {[Pb₃(4-SPA)₂(H₂O)](H₂O)}_n (1), [Mn(4,4′-bpy)₂(H₂O)₄][Mn₂(4-SPA)₂-(4,4′-bpy)₄(H₂O)₄]·7.5(H₂O) (2) and Cu₂(4-HSPA)₂(2,2′-bpy)₂(H₂O)₂ (3) (4,4′-bpy = 4,4′-bipyridine and 2,2′-bpy = 2,2′-bipyridine), have been synthesized. The structures exhibit different dimensionality depending on the nature of the metal ions and/or the ancillary ligands. Compound 1 has a 2D layered architecture constructed from one-dimensional inorganic lead(II) oxygen chains containing tetranuclear [Pb₄(μ₂-O)₄] cluster. Compound 2 has a dinuclear manganese [Mn₂(4-SPA)₂(4,4′-bpy)₄(H₂O)₄] motif charged with mononuclear [Mn(4,4′-bpy)₂(H₂O)₄]²⁺ cation. Compound 3 is a discrete dinuclear copper(II) structure that linked by extensive hydrogen bonds to form a three-dimensional supramolecular structure. In the solid state, compound 1 exhibits blue photoluminescence with the maximum at 432 nm upon excitation at 350 nm. The temperature-dependent magnetic susceptibility data of 2 have been investigated. The Curie constant C and Weiss constant θ are 3.14 emu K mol⁻¹ and −2.09 K, respectively, revealing antiferromagnetically magnetic interactions between the Mn²⁺ ions. In addition, these compounds are characterized by powder X-ray diffraction, IR, elemental analysis, and thermogravimetric analysis.     

A Co-monosubstituted Keggin polyoxometalate with an antenna ligand and three cobalt(II) chains as counterion

A Co-monosubstituted Keggin polyoxometalate with an antenna ligand linked to the Co(II) center with a Co(II)-containing cation has been prepared. The title compound, formulated as {Co(H₂O)₄(4,4′-bpy)}₂(4,4′-Hbpy)₂[SiW₁₁Co(4,4′-bpy)O₃₉] · 5H₂O (1) (4,4′-bpy = 4,4′-bipyridine), was synthesized and characterized by elemental analysis, IR spectra, TG analysis, X-ray single crystal structure analysis and magnetic measurements. As far as we know, the title compound represents the first Co(II) substituted Keggin polyoxometalate with an antenna ligand structurally and magnetically characterized.     

Artificial photosynthesis based on dye-sensitized nanocrystalline TiO2 solar cells

A new series of amphiphilic heteroleptic ruthenium(II) sensitizers [Ru(H₂dcbpy)(dhbpy)(NCS)₂] (C1), [Ru(H₂dcbpy)(bccbpy)(NCS)₂] (C2), [Ru(H₂dcbpy)(mpubpy)(NCS)₂] (C3), [Ru(H₂dcbpy)(bhcbpy)(NCS)₂] (C4) have been synthesized and fully characterized by UV-Vis, emission, NMR and cyclic voltammetric studies (where dhbpy = 4,4′-dihexyl-2,2′-bipyridine, bccbpy = 4,4′-bis(cholesteroxycarbonyl)-2,2′-bipyridine, mpubpy = 4-methyl-4′-perfluoro-1H,1H,2H,2H,3H,3H-undecyl-2,2′-bipyridine, bhcbpy = 4,4′-Bis(hexylcarboxamido)-2,2′-bipyridine). The amphiphilic amide heteroleptic ruthenium(II) sensitizers, self-assembled on TiO₂ surface from ethanol solution, reveal efficient sensitization in the visible window range yielding ≈80% incident photon-to-current efficiencies (IPCE). Under standard AM 1.5 sunlight, the C4 sensitizer gave 15 mA/cm² short circuit photocurrent density, 0.66 fill factor and an open circuit voltage of 0.75 V, corresponding to an overall conversion efficiency of 7.4%.     

Fluorous interactions in complexes of lead(II) hexafluoroacetylacetonate

Structure determinations for 2,2′-bipyridine and 1,10-phenanthroline adducts of lead(II) hexafluoroacetylacetonate, [Pb(bipy)₂(hfacac)₂] (1), [Pb(bipy)(hfacac)₂] (2), and [Pb(phen)(hfacac)₂] (3), show that the balance of intermolecular forces within the lattices is seemingly sensitive to the adduct stoichiometry but not to the nature of the heteroaromatic base. In 3, a structure, in which there is an apparent preference for CF/aromatic interactions over separate CF/CF and aromatic/aromatic interactions, is essentially identical at both 120 and 293 K.     

Coordination compounds of tetrazolate-5-carboxylate with cobalt(II): Synthesis, structure and magnetic properties

Four coordination compounds of tetrazolate-5-carboxylate (tzc) with cobalt(II), [Co₂(tzc)₂(H₂O)₆]·2H₂O (1), [Co₂(tzc)₂(phen)₂(H₂O)₂]·2H₂O (2), [Co₂(tzc)₂(2,2′-bpy)₂(H₂O)₂]·H₂O (3), and [Co(tzc)(4,4′-bpy)] (4), where phen = 1,10-phenanthroline, 2,2′-bpy = 2,2′-bipyridyl, and 4,4′-bpy = 4,4′-bipyridyl, have been synthesized by the hydrothermal methods involving the in situ generation of the ligand from sodium ethyl tetrazolate-5-carboxylate. Compounds 1, 2 and 3 all contain dinuclear molecules in which metal ions are linked by the double N-N bridges from two tzc ligands in the μ₂-N₁,O₁:N₂ mode, and the dinuclear molecules are associated into 3D architecture through extensive hydrogen bonding and π-π stacking interactions in various fashions. Compound 4 exhibits a two-dimensional layer structure in which Co(tzc) chains with μ₃-N₁,O₁:O₁:N₂ tzc are cross-linked by 4,4′-bpy. Magnetic investigations on 1-3 revealed intramolecular ferromagnetic coupling through the double N-N bridges with intermolecular ferromagnetic or antiferromagnetic interactions. The interaction through the mixed N-N and μ₂-O_carboxylate bridges in 4 is antiferromagnetic.     

Syntheses, structures, and magnetic properties of heterobimetallic Fe2M (M = Cu, Mn) chains based on tetracyanometallic building block

Using the tetracyanometalate precursor [Fe(4,4′-dmbipy)(CN)₄]^- (4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine) as the building block, two new cyano-bridged one-dimensional heterobimetallic coordination polymers, [M(CH₃OH)₂Fe₂(4,4′-dmbipy)₂(CN)₈]_n (M = Cu, 1; Mn, 2), have been synthesized and structurally characterized. X-ray crystallography reveals that complexes 1 and 2 consist of heterobimetallic chains of squares, and the central M^II ion is six-coordinated as an elongated distorted octahedral geometry. Magnetic studies show ferromagnetic coupling between Fe^III and Cu^II ions in complex 1. Complex 2 exhibits ferrimagnetic behavior caused by the noncompensation of the local interacting spins (S_Mn = 5/2 and S_Fe = 1/2), which interact antiferromagnetically through bridging cyanide groups. magpack program has been employed to investigate the magnetic nature of squares chain structure.     

Ligand-directed metal(II) coordination polymers: Unusual disorder, and photoluminescence

2,6-Dimethyl-4-phenylpyridine-3,5-dicarboxylic acid (H₂mppdc, H₂L) is firstly employed in coordination chemistry. Two metal-organic coordination polymers with a general formula of M₂L₂(4,4′-bpy)_x(H₂O)_4−2x (M = Zn or Co, x = 1 or 2) are assembled from H₂L, 4,4′-bipyridine, zinc and cobalt salt under hydrothermal conditions, and characterized by single-crystal X-ray diffraction analyses. Of the crystal structures of title compounds, L ligands, limited in the environment from 4,4′-bipyridine, array in head-to-head and head-to-tail modes which are corresponding to the 1D (1) and 3D (2) polymeric structures, respectively. Interesting disorders occur in the crystal lattice of compound 1. And compound 2 has a 3D 4² · 6¹⁰ · 8³ topology. Solid-state H₂L and 1 have expected photoluminescence at room temperature.     

The key role of hydrogen bonding in the nuclearity of three copper(II) complexes with hydrazone-derived ligands and nitrogen donor heterocycles

Three new Cu(II) complexes of formula [Cu(L¹)(pyz)(CH₃OH)]ClO₄ (1), [Cu(L¹)(4,4′-bpy)(ClO₄)]·0.5H₂O (2) and [{Cu(L²)(ClO₄)}₂(μ-4,4′-bpy)] (3) have been synthesised by using pyrazine (pyz) and 4,4′-bipyridine (4,4′-bpy) and tridentate O,N,O-donor hydrazone ligands, L¹H and L²H, obtained by the condensation of 1,1,1-trifluoro-2,4-pentanedione with salicyloylhydrazide and benzhydrazide, respectively. The ligands and their complexes have been characterized by elemental analyses, FT-IR, and UV-Vis spectroscopies. Single crystal X-ray structure analysis evidences the metal ion in a slightly deformed square pyramidal geometry in all the complexes. However complexes 1 and 2 are mononuclear with pyz and 4,4′-bpy, respectively, showing an unusual monodentate behavior, while complex 3 is dinuclear with 4,4′-bpy adopting the typical bridging coordination mode. Self assembly of the complex units by hydrogen bonding interactions produces one-dimensional arrangement in each crystal packing. The magnetic characterization of complex 3 indicates a weak antiferromagnetic exchange interaction between the Cu(II) ions (J = −0.96 cm⁻¹) mediated through the long 4,4′-bpy bridge. Electrochemical behavior of the complexes is also discussed.     

Substitution reactions of tetrahydrofuran in [Cr(thf)3Cl3] with mono and bidentate N-donor ligands: X-ray crystal structures of [Cr(bipy)(OH2)Cl3] and [HpyNH2][Cr(bipy)Cl4]

Substitution of thf ligands in [Cr(thf)₃Cl₃] and [Cr(thf)₂(OH₂)Cl₃] was investigated. 2,2′-Bipyridine (bipy) was reacted with [Cr(thf)₃Cl₃] to form [Cr(bipy)(thf)Cl₃] (1), which was subsequently reacted with water to give [Cr(bipy)(OH₂)Cl₃] (2). Reaction of 1 with acetonitrile (CH₃CN), pyridine (py) and pyridine derivatives to form [Cr(bipy)(L)Cl₃] (L = CH₃CN 3, py 4 and 4-pyR with R = NH₂5, Bu^t6 and Ph 7). In addition, the substitution of bipy in [Cr(thf)₃Cl₃] was followed by ¹H NMR spectroscopy at room temperature, which showed completion of the reaction in ca. 100 min. Complex 2 was characterised by single crystal X-ray diffraction. The theoretical powder diffraction pattern of 2 was compared to the experimentally obtained powder X-ray diffraction pattern, and shows excellent agreement. The dimer [Cr₂(bipy)₂Cl₄(μ-Cl)₂] was cleaved asymmetrically to give the anionic complex [Cr(bipy)Cl₄]⁻ (8) and [Cr(bipy)₂Cl₂]⁺ (9). Complexes 8 and 9 were characterised by single crystal X-ray diffraction.     

Preparation and characterization of macrocyclic dinickel complexes coligated by monoalkyl- and dialkylcarbamates

The dinuclear nickel(II) complex [Ni₂L(Cl)]⁺ (1), where (L)²⁻ represents a 24-membered binucleating hexamine-dithiophenolate ligand, reacts readily with primary and secondary amines RR′NH in the presence of CO₂ (1 bar) to give dinuclear monoalkyl- and dialkylcarbamate complexes [Ni₂L(O₂CNRR′)]⁺ (R = H, R′ = CH₂Ph (2), R = H, R′ = n-Bu (3), R = H, R′ = n-Oct (4), R = H, R′ = CH₂CH₂OH (5), R = R′ = Et (6), and R = R′ = CH₂CH₂OH (7)). Complexes 2-7 can also be prepared by the reaction of 1 with CO₂(air)/amine. The carbamate complexes are hydrolyzed in methanolic solution to give the known alkylcarbonate complex [Ni₂L(O₂COMe)]⁺ (8). These conversions are less rapid than the transesterification reactions of 8, due to a less electron-demanding carboxyl C(carbamate) atom. All new complexes were either isolated as perchlorate or tetraphenylborate salts and fully characterized by elemental analysis, UV/Vis, and IR spectroscopy. The structures of 2[BPh₄] and 7[BPh₄] have also been determined by X-ray crystallography. They confirm the presence of μ_1,3-bridging alkylcarbamate units in the products.