Syntheses, structures and electrochemistry of two complexes containing quadruply bonded dimolybdenum atoms

The syntheses, electrochemistry and structures of Mo₂(O₂CCH₂-p-C₆H₄OH)₄, (1·2THF), and Mo₂(O₂CC(OH)(C₆H₅)₂)₄, (2·4THF), as determined by single-crystal X-ray diffraction, are reported. Both molecules crystallized with two axially coordinated THF molecules and 2 contained two additional THF molecules hydrogen bonded to two of the OH groups on the benzilato ligands. Complex 1 crystallized in an extended geometric arrangement involving hydrogen bonds between layers of molecules. The MoMo distance in 1 at 2.0972(8) Å is shorter than that in 2 at 2.1044(10) Å. There was also a large difference in the oxidation potentials of these two compounds with 1 and 2 exhibiting E_1/2 (ox) of 526 and 820 mV, respectively. These effects are attributed to differences in the electron donation ability in the ligands (p-hydroxy phenylacetic and benzilic acids) as assessed by their pK_a values.     

Syntheses, spectroscopies and structures of zinc complexes with malate

Reactions of zinc(II) ion with racemic malic acid (C₄H₆O₅ = H₃mal) result in the isolation of four new zinc(II) malato complexes: (NH₄)[Zn(R-H₂mal)₃] · H₂O (1), trans-[Zn(R-H₂mal)(S-H₂mal)(H₂O)₂] · 2H₂O (2), (NH₄)₂[Zn(R-Hmal)(S-Hmal)] · 2H₂O (3), and [Zn₂(R-Hmal)(S-Hmal)(H₂O)₄]_n · 2nH₂O (4). Three R-malic acids in 1 act as bidentate ligands via their alcoholic and the central carboxy groups with Zn(II) ion, leaving the terminal carboxylic acid groups free. The R- and S-malates of 2 coordinate in a bidentate manner with zinc ion in trans-form. In 3, Zn(II) ion is coordinated by R- and S-malates in a tridentate fashion via their alcoholic and two carboxy groups. Complex 4 forms a two-dimensional layered structure through the links of a new dimeric unit [Zn₂(R-Hmal)(S-Hmal)(H₂O)₄] with one of the oxygen atoms from the terminal carboxy group of malate ligand. The coordination of malates depends on pH variation, on Zn:malate ratio, and also on temperature. Tridentate chelation of malate in 3 is found between pH 4.5-9.0. The soluble monomeric species 1-3 have been investigated using ¹³C NMR spectra by long-time acquisition. The solution NMR spectra indicate that zinc malate complexes dissociate in H₂O (D₂O). Obvious downfield shifts of the central carboxy carbon atoms in 1-3 are observed compared with those of free malate, which indicate that these zinc malate complexes dissociate in aqueous solution.     

Crystal structures of valinomycin with potassium tetrachloroaurate and rubidium tetrachloroaurate with comparisons to other monovalent cation complexes

A total of 19 different crystal forms of complexes of valinomycin or its analogues with monovalent cations have been observed. The crystal structure determinations of valinomycin potassium tetrachloroaurate and valinomycin rubidium tetrachloroaurate are given here.Including this work complete structure determinations have now been published on 7 with 2 more soon to appear. Comparisons of these structural results suggest that the valinomycin complex opens at the D-valyl (lactyl) end and that contacts are possible between the complexed cation and other molecules. Such contacts may play an important part in membrane transport.     

Syntheses, reactions, and structures of osmium(II) stannyl complexes with the simple stannyl ligands SnH3, SnH2Me, and SnHMe2

Reaction between Os(SnI₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ and NaBH₄ produces the unusual, air-stable, trihydridostannyl complex, Os(SnH₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (1), which has been fully characterised including by X-ray crystal structure determination.Similarly, reaction between Os(SnI₂Me)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ or Os(SnClMe₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ and NaBH₄ produces the dihydridostannyl complex, Os(SnH₂Me)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (4) or the monohydridostannyl complex, Os(SnHMe₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (6), respectively.The SnH bonds in these complexes are reactive towards acids and in selected reactions complexes 1 and 4 with aqueous HF give Os(SnF₃)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (3) and Os(SnF₂Me)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (5), respectively, and complex 6 with aqueous HCl gives Os(SnClMe₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂.The trihydridostannyl complex 1 reacts with chloroform to form the trichlorostannyl complex, Os(SnCl₃)(κ²- S₂CNMe₂)(CO)(PPh₃)₂ (2). The crystal structures of 1-3, 5, and 6 have been determined.     

Syntheses, structures and magnetic properties of two new metal complexes based on a pyridyl-diphosphonate ligand

Two new first-raw transition metal diphosphonate complexes, namely, {[Ni₃([hpyedpH)₂(H₂O)₄]·(H₂O)₂}_n (1) and [Mn[hpyedpH₂](H₂O)]_n (2), based on a multidentate ligand 1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid (hpyedpH₄) have been synthesized under hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and element analyses. The data reveals that complex 1 is a 2D layer structure, whereas the complex 2 possesses a 1D motif. The powder X-ray diffraction (PXRD) patterns for complexes 1 and 2 were collected as well, which match well with the ones calculated from their single-crystal structure data. Magnetic measurements show that complex 1 is a ferrimagnet with T_c = 5.0 K. Magnetic studies of complex 2 indicate antiferromagnetic behavior.     

Coordination chemistry of two new tetraaza Ni(II) and Cu(II) macrocyclic and two new Co(II) and Zn(II) macroacyclic Schiff base complexes containing piperazine moiety: X-ray crystal structures of Ni(II) and Zn(II) complexes

A new potentially tetradentate (N₄) Schiff base ligand (L), 1,9,12,20-tetraazatetracyclo[18.2.2.02,7.014,19]tetracosa-2(7),3,5,8,12,14(19),15,17-octaene containing a piperazine moiety is described. Macrocyclic Schiff base complexes, [NiL](ClO₄)₂ (1) and [CuL](ClO₄)₂ (2) have been obtained from equimolar amounts of ligand (L) with nickel(II) and copper(II) metal ions. While the equilibrium reaction in the presence of cobalt(II) and zinc(II) metal ions with ligand L in a 1:1 molar ratio yielded the open-chain Schiff base complexes, [CoL′](ClO₄)₂ (3) and [ZnL′](ClO₄)₂ (4) containing two terminal primary amino groups. The ligand L′ is 1,4-bis(2-(2-aminoethyliminomethyl)phenyl)piperazine. The crystal structures of (1) and (4) have been also determined by X-ray diffraction. It was shown that the Ni(II) is coordinated to the ligand L by two nitrogen atoms of piperazine group and two nitrogen atoms of the imine groups, in a slightly distorted square-planar geometry. Also single crystal X-ray analysis of (4) confirmed a distorted octahedral arrangement in the vicinity of Zn atom with N₆ donor set. The spectroscopic characterization of all complexes is consistent with their crystal structures.     

Early transition metal complexes of dinucleating Pacman ligands: X-ray crystal structures of mixed-valence V/V complexes

The use of a Schiff-base calixpyrrole (L) as a dinucleating ligand for early transition metals is described. Salt elimination reactions between the crystallographically-characterised [K₄(THF)₃(PhMe)(L)] and titanium(III) and vanadium(III) halides form the new dinuclear complexes [(MCl)₂(L)] (M = Ti, V). Adventitious, and partial, oxidation of [(VCl)₂(L)] resulted in the formation of the unusual mixed-valence vanadyl complexes [(VO)(S)(VCl)(L)] (S = THF or pyridine), which both adopt desired Pacman geometries in the solid state in which the oxo ligand is accommodated within the dinuclear molecular cleft.     

Dioxycarbene complexes derived from reactions of tetrairidium carbonyl clusters with oxirane: X-ray crystal structures of and

Some novel cyclic-dioxycarbene derivatives of general formula (L = P^tBu₃, n = 1 (2), PPh₃: n = 1 (3), 2 (4)) and (L-L = PPh₂PCH₂PPh₂, n = 1 (5), norbornadiene, n = 1 (6) and 1,5-cyclooctadiene, n = 1 (7), 2 (8)) have been obtained by reaction of oxirane with the tetrairidium cluster derivatives [Ir₄(CO)₁₁(L)] and [Ir₄(CO)₁₀(L-L)] in the presence of bromide ion as catalyst. Elemental analysis, IR, and NMR spectra (¹H, ³¹P{¹H}, ¹³C{¹H}), and for compounds 2 and 5 also the X-ray crystal structures, were carried out for their characterisation. All the derivatives have 3 edge-bridging CO’s on the basal face of the iridium tetrahedron with non-CO ligands in axial and/or radial positions. For the mixed-ligand cluster compounds, two or three stereoisomers were observed in solution by ¹H, ³¹P and ¹³C NMR spectroscopies at low temperature. All these clusters are fluxional at room temperature.     

Synthesis and spectroscopic properties of cobalt(III) complexes of some aroyl hydrazones: X-ray crystal structures of one cobalt(III) complex and two aroyl hydrazone ligands

Cobalt(III) complexes of diacetyl monooxime benzoyl hydrazone (dmoBH₂) and diacetyl monooxime isonicotinoyl hydrazone (dmoInH₂) have been synthesized and characterized by elemental analyses and spectroscopic methods. The X-ray crystal structures of the two hydrazone ligands, as well as that of the cobalt(III) complex [Co^III(dmoInH)₂]Cl·2H₂O, are also reported. It is found that in the cobalt(III) complexes the Co(III) ion is hexa-coordinated, the hydrazone ligands behaving as mono-anionic tridentate O,N,N donors. In the [Co^III(dmoInH)₂]Cl·2H₂O complex, the amide and the oxime hydrogens are deprotonated for both the ligands, while the isonicotine nitrogens are protonated. In the [Co^III(dmoBH)₂]Cl complex, only the amide nitrogens are deprotonated. It is shown that the additional hydrogen bonding capability of the isonicotine nitrogen results in different conformation and supramolecular structure for dmoInH₂, compared to dmoBH₂, in the solid state. Comparing the structure of the [Co^III(dmoInH)₂]Cl·2H₂O with that of the Zn(II) complex of the same ligand, reported earlier, it is seen that the metal ion has a profound influence on the supramolecular structure, due to change in geometrical dispositions of the chelate rings.     

New organoantimony complexes with the isomers of chlorophenylacetic acid: Syntheses, characterizations and crystal structures of 1D polymeric chain, 2D network structure and 3D framework

A series of novel organoantimony(V) complexes have been synthesised by the reactions of the isomers of chlorophenylacetic acids with triphenylantimony(V) dichloride or tetraphenylantimony(V) bromide in 1:2 or 1:1 stoichiometries. All the complexes have been characterized by elemental analysis, IR and NMR (¹H, ¹³C) spectra analyses; furthermore, complexes 1, 2, 3 and 4 have been determined by X-ray single crystal diffraction. The structure of complexes show that the five-coordinated and six-coordinated antimony(V) atoms adopt distorted trigonal bipyramidal geometry and octahedral geometry. And the structural analyses show that complexes 1 and 3 have 2D network structures; complex 2 possesses a 1D polymeric chain structure and complex 4 has a 3D supramolecular framework.     

Syntheses, structures, and spectroscopy of mono- and polynuclear lanthanide complexes containing 4-acyl-pyrazolones and diphosphineoxide

Lanthanide coordination compounds are important due to their unique luminescence and magnetic properties. Direct synthesis of oligo- and polymeric Ln complexes with a predicted structure is hampered due to high coordination numbers and unstable coordination polyhedra. A «building blocks» strategy for the synthesis of Ln(Q)₃L polymers (Ln = Eu, Tb or Gd; HQ = 1-phenyl-3-methyl-4-RC(O)pyrazol-5-one in general, in detail HQ_S, R = thienyl; HQ_CP: R = cyclopentyl; L = bis(diphenylphosphine)methane dioxide dppMO₂, bis(diphenylphosphine)ethane dioxide dppEO₂, and bis(diphenylphosphine)butane dioxide dppBO₂) has been used: {Ln(Q)₃} mononuclear fragments have been linked by dppXO₂ bridges when X = E or B, while monomeric molecular derivatives have been isolated with dppMO₂. Eighteen new complexes were prepared, 12 of them showing a polymeric nature and 6 being monomers. Three compounds have been structurally characterized, further confirming the hypothesized connectivity where metal centers have been found to exist in LnO₈ square antiprismatic environments. Luminescence properties have been also investigated.     

Synthesis and structures of new salen complexes with bulky groups

A new series of Schiff base complexes [Fe(III), VO(II), Pd(II), Cu(II), and Ni(II)] has been developed. The ligand possesses bulky t-pentyl groups at the 3- and 5-positions. The iron (III) complex is obtained in monomeric form with a square-pyramidal configuration while the copper complex is with square-planar configuration.     

Sodium halide complexes of ribose derivatives and their unusual crystal structures

Crystalline complexes of d-ribose, d-ribono-1,4-lactone and methyl β-d-ribopyranoside with sodium halides were synthesized and some of their crystal structures determined. Crystal structures of two lactone complexes and a methyl β-d-ribopyranoside reveal the mode of the salt binding and the intricate interplay of cation coordination and hydrogen bonding in these complexes. When complexed with NaBr, the ribopyranoside is in the ¹C₄ shape whereas ribose with no salt present has the ⁴C₁ shape. It is also demonstrated that such complexes can be easily prepared in solid state reaction using a ball mill.     

Syntheses, crystal structures and properties of Cd(II) and Co(II) complexes with 4,4′-dipyridylsulfide ligand

Two new coordination polymers [Cd(dps)₂Cl₂] (1) and [Co(dps)₂(H₂O)₂]·(abs)₂(H₂O)₂ (2) (dps = 4, 4′-dipyridylsulfide, Habs = 4-amino benzenesulfonic acid) have been synthesized under similar conditions and characterized by elemental analysis, fluorescence spectra and single crystal X-ray diffraction. Compound 1 displays a dps-bridged 2D puckered, grid-like layer, which is further linked by C-H?Cl hydrogen bonds to form a 3D supramolecular architecture. Compound 2 shows a dps-bridged double-stranded chain structure, which is extended by N-H?O and O-H?O hydrogen bonds generating a 3D network. Solid-state fluorescence results reveal that both complexes can emit strong emission bands, at 467 nm and 518 nm for 1 and 344 nm for 2, respectively. Magnetic measurements show that there are weak antiferromagnetic interactions between the adjacent Co(II) ions in 2.     

Lanthanide complexes with disulfide ligand generated in situ: Syntheses, crystal structures and fluorescent properties

Five new lanthanide complexes [Ln₂(DTDN)₄(phen)₄]·7H₂O·2H₃O⁺ (Ln = Nd (1), Sm (2), Eu (3), Tb (4), Dy (5), H₂DTDN = 2,2′-dithiodinicotinic acid, phen = 1,10-phenanthroline) have been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. By in situ oxidation of 2-mercaptonanicotinic acid (2-H₂MN), the expected ligand H₂DTDN was generated. All crystals are isostructural and crystallize in monoclinic system with space group C2/c. The metal center is eight-coordinated completely by four carboxylic oxygen atoms from four different DTDN²⁻ ligands, and four nitrogen atoms from two phen molecules with a distorted square-antiprismatic geometry. The structures can be considered as two-dimensional (2D) structures and further linked by hydrogen bonds into the final trinodal 4-connected network. Photoluminescence studies revealed that complexes 2-5 exhibit strong fluorescent emission bands in the solid state at room temperature.     

Osmadisiloxane and osmastannasiloxane complexes derived from silanolate complexes of osmium(II)

Treatment of the five-coordinate chlorodimethylsilyl complex, Os(SiMe₂Cl)Cl(CO)(PPh₃)₂ with hydroxide readily produces Os(SiMe₂OH)Cl(CO)(PPh₃)₂ (1). Complex 1 is deprotonated by ^tBuLi giving the silanolate complex, Os(SiMe₂OLi)Cl(CO)(PPh₃)₂ (2), which reacts further with Me₃SiCl or Me₃SnCl to give Os(SiMe₂OSiMe₃)Cl(CO)(PPh₃)₂ (3) or Os(SiMe₂OSnMe₃)Cl(CO)(PPh₃)₂ (4), respectively. The structures of 3 and 4 have been determined by X-ray crystallography. Reaction between OsH(κ²-S₂CNMe₂)(CO)(PPh₃)₂ and HSiMe₂Cl gives Os(SiMe₂Cl)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (5). This six-coordinate chlorodimethylsilyl complex, is unreactive towards hydroxide at room temperature and at 60 °C forms Os[Si(OH)₃](κ²-S₂CNMe₂)(CO)(PPh₃)₂ (7). Complex 5 is, however, smoothly converted to the hydroxy derivative, Os(SiMe₂OH)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (6) upon chromatography on silica gel. Complex 6 is deprotonated by ^tBuLi giving the intermediate silanolate complex, Os(SiMe₂OLi)(κ²-S₂CNMe₂)(CO)(PPh₃)₂, which reacts further with Me₃SiCl to give Os(SiMe₂OSiMe₃)(κ²-S₂CNMe₂) (CO)(PPh₃)₂ (8). Crystal structure determinations for 5, 6, 7, and 8 have been obtained and structural comparisons of these related compounds are made.     

Syntheses and molecular structures of 6-halogeno-pyridin-2-olate complexes with the diruthenium(2+) core

The complexes [Ru₂(CO)₅(μ-FpyO)₂]₂ (1), [Ru₂(CO)₄(μ-ClpyO)₂]₂ (2), and [Ru₂(CO)₄(μ-BrpyO)₂]₂ (3) were prepared from Ru₃(CO)₁₂ and 6-fluoro-2-hydroxypyridine (FpyOH), 6-chloro-2-hydroxypyridine (ClpyOH) and 6-bromo-2-hydroxypyridine (BrpyOH), respectively, in hot toluene. Compounds 1-3 are coordination dimers with a cyclo-RuORuO motif. By carrying out the reaction in hot methanol, the dinuclear complexes [Ru₂(CO)₄(μ-ClpyO)₂(CH₃OH)] (4) and [Ru₂(CO)₄(μ-BrpyO)₂(CH₃OH)] (5), respectively, were obtained. Treatment of 2 and 3 with triphenylphosphane provided the complexes [Ru₂(CO)₄(μ-ClpyO)₂(PPh₃)] (6) and [Ru₂(CO)₄(μ-BrpyO)₂(PPh₃)] (7), respectively. The solid-state structures of complexes 1, 2, 4, 6, and 7 were determined by single crystal X-ray diffraction. In all cases, a head-head coordination of the two 6-halopyridinolate ligands at the core was found. In all chlorine- or bromine-containing complexes, the axial coordination site at the ruthenium atom neighbored by two Cl or Br atoms remains unoccupied due to steric shielding by the halogen atom. In the fluoropyridinolate complex 1, the same coordination site is occupied by a carbonyl ligand.     

Syntheses, crystal structures, and luminescence properties of lanthanide complexes with 5-carboxy-1-carboxymethyl-2-oxidopyridinium

Five new lanthanide complexes Ln(HL)₃(H₂O)₅ · 3H₂O (H₂L = 5-carboxy-1-carboxymethyl-2-oxidopyridinium, Ln = La (1), Sm (2), Eu (3),Tb (4), Dy (5)) have been synthesized and characterized by elemental analyses, FT-IR spectra and X-ray single crystal diffraction. All crystals are isostructural and crystallize in the triclinic space group . The metal center is nine-coordinated completely by two phenol O atoms, two chelating carboxylic O atoms from three HL ligands and five water molecules with a distorted tri-capped trigonal prismatic geometry. Photoluminescence studies revealed that complexes 2-4 exhibit strong fluorescent emission bands in the solid state at room temperature. The transition intensity varies in the order of Tb³⁺ > Dy³⁺ > Eu³⁺ > Sm³⁺.     

Syntheses and structures of some adducts of silver(I) oxyanion salts with some 2-N,O-donor-substituted pyridine bases

Syntheses and room-temperature single crystal X-ray structural characterizations are recorded for a variety of silver(I) oxyanion (perchlorate, nitrate and trifluoroacetate (‘tfa’) (increasing basicity)) adducts, AgX, with a number of pyridine (‘py’) bases, L, functionalized in the 2-position with N- or O-donor groups, namely 2-amino-, 2-amino-6-methyl-, 2-aminomethyl-, 2-hydroxy-, 2-methoxy- and 2-acetyl- pyridines, ‘2np’, ‘nmp’, ‘amp’, ‘ohp’, ‘mop’, and ‘acp’. A variety of stoichiometries and associated structural types are defined: [Ag(chelate)₂]X, L/X = amp,acp/ClO₄, [XAg(chelate)₂], L/X = acp/tfa, of 1:2 AgX:L stoichiometry; for 1:1 stoichiometry, although a discrete mononuclear complex [(chelate)Ag(O₂NO)] is defined for AgNO₃: acp (1:1), all others are polymers, successive silver atoms being linked by N,N′-bridging ligands singly (L/X = 2np/ClO₄ (?HAgHTAgTHAgH?), amp/ClO₄, NO₃ (?HTAgHTAg?) (‘H’ ≡ head, ‘T’ = tail)) or pairwise, ?L₂AgX₂AgL₂Ag? (L/X = 2np/tfa, nmp/NO₃). More complex polymeric arrays are found with L/X = ohp/NO₃, tfa, where interaction with the metal takes place via the O-donor only, the py functionality being protonated, and in adducts of more complex stoichiometry AgNO₃:mop (2:3) and AgNO₃:2np (3:4).