Novel seven coordination geometry of Sn(IV): crystal structures of phthalocyaninato bis(undecylcarboxylato)Sn(IV), its Si(IV) analogue, and phthalocyaninato bis(chloro)silicon(IV). The electrochemistry of the Si(IV) analogue and related compounds

Three newly elucidated crystal structures of group IV phthalocyaninato complexes are reported, along with data for two further SiPc carboxylate complexes. In one of these crystal structures, bis(undecylcarboxylate)Sn(IV) phthalocyanine, the tin ion is seven coordinate, which is a unique finding for this atom in phthalocyanine ring coordination. Comparison of these structures with other group IV phthalocyaninato and related structures reveals differences, illustrating features significant in the chemistries of Si(IV) and Sn(IV) ions. These differences are thought to originate from their differing sizes and polarizabilities. The structures show that the Sn(IV) ion can only occupy an in-plane location in the phthalocyaninato ring where it elongates toward the two axial ligands. When the axial ligands do not facilitate this elongation cis coordination is preferred and the Sn(IV) ion sits above the phthalocyaninato ring plane. In contrast, the Si(IV) structures, with smaller, harder (i.e., less polarizable) Si(IV) ions, are six coordinate with the Si(IV) ion in the phthalocyaninato ring plane in a distorted octahedral symmetry. The electronic spectra and cyclic voltammetry of some of the Si compounds indicate that on the electrode the oxidized/reduced species behave as though they are in a solid film, rather than a soluble freely diffusing species.     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

Trimethylphosphine complexes of tungsten(O) and (IV). X-ray crystal structures of trimethylphosphine tris (phenylacetylene) tungsten(O); bis(trimethylphosphine) tetrakis (methylisocyanide) tungsten(O), and oxodichlorotris (trimethylphosphine) tungsten (IV)

The reduction of WCl₄(PMe₃)₃ by sodium amalgam in presence of phenylacetylene gives W(PMe₃)(PhCCH)₃ (A). Reduction in presence of methylisocyanide gives W(PMe₃)₂(MeNC)₄ (B), while in presence of excess PMe₃ in tetrahydrofuran under hydrogen, WH₂Cl₂(PMe₃)₄ (C) is formed. The reaction of WCl₂(PMe₃)₄ with methanol in tetrahydrofuran gives mixtures of WH₂Cl₂(PMe₃)₄ and WOC1₂(PMe₃)₃ (D).The structures of A, B, and D have been determined by X-ray diffraction.     

Synthesis,characterization, electrochemical and crystal structure investigation of bis(2-((2-aminoethylimino)methyl)-6-methoxyphenolato) cobalt(III)

The mononuclear cobalt(III) complex [Co(L)₂]Cl ·?H₂O (1) (where L is H₂N(CH₂)₂N=CC₆H₃(OMe)(O^?)) has been prepared and characterized by IR, UV-Vis spectroscopy, conductivity measurements, elemental analysis, TGA, cyclic voltammetry and an X-ray structure determination. The cobalt(III) coordination sphere in [Co(L)2] is cis-CoN₄O₂ with the NNO ligands. Electrochemical studies of 1 using cyclic voltammetry indicate an irreversible cathodic peak (E _pc, ca ?0.60 V) corresponding to reduction of cobalt(III) to cobalt(II).     

Synthesis, X-ray structure, electrochemistry, and theoretical studies of palladium(II) complex with a tetradentate bis(quinoline-2-carboxamide) ligand

The title complex [Pd(Me₂bqb)] (1), [Me₂bqb^2?C?=?1,2-bis(quinoline-2-carboxamide)-4,5-dimethyl-benzene dianion], has been synthesized and characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structure of [Pd(Me₂bqb)] has been determined by X-ray crystallography. The complex exhibits distorted square-planar PdN4 coordination geometry with two short and two long Pd?CN bonds (Pd?CN ~1.957 and ~2.095 ?, respectively). In addition to the molecular geometry from X-ray experiment, theoretical studies have been carried out on the structure of the complex at the density functional theory (DFT-B3LYP) level in conjunction with effective core potential basis set (LANL2DZ) for Pd atom and 6-311++G(d,p) basis set for N, O, C and H atoms. Electrochemical studies in CH₂Cl₂ solution revealed A reversible redox process corresponding to the Pd^II/Pd^III couple with E _1/2 at 0.924?V (vs. SCE).     

Synthesis and X-ray crystal structures of bis(3-hydroxy-4-methyl-2(3H)-thiazolethiolato-S 2,O)bis(dimethylsulfoxide-O)M,M = cobalt(II) and nickel(II)

Crystallisation of the divalent nickel and cobalt complexes of 3-hydroxy-4-methyl-2(3H)-thiazolethione (HMTT) from DMSO yields isostructural chelate complexes M(MTT)₂(dmso)₂, M = Co^II/Ni^II. The metal atom adopts distorted octahedral coordination via two bidentate MTT ligands arranged in a trans-conformation and two DMSO molecules coordinated through oxygen. Powder X-ray diffraction (PXRD) and energy-dispersive X-ray (EDX) analysis show that the materials form a continuous solid solution Co _x Ni_1–x (MTT)₂(dmso)₂ over the entire composition range 0 x 1.     

Ruthenium(III)-Phthalocyanine: Darstelllung und Eigenschaften von Di(halogeno)phthalocyaninato(1−)ruthenium(III), [Ru(X)2Pc] (X = Cl,Br, I)

Ruthenium(III) Phthalocyanines: Synthesis and Properties of Di(halo)phthalocyaninato(1?)ruthenium(III) Di(halo)phthalocyaninato(1?)ruthenium(III), [Ru(X)₂Pc^?] (X = Cl, Br, I) is prepared by oxidation of [Ru(X)₂Pc^2?]^? (Cl, Br, OH) with halogene in dichloromethane. The magnetic moment of [Ru(X)₂Pc^?] is 2,48 μ_B (X = Cl) resp. 2,56 μ_B (X = Br) in accordance with a systeme of two independent spins (low spin Ru^III and Pc^?: S = 1/2). The optical spectra of the red violet solution of [Ru(X)₂Pc^?] (Cl, Br) are typical for the Pc^? ligand with the “B” at 13.5 kK, “Q₁” at 19.3 kK and “Q₂ region” at 31.9 kK. Sytematic spectral changes within the iron group are discussed. The presence of the Pc^? ligand is confirmed by the vibrational spectra, too. Characteristic are the metal dependent bands in the m.i.r. spectra at 1 352 and 1 458 cm^?1 and the strong Raman line at 1 600 cm^?1. The antisymmetric Ru? X stretch (v_as(Ru? X)) is observed at 189 cm^?1 (X = I) resp. 234 cm^?1 (X = Br). There are two interdependent bands at 295 and 327 cm^?1 in the region expected for v_as(Ru? Cl) attributed to strong interaction of v_as(Ru? Cl) with an out-of-plane Pc^? tilting mode of the same irreducible representation. Only the symmetric Ru? Br stretch at 183 cm^?1 is selectively enhanced in the resonance-Raman(RR) spectra. The Raman line at 168 cm^?1 of the diiodo complex is assigned to loosely bound iodine. The broad band at 978 cm^?1 in the RR spectra of the dichloro complex is due to an intraconfigurational transition within the electronic ground state of low spin Ru^III split by spin orbit coupling.     

Darstellung und spektroskopische Charakterisierung von Di(halogeno)phthalocyaninato(1–)rhodium(III), [RhX2Pc1−] (X = Cl,Br, I)

Synthesis and Spectroscopical Characterization of Di(halo)phthalocyaninato(1–)rhodium(III), [RhX₂Pc^1?] (X = Cl, Br, I) Bronze-coloured di(halo)phthalocyaninato(1–)-rhodium(III), [RhX₂Pc^1?] (X = Cl, Br) and [RhI₂Pc^1?] · I₂ is prepared by oxidation of (ⁿBu₄N)[RhX₂Pc^2?] with the corresponding halogene. Irrespective of the halo ligands, two irreversible electrode reactions due to the first ringreduction (E_R = ?0,90 V) and ringoxidation (E_O = 0,82 V) are present in the cyclovoltammogram of (ⁿBu₄N)[RhX₂Pc^2?]. The optical spectra show typical absorptions of the Pc^1?-ligand at 14.0 kK and 19.1 kK. Characteristic vibrational bands are at 1 366/1 449 cm^?1 (i. r.) and 569/1 132/1 180/1 600 cm^?1 (resonance Raman (r. r.)). The antisym. (Rh? X)-stretching vibration is observed at 294 cm^?1 (X = Cl), 240 cm^?4 (Br) and 200 cm^?1 (I). Only the sym. (Rh? I)-stretching vibration at 133 cm^?1 is r. r. enhanced together with a strong line at 170 cm^?1, which is assigned to the (I? I)-stretching vibration of the incorporated iodine molecule. Both modes show overtones and combinationbands.     

Syntheses,crystal structures,electrochemical studies,and antioxidant activities of zinc(II) and copper(II) complexes with bis(2-benzimidazolyl) aniline derivatives

Two ligands, bis(benzimidazol-2-ylmethyl) aniline (bba) and bis(N-methyl-benzimidazol-2-ylmethyl) aniline (Mebba), and their transition metal complexes [Zn(bba)(Br)₂]·2DMF (1) and [Cu(Mebba)(Br)₂]·2DMF (2) have been synthesized and characterized by elemental analyses, molar conductivities, UV–vis spectra, IR spectra, NMR spectroscopy, and X-ray crystallography. The structure around Zn(II) can be described as distorted tetrahedral. Complex 2 can be described as distorted trigonal bipyramidal. Cyclic voltammograms of 2 indicate a quasireversible Cu²⁺/Cu⁺ couple. Additionally, the antioxidant activities of the free ligands and their complexes were determined by the superoxide and hydroxyl radical scavenging methods in vitro. Complexes 1 and 2 possess potent hydroxyl radical scavenging activity and better than standard antioxidants such as vitamin C and mannitol. Complex 2 possesses excellent superoxide radical activity.     

Tin(IV) and organotin(IV) derivatives of bis(pyrazolyl)acetate: Synthesis, spectroscopic characterization and behaviour in solution.: X-ray single crystal study of bis(pyrazol-1-yl)acetatotri-iodotin(IV) [SnI3(bdmpza)]

Novel heteroscorpionate-containing tin and organotin(IV) complexes, [SnR_nX_3 − n(L)], R = Me, Buⁿ, Ph, or cy; X = Cl, Br or I, n = 0, 1, 2 or 3; L = bis(pyrazol-1-yl)acetate (bpza) or bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza), have been synthesized and characterized by spectral (IR, ¹H, ¹³C and ¹¹⁹Sn NMR, ^119mSn Mössbauer) and analytical data. In [SnI₃(bdmpza)], the ligand is fac-N,N′,O-tridentate, the three iodine atoms thus also fac about the six-coordinate tin(IV) atom. Neutral bpzaH reacts with BuⁿSnCl₃, PhSnCl₃ and SnCl₄ in Et₂O in the absence of base, yielding 1:1 adducts [XSnCl₃(bpzaH)] (X = R or Cl).     

Formation and crystal structures of [(alkoxy)bis(pyridin-2-yl)methanolato-N,O,N]tin(IV) complexes

Reactions of bis(pyridin-2-yl)ketone with tin tetrahalides, SnX₄ (X = Cl or Br), or organotin trichlorides, R^′SnCl₃ (R^′ = Ph, Bu or CH₂CH₂CO₂Me), in ROH (R = Me or Et) readily produces RObis(pyridin-2-yl)methanolato)tin complexes, [5: RO(py)₂C(OSnX₃)] (5: R,X = Me,Cl; Et,Cl; Et,Br) or [6: MeO(py)₂C(OSnCl₂R^′)] (R^′ = Ph, Bu, CH₂CH₂CO₂Me). In addition, halide exchange reaction between SnI₄ and (5: R,X = Me,Cl) occurred to give (5: R,X = Me,I). The crystal structures of six tin(IV) derivatives indicated, in all cases, a monoanionic tridentate ligand, [RO(py)₂C(O⁻)-N,O,N], arranged in a fac manner about a distorted octahedral tin atom. The Sn–O and Sn–N bonds lengths do not show much variation amongst the six complexes despite the differences in the other ligands at tin.     

Nickel(II) and copper(II) complexes of allyl 2-(thiophen-2-ylmethylene)hydrazinecarbodithioate: synthesis,X-ray crystal structures,and theoretical study

We report allyl 2-(thiophen-2-ylmethylene)hydrazine-carbodithioate (HL) and its Ni(II) and Cu(II) complexes, [ML₂]. The compounds were fully characterized by elemental analysis, IR, ¹H-NMR, UV-Vis, and molar conductivity. The crystal structure analysis indicates that the metal is four-coordinate square planar and that a parallel stacking of the molecular planes is present in the crystals, with stacking distances of 3.642 and 3.676?Å for the Ni(II) and Cu(II) complexes, respectively. Gas phase DFT computations indicate that the thione tautomeric form of the free ligand is more stable than the thiol form by 14.52?kJ?mol^–1. For HL and ML₂, comparison between the computed and experimental data shows good agreement.     

The electrochemical behaviour of butyltrimethylammonium bis(trifluoromethylsulfonyl)imide at negatively polarised aluminium electrode studied by in situ soft X-ray photoelectron spectroscopy,electrochemical impedance spectroscopy and cyclic voltammetry techniques

The in situ X-ray photoelectron spectroscopy data indicate that butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N4111(TFSI)) adsorbs strongly within the potential range −3.25 V < E < −2.25 V and specifically at E < −3.25 V (vs. Ag-QRE) at the Al electrode. Strong adsorption of the intermediates of N4111(TFSI) electrochemical decomposition was observed in electrochemical impedance spectroscopy and cyclic voltammetry measurements. At E < −4.25 V (vs. Ag-QRE), very intensive electrochemical reduction of N4111(TFSI) took place at the Al electrode giving gaseous products. In the potential range from − 2.25 to 0.00 V (vs. Ag-QRE), non-specific adsorption of N4111(TFSI) exists et al. surface.

     

Synthesis, X-ray crystal structures, and phosphate ester cleavage properties of bis(2-pyridylmethyl)amine copper(II) complexes with guanidinium pendant groups

Three new derivatives of bis(2-pyridylmethyl)amine (DPA) featuring ethylguanidinium (L (1)), propylguanidinium (L (2)), or butylguanidinium (L (3)) pendant groups have been prepared by the reaction of N, N- bis(2-pyridylmethyl)alkane-alpha,omega-diamines with 1 H-pyrazole-1-carboxamidine hydrochloride. The corresponding mononuclear copper(II) complexes were prepared by reacting the ligands with copper(II) nitrate and were isolated as [Cu(LH (+))(OH 2)](ClO 4) 3. xNaClO 4. yH 2O ( C1: L = L (1), x = 2, y = 3; C2: L = L (2), x = 2, y = 4; C3: L = L (3), x = 1, y = 0) following cation exchange purification. Recrystallization yielded crystals of composition [Cu(LH (+))(X)](ClO 4) 3.X ( C1': L = L (1), X = MeOH; C2': L = L (2), X = H 2O; C3': L = L (3), X = H 2O), which were suitable for X-ray crystallography. The crystal structures of C1', C2', and C3' indicate that the DPA moieties of the ligands coordinate to the copper(II) centers in a meridional fashion, with a water or methanol molecule occupying the fourth basal position. Weakly bound perchlorate anions located in the axial positions complete the distorted octahedral coordination spheres. The noncoordinating, monoprotonated guanidinium groups project away from the Cu(II)-DPA units and are involved in extensive charge-assisted hydrogen-bonding interactions with cocrystallized water/methanol molecules and perchlorate anions within the crystal lattices. The copper(II) complexes were tested for their ability to promote the cleavage of two model phosphodiesters, bis( p-nitrophenyl)phosphate (BNPP) and uridine-3'- p-nitrophenylphosphate (UpNP), as well as supercoiled plasmid DNA (pBR 322). While the presence of the guanidine pendants was found to be detrimental to BNPP cleavage efficiency, the functionalized complexes were found to cleave plasmid DNA and, in some cases, the model ribose phosphate diester, UpNP, at a faster rate than the parent copper(II) complex of DPA.     

Electrochemistry of niobium(V) in sulfuric and methanesulfonic acids: formation of the Nb3O2(SO4)6(H2O)(3)(5-) cluster and designed electrochemical generation of "Nb3O2" core clusters by double potential pulse electrolysis

The electrochemical and spectroelectrochemical properties of niobium(V) and the Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) cluster in sulfuric acid and methanesulfonic acid were investigated using cyclic voltammetry, constant potential electrolysis, and spectroelectrochemistry. These chemical systems were suitable to probe the formation of "Nb(3)O(2)" core trinuclear clusters. In 9 M H(2)SO(4) the cluster Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) exhibited a reversible 1-electron reduction peak at E(pc) = -1.30 V vs Hg/Hg(2)SO(4) electrode, as well as a 4-electron irreversible oxidation peak at E(pa) = -0.45 V. Controlled potential reduction at E = -1.40 V produced the green Nb(3.33+) cluster anion Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(6-). In 12 M H(2)SO(4) Nb(V) displayed two reduction peaks at E(pc) = -1.15 V and E(pc) = -1.30 V. It was determined that the first process involves a quasi-reversible 2-electron reduction. After reduction of Nb(V) to Nb(III) the following chemical step involves formation of [Nb(III)](2) dimer, which further reacts with Nb(V) to produce the Nb(3)O(2)(SO(4))(6(H(2)O)(3)(5-) cluster (ECC process). The second reduction peak at E(pc) = -1.30 V corresponds to further 2-electron reduction of Nb(III) to Nb(I). The electrogenerated Nb(I) species also chemically reacts with starting material Nb(V) to produce additional [Nb(III)](2). In 5 M H(2)SO(4), the rate of the second chemical step in the ECC process is relatively slower and reduction of Nb(V) at E = -1.45 V/-1.2 V produces a mixture of Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) and [Nb(III)](2) dimer. [Nb(III)](2) can be selectively oxidized by two 2-electron steps at E = -0.65 V to Nb(V). However, if the oxidation is performed at E = -0.86 V, the product is Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-). A double potential pulse electrolysis waveform was developed to direct the reduction of Nb(V) toward selective formation of the Nb(3)O(2)(SO(4))(6)(H(2)O)(3)(5-) cluster. Proper application of dc-voltage pulses alternating between E(1) = -1.45 V and E(2) = -0.86 V yields only the target trinuclear cluster. Analogous double potential pulse electrolysis of Nb(V) in methanesulfonic acid generates the "Nb(3)O(2)" core cluster Nb(3)O(2)(CH(3)SO(3))(6)(H(2)O)(3)(+).     

Preparation, properties, and reactivities of unprecedented oxo-sulfido Nb(IV) aqua ions and crystal structure of (Me2NH2)6[Nb5(mu3-S)2(mu3-O)2(mu2-O)2(NCS)14].3.5H2O

By treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of sulfide followed by cation-exchange chromatography, two oxo-sulfido niobium aqua ions, the red [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ and the yellow-brown [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+, were isolated. Both readily form their respective thiocyanate complexes, for which the structure for the former has been previously reported. Brown crystals of (Me2NH2)6[Nb5S2O4(NCS)14].3.5H2O (1) were isolated in the case of the latter, and the structure was determined by X-ray crystallography (space group: a = 15.4018(5) A, b = 21.1932(8) A, c = 22.0487(8) A, alpha=gamma = 90 degrees , beta = 103.4590(10) degrees , and R(1) = 0.0659). An unprecedented pentanuclear Nb5S2O48+ core is revealed in which short Nb-Nb distances (2.7995(8)-2.9111(8) A) are consistent with metal-metal bonding. A stopped-flow kinetic study of the 1:1 equilibration of NCS- with [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ has been carried out. Equilibration rate constants are independent of [H(+)] in the range investigated (0.5-2.0 M) and at 25 degrees C; kf= 9.5 M(-1) s(-1), kaq = 2.6 x 10(-2) s(-1), and K = 365 M1). Conditions with first NCS- and then [Nb4(mu4-S)(mu2-O)5(H2O)10]4+ in excess revealed a statistical factor of 4, suggesting the presence of four kinetically equivalent Nb atoms. Attempts to study the 1:1 substitution of NCS- with [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+ showed signs of saturation kinetics. Quantum chemical calculations using the density functional theory (DFT) approach were performed on both the Nb4O5S4+ and Nb5O4S28+ naked clusters. The highest occupied and lowest unoccupied molecular orbitals have dominant Nb(4d) character. The HOMO for Nb4O5S4+ is a nondegenerate fully filled MO, whereas for Nb5O4S28+, it is a nondegenerate partially filled MO with one unpaired electron. EPR spectroscopy on [Nb5(mu3-S)2(mu3-O)2(mu2-O)2(H2O)14]8+ shows that the molecule has total anisotropy (C2v), with all three tensors, gx= 2.399, gy= 1.975, and gz= 1.531, resolved. No hyperfine interaction expected from the nuclear moment of I = 9/2 for 93Nb was observed.     

Hydridotris(thioxotriazolyl)borate (Tt), an ambidentate (N(3)/S(3)) tripodal ligand. X-ray crystal structures of sodium, bismuth(III), tin(IV), and manganese(I) complexes

Treatment of the heterocycle 5-thioxo-4,5-dihydro-3,4-dimethyl-1,2,4-triazole (thioxotriazole) with sodium tetrahydroborate at 210 degrees C provides the new [N(3)/S(3)] ambidentate tripod ligand hydridotris(thioxotriazolyl)borate (Tt) as its sodium complex salt. Complexes of this ligand with sodium, bismuth(III), tin(IV), and manganese(I) have been synthesized and characterized by X-ray crystallography. The structures of these complexes illustrate the ambidentate character of the ligand with the softer metals bismuth and tin exhibiting sulfur coordination, while sodium and manganese(I) bond via the ligand nitrogen donors. In the [S(3)] coordination mode the ligand creates eight-membered chelate rings with the metal with the consequence that the metal ligand unit adopts a propeller-type conformation with C(3)-symmetry. However, in the [N(3)] mode six-membered chelate rings are formed analogous to the familiar hydrotris(pyrazolyl)borate (Tp) ligand.