Mononuclear Anions Research Articles

Synthesis and structure of the platinum complexes [Bu4N]+[PtBr5(DMSO)]−, [Ph4P]+[PtBr5(DMSO)]−, and [Ph3(n-Am)P]+[PtBr5(DMSO)

The complexes [Bu4N]2+[PtBr6]2− (I), [Ph4P]2+[PtBr6]2− (II), and [Ph3(n-Am)P]2+ (III) are synthesized by the reactions of tetrabutylammonium bromide, tetraphenylphosphonium bromide, and triphenyl(n-amyl)-tetraphenylphosphonium bromide, respectively, with potassium hexabromoplatinate (mole ratio 2: 1). After recrystallization from dimethyl sulfoxide, complexes I, II, and III transform into [Bu4N]+[PtBr5(DMSO)]− (IV), [Ph4P]+[PtBr5(DMSO)]− (V), and [Ph3(n-Am)P]+[PtBr5(DMSO)]− (VI). According to the X-ray diffraction data, the cations of complexes IV–VI have a slightly distorted tetrahedral structure. The N-C and P-C bond lengths are 1.492(7)–1.533(6) and 1.782(10)–1.805(10) A, respectively. The platinum atoms in the mononuclear anions are hexacoordinated. The dimethyl sulfoxide ligands are coordinated with the Pt atom through the sulfur atom (Pt-S 2.3280(18)–2.3389(11) A). The Pt-Br bond lengths are 2.4330(6)–2.4724(6) A.

Self assembly of asymmetric tetranuclear Cu(II) [2 × 2] grid-like complexes and of a dinuclear Ni(II) complex from pyridyl-phenol Schiff base ligands

Self assembly of N-salicylidene 2-aminopyridine ( L1H) with Cu(NO 3) 2·3H 2O affords [Cu 4( L1) 4(NO 3) 3(CH 3OH)][Cu( L1)(NO 3) 2](2-aminopyridinium)(NO 3)·5CH 3OH ( 1) which is composed of an asymmetric [2 × 2] grid-like cationic complex that co-crystallizes with a Cu(II) mononuclear anion. This remarkable tetranuclear unit presents three penta-coordinated and one hexa-coordinated Cu(II) sites. This quadruple helicate structure reveals strong anti-ferromagnetic coupling ( J = −340(2) cm −1) between Cu(II) ions through a double alkoxo bridge. Reacting L1H with Cu(NO 3) 2·3H 2O in slightly different conditions affords however a more symmetric tetranuclear grid-like complex: [Cu 4( L1) 4(NO 3) 2(OH) 2](2-aminopyridinium)(OH)·CH 3OH) ( 2). A dinuclear Ni(II) complex, [Ni 2( L2) 2( L2H) 2(NCS) 2(CH 3OH) 2]·2CH 3OH ( 3), obtained with another related donor ligand ( L2H = N-salicylidene 3-aminomethylpyridine) was also prepared .

Solvatothermal chemistry of organically-templated vanadium fluorides and oxyfluorides

The solvatothermal reactions of V 2O 5, the appropriate organoamine and HF in the temperature range 100–180 °C yielded a series of vanadium fluorides and oxyfluorides. The compounds [NH 4][H 3N(CH 2) 2NH 3][VF 6] ( 1) and [H 3N(CH 2) 2NH 3][VF 5(H 2O)] ( 2) contain mononuclear V(III) anions, while [H 3N(CH 2) 2NH 2(CH 2) 2NH 3] 2 [VF 5(H 2O)] 2[VOF 4(H 2O)] ( 3) exhibits both V(IV) and V(III) mononuclear anions. Both compound 4, [H 3NCH 2(C 6H 4)CH 2NH 3][VOF 4]·H 2O ( 4·H 2O) and compound 5, [HN(C 2H 4) 3NH][V 2O 2F 6 (H 2O) 2] ( 5) contain binuclear anions constructed from edge-sharing V(IV) octahedra. In contrast, [H 3N(CH 2) 2NH 2(CH 2) 2NH 3] 2[V 4O 4F 14(H 2O) 2], ( 6) exhibits a tetranuclear unit of edge- and corner-sharing V(IV) octahedra. Compound 7, [H 3N(CH 2) 2NH 2][VF 5], contains chains of corner-sharing {V IVF 6} octahedra, while [H 2N(C 2H 4) 2NH 2] 3[V 4F 17O]·1.5H 2O ( 8·1.5H 2O) is two-dimensional with a layer of V(III) and V(IV) octahedra in an edge- and corner-sharing arrangement. In the case of [H 3N(CH 2) 2NH 3][V 2O 6] ( 9), there was no fluoride incorporation, and the { V 2 O 6 } n 2 n - anion is a one-dimensional chain of corner-sharing V(V) tetrahedra.

Solvothermal synthesis and characterization of a new ZnII-PMIDA phosphonate

A new Zn(II) phosphonate, (NH4)[Zn(HPMIDA)(H2O)2] (1) (H4PMIDA = N-(phosphonomethyl)iminodiacetic acid), has been solvothermally synthesized and characterized by elemental analysis, IR, TGA fluorescence, and X-ray single-crystal diffraction. Compound 1 is an example of a six-coordinate Zn-carboxylate-phosphonate and possesses a 3-D supramolecular structure built from mononuclear anions through hydrogen bonding. Compound 1 exhibits a solid-state fluorescent emission band at 593 nm under excitation of 413 nm.

Characterization and thermal analysis of thiourea and bismuth trichloride complex

Abstract A complex of thiourea and bismuth trichloride has been synthesized. Its composition is Bi3Cl9[SC(NH2)2]7. Crystallographic data are a = 7.141(2) A, b = 8.820(3) A, c = 16.365(5) A, α = 99.389(4)°, β = 95.422(4)°, γ = 106.177(4)°, triclinic system. There are the mononuclear anion [BiCl5SC(NH2)2]2− and the dinuclear cation {Bi2Cl4[SC(NH2)2]6}2+ with the Bi–Cl–Bi bridge bonds in the complex. The electric conductance of the absolute methanol solution contained the complex indicates that the complex is an ionic compound. Raman spectra indicate that the bismuth ion is coordinated by the sulfur atoms of the thiourea. The thermal analysis verifies the structure of complex. The TG–MASS curves show the structure rearrangement in the complex at about 118 °C. The DSC curves and calculation means that the structure rearrangement is irreversible.

N,N-Di-iso-propylcarbamato Complexes of Boron

N,N-di- iso-propylcarbamato derivatives of boron(III) have been synthesized from di-iso-propylamine and boron trichloride in the presence of carbon dioxide. With a large excess of amine, a single boron product was obtained, [NH2i)Pr2][B(O2CNiPr2)4], 1, while with a lower excess a mixture of 1 and of the dinuclear derivative [B2(O2CNiPr2)6], 2, was produced. By heating in vacuo at 60 degrees C, solid 1 slowly converted to 2. The transformation was reversible, 2 giving 1 back with di- iso-propylamine under carbon dioxide at atmospheric pressure. The molecular structure of both compounds was established by X-ray diffraction methods. Compound 1 is constituted by ion-pairs where the ammonium cation is hydrogen-bonded to the mononuclear anion. Compound 2 is a dinuclear species with two bridging carbamato ligands. In both derivatives, boron shows tetrahedral coordination. As IR- and 1H NMR spectra of the two species are well differentiated, it is possible to monitor the interconversion of 1 and 2 by both spectroscopic methods.

Synthesis and crystal structure of a complex Cu(II) salt containing a taurine Schiff base and 2,2′-bipyridyl

The complex salt [Cu3(TFSSB)2(bpy)4][Cu(TFSSB)2] · 2H2O (TFSSB = the Schiff base formed by 5-formylsalicylaldehyde and taurine, bpy = 2,2′-bipyridyl) was synthesized by reaction of Cu(CH3COO)2 · 2H2O, TFSSB and 2,2′-bipy in aqueous methanol (1 : 1, v/v). The complex is triclinic, space group P , with a = 11.2433(5), b = 13.6717(2), c = 14.4022(11) Å, α = 83.588(10), β = 87.919(12), γ = 69.059(9)°, V = 2054.66(18) Å3, Z = 1. The asymmetric unit is comprised of a trinuclear coordinaton cation together with a mononuclear coordination anion and two water molecules, all of which are linked by hydrogen bonding and π–π interactions into a three-dimensional framework. The sulfonate group of the TFSSB ligand coordinates to copper(II) in the cation but not in the anion.

Electronic structure calculations on multiply charged anions containing MS bonds (M = Cr, Mo, W) and their heterobimetallic cluster complexes

AbstractMolecular and electronic structures of multiply charged mononuclear [CrS4]2−/3−, [MoOxS4−x]2−/3− (x = 0–4) and [WS4]2−/3− anionic species, and their heterobimetallic dinuclear and trinuclear clusters formulated as [MoOS3(CuCl)]2−, [WOS3(CuCl)]2−, [MoS4{Cu(CN)}]2−, [(CN)Cu(μ‐CrS4)Cu(CN)]2−, [(CN)Cu(μ‐MoS4)Cu(CN)]2−, [ClCu(μ‐MoS4)CuCl]2−, [Cl2Fe(μ‐MoS4)CuCl2]2−, and [(CN)Cu(μ‐WS4)Cu(CN)]2− have been investigated using electronic structure calculation (HF, MP4SDQ and DFT) methods. For the discrete mononuclear anions HF/lanl2dz(M)∪6‐31+G*(S,O) method provided the best description of their molecular structures, while for the heterobimetallic dinuclear and trinuclear clusters the B3LYP/lanl2dz(M)∪6‐31+G* method gave equilibrium geometries closely resembling the experimental ones. Electronic and spectroscopic (IR, UV‐Vis) properties of the thiometalates are discussed in relation to their structures, while the bonding mechanism was analyzed in the framework of the natural bond orbital (NBO) approach. The nature of the highest occupied molecular orbitals (HOMOs) of all thiometalates indicated their ability to act as ligands coordinated with metal centers and forming clusters of higher nuclearity. The lowest‐lying vertical one‐electron detachment processes from the ground state of the [CrS4]2/3−, [MoOxS4−x]2/3− (x = 0–4) and [WS4]2/3− anions have been calculated using the outer valence Green's function (OVGF) method. Interestingly, in the heterobimetallic dinuclear and trinuclear clusters intemetallic M…M′ interactions exist corresponding to d10 → d0 dative bonding. Finally, the complete energetic and geometric profile of the successive acid‐catalyzed formation reactions: equation image and the reverse hydrolysis reactions have been delineated and details of the mechanism have been furnished. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007

Synthesis and Structure of Phosphorus-Containing Complexes [Ph4P] 2 + [Hg4I10]2− and [Ph4P] 2 + [BiI5(Me2S=O)]2−

Complexes [Ph4P]2+[Hg4I10]2− (I) and [[Ph4P]2+[BiI5(Me2S=O)]2− (II) are synthesized by the reactions of tetraphenylphosphonium Ph4PI with mercury diiodide in acetone and with bismuth triiodide in dimethyl sulfoxide, respectively. According to X-ray diffraction analysis, structural units of these complexes are tetraphenylphosphonium cations and tetra- and mononuclear anions, respectively. The phosphorus atoms in the tetraphenylphosphonium cations have a distorted tetrahedral coordination. In the central fragment of the centrosymmetric anion [Hg4I10]2−, the distances between the terminal mercury atoms and iodine atoms are 3.503(2) A. The mercury atoms in the central and terminal fragments of compound I have distorted tetrahedral and trigonal coordinations, respectively. The bismuth atom in the mononuclear octahedral anion of complex II contains a dimethyl sulfoxide molecule along with five iodine atoms in the coordination sphere.

A chiral supramolecular architecture [Cu 2(4,4′-bipyridine) 2 (sala) 2] n·4.5 nH 2O(sala= N-(2-hydroxybenzyl)- l-alanine anion)

A chiral supramolecular architecture, [Cu 2(4,4′-bipy) 2(sala) 2] n ·4.5nH 2O ( 1) (sala= N-(2-hydroxybenzyl)- l-alanine anion), has been synthesized by the reaction of Cu(NO 3) 2·2H 2O with 4,4′-bipyridine (4,4′-bipy) and N-(2-hydroxybenzyl)- l-alanine (H 2sala) in basic ethanol/aqueous solution. X-ray single crystal diffraction analysis reveals that complex 1 has a 3D extended structure in which the mononuclear anions [Cu(sala) 2] 2− are bonded to [Cu(4,4′-bipy) 2] 2+ cations through Cu–O bond at a distance of 2.528 Å. One Cu(II) center is in lengthened octahedral geometry and another one is in planar square environment. The cyclic voltammetry shows that two Cu(II) centers have different electrochemical properties.

Cr(AA)(C 2O 4) 2] − and [Cu(bpca)] + as building blocks in designing new oxalato-bridged Cr IIICu II compounds [AA=2,2′-bipyridine and 1,10-phenanthroline; bpca=bis(2-pyridylcarbonyl)amide anion

The monouclear complex PPh 4[Cr(bipy)(ox) 2]·H 2O ( 1) and the heterodinuclear compounds [Cu(bpca)(H 2O)Cr(bipy)(ox) 2]·2.5H 2O ( 2) and [Cu(bpca)(H 2O)Cr(phen)(ox) 2]·2H 2O ( 3) [PPh 4 +=tetraphenylphosphonium cation, bpca=bis(2-pyridylcarbonyl)amide anion, ox=oxalate dianion, bipy=2,2′-bipyridine and phen=1,10-phenanthroline] have been synthesized and characterized by single-crystal X-ray diffraction. Discrete [Cr(bipy)(ox) 2] − mononuclear anions and tetraphenylphosphonium cations are present in 1 whereas the structures of 2 and 3 are made up neutral oxalato-bridged bimetallic Cr IIICu II units. The chromium environment is distorted octahedral in the three complexes: two nitrogen atoms from a bidentate bipy ( 1 and 2) or phen ( 3) ligand and four oxygen atoms from two oxalate groups ( 1– 3) build the coordination polyhedron around the chromium atom. The CrN(bipy) [2.055(3) and 2.078(3) Å for 1 and and 2.060(3) and 2.066(3) Å for 2] and CrN(phen) bond lengths [2.056(5) and 2.069(5) Å ( 3)] are somewhat longer than the CrO(ox) ones [values in the ranges 1.944(2)–1.955(2) ( 1), 1.948(2)–1.960(2) ( 2) and 1.945(4)–1.953(4) Å ( 3)]. The copper atom in 2 and 3 exhibits a distorted square-pyramidal surrounding: three bpca-nitrogen atoms [values of the CuN(bpca) bonds in the ranges 1.922(3)–2.017(3) ( 2) and 1.918(5)–2.004(6) Å ( 3)] and a water molecule [CuO w=1.952(3) ( 2) and 1.952(5) Å ( 3)] define the equatorial positions whereas an oxalate-oxygen atom occupies the axial site [CuO ox=2.253(2) ( 2) and 2.325(4) Å ( 3)]. The oxalate bridge in 2 and 3 exhibits a unusual bidentate/monodentate coordination mode, the metalmetal separation across this bridge being 5.283(1) ( 2) and 5.407(1) Å ( 3). Magnetic susceptibility measurements of 1– 3 in the temperature range 1.9–290 K reveal a Curie law behavior for the three complexes. The preparation of bimetallic systems by using [Cr(AA)(ox) 2] − (AA=α-diimine type ligand) as a complex ligand towards coordinatively unsaturated metal complexes is analyzed and discussed.

Catalytic gas phase oxidation of methanol to formaldehyde.

Two gas-phase catalytic cycles for the two-electron oxidation of primary and secondary alcohols were detected by multistage mass spectrometry experiments. A binuclear dimolybdate center [Mo(2)O(6)(OCHR(2))](-) acts as the catalyst in both these cycles. The first cycle proceeds via three steps: (1) reaction of [Mo(2)O(6)(OH)](-) with alcohol R(2)HCOH and elimination of water to form [Mo(2)O(6)(OCHR(2))](-); (2) oxidation of the alkoxo ligand and its elimination as aldehyde or ketone in the rate-determining step; and (3) regeneration of the catalyst via oxidation by nitromethane. Step 2 does not occur at room temperature and requires the use of collisional activation to proceed. The second cycle is similar but differs in the order of reaction with alcohol and nitromethane. The nature of each of these reactions was probed by kinetic measurements and by variation of the substrate alcohols (structure and isotope labeling). The role of the binuclear molybdenum center was assessed by examination of the relative reactivities of the mononuclear [MO(3)(OH)](-) and binuclear [M(2)O(6)(OH)](-) ions (M = Cr, Mo, W). The molybdenum and tungsten binuclear centers [M(2)O(6)(OH)](-) (M = Mo, W) were reactive toward alcohol but the chromium center [Cr(2)O(6)(OH)](-) was not. This is consistent with the expected order of basicity of the hydroxo ligand in these species. The chromium and molybdenum centers [M(2)O(6)(OCHR(2))](-) (M = Cr, Mo) oxidized the alkoxo ligand to aldehyde, while the tungsten center [W(2)O(6)(OCHR(2))](-) did not, instead preferring the non-redox elimination of alkene. This is consistent with the expected order of oxidizing power of the anions. Each of the mononuclear anions [MO(3)(OH)](-) (M = Cr, Mo, W) was inert to reaction with methanol, highlighting the importance of the second MoO(3) unit in these catalytic cycles. Only the dimolybdate center has the mix of properties that allow it to participate in each of the three steps of the two catalytic cycles. The three reactions of these cycles are equivalent to the three essential steps proposed to occur in the industrial oxidation of gaseous methanol to formaldehyde at 300-400 degrees C over solid-state catalysts based upon molybdenum(VI)-trioxide. The new gas-phase catalytic data is compared with those for the heterogeneous process.

Na 5AuSe 12-the first selenoaurate(III) with discrete complex anions

The novel polyselenoaurate(III) Na 5AuSe 12 was prepared by reacting a stoichiometric mixture of Na 2Se, Au and Se at 345°C followed by slow cooling. Na 5AuSe 12 forms transparent red crystals of lamellar habit. It is monoclinic, m P36, s.g. P2 1, with a=7.145(1) Å, b=16.790(6) Å, c=8.291(1) Å, β=107.13(1)°, Z=2. The crystal structure was determined from diffractometer data and refined to a conventional R of 0.032 (3830 F o's, 163 variables). Na 5AuSe 12 contains discrete mononuclear anions [AuSe 12] 5− which are formed by four triselenide chains in end-on coordination with the central atom. The Au-atom is in an almost undistorted square planar coordination through Se. The mean Au–Se bond length is 2.500 Å, Se–Se bond lengths in the Se 3−chains are in the range of 2.346–2.363 Å. The shortest intra-anionic Se–Se-contacts are in the range of 3.19–3.27 Å. In the crystal structure the [AuSe 12] 5− anions are stacked in columns along [100]. Together with three of the five crystallographically independent Na +-ions the columns are arranged in slabs parallel to (010)-plane which are separated by layers of the remaining Na +-ions. Na 5AuSe 12 is the first alkali selenoaurate(III) containing molecular anions. It undergoes peritectic decomposition at 275°C and is soluble in dimethylformamide.

Influence of the counterion on the coordinating properties of (2,2′-bipyridyl)bis(oxalato)chromate(III) anion: crystal structures and magnetic properties of AsPh4[Cr(bipy)(ox)2]·H2O and [NaCr(bipy)(ox)2(H2O)]·2H2O

Two new chromium(III)-containing complexes of formula AsPh4[Cr(bipy)(ox)2]·H2O 1 and [NaCr(bipy)(ox)2(H2O)]· 2H2O 2 (bipy = 2,2′-bipyridine and ox = oxalate dianion) have been synthesized and characterized by single-crystal X-ray diffraction. The structure of 1 consists of discrete [Cr(bipy)(ox)2]– mononuclear anions, tetraphenylarsonium cations and uncoordinated water molecules. The structure of 2 reveals a novel two-dimensional framework which is made up of oxalato-bridged bimetallic CrIII–NaI helical chains which are interconnected through centrosymmetric Na2O2 units. Within the chain, a regular alternation of the metal ions is observed, the oxalate group acting as a bis(chelating) ligand. In addition to this coordination mode, two oxalates each act as monodentate ligands towards a sodium atom of a neighbouring chain thus leading to a sheetlike polymeric structure. The chromium environment is distorted octahedral in both complexes: two nitrogen atoms from a bidentate bipy ligand and four oxygen atoms from either two chelating (1) or two bis(chelating) (2) oxalate groups build the coordination polyhedron around the chromium atom. The Cr–N bond lengths [values in the ranges 2.077(3)–2.057(3) (1) and 2.067(4)–2.058(4) A (2)] are somewhat longer than the Cr–O ones [values in the ranges 1.960(2)–1.946(2) (1) and 1.968(3)–1.949(3) A (2)]. The sodium atom in 2 is also six-coordinated: a coordinated water molecule [2.371(5) and 2.325(4) A for Na(1)–O(17) and Na(2)–O(18), respectively] and five oxygens from three oxalate groups [values of the Na–O (ox) bonds in the ranges 2.511(4)–2.331(4) and 2.481(4)–2.364(4) A around Na(1) and Na(2), respectively] build a distorted octahedral NaO6 environment. The intralayer chromium–sodium and sodium–sodium distances through bridging oxalate in 2 vary in the ranges 5.657(4)–5.579(2) and 3.534(3)–3.497(4) A, respectively. Variable-temperature magnetic susceptibility measurements of 1 and 2 reveal the occurrence of very weak antiferromagnetic interactions together with zero-field splitting effects in both compounds. The use of the [Cr(bipy)(ox)2]– unit as a ligand towards different univalent and divalent metal ions aimed at designing new heterobimetallic systems is analysed and discussed in the light of available structural data.

Mn(SPh)Cl3]2-, [Mn(SPh)3Cl]2-, [Mn2(SPh)6]2- und [Mn4(SPh)6Br4]2–: Synthese, Struktur und ausgewählte Eigenschaften einiger neuer Chalkogenolatkomplexe des zweiwertigen Mangans / [Mn(SPh)Cl3]2-, [Mn(SPh)3Cl]2-, [Mn2(SPh)6]2- und [Mn4(SPh)6Br4]2-: Synthesis, Structure and Selected Properties of Some New Chalkogenolate Complexes of Divalent Manganese

[Me4N]2[Mn(SPh)Cl3] (1) was obtained by reaction of MnCl2·4H2O with one equivalent of NaSPh from methanolic solutions in the presence of [Me4N]Cl. Under similar conditions the compound [Et4N]2[Mn(SPh)3Cl] (2) waso isolated using [Et4N]+ cations. Crystal data: 1: a = 9.425(3), b = 11.903(3)t c -19.073(4) Å, space group P 21cn, Z = 4; 2: a = 14.420(7), b = 13.834(8), c = 17.918(10) Å, β = 90.69(4)°, space group P21/c, Z = 4. The structures were refined to R = 0.0839 (1) and 0.0328 (2), respectively. Besides the dianion [Mn(SPh)3Cl]2- (6), crystals of 2 contain traces of [Mn(SPh)2Cl2]2- (7) distributed over 3.8% of the anion positions. The existence of [Mn(SPh)Cl3]2- (5), 6 and 7 under similar conditions is interpreted in terms of ligand exchange solution equilibria. Within these mononuclear anions, the central metal/sulfur/halide cores show distorted tetrahedral stereochemistries. The reaction of MnCl2 with NaSPh (molar ratio 1:3) in hot mixtures of acetonitrile and DMF leads to [Mn2(SPh)6]2- (8), which can be isolated as crystalline [Ph4P]2[Mn2(SPh)6] (3) with a = 13.383(2), b = 13.565(2), c = 20.438(4) Å, β = 106.41(1)°, space group P21/c, Z = 2. The final refinement converged to R = 0.0380. 8 consists of two edge-sharing MnS4 tetrahedra showing structural similarities with other tetrahedral complexes of the type [M2(SR)6]2-. According to magnetochemical studies, the manganese atoms are antiferromagnetically coupled with J=-18.6(2) cm-1. Reaction of 3:2:1 molar ratio mixtures of NaSPh/MnBr2/[Et4N]Br in hot acetonitrile leads to [Et4N]2[Mn4(SPh)6Br4] (4) which crystallizes with a = 14.109(3), b = 27.556(5), c = 16.194(4) Å, β = 95.35(2)°, space group P 21/n, Z=4. The structure was refined to R = 0.0583. This compound is also available by reaction of [Et4N]2[Mn(SPh)4] with MnBr2 in a molar ratio of 3:5. The anion [Mn4(SPh)6Br4]2- (9) contains a central {Mn4S6Br4} core which exhibits an adamantane-like structure: A Mn4 tetrahedron is inscribed into a S6 octahedron with the S atoms bridging the edges of the Mn4 tetrahedron. Terminally bonded Br atoms complete the tetrahedral coordination spheres of the manganese atoms and thus form an outer Br4 tetrahedron. As a result, the symmetry of the central core comes close to Td. The observed distortion is attributed to intramolecular repulsions of the organic residues. Selected properties of compounds 1-4 are reported.

Novel binuclear vanadium(V)–Schiff base cations containing single fluorine bridges and the structure of difluorodioxovanadate(1–)

The complex [VO (salen)][H2salen =N,N′-ethylenebis(salicylideneimine)] reacted with HBF4·Et2O in air to produce the novel linear species [{VO (salen)}2(µ-F)]+, the structure of which has been determined as its BF4– and [VO2F2]– salts. The perchlorate and triflate (O3SCF3)– salts have been characterised spectroscopically and analytically, as well as the tetrafluoroborate homologues from salicylaldehyde and 2-methylpropylenediamine, and from ethylenediamine and 3-methoxysalicylaldehyde. The [VO2F2]– is mononuclear in the above salt, as well as in [PPh4][VO2F2], compared to a polynuclear form found in [NH4][VO2F2]. The mononuclear anion was also fully characterised by 19F and 51V NMR spectroscopy.

Mn(SPh)3Cl]2-, [Mn(SPh)3Br]2-, [Mn(SePh)4]2-, [Mn(TePh)4]2-, and [Co4(SPh)6Cl4]2-: New Mixed Halide/Thiolate and Chalcogenolate Complexes of Manganese and Cobalt

The reactions of 1:1:1 molar ratio mixtures of NaSPh/MnCl2/Et4NBr and NaSPh/CoCl2/ Et4NCl in methanol afford the compounds [Et4N]4[Mn(SPh)3Br][Mn(SPh)3Cl] (1) and [Et4N]2[Co4(SPh)6Cl4] · MeCN (2), respectively, with the following crystal data: a = 14.408(5), b = 13.788(4), c = 17.984(5) Å, β = 90.16(2)°, space group P21/c and Ζ = 4 for 1, and a = 21.976(4), b = 13.081(2), c = 22.012(4) Å, β = 105.48(1)°, space group P 21/c for 2. The structures were refined to R values of 0.049 and 0.037, respectively. Crystals of 1 contain both of the paramagnetic (S = 5/2) mononuclear anions [Mn(SPh)3Br]2- (3 a) and [Mn(SPh)3Cl]2- (3b). The anions 3 a and 3 b are superimposed in an averaged unit cell and thus occupy crystallographically equivalent sites, the positions of the chlorine and bromine atoms being unresolved. The monohalide species are distributed statistically over 93% of the total anion positions. The remaining 7% are occupied by the dihalide species [Mn(SPh)2Br2]2- (4a) and [Mn(SPh)2BrCl]2- (4b) in equal amounts. In all these cases the metal atoms exhibit a distorted tetrahedral stereochemistry. In crystals of 2 [Co4(SPh)6Cl4]2- anions (5) are observed which feature a {Co4S6Cl4} core consisting of a distorted (D2d) Co4 tetrahedron inscribed in a moderately irregular S6 octahedron defined by bridging S atoms of an adamantane type cage. The four chlorine atoms each bind to different Co atoms and define an outer Cl4 tetrahedron, such that the overall symmetry of the {Co4S6Cl4} core comes close to Td. The results presented show that [M3(SPh)3Hal6]3- type species reported for M = Fe are not as readily formed for M = Mn and Co in methanolic solution, where other species are found instead. Physical properties such as solid state susceptibilities and 1H NMR spectra confirm the identity of 1 and 2. Reactions of 4:1:2 molar ratio mixtures of NaSePh/MnCl2/Et4NCl and NaTePh/MnCl2/Et4NCl in methanol lead to [Et4N]2[Mn(SePh)4] (6) and [Et4N]2[Mn(TePh)4] (7). Both compounds crystallize in the monoclinic space group P21/n with a = 16.162(4), b = 15.323(4), c = 16.949(4) Å, β = 91.28(2)°, Z = 4 for 6, and a = 16.367(6), b = 15.641(7), c = 17.220(7) Å, β = 92.00(3)°, Z = 4 for 7. Their structures were refined to R = 0.077 and 0.026, respectively. Four benzeneselenolate and benzenetellurolate ligands provide a slightly distorted tetrahedral coordination about the Mn(II) center for 6 and 7, respectively. The Mn–Se and Mn–Te distances average 2.567 and 2.742 Å, the Se– Mn– Se and Te–Mn–Te angles range from 99.1(1) to 124.2(1) and from 94.7(1) to 127.0(1)°, respectively.

Structural and spectroscopic studies of halogenocuprate(I) complexes

Reaction of tetraalkylammonium halides, PPh3 and copper(I) halides in a 1 : 1 : 1 mole ratio in dichloromethane yields complexes [NR4][Cu(PPh3)X2](R = Et, X = Cl or Br; R = Pr, X = Br, I; R = Bu, X = Br) and [NEt4]2[Cu2(PPh3)2I4]. These have been characterized by infrared and cross polarization magic angle spinning (CP MAS)31P NMR spectroscopy, and the structures of most have been determined by single-crystal X-ray diffraction. The compounds [NR4][Cu(PPh3)X2] in the first group above contain mononuclear anions [Cu(PPh3)X2]– with essentially trigonal planar PCuX2 co-ordination. The P–Cu–X and X–Cu–X angles are all within 5 ° of the ideal trigonal angle of 120 °. The compound [NEt4]2[Cu2(PPh3)2I4] contains the centrosymmetric binuclear anion [Cu2(PPh3)2I4]2–{a dimer of [Cu(PPh3)I2]–} in which the two copper atoms are bridged by two iodine atoms, and each copper atom is also bound to a terminal iodine atom and PPh3 molecule. The FIR spectra of the mononuclear complexes [Cu(PPh3)X2]– show strong bands at 264, 195 and 175 cm–1 for X = Cl, Br and I respectively, which are assigned to the asymmetric v(CuX) stretching mode of the bent X–Cu–X units, and weak bands at 194, 150 and 128 cm–1 due to the symmetric v(CuX) mode. In addition, the X = Cl complex shows a strong band at 126 cm–1 which is assigned as the δ(CuCl2) bending mode. The dimer [Cu2(PPh3)2I4]2– shows a remarkably simple spectrum in the v(CuI) region: a partially resolved doublet at 113 and 126 cm–1. The above vibrational frequencies are compared with those of the species [CuX2]– and [Cu2I4]2–, from which the present species can be considered to be derived by addition of one PPh3 molecule per copper atom. The solid state CP MAS 31P NMR spectra generally consist of asymmetric quartets due to coupling of the 31P nucleus to the quadrupolar copper nucleus, and the splitting patterns are interpreted in terms of the copper co-ordination environment.

Cryoelectrochemical study of the cleavage of radical anions of diiron and diruthenium carbonyl dimers

Electrochemical reduction of the diiron complexes [Fe(CO) 2 (η 5 -Cp)] 2 and [Fe(CO) 2 (η 5 -Cp * )] 2 proceeds at room temperature by two electrons, but at low temperature is a one-electron reaction producing dimer radical anions that are stable on the voltammetric time scale. Analysis of the reaction kinetics at intervening temperatures shows that the two-electron reaction occurs through the radical anion, which dissociates to a mononuclear anion and a radical. The second electron is delivered homogeneously to the radical by a second dimer radical anion

Colored species formation between mononuclear copper(II) complex and superoxide anion

Colored species formation between mononuclear copper(II) complex and superoxide anion