Mechanistic disparity in the electron transfer reactions of thiosulfate with di‐μ‐oxo‐bis(1,4,8,11‐tetraazacyclotetradecane)‐dimanganese(III,IV) and di‐μ‐oxo‐bis(1,4,7,10‐tetraazacyclododecane)‐dimanganese(III,IV) complexes

A comparative kinetic study of the reactions of two mixed valence manganese(III,IV) complexes of macrocyclic ligands, [L¹Mn^IV(O)₂Mn^IIIL¹], 1 (L¹ = 1,4,8,11‐tetraazacyclotetradecane) and [L²Mn^IV(O)₂Mn^IIIL²], 2 (L² = 1,4,7,10‐tetraazacyclododecane) with thiosulfate has been carried out by spectrophotometry in aqueous buffer at 30°C. Reaction between complex 1 and thiosulfate follows a first‐order rate saturation kinetics. The pH dependency and kinetic evidences suggest the participation of two complex species of Mn^III(μ‐O)₂Mn^IV under the experimental conditions. Detailed kinetic study shows that reduction of 2 proceeds through an autocatalytic path where the intermediate (Mn^III)₂ species has been assumed to catalyze the reaction. The difference in the reaction mechanisms is ascribed to the difference in stability of the intermediate complex species, the evidence for which comes from the electrochemical behavior of the complexes and time dependent EPR spectroscopic measurements during the reduction of 2 . © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 119–128, 2004     

Bis[μ3‐1,8‐bis(triisopropylsilylamido)naphthalene]bis(tetrahydrofuran)di‐μ3‐oxido‐dimanganese(III)disodium

The solid‐state structure of the title compound, [Na₂Mn₂(C₃₂H₅₆N₂OSi₂)₂O₂] or [1,8‐C₁₀H₆(NSiⁱPr₃)₂Mn(μ₃‐O)Na(THF)]₂, which lies across a crystallographic twofold axis, exhibits a central [Mn₂O₂Na₂]⁴⁺ core, with two oxide groups, each triply bridging between the two Mn^III ions and an Na⁺ ion. Additional coordination is provided to each Mn^III centre by a 1,8‐C₁₀H₆(NSiⁱPr₃)₂ [1,8‐bis(triisopropylsilylamido)naphthalene] ligand and to the Na⁺ centres by a tetrahydrofuran molecule. The presence of an additional Na...H—C agostic interaction potentially contributes to the distortion around the bridging oxide group.     

Crystal structures of two (5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) complexes

Reported in this contribution are the synthesis and crystal structures of two new Fe^III complexes of 5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane (HMC), namely, dichlorido(5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) chloride, [FeCl₂(C₁₆H₃₆N₄)]Cl or cis‐[FeCl₂(rac‐HMC)]Cl ( 1 ), and dichlorido(5,5,7,12,12,14‐hexamethyl‐1,4,8,11‐tetraazacyclotetradecane)iron(III) tetrachloridoferrate, [FeCl₂(C₁₆H₃₆N₄)][FeCl₄] or trans‐[FeCl₂(meso‐HMC)][FeCl₄] ( 2 ). Single‐crystal X‐ray diffraction studies revealed that both 1 and 2 adopt a pseudo‐octahedral geometry, where the macrocycles adopt folded and planar geometries, respectively. The chloride ligands in 1 are cis to each other, while those in 2 have a trans configuration. The relevant bond angles in 1 deviate substantially from an ideal octahedral coordination geometry, with the angles between the cis substituents varying from 81.55 (5) to 107.56 (4)°, and those between the trans‐ligating atoms varying from 157.76 (8) to 170.88 (3)°. In contrast, 2 adopts a less strained configuration, in which the N—Fe—N angles vary from 84.61 (8) to 95.39 (8)° and the N—Fe—Cl angles vary from 86.02 (5) to 93.98 (5)°.     

Tetra­piperidinium di‐μ‐methoxy‐di‐μ5‐oxo‐tetra‐μ3‐oxo‐dodeca‐μ2‐oxo‐octa­oxodeca­vanadate

The structure of the title compound, (C₅H₁₂N)₄[V₁₀O₂₆(CH₃O)₂], reveals the presence of four protonated piperidin­ium cations and a [{V₁₀O₂₆}(OCH₃)₂]⁴⁻ polyanion having an embedded centre of inversion. The compound is distinguished by presenting, in contrast with other anionic deca­vanadates, two meth­oxy groups bridging the outermost V atoms, and it becomes the first example of this type among reported deca­vanadates.     

Hexaaquanickel(II) disulfato(1,4,8,11‐tetraazacyclotetradecane)nickelate(II) dihydrate

The title compound, [Ni(H₂O)₆][Ni(SO₄)₂(C₁₀H₂₄N₄)]·2H₂O, is an unusual compound in that it is composed of a hexaaqua complex, formally a dication, and a mixed‐donor complex (four N and two O atoms), formally a dianion, with substantial charge separation between the two nickel centres (6.536 Å). The homoleptic dication complex consists of the weaker‐field ligands, whilst the dianion retains the coordination of all the higher‐field donors. Both nickel ions are located at centres of symmetry. This rare compound is placed in the context of previously reported structures which emphasizes its peculiarity.     

catena‐Poly[copper(II)‐di‐μ‐acetylacetonato‐copper(II)‐bis(μ‐4‐hydroxy‐3‐methoxybenzaldehyde picoloylhydrazonato)] and (acetylacetonato)(4‐methoxybenzaldehyde picoloylhydrazonato)copper(II)

In the two title copper(II) complexes, [CuL(C₅H₇O₂)]_n, (I), and [CuL′(C₅H₇O₂)], (II), respectively, where HL is 4‐hydroxy‐3‐methoxybenzaldehyde picoloylhydrazone, C₁₄H₁₂N₃O₃, and HL′ is 4‐methoxybenzaldehyde picoloylhydrazone, C₁₄H₁₂N₃O₂, the Cu^II ions display a highly Jahn–Teller‐distorted octahedral and a square‐planar coordination geometry, respectively. In complex (I), two neighbouring Cu^II atoms are bridged by L⁻ and acetylacetonate, alternately, giving rise to a one‐dimensional chain of CuN₂O₄ octahedra interconnected by these two ligands along the a axis. In addition, the hydroxy H atom of the vanillin group connects to the carboxyl O atom of the adjacent chain via an O—H...O hydrogen bond, giving rise to a three‐dimensional supramolecular assembly. Complex (II) displays a discrete structure.     

A new copper(II) basic sulfate: poly[3‐aminopyridinium μ3‐hydroxido‐di‐μ3‐sulfato‐bis[aquacopper(II)]]

The crystal structure of the title basic copper(II) sulfate, {(C₅H₇N₂)[Cu₂(OH)(SO₄)₂(H₂O)₂]}_n, shows an unprecedented structural arrangement of two distinct copper centres. CuO₆ and CuO₅ polyhedra are linked through bridging hydroxide and sulfate anions to form negatively charged infinite chains propagated along the a axis. The negative charge is balanced by 3‐aminopyridinium cations that are held in the structure by extensive hydrogen bonding to the inorganic chains. Additionally, the cationic arrangement features π–π stacking.     

The dinuclear copper(II) complexes di‐μ‐chlorido‐bis{[N,N′‐bis(4‐chlorobenzyl)propane‐1,2‐diamine]chloridocopper(II)} and di‐μ‐chlorido‐bis{[N,N′‐bis(3,4‐methylenedioxybenzyl)propane‐1,2‐diamine]chloridocopper(II)}

The two title dinuclear copper(II) complexes, [Cu₂Cl₄(C₁₇H₂₀Cl₂N₂)₂], (I), and [Cu₂Cl₄(C₁₉H₂₂N₂O₄)₂], (II), have similar coordination environments. In each complex, the asymmetric unit consists of one half‐molecule and the two copper centres are bridged by a pair of Cl atoms, resulting in complexes with centrosymmetric structures containing Cu(μ‐Cl)₂Cu parallelogram cores; the Cu...Cu separations and Cu—Cl—Cu angles are 3.4285 (8) Å and 83.36 (3)°, respectively, for (I), and 3.565 (2) Å and 84.39 (7)° for (II). Each Cu atom is five‐coordinated and the coordination geometry around the Cu atom is best described as a distorted square‐pyramid with a τ value of 0.155 (3) for (I) and 0.092 (7) for (II). The apical Cu—Cl bond length is 2.852 (1) Å for (I) and 2.971 (2) Å for (II). The basal Cu—Cl and Cu—N average bonds lengths are 2.2673 (9) and 2.030 (2) Å, respectively, for (I), and 2.280 (2) and 2.038 (6) Å for (II). The molecules of (I) are linked by one C—H...Cl hydrogen bond into a complex [10] sheet. The molecules of (II) are linked by one C—H...Cl and one N—H...O hydrogen bond into a complex [100] sheet.     

μ‐1,4‐Benzenedicarboxylato‐bis[trans‐aqua(1,4,8,11‐tetraazacyclotetradecane)nickel(II)] diperchlorate forms a three‐dimensional hydrogen‐bonded framework

The title compound, [Ni₂(C₈H₄O₄)(C₁₀H₂₄N₄)₂(H₂O)₂](ClO₄)₂, contains two independent octahedral Ni^II centres with trans‐NiN₄O₂ chromophores. The bridging benzene­dicarboxyl­ate ligand is bonded to the two Ni atoms, each via one O atom of each carboxyl­ate, while the other O atom participates in an intramolecular N—H?O hydrogen bond, forming an S(6) motif. The cations are linked to the perchlorate anions via O—H?O and N—H?O hydrogen bonds [O?O 2.904 (6) and 2.898 (6) Å; O—H?O 158 (6) and 165 (6)°; N?O 3.175 (7) and 3.116 (7) Å; N—H?O 168 and 166°] to form molecular ladders. These ladders are linked by further O—H?O and N—H?O hydrogen bonds [O?O 2.717 (6) and 2.730 (5) Å; O—H?O 170 (4) and 163 (6)°; N?O 3.373 (7) and 3.253 (7) Å; N—H?O 163 and 167°] to form a continuous three‐dimensional framework. The perchlorate anions both participate in three hydrogen bonds, and both are thus fully ordered.     

Poly[bis(μ4‐benzene‐1,2‐dicarboxylato)di‐μ3‐isonicotinato‐dilanthanum(III)]

In the title compound, [La₂(C₈H₄O₄)₂(C₆H₄NO₂)₂]_n, there are two crystallographically independent La centres, both nine‐coordinated in tricapped trigonal prismatic coordination geometries by eight carboxylate O atoms and one pyridyl N atom. The La centres are linked by the carboxylate groups of isonicotinate (IN⁻) and benzene‐1,2‐dicarboxylate (BDC²⁻) ligands to form La–carboxylate chains, which are further expanded into a three‐dimensional framework with nanometre‐sized channels by La—N bonds. In the construction of the resultant architecture, in tricapped trigonal prismatic coordination geometries by eight carboxylate O atoms and one pyridyl N atom, while the BDC ligands link to four different cations each, displaying penta‐ and heptadentate chelating–bridging modes, respectively.     

catena‐Poly[bis[(η2‐1‐allyl‐3‐aminopyridinium)copper(I)]‐di‐μ‐chloro‐copper(I)‐di‐μ‐chloro‐copper(I)‐di‐μ‐chloro]

Crystals of the title π‐complex, [Cu₄Cl₆(C₈H₁₁N₂)₂]_n, were obtained by means of alternating‐current electrochemical synthesis. The structure consists of infinite copper–chlorine chains to which 1‐allyl‐3‐amino­pyridinium moieties are attached via a η² Cu—(C=C) interaction. The two independent Cu atoms have distinct coordination environments. One is three‐coordinate, surrounded by two chloro ligands and the olefinic bond, whereas the second copper center is surrounded by a tetrahedral arrangement of four Cl atoms. The lower basicity of 3‐amino­pyridine as compared with 2‐ and 4‐amino­pyridine lowers the capacity of the organic ligand for donating to N—H⋯Cl hydrogen bonds and results in the formation of a large inorganic fragment.     

Enantiomeric bis(μ‐N,N′‐hexamethylenedisalicylaldiminato)dicopper(II) complexes

The title dimeric complex, bis{μ‐2,2′‐[hexane‐1,6‐diyl­bis(nitrilo­methyl­idyne)]­diphenolato‐1:2κ⁴O,N:N′,O′}dicopper(II),[Cu₂(C₂₀H₂₂N₂O₂)₂], has been investigated by single‐crystal X‐ray diffraction, by thermogravimetric analysis and differential scanning calorimetry, and also by FT–IR spectroscopy. Different synthetic and crystallization procedures gave crystals which were quite different in appearance, and it was initially thought that these were different polymorphic forms. Subsequent structure determination showed, in fact, serendipitous preparation of crystals in the P4₁ space group by one method and in space group P4₃ by the other. In these enantiomorphic structures, the Cu atoms have a distorted flattened tetrahedral coordination, with Cu—N and Cu—O distances in the ranges 1.954 (4)–1.983 (4) and 1.887 (4)–1.903 (4) Å, respectively.     

Poly[[di‐μ‐aqua‐tetraaquadi‐μ‐hydroxido‐bis(μ3‐3‐nitrophthalato)tricopper(II)] dihydrate]

The novel title complex, {[Cu₃(C₈H₃NO₆)₂(OH)₂(H₂O)₆]·2H₂O}_n, has a one‐dimensional polymeric double chain structure where the three Cu atoms are linked by μ₂‐OH and μ₂‐H₂O groups, and these trinuclear centres are bridged by two 3‐nitrophthalate ligands. The asymmetric unit contains one and a half crystallographically independent Cu atoms (one lying on a centre of inversion), both coordinated by six O atoms and exhibiting distorted octahedral coordination geometries, but with different coordination environments. Each 3‐nitrophthalate ligand connects to three Cu atoms through two O atoms of one carboxylate group and one O atom of the nitro group. The remaining carboxylate group is free and is involved in intrachain hydrogen bonds, reinforcing the chain linkage.     

catena‐Poly­[[heptakis­(di­methyl­form­amide‐κO)­di‐μ4‐oxo‐tetra‐μ3‐oxo‐hexa­deca‐μ2‐oxo‐tetra­oxo­lan­than­um(III)­octamolybdenum(IV)]‐μ‐sodium(I)]

The title compound, [NaLaMo₈O₂₆(C₃H₇NO)₇]_n, contains infinite chains of [Mo₈O₂₆]⁴⁻ units supporting di­methyl­form­amide‐coordinated La^III cations and linked by Na⁺ cations. The lanthanum center adopts a nine‐coordinate geometry and the Na atom is sandwiched between two β‐[Mo₈O₂₆]⁴⁻ units.     

Poly[bis[aquaneodymium(III)]‐μ2‐oxalato‐di‐μ4‐succinato]

In the title compound, [Nd₂(C₄H₄O₄)₂(C₂O₄)(H₂O)₂]_n, the flexible succinate anion assumes the gauche conformation and bridges the nine‐coordinate Nd atoms to generate two‐dimensional layers parallel to (010). The coordination polymer layers are linked into a three‐dimensional framework by the rigid oxalate ligands. The oxalate ions are located on a center of inversion.     

μ‐Glycine‐O:O′‐di‐μ‐oxo‐bis[(gly­cinato‐N,O)­oxomolybdenum(V)]

In the title compound, [Mo₂O₄(C₂H₄NO₂)₂(C₂H₅NO₂)], two Mo atoms sit in the same distorted pentagonal bipyramid coordination environment. There are four ligand types: oxo‐O, μ₂‐O, μ₂‐glycine and chelate glycine. There is an Mo—Mo bond between the two Mo atoms [2.552 (1) Å]. All amino groups participate in hydrogen bonding with O atoms of other mol­ecules, thus connecting the mol­ecules into a three‐dimensional structure.     

Kinetics and mechanism of oxidation of 2‐mercaptosuccinic acid by bis(μ‐oxo)‐ manganese(III,IV)‐cyclam complex in aqueous medium: Influence of externally added copper(II)

Kinetic studies on the oxidation of 2‐mercaptosuccinic acid by dinuclear [Mn₂^III/IV(μ‐O)₂(cyclam)₂](ClO₄)₃] ( 1 ) (abbreviated as Mn^III–Mn^IV) (cyclam = 1,4,8,11‐tetraaza‐cyclotetradecane) have been carried out in aqueous medium in the pH range of 4.0–6.0, in the presence of acetate buffer at 30°C by UV–vis spectrophotometry. In the pH region, two species of complex 1 (Mn^III–Mn^IV and Mn^III–Mn^IVH, the later being μ‐O protonated form) were found to be kinetically significant. The first‐order dependence of the rate of the reactions on [Thiol] both in presence and absence of externally added copper(II) ions, first‐order dependence on [Cu²⁺] and a decrease of rate of the reactions with increase in pH have been rationalized by suitable sequence of reactions. Protonation of μ‐O bridge of 1 is evidenced by the perchloric acid catalyzed decomposition of 1 to mononuclear Mn(III) and Mn(IV) complex observed by UV–vis and EPR spectroscopy. The kinetic features have been rationalized considering Cu(RSH) as the reactive intermediate. EPR spectroscopy lends support for this. The formation of a hydrogen bonded outer‐sphere adduct between the reductant and the complex in the lower pH range prior to electron transfer reactions is most likely to occur. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 170–177 2004     

Bis{μ‐2‐[(2,3‐dichloro­phenyl)­amino]­benzoato‐κO}di‐μ2‐ethoxo‐octa­methyl­di‐μ3‐oxo‐tetra­tin(IV)

The title compound, [Sn₄(CH₃)₈(C₁₃H₈Cl₂NO₂)₂(C₂H₅O)₂O₂], is a centrosymmetric dimer, with three linearly fused four‐membered Sn—O—Sn—O rings. The coordination poly­hedron of the Sn atom bonded to the carboxyl­ate can be described as trigonal–bipyramidal distorted toward square‐pyramidal. That of the second Sn atom is similar, but the distortion towards square‐pyramidal geometry is greater. The Sn—O and Sn—C distances are 2.020 (2)–2.226 (2) and 2.096 (4)–2.114 (4) Å, respectively. The benzene rings of the 2‐[(2,3‐dichloro­phenyl)­amino]benzoate ligand subtend an angle of 50.49 (17)°; the conformation of the ligand is stabilized by intra­molecular N—H⋯Cl and N—H⋯O hydrogen bonds. The structure is assembled viaπ–π stacking inter­actions to form chains parallel to [10].     

Tetrakis(μ2‐4‐aminobenzoato)di‐μ3‐oxido‐tetrakis[dibutyltin(IV)]

The molecule of the title compound, [Sn₄(C₄H₉)₈(C₇H₆NO₂)₄O₂], lies about an inversion centre and is a tetranuclear bis(tetrabutyldicarboxylatodistannoxane) complex containing a planar Sn₄O₂ core in which two μ₃‐oxide O atoms connect an Sn₂O₂ ring to two exocyclic Sn atoms. Each Sn atom has a highly distorted octahedral coordination. In the molecule, the carboxylate groups of two aminobenzoate ligands bridge the central and exocyclic Sn atoms, while two further aminobenzoate ligands have highly asymmetric bidentate chelation to the exocyclic Sn atoms plus long O...Sn interactions with the central Sn atoms. Each Sn atom is also coordinated by two pendant n‐butyl ligands, which extend roughly perpendicular to the plane of the Sn₄O₁₀ core. Only one of the four unique hydrogen‐bond donor sites is involved in a classic N—H...O hydrogen bond, and the resulting supramolecular hydrogen‐bonded structure is an extended two‐dimensional network which lies parallel to the (100) plane and consists of a checkerboard pattern of four‐connected molecular cores acting as nodes. The amine groups not involved in the hydrogen‐bonding interactions have significant N—H...π interactions with neighbouring aminobenzene rings.     

μ‐Acetato‐μ‐aqua‐μ‐hydroxido‐bis[(1,10‐phenanthroline)copper(II)] dinitrate monohydrate

The triply bridged title dinuclear copper(II) compound, [Cu₂(C₂H₃O₂)(OH)(C₁₂H₈N₂)₂(H₂O)](NO₃)₂·H₂O, (I), consists of a [Cu₂(μ₂‐CH₃COO)(μ₂‐OH)(phen)₂(μ₂‐OH₂)]²⁺ cation (phen is 1,10‐phenanthroline), two uncoordinated nitrate anions and one water molecule. The title cation contains a distorted square‐pyramidal arrangement around each metal centre with a CuN₂O₃ chromophore. In the dinuclear unit, both Cu^II ions are linked through a hydroxide bridge and a triatomic bridging carboxylate group, and at the axial positions through a water molecule. The phenanthroline groups in neighbouring dinuclear units interdigitate along the [010] direction, generating several π–π contacts which give rise to planar arrays parallel to (001). These are in turn connected by hydrogen bonds involving the aqua and hydroxide groups as donors with the nitrate anions as acceptors. Comparisons are made with isostructural compounds having similar cationic units but different counter‐ions; the role of hydrogen bonding in the overall three‐dimensional structure and its ultimate effect on the cell dimensions are discussed.