Octakis(ɛ‐caprolactam‐κO)erbium(III) hexaisothiocyanatochromate(III)

The title compound, [Er(C₆H₁₁NO)₈][Cr(NCS)₆], is a new structure type for [Ln(ɛ‐caprolactam)₈][Cr(NCS)₆], where Ln is a lanthanide. There are two independent cations and two independent anions in the asymmetric unit. The Er atom is in a distorted square‐antiprismatic environment of eight O atoms of the organic ligands; Er—O bond distances are in the range 2.29–2.44 Å. The coordination environment of the Cr atom is a slightly distorted octahedron; Cr—N bond distances vary from 1.99 to 2.01 Å. The mutual packing of the cations and the anions follows a distorted NaCl motif. One cation has the Er atom on a twofold axis and one of the anions has the Cr atom on a twofold axis.     

A pentanuclear bimetallic complex of manganese(II) and aluminium(III) ions: tetra‐μ2‐iodido‐iodidobis(μ3‐2‐methoxyethanolato)bis(μ2‐2‐methoxyethanolato)dimethyl(tetrahydrofuran‐κO)aluminium(III)tetramanganese(II)

The molecule of the title compound, [Mn₄Al(CH₃)₂(C₃H₇O₂)₄I₅(C₄H₈O)], contains one Al^III and four Mn^II ions. Two Mn atoms are five‐coordinate in the form of a trigonal bipyramid or a square pyramid. The two other Mn atoms are six‐coordinate with an octahedral geometry. The fourcoordinate Al atom is linked to the manganese core by μ‐O_alkoxo bridges, forming an almost planar five‐membered ring.     

Triaquatris(μ‐oxydiacetato)dipraseodymium(III) pentahydrate and hexaaquatris(μ‐oxydiacetato)dineodymium(III) oxydiacetic acid solvate dihydrate

Two new complexes of the Ln₂(oda)₃·nH₂O (oda =–O₂CCH₂OCH₂CO₂–) series are reported, i.e. {[Pr₂(C₄H₄O₅)₃(H₂O)₃]·5H₂O}_n and {[Nd₂(C₄H₄O₅)₃(H₂O)₆]·C₄H₆O₅·‐2H₂O}_n. The former is isostructural with the reported La analogue, while the latter is a new structural variety within the series. Each compound exhibits two independent nine‐coordinated Ln centres showing a variety of coordination geometries.     

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.     

Crystallographic report: (η5‐Fluorenyl)‐tris‐pyridine‐di‐iodo‐lanthanum(III) and ‐neodymium(III)

The structures of the title compounds are mononuclear with each lanthanide bound by a single η⁵‐fluorenyl ligand, two trans‐disposed iodides and three meridionally oriented pyridine molecules. Copyright © 2005 John Wiley & Sons, Ltd.     

Gold(III) π‐Allyl Complexes

Gold(III) π‐complexes have been authenticated recently with alkenes, alkynes, and arenes. The key importance of Pd^II π‐allyl complexes in organometallic chemistry (Tsuji–Trost reaction) prompted us to explore gold(III) π‐allyl complexes, which have remained elusive so far. The (P,C)Au^III(allyl) and (methallyl) complexes 3 and 3′ were readily prepared and isolated as thermally and air‐stable solids. Spectroscopic and crystallographic analyses combined with detailed DFT calculations support tight quasi‐symmetric η³‐coordination of the allyl moiety. The π‐allyl gold(III) complexes are activated towards nucleophilic additions, as substantiated with β‐diketo enolates.     

Poly[aqua(μ3‐benzene‐1,2‐dicarboxylato)bis(μ3‐hydroxido)bis(μ2‐isonicotinato)dierbium(III) monohydrate] and the thulium analogue

The two isomorphous lanthanide coordination polymers, {[Ln₂(C₆H₄NO₂)₂(C₈H₄O₄)(OH)₂(H₂O)]·H₂O}_n (Ln = Er and Tm), contain two crystallographically independent Ln ions which are both eight‐coordinated by O atoms, but with quite different coordination environments. In both crystal structures, adjacent Ln atoms are bridged by μ₃‐OH groups and carboxylate groups of isonicotinate and benzene‐1,2‐dicarboxylate ligands, forming infinite chains in which the Er...Er and Tm...Tm distances are in the ranges 3.622 (3)–3.894 (4) and 3.599 (7)–3.873 (1) Å, respectively. Adjacent chains are further connected through hydrogen bonds and π–π interactions into a three‐dimensional supramolecular framework.     

Synthesis,Crystal Structure,Fluorescent and Antioxidation Properties of Cerium(III) and Europium(III) Complexes with Bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine

Two aliphatic ether Schiff base lanthanide complexes (Ln = Eu, Ce) with bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine (Bod), were synthesized and characterized by physicochemical and spectroscopic methods. [Eu(Bod)(NO₃)₃] ( 1 ) is a discrete mononuclear species and [Ce(Bod)(NO₃)₃DMF]_∞ ( 2 ) exhibits an inorganic coordination polymer. In the two complexes, the metal ions both are ten‐coordinated and the geometric structure around the Ln^III atom can be described as distorted hexadecahedron. Under excitation at room temperature, the red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Moreover, the antioxidant activities of the two complexes were investigated. The results demonstrated that the complexes have better scavenging activity than both the ligand and the usual antioxidants on the hydroxyl and superoxide radicals.     

meso‐(2‐Pyridyl)‐boron(III)‐subporphyrin: Perimeter Iridium(III) Coordination

Peripherally metalated porphyrinoids are promising functional π‐systems displaying characteristic optical, electronic, and catalytic properties. In this work, 5‐(2‐pyridyl)‐ and 5,10,15‐tri(2‐pyridyl)‐B^III‐subporphyrins were prepared and used to produce cyclometalated subporphyrins by reactions with [Cp*IrCl₂]₂, which proceeded through an efficient C?H activation to give the corresponding mono‐ and tri‐Ir^III complexes, respectively. While the mono‐Ir^III complex was obtained as a diastereomeric mixture, a C₃‐symmetric tri‐Ir^III complex with the three Cp*‐units all at the concave side was predominantly obtained in a high yield of 90 %, which displays weak NIR phosphorescence even at room temperature in degassed CH₂Cl₂, differently from the mono‐Ir^III complexes.     

fac‐Tris(2‐ethyl‐4‐oxo‐4H‐pyran‐3‐olato‐κ2O3,O4)­iron(III) and its aluminium(III) analog

The crystal structures of the title iron(III) and aluminium(III) ethyl maltolate complexes, [Fe(C₇H₇O₃)₃] and [Al(C₇H₇O₃)₃], respectively, are isomorphous. In each case, the three bidentate ligand mol­ecules are bound to the metal atom, forming a distorted octahedral coordination geometry in a fac configuration.     

Amido‐3‐hydroxypyridin‐4‐ones as Iron(III) Ligands

The synthesis and physicochemical properties of a range of 2‐ and 6‐amido‐3‐hydroxypyridin‐4‐ones are described. All the amido‐substituted 3‐hydroxypyridin‐4‐ones have lower pK_a values than 1,2‐dimethyl‐3‐hydroxypyridin‐4‐one (deferiprone). This is due to the inductive effect of the amido group. Furthermore, the pK_a values of the 3‐hydroxy group in 1‐nonsubstituted pyridinones are dramatically lower than those of the corresponding 1‐alkyl analogues, indicating that a strong hydrogen bond exists between the 2‐amido function and the 3‐oxygen anion, which stabilises the anion. As a result of the decreased competition with protons, the pFe³⁺ values of this group of molecules are higher than that of deferiprone. The distribution coefficients of these molecules are also increased despite the lack of a hydrophobic 1‐alkyl substituent and this is ascribed to the intramolecular hydrogen bond. X‐ray diffraction studies confirm the existence of the intramolecular hydrogen bond.     

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.     

Phosphorylation of 2‐(3‐methyl‐1,3‐diazabuten‐1‐yl)‐3‐ethoxycarbonylthiophenes with phosphorus(III) halides

2‐(3‐Methyl‐1,3‐diazabuten‐1‐yl)‐3‐ethoxycarbonylthiophenes are phosphorylated with phosphorus(III) halides in basic media at position 5 of the thiophene ring. Up to three heteroaromatic substituents can be introduced one by one at the same phosphorus atom. On this basis, mono‐, bis‐, and trishetaryl substituted P(III) and P(V) derivatives have been obtained. Phosphorylated 2‐(N,N‐dimethylformamidino)‐3‐ethoxycarbonylthiophenes provide a synthetic access to phosphorylated thienopyrimidines. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:641–651, 2001     

The dinuclear scandium(III) cyclooctatetraenyl chloride complex di‐μ‐chlorido‐bis[(η8‐cyclooctatetraene)(tetrahydrofuran‐κO)scandium(III)]

Only a few cyclooctatetraene dianion (COT) π‐complexes of lanthanides have been crystallographically characterized. This first single‐crystal X‐ray diffraction characterization of a scandium(III) COT chloride complex, namely di‐μ‐chlorido‐bis[(η⁸‐cyclooctatetraene)(tetrahydrofuran‐κO )scandium(III)], [Sc₂(C₈H₈)₂Cl₂(C₄H₈O)₂] or [Sc(COT)Cl(THF)]₂ (THF is tetrahydrofuran), (1), reveals a dimeric molecular structure with symmetric chloride bridges [average Sc—Cl = 2.5972 (7) Å] and a η⁸‐bound COT ligand. The COT ring is planar, with an average C—C bond length of 1.399 (3) Å. The Sc—C bond lengths range from 2.417 (2) to 2.438 (2) Å [average 2.427 (2) Å]. Direct comparison of (1) with the known lanthanide (Ln) analogues (La, Ce, Pr, Nd, and Sm) illustrates the effect of metal‐ion (M ) size on molecular structure. Overall, the M —Cl, M —O, and M —C bond lengths in (1) are the shortest in the series. In addition, only one THF molecule completes the coordination environment of the small Sc^III ion, in contrast to the previously reported dinuclear Ln–COT–Cl complexes, which all have two bound THF molecules per metal atom.     

Poly[[tetraaquatris(μ3‐2,2‐dimethylmalonato)dilanthanum(III)] monohydrate]

In the title complex, {[La₂(C₅H₆O₄)₃(H₂O)₄]·H₂O}_n, the La atoms are connected by bridging O atoms from carboxylate groups to build, through centres of inversion, two‐dimensional layers parallel to the ac plane containing decanuclear 20‐membered rings. The coordinated water molecules are involved in intralayer hydrogen‐bond interactions. Adjacent layers are linked via hydrogen bonding to the solvent water molecules. This work represents the first example of a new substituted malonate–lanthanide complex.     

trans‐Bis(cyano‐κC)(1,4,8,11‐tetraazacyclotetradecane‐κ4N)manganese(III) perchlorate,a low‐spin manganese(III) complex

The crystal structure of the low‐spin (S = 1) Mn^III complex [Mn(CN)₂(C₁₀H₂₄N₄)]ClO₄, or trans‐[Mn(CN)₂(cyclam)](ClO₄) (cyclam is the tetradentate amine ligand 1,4,8,11‐tetra­aza­cyclo­tetra­decane), is reported. The structural parameters in the Mn(cyclam) moiety are found to be insensitive to both the spin and the oxidation state of the Mn ion. The difference between high‐ and low‐spin Mn^III complexes is that a pronounced tetragonal elongation of the coordination octahedron occurs in high‐spin complexes and a slight tetragonal compression is seen in low‐spin complexes, as in the title complex.     

Phenyliodine(III) Triflate Mediated Synthesis of 5‐Benzoyldihydro‐2(3H)‐furanones

A direct and efficient method for the preparation of 5‐benzoyldihydro‐2(3H)‐furanones was realized by cyclization of 4‐benzoylbutyric acids in the presence of phenyliodine(III) triflate.     

Crystal Structure of μ‐Oxo‐bis[9,22‐(bisbutyloxy)hemiporphyrazinato]iron(III)

The crystal structure of the title compound, C₆₈H₆₀N₁₆O₅Fe₂, shows a dinuclear complex of two crystallographically independent, distorted hemiporphrazinato iron complexes with five‐coordinate iron and oxygen as bridging ligand. The Fe1‐O1‐Fe2 angle is 151.16°, the Fe‐O bond lengths are Fe1‐O1 [1.771(2) Å] and Fe2‐O1 [1.773(2) Å]. The dinuclear complexes have a staggered conformation with a dihedral angle of 26.2°, but coaxially to form tetrameric units is not observed. The molecule is characterized by short Fe‐N (isoindole) bonds [1.998(3) Å] and long Fe‐N (pyridine) bonds, values range from [2.175(3) Å] to [2.245(3) Å].     

A comparative kinetic study for the oxidation of 2‐mercaptoethanol by di‐μ‐oxo‐bis(1,4,7,10‐tetraazacyclododecane)‐dimanganese(III,IV) and di‐μ‐oxo‐bis(1,4,8,11‐tetraazacyclotetradecane)‐dimanganese(III,IV) complexes: Influence of copper(II)

A comparative kinetic study of the reactions of two mixed valence manganese(III,IV) complexes with macrocyclic ligands, [L¹Mn^IV(O)₂Mn^IIIL¹], 1 (L¹ = 1,4,7,10‐tetraazacyclododecane) and [L²Mn^IV(O)₂Mn^IIIL²], 2 (L² = 1,4,8,11‐tetraazacyclotetradecane) with 2‐mercaptoethanol (RSH) has been carried out by spectrophotometry in aqueous buffer at (30 ± 0.1)°C. Rate of the reactions between the oxidants and the reductant was found to be negligibly slow with no systematic dependence on either redox partners. Externally added copper(II) (usually 5 × 10^?7 mol dm^?3), however, increases the rate of the reduction of 1 and 2 significantly. In the presence of catalytic amount of copper(II), the rate of the reaction is nearly proportional to [RSH] at lower concentration of the reductant but follows a saturation kinetics at higher concentration of the latter for the reaction between 1 and the thiol. Reaction rate was found to be strongly influenced by the variation of acidity of the medium and the observed kinetics suggests that the two reductant species ([Cu(RSH)]²⁺ and [Cu(RS)]⁺) are significant for the reaction between 1 and the thiol. The dependence of the rate on [RSH] for the reduction of 2 by the thiol was complex and rationalized considering two equilibria involving the catalyst (Cu²⁺) and the reductant. The pH rate profile suggests that both the μ‐O protonated [Mn^III(O)(OH)Mn^IV] and the deprotonated [Mn^III(O)₂Mn^IV] forms of the oxidant 2 become important. The kinetic results presented in this study indicate the domination of outer‐sphere path. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 129–137, 2004