Showing papers in "European Journal of Inorganic Chemistry in 2002"

Anderson‐Type Heteropolymolybdates Containing Tris(alkoxo) Ligands: Synthesis and Structural Characterization

Abstract: Anderson-type molybdopolyanions containing tris(alkoxo) ligands [MMo6O18{(OCH2)3CR}2]3− (M = MnIII, FeIII) and [H2MMo6O18{(OCH2)3CR}2]2− (M = NiII, ZnII), (R = CH3, NO2, CH2OH), were prepared by treatment of [N(C4H9)4]4[α-Mo8O26] with tris(hydroxymethyl)methane derivatives in the presence of manganese(III) acetylacetonate, iron(III) acetylacetonate, nickel(II) acetate, or zinc(II) acetate. The complexes were structurally characterized in solution, and also by single-crystal X-ray diffraction in the cases of [N(C4H9)4]3[MnMo6O18{(OCH2)3CNO2}2], [N(C4H9)4]2[H2NiMo6O18{(OCH2)3CCH2OH}2], and [N(C4H9)4]2[H2ZnMo6O18{(OCH2)3CCH3}2]. Two tris(alkoxo) ligands replace the six hydroxo groups usually found in Anderson polyanions of formula [H6MMo6O24]n−. The complex structures may be divided into two groups: In the first one the tris(alkoxo) ligands are bound entirely to the central heteroatom, while in the second one they cap a tetrahedral cavity. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

CH/π Interactions Implicated in the Crystal Structure of Transition Metal Compounds − A Database Study

Abstract: A statistical study was carried out to investigate the role of the CH/π interaction in the crystal structure of transition metal compounds. Thus, short CH/π distances were surveyed in crystal structures deposited in the Cambridge Structural Database. Among organometallic entries bearing C6 or C5 aromatic rings, a substantial part of the structures has been found to have intermolecular CH/π contacts shorter than the van der Waals distance. Further, in many structures short intramolecular CH/π contacts have been found. Interligand and intraligand CH/π interactions were also surveyed in coordination compounds bearing the typical ligands 1,10-phenanthroline, 2,2′-bipyridine, and 2,2′:6′,2′′-terpyridine, as well as triphenylphosphane complexes of ruthenium, rhenium, and rhodium. The results were discussed in the context of the CH/π interaction in controlling the crystal packing and the molecular structure of transition metal compounds. The compact structure with CH/π interactions is a general aspect in coordination and organometallic chemistry. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Salts of 5,5′‐Azotetrazolate

Abstract: Salts of 5,5′-azotetrazolate with alkali metal, alkaline earth metal and several trivalent cations were synthesized as potential initial explosives. The synthesis in water yields hydrates of these salts that were studied by NMR and vibrational spectroscopy as well as X-ray diffraction. Their thermal properties were studied by DSC and TG.

Chalcogen-Bridged Copper Clusters

Abstract: The investigation of coinage metal molecular clusters bridged by chalcogen atoms represents an area of ever increasing activity in recent chemical and material science research. This is largely due to the relatively high ionic and even higher electric conductivity of binary coinage metal chalcogenides, which leads to properties intermediate between those of semiconducting and metallic phases. In addition, the size-dependency of the chemical, physical, and structural properties of substances on going from small molecules to bulk materials is of general interest. Approaches towards the synthesis and investigation of such clusters have included the study of colloidal nanoparticles with a narrow size distribution, as well as the formation and isolation of crystalline cluster compounds amenable to structural determination by single-crystal X-ray diffraction analysis. Irrespective of the chosen synthesis route, the molecules have to be kinetically protected from decomposition to the thermodynamically favored binary phases by a suitable ligand sphere, often consisting of tertiary phosphane molecules, or a combination of phosphanes and organic groups. In this report, we concentrate on the syntheses and structural as well as physical properties of ligand-stabilized, chalcogen-bridged copper clusters, which have been comprehensively studied by means of experimental and quantum chemical investigations.

The Structure and Fluorescence Properties of Two Novel Mixed-Ligand Supramolecular Frameworks with Different Structural Motifs

Abstract: Two novel coordination polymers formed by cobalt nitrate and 1,2-bis(4-pyridyl)ethane with the homologous ligands 2-aminoterephthalic acid and terephthalic acid, respectively, have been prepared. One displays a fivefold diamond-type feature while the other exhibits a twofold interpenetrating structural motif. The thermal and photoluminescence properties associated with their structures have been characterized and studied. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis, Structure and Dehalogenation of the Disilene RClSi=SiClR [R = (tBu3Si)2MeSi]

Abstract: The reaction of R*2MeSi−SiX2X′ (X/X′ = Cl/Br, Br/Cl) with NaR* (R* = supersilyl SitBu3) leads, probably via the silylenes R*2MeSi−SiX, to the trans-configurated disilene (R*2MeSi)ClSi=SiCl(SiMeR*2), which could be isolated as orange-red crystals. According to an X-ray structure analysis, the central SiClSi=SiClSi framework of the disilene − the formation mechanisms of which are discussed − is planar. The Si=Si double bond is as short as 2.163(4) A and shows a band in the Raman spectrum at 589 cm−1. Due to its insolubility in organic solvents, no NMR spectra of the disilene in solution were obtained. The spatially overcrowded disilene is stable towards H2O, MeOH, HF, and NaR*. It melts at 228 °C with decomposition. Reduction of the disilene occurs with LiC10H8 in THF with formation of a reaction mixture containing a chlorine-free product that gives a low field 29Si NMR signal at δ = 91.5 (the region for unsaturated Si atoms). It transforms in solution with traces of oxygen into a substance which, according to mass spectrometry (chemical ionization), shows a mass for the disilyne R*2MeSi−Si≡Si−SiMeR*2 plus two oxygen atoms. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Not Just Heavy “Grignards”: Recent Advances in the Organometallic Chemistry of the Alkaline Earth Metals Calcium, Strontium and Barium

Abstract: Since their initial development in the early 1900’s, Grignard reagents have proven to be immensely useful and are among the most common organometallic reagents. The nature of the reagents in solution is complex and depends on substituents, solvent, concentration and temperature. Despite continuing questions about their solid state and solution composition and conformation, organomagnesium reagents find new applications continually. In contrast, little information about the heavier alkaline earth organometallic compounds RMX and R2M (R = alkyl, aryl; M = Ca, Sr, Ba, X = halide) exists. High reactivity due to the predominantly ionic character of the metal-ligand bond and increased lability complicates synthetic access. Recent interest in the organometallic chemistry of the alkaline earth metals calcium, strontium and barium has been sparked by the realization that heavy alkaline earth metal organometallics play unique roles in synthetic applications, such as polymerization initiators and as reagents to modify polymers. As a result, the organometallic chemistry of calcium, strontium and barium has received significant attention over the last few years. This article summarizes recent results in this emerging area of chemistry. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Iridium‐Catalysed Allylic Substitution: Stereochemical Aspects and Isolation of IrIII Complexes Related to the Catalytic Cycle

Abstract: Ir-catalysed allylic alkylations of enantiomerically enriched monosubstituted allylic acetates proceed with up to 87% retention of configuration using P(OPh)3 as ligand. High regio- and enantioselectivity of up to 86% ee in asymmetric allylic alkylations of achiral or racemic substrates is achieved with monodentate phosphorus amidites as ligands. Lithium N-tosylbenzylamide was identified as a suitable nucleophile for allylic aminations. Of particular importance is the use of lithium chloride as an additive, generally leading to increased enantioselectivities. Two (π-allyl)IrIII complexes were characterised by X-ray crystal structure analysis and spectroscopic data.

The Construction of (Salophen)ruthenium(II) Assemblies Using Axial Coordination

Abstract: Mononuclear and binuclear carbonylruthenium(II) complexes with N2O2 Schiff base ligands based on 3,5-di-tert-butylsalicylaldehyde and three different ortho-diamines have been prepared. The mononuclear Ru(BSP)(CO) [BSP = N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-phenylenediamine] complex 4 acts as a versatile supramolecular synthon, as illustrated by the fact that it spontaneously forms linear and three-dimensional assemblies through axial coordination with pyridyl Lewis bases. Using this motif, neutral and charged assemblies 6, 9, and 12 were prepared. The versatility of the salophen ligand was highlighted by the preparation of bimetallic carbonylruthenium(II) compounds 14−17 from 1,2,4,5-tetraaminobenzene and 2,3,7,8-tetraaminodibenzo[1,4]dioxin. The bimetallic complexes were isolated as a mixture of cis and trans diastereomers with respect to the spatial relationship between the two axially bound carbon monoxide ligands. The electronic spectral and electrochemical properties of the pyridyl adducts 5, 15, and 17 were compared. The properties of 17 closely resembled 5 due to the insulating effect of the extended central tetraamino fragment, while 15 behaved as a single, novel chromophore. The electrochemical studies revealed that the central tetraamino linker regulates the communication between the two metal centers of 15 and 17. It was found that the two metal atoms of 15 sense each other to a larger extent than those of 17.

Formation and Characterization of Zwitterionic Stereoisomers from the Reaction of B(C6F5)3 and NEt2Ph: (E)‐ and (Z)‐[EtPhN+=CHCH2‐B−(C6F5)3]

Abstract: The stoichiometric reaction of B(C6F5)3 and NEt2Ph I, at room temperature, in an aromatic solvent, has been investigated by 1D and 2D NMR spectroscopy (1H, 11B,13C, 15N and 19F). No Et2PhN·B(C6F5)3 adduct was observed. An equilibrium between free B(C6F5)3, NEt2Ph, [HB(C6F5)3]−(HNEt2Ph)+ and two zwitterionic stereoisomers (E)- and (Z)-[EtPhN+=CH-CH2-B−(C6F5)3] (30%) in an E/Z ratio of 3:2 was observed. Whatever the protic reagent Z-OH [Z = H, SiPh3, (c-C5H9)7O12Si8, or silanol group of silica], all the equilibria involved in solutions of I are quantitatively displaced towards the ionic form [Z-O-B(C6F5)3]−(HNEt2Ph)+. In the case of dimethylaniline, besides free B(C6F5)3 and Me2NPh, the 1:1 adduct (C6F5)3B·NMe2Ph and an iminium salt [PhCH3N=CH2]+[HB(C6F5)3]− have been identified. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Some Copper and Cobalt Complexes of Schiff‐Base Macrocycles Containing Pyridazine Head Units

Abstract: The Schiff-base macrocycle L14, formed by the [2+2] condensation of 3,6-diformylpyridazine and 1,3-diaminopropane, has facilitated the preparation of the first extensive family of pyridazine-bridged macrocyclic complexes. The structural, magnetic and electrochemical behaviour of these complexes is of considerable interest. This microreview provides an overview of prior relevant studies and then describes some of the recent copper and cobalt chemistry of the macrocyclic ligand L14. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Cucurbituril as a New Macrocyclic Ligand for Complexation of Lanthanide Cations in Aqueous Solutions

Abstract: (Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Evidence Based on Crystal Structures and Calculations of a C−H···π Interaction Between an Organic Moiety and a Chelate Ring in Transition Metal Complexes

Abstract: Structural and computational evidence is given for a special type of C−H···π interaction where the C−H group interacts with the π-system of a six-membered chelate ring. An investigation of crystal structures shows that these interactions take place in quite a number of metal complexes, including organometallic compounds; in the CSD we found over 1200 structures with these interactions. These interactions exist in complexes of different metals and various chelate rings. DFT calculations on three model systems show that the energy of these interactions is about 1 kcal/mol. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Polynuclear MnII Complexes with Chloroacetate Bridge − Syntheses, Structure, and Magnetic Properties

Abstract: Three new polynuclear MnII complexes with chloroacetate bridges were obtained and characterized by X-ray diffraction: [Mn3(μ-ClCH2COO)6(bpy)2] (1), [Mn2(μ-ClCH2COO)2(phen)4](ClO4)2 (2), and [Mn(μ-ClCH2COO)2(phen)]n (3). The Mn···Mn distance for 1 (3.624 A) is smaller than for 2 (4.613 A) and 3 (4.530 A); this is in agreement with the number of carboxylate bridges. The three compounds show a weak antiferromagnetic coupling. The J values are −3.82 cm−1 for 1, −0.85 cm−1 for 3, and no coupling was observed for 2. Each compound showed a characteristic EPR spectrum at 4 K. Simulation of these spectra could be obtained with D = −0.16 cm−1 and E = −0.015 cm−1 for compound 1, and D = −0.045 cm−1 and E = −0.004 cm−1 for compound 2. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Three Novel End-to-End Single Azido-Bridged Ferromagnetic Copper(II) Chains: Synthesis, Crystal Structure, and Magnetic Behavior

Abstract: Three new single end-to-end azido-bridged copper(II) chains [Cu(L1)(N3)]n(ClO4)n (1), [Cu(L2)(N3)]n(ClO4)n (2), and [Cu(L3)(N3)]n(ClO4)n (3) using three different tridentate Schiff bases L1, L2, and L3, obtained from condensation of pyridine-2-carbaldehyde with N,N-dimethylethane-1,2-diamine, N,N-diethylethane-1,2-diamine, and 4-(2-aminoethyl)morpholine, respectively, have been synthesized, and their crystal structures have been determined by X-ray diffraction methods. Complex 1, C10H15CuN6ClO4, crystallizes in an orthorhombic system, space group P212121, with a = 7.434(3), b = 12.047(4), c = 17.404(6) A, and Z = 4; complex 2, C12H19CuN6ClO4, crystallizes in an orthorhombic system, space group Pna21, with a = 14.723(5), b = 13.829(5), c = 8.002(5) A, and Z = 4 and complex 3, C12H17CuN6ClO5, crystallizes in an orthorhombic system, space group Pna21, with a = 13.837(15), b = 14.804(2), c = 8.050(4) A, and Z = 4. Each structure consists of a single end-to-end azido-bridged copper(II) 1D chain where each copper(II) center possesses a square pyramidal geometry. Magnetic susceptibility data, measured from 4 to 300 K, show weak ferromagnetic interaction through the end-to-end bridging azido pathway in all the complexes. The magnetic data were fitted to a high temperature series-expansion for a one-dimensional system with S = 1/2 local spin based on the Hamiltonian H = −JΣSi·Si+1 for all the complexes, giving the parameters J = +2.15 cm−1, g = 2.23 for 1, J = +3.61 cm−1, g = 2.16 for 2, and J = +2.06 cm−1, g = 2.17 for 3. This unusual magnetic behavior through the end-to-end bridging azido pathway has been correlated to the structural parameters. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis, Crystal Structure and Magnetic Properties of the Helical‐Chain Compounds [M2(O2CC12H8CO2)2(H2O)8] [M = Cobalt(II), Nickel(II)]

Abstract: New 1D complexes are obtained from the reaction of 1,1′-biphenyl-2,2′-dicarboxylic acid (diphenic acid) with KOH and [Co(NO3)2·6H2O] or [Ni(NO3)2·6H2O] under hydrothermal conditions. Compounds 1 and 2 are isostructural and their structure consists of stacked helical chains of octahedral metal(II) ions. Magnetic measurements show that the CoII atoms in compound 1 are quasi-isolated. In compound 2, the NiII chains exhibit a ferromagnetic behaviour. From a simple model derived from the scaling theory of phase transition, the exchange coupling between neighbouring NiII atoms is evaluated at J = +1.06 K. A zero-field splitting effect is observed below 16 K.

Luminescent Star-Shaped Zinc(II) and Platinum(II) Complexes Based on Star-Shaped 2,2′-Dipyridylamino-Derived Ligands

Abstract: New ZnII and PtII complexes of the star-shaped ligands 2,4,6-tris(2,2′-dipyridylamino)-1,3,5-triazine (tdat), 1,3,5-tris(2,2′-dipyridylamino)benzene (tdab), 2,4,6-tris[p-(2,2′-dipyridylamino)phenyl]-1,3,5-triazine (tdapt) and 1,3,5-tris[p-(2,2′-dipyridylamino)phenyl]benzene (tdapb) have been synthesized and characterized. 1:1, 1:2 and 1:3 (ligand vs. the number of Zn atoms) ZnII complexes of the tdat ligand have been identified. The 1:1 and 1:2 ZnII complexes of tdat are dynamic in solution. For the tdab, tdapt and tdapb ligands, only 1:3 complexes of PtII and ZnII have been isolated. Single-crystal X-ray diffraction analyses have been carried out for some of these new complexes, which revealed that there is a distinct difference in the arrangement of star-shaped ligands in the complexes of ZnII and those of PtII. The PtII complexes of tdat and tdab adopt an unusual “bowl” shape and stack in a “head-to-tail” fashion in the crystal lattice. In contrast, the corresponding ZnII complexes do not have a “bowl” shape. The difference between the ZnII complexes and the PtII complexes can be attributed to the different coordination geometry preferred by the two metal ions. The ZnII complex of tdapb displays several crystal motifs, two of which contain benzene molecules in the crystal lattices. All complexes are luminescent in the blue region, attributable to ligand-based π ⇄ π* transitions. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Iron- and Ruthenium-Containing Triple-Decker Complexes with a Central Pentaphospholyl Ligand − X-ray Structures of [(η-C5H5)Fe(μ-η:η-P5)Ru(η-C5Me5)]PF6 and [(η-C5Me5)Ru(μ-η:η-P5)Ru(η-C5Me5)]PF6

Abstract: Triple-decker cationic complexes with a central pentaphospholyl (pentaphosphacyclopentadienyl) ligand [Cp*M(μ-η:η-P5)M′(η-C5R5)]+ (3b: M = M′ = Fe, R = Me; 4a: M = Ru, M′ = Fe, R = H; 4b: M = Fe, M′ = Ru, R = H; 4c: M = Fe, M′ = Ru, R = Me; 5a: M = M′ = Ru, R = H; 5b: M = M′ = Ru, R = Me) were synthesized by exploitation of the stacking reactions of pentaphosphametallocenes Cp*M(η-P5) (1: M = Fe; 2: M = Ru) with half-sandwich fragments [(η-C5R5)M′]+. They were isolated as salts with BF4− or PF6− anions, and the structures of 4aPF6 and 5bPF6 were determined by X-ray diffraction. Triple-decker complexes with a central pentaphospholyl ligand are less reactive in nucleophilic degradation reactions than analogous complexes with C4Me4P and Cp* ligands in the bridging position. Only 4a and the previously known analogue 3a (M = M′ = Fe, R = H), containing the CpFe fragment, are nucleophilically destroyed by MeCN and NaI. The electrochemical properties of 2, 3a, 3b, 4a−c, 5a and 5b and the related cobalt-containing complexes [(η-C4Me4)Co(μ-η:η-P5)MCp*]+ (6: M = Fe; 7: M = Ru) were investigated. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Hydrothermal Syntheses, Structures, and Properties of First Examples of Lanthanide(III) 2,3‐Pyrazinedicarboxylates with Three‐Dimensional Framework

Abstract: Lanthanide 2,3-pyrazinedicarboxylate complexes with three-dimensional frameworks, [Ln(2)(pzdc)(3)(H2O)]x.2xH(2)O [Ln = Pr (2), Nd (3), and Eu (4)], were obtained by hydrothermal reactions of 2,3-pyrazinedicarboxylic acid (H(2)pzdc) and the lanthanide(III) chlorides, while [La-2(pzdc)(3)(H2O)](x).2xH(2)O (1) was obtained by hydro(solvo)thermal reaction of LaCl3.7H(2)O and 2,3-pyrazinedicarboxylic acid. They are isomorphous and exhibit complicated 3-D structures based on [Ln(2)(pzdc)(3)(H2O)] building blocks. In the asymmetric unit, the two Ln(3+) ions are both nine-coordinate, but with different coordination environments. The ligand pzdc coordinates to the central Ln(3+) ions in a tetradentate, hexadentate, or heptadentate manner. Utilizing the characteristic of Eu3+ ion to act as a conformational probe, we determined the high-resolution spectra of 4, which show that there are two Eu3+ ion sites in the coordination polymer. This is also in agreement with the results of the X-ray single-crystal diffraction study. It was concluded that there are two La3+, two Pr3+ and two Nd3+ ion sites in polymers 1, 2, and 3, respectively. The thermogravimetric analyses of these complexes show that all coordinated and uncoordinated water molecules were lost at the first weight loss above 240 C. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002.

Half‐Sandwich Complexes with Aminocarboxylate Ligands and Their Use as Enantioselective Hydrogen Transfer Catalysts

Abstract: Chiral-at-metal half-sandwich complexes of rhodium, iridium, ruthenium, or osmium of the general formula [(ηn-ring)M(Aa)Cl] [(ηn-ring)M = (η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru, (η6-p-MeC6H4iPr)Os; Aa = L-α-aminocarboxylate] can readily be prepared from the corresponding dimers [{(ηn-ring)MCl}2(μ-Cl)2]. The compounds have been prepared as diastereomeric mixtures of the two epimers at the metal center. In general, alkynyl aminocarboxylate derivatives [(ηn-ring)M(Aa)(C≡CR)] are obtained by treating the aforementioned chlorides with the corresponding alkynes in basic media. However, the reaction of the (alaninato)rhodium chloride [(η5-C5Me5)Rh(Ala)Cl] with the alkynes HC≡CR (R = Ph, p-tolyl) produced the alkynylcyclobutadiene complexes [(η5-C5Me5)Rh(η4-C4HR2C≡CR)] (R = Ph, p-tolyl). Treatment of the chlorides [(ηn-ring)M(Aa)Cl] with AgBF4 afforded the cationic trimers [{(ηn-ring)M(Aa)}3](BF4)3. Trimerization occurs with chiral self-recognition: only the (R,R,R) or (S,S,S) configuration at the metal trimers can be detected. The trimers [{(ηn-ring)M(Aa)}3](BF4)3 reacted with tertiary phosphanes, leading to the cationic mononuclear complexes [(ηn-ring)M(Aa)(PR3)](BF4). The assignment of the configuration at the metal center was accomplished by X-ray diffraction, circular dichroism and NMR spectroscopy. Most of the aminocarboxylate derivatives epimerized at the metal center. On the basis of kinetic and spectroscopic data, a general mechanism is proposed for the epimerization process. Neutral [(ηn-ring)M(Aa)Cl] and cationic [{(ηn-ring)M(Aa)}3](BF4)3 complexes are active catalysts for the hydrogen transfer reaction from 2-propanol to acetophenone. Conversions of up to 97% and enantioselectivities up to 75% were achieved. A proposal about the origins of the enantioselectivity is given. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Cobalt(II)/(III) Complexes Containing o‐Iminothiobenzosemiquinonato(1−) and o‐Iminobenzosemiquinonato(1−) π‐Radical Ligands

Abstract: The coordination chemistry of 6-amino-2,4-di-tert-butylthiophenol (H[LSAP]) and of 2-anilino-4,6-di-tert-butylphenol (H[LOAP]) with cobalt(II) ions was investigated in the presence and absence of dioxygen. It was shown that both compounds were redox-non-innocent ligands, existing in different protonation and oxidation levels as: (i) o-aminophenolates(1−) [(LXAP)1−], (ii) o-imidophenolates(2−) [(LXIP)2−], and (iii) one-electron oxidized forms o-iminobenzosemiquinonates(1−) [(LXISQ)1−], which are π-radicals (X = S, O for the sulfur or oxygen derivative). The following complexes were synthesized: [CoII(LSAP)2]2 (1), [CoII(LSISQ)2]2·0.5n-hexane (2·0.5n-hexane), [CoIIII(LSISQ)2] (3), [CoIIII(LOISQ)2] (4), and [CoIIICl(LOISQ)2] (5). The compounds 2·0.5n-hexane, 4, and 5 were structurally characterized by X-ray crystallography. It was shown that the different protonation and oxidation levels of the ligands could readily be identified by X-ray crystallography. Complex 2 could be reversibly oxidized and reduced electrochemically, yielding a monocation and a monoanion, respectively. It was shown that these processes were metal-centered ([CoIII(LSISQ)2]+, [CoII(LSISQ)2], and [CoI(LSISQ)2]−). The electronic structures were elucidated by UV/Vis and EPR spectroscopy and magnetochemistry. Complexes 3, 4, and 5 were shown to be singlet diradicals. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

cine and tele Nucleophilic Substitutions in (η6-Arene)tricarbonylchromium and Tricarbonyl(η5-cyclohexadienyl)manganese Complexes

Abstract: Addition of a nucleophile to an (η6-arene)tricarbonylchromium or a tricarbonyl(η5-cyclohexadienyl)manganese complex substituted with a leaving group X (X = F, Cl, OMe, OPh, NR2) affords (after treatment with acid) new complexes with the same η6 or η5 hapticity. The overall reaction involves addition of the nucleophile ortho, meta, or para with respect to the leaving group and HX elimination. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The Structure and Physical Properties of a Novel Three‐Dimensional Zeolite‐Like Nanoporous Architecture Formed by Two Different Polymeric Layers: [Eu2(btc)(H2btc)(H2O)]·4H2O

Abstract: The open framework of [Eu2(btc)(H2btc)(H2O)]·4H2O (1), prepared by hydrothermal reaction of EuCl3 with 1,2,4,5-benzenetetracarboxylic anhydride in acidified aqueous solution, is built up from two types of polymeric layers with [EuO6(H2O)]n units as tethers, resulting in nanoporous channels that host water molecules through complex hydrogen bonding. Crystallographic data for 1: monoclinic, P21/n, with a = 10.7562(2) A, b = 7.2075(2) A, c = 17.2180(5) A, β = 97.072(2)° and Z = 2. A study of the temperature dependence of the magnetic susceptibility data reveals that the paramagnetic behavior of 1 is mainly due to the effective spin-orbital coupling between the ground and exited states through the Zeeman perturbation; the magnetic interaction between europium(III) centers is very weak. A study of the electronic properties demonstrates that compound 1 is a semiconductor. A TGA analysis between 30 and 600 °C for 1 suggests that when the lattice water molecules are removed from the network, the skeleton of the network still remains stable up to 150 °C; this is also confirmed by XRPD. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

On the Intra- and Intermolecular Bonding in Polyiodides

Abstract: The nature of intra- and intermolecular interactions of poly-iodides has been investigated by means of quantum chemical methods and structural statistical data. In the region of "secondary bonds" t ...

Formation of Isomeric BAr3 Adducts of 2‐Lithio‐N‐methylimidazole

Abstract: N-Methylimidazole added to the strong organometallic Lewis acid B(C6F5)3 at the donor nitrogen atom to form the adduct 3 (characterized by X-ray diffraction). Deprotonation at the imidazole carbon atom C-2 was achieved by treatment with methyllithium to generate the reactive “Arduengo carbene anion” intermediate 4, which underwent a rapid subsequent intramolecular nucleophilic aromatic substitution reaction at one of the adjacent C6F5 groups to form the tricyclic betaine-type product 5. Rearrangement of 4 by 1,2-boron migration was not observed. The respective isomer 7 was prepared independently by deprotonation of N-methylimidazole, followed by C-2 addition of B(C6F5)3. The corresponding N-methylimidazolide-2−B(C6H5)3 adduct 8 was characterized by X-ray diffraction and shown to have a cyclodimeric structure made up of intermolecular bis(π-arene)(imidazole)lithium units. A DFT study revealed that the N-borated Arduengo carbene anions are in general very effectively kinetically protected from undergoing intramolecular rearrangement to their thermodynamically favored 2-boratoimidazole anion isomers by 1,2-BR3 migration. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

η1 to η6 Ru−Arene π Complexation: New Bonding Modes and P−C Bond Cleavage Chemistry

Abstract: Binap and MeOBiphep biarylbis(phosphane) complexes of RuII are shown to undergo a series of stereospecific P−C bond cleavage reactions. The products are novel cationic chiral arenebis(phosphane) compounds which contain stereogenic Ru centers. Upon further solvolysis in alcohols, additional P−C cleavage reactions lead to stereogenic P atoms. Several novel olefin π-bonding modes are recognised, including one in which only a single arene carbon atom i.e. an η1 π-bond, weakly coordinates to RuII. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)