Binuclear metal carbonyl dab complexes : II. The syntheses and coordination properties of Mn(CO)5M′(CO)3DAB (M′ = Mn,Re; DAB = 1,4-diazabutadiene)

Mn(CO)₅M′(CO)₃DAB complexes (M′ = Mn, Re; DAB = R₁N=C(R₂)-C(R′₂)=NR₁) can be easily obtained from the reaction between Mn(CO)₅^? and M′(CO)₃X(DAB) (M′ = Mn, Re; X = Cl, Br, I). The complexes are formed by a nucleophilic mechanism, while a redistribution is responsible for the formation of a small amount of Mn₂(CO)₁₀.A diastereotopic effect can be observed in the ¹H and ¹³C NMR spectra of complexes having isopropyl groups attached to the DAB ligand skeleton. A comparison is made with mononuclear complexes of the same symmetry, and the chemical shift differences for the methyl groups strongly depend on the substituent on the central metal responsible for the asymmetry.The low temperature enhancement of the σ → σ^★ transition localised on the metal—metal bond, which is normally observed for this type of compounds, was not observed for the Mn(CO)₅M′(CO)₃(DAB) complexes. The metal—metal bond can be activated by irradiating at the wave lengths associated with the CT transitions between the metal and the DAB ligand. Metal—metal bond cleavage occurs and Mn₂(CO)₁₀ is formed.     

Unexpected Migratory Insertion Reactions of M(alkyl)2 (M=Zn,Cd) and Diamidocarbenes

The electrophilic character of free diamidocarbenes (DACs) allows them to activate inert bonds in small molecules, such as NH₃ and P₄. Herein, we report that metal coordinated DACs also exhibit electrophilic reactivity, undergoing attack by Zn and Cd dialkyl precursors to afford the migratory insertion products [(6‐MesDAC‐R)MR] (M=Zn, Cd; R=Et, Me; Mes=mesityl). These species were formed via the spectroscopically characterised intermediates [(6‐MesDAC)MR₂], exhibiting barriers to migratory insertion which increase in the order MR₂ = ZnEt₂ < ZnMe₂ < CdMe₂. Compound [(6‐MesDAC‐Me)CdMe] showed limited stability, undergoing deposition of Cd metal, by an apparent β‐H elimination pathway. These results raise doubts about the suitability of diamidocarbenes as ligands in catalytic reactions involving metal species bearing nucleophilic ligands (M‐R, M‐H).     

Author index for volume 31

The solid state reactions of MMoO₄ (M = Mg²⁺, Fe²⁺, and Ni²⁺) and orthorhombic TeO₂ were investigated. A new metal telluromolybdate MgTeMoO₆ was obtained in the case of Mg; its structure belongs to the orthorhombic system with unit-cell dimensions a = 5.262Å, b = 5.028 Å, c = 8.880 Å. Fe₂(MoO₄)₃ and a new compound were formed in the case of Fe. The new compound is made up with Fe³⁺ ions and its chemical formula cannot be recognized as FeTeMoO₆. In the case of Ni a complex reaction mixture is obtained. An explanation is given of the ability of M²⁺ ions to form the metal telluromolybdates. The catalytic properties of MgTeMoO₆ are discussed and compared to those of the other metal telluromolybdates.     

Neue Erdalkalimetall‐Phosphide und ‐Arsenide des Cobalts

New Alkaline‐Earth Metal Phosphides and Arsenides of Cobalt Five new compounds of cobalt were prepared by heating mixtures of the elements and investigated by means of single crystal X‐ray methods. Mg₂Co₁₂As₇ (a = 12.096(6), b = 3.670(2), c = 24.93(1) Å) crystallizes in a new structure type (Pnma; Z = 4). Most of the Co atoms are coordinated tetrahedrally by arsenic, the other ones in the form of a square pyramid. Due to the linking of these polyhedra channels of hexagonal cross section are formed along [010], in which the Mg atoms are arranged. Mg₂Co₁₂P₇ (a = 9.012(2), c = 3.504(1) Å), Ca₂Co₁₂P₇ (a = 9.073(1), c = 3.585(1) Å) as well as Ca₂Co₁₂As₇ (a = 9.428(5), c = 3.728(2) Å) crystallize in the Zr₂Fe₁₂P₇ structure type (P6; Z = 1). Micro domains of the arsenide required refinements of the structure parameters in space group P6₃/m. MgCo₆P₄ (a = 6.609(1), c = 3.380(1) Å) is isotypic with LiCo₆P₄ (P6m2; Z = 1). The compounds belong to the large family of phosphides and arsenides with a metal : non‐metal ratio of about 2 : 1. Their structures can be described by the linkings of non‐metal centred trigonal prisms of metal atoms with additional metal atoms capping the rectangular faces of the prisms.     

Bis(dimethylmetall(III)glyoximato)metallate(II) (metall(III) = Al,Ga, In,metall(II) = Ni,Pd, Pt,Cu)

When the trimethyl derivatives of aluminium, gallium and indium react with glyoximato metallates, (R₂C₂N₂(O)OH)₂Met^II (R = H, CH₃; Met^II = Ni, Pd, Pt, Cu), in a $\text{2}\text{1}$ molar ratio, 2 mol of methane are evolved and monomeric bis(dimethylmetal(III)glyoximato)metallates(II) (metal(III) = Al, Ga, In) are formed in high yields. The vibrational and NMR spectra of the new complexes were measured and were partly resolved. The X-ray structure determinations of two of these compounds show non-planar structures of approximate C_2h and C₂ symmetry, respectively, with weak metal(III)?metal(II) π-interactions.     

Synthesis and Structure of the Ordered Modification of Ba6EuF12Cl2

Crystals of ordered Ba₆EuF₁₂Cl₂ were found to form during high temperature flux growth. The structure was refined in the hexagonal space group P 6 to R^F(R ) = 0.024(0.024) for 326 reflections and 46 parameters. Lattice parameters are a = b = 1059.27(8) pm and c = 416.36(2) pm; Z = 1. The structure is isotypic to Ba₇F₁₂Cl₂. No solid solution of Ba/Eu was observed, the Eu²⁺ ions are located in the channels formed by 3 + 6 fluorine ions, occupying only one of the three metal sites of the Ba₇F₁₂Cl₂ structure.     

Darstellung und Eigenschaften von Alkalimetall-Tetrathioterephthalaten. Die Kristallstruktur von K2[S2C?C6H4?CS2] · 2 H2O

Preparation and Properties of Alkalimetal-Benzene-1,4-dicarbotetrathioates. The Crystal Structure of K₂[S₂C? C₆H₄? CS₂] · 2 H₂O By oxidation of α,α′-dichloro-p-xylene with elemental sulfur alkali metal salts of tetrathioterephthalic acid (H₂TTTP) are formed. The complexing properties of the bischelating TTTP-dianion are investigated. Only one stable complex, the dimeric [(CO)₅Mn]₂TTTP, was obtained so far. K₂TTTP crystallizes with a = 744.1(2), b = 1322.1(3), c = 691.5(2) pm, β = 106.11(2)°, Z = 2. The centrosymmetric dianion is nonplanar.     

Quantum chemical calculation of the molecular structures of (666)macrotricyclic chelates of 3D elements in the M(II)-propanedithioamide-formaldehyde systems by the density functional theory method

The nonhybrid OPBE/TZVP density functional theory (DFT) method and the Gaussian09 program package were used to calculate the thermodynamic and geometric parameters of asymmetric macrocyclic M(II) complexes with three six-membered metal rings and (NNNN)-coordination of the donor sites of the ligand. The complexes are formed upon self-assembly (template synthesis) of hexacyanoferrates(II) of the corresponding M(II), propanedithioamide H₂N-C(=S)-CH₂-C(=S)-NH₂, and formaldehyde H₂C(=O) in gelatin-immobilized matrix implants. Note that complexes of this type are formed only for M = Ni, Cu, and Zn, while for M = Mn, Co, and Fe, these compounds are unstable. Bond lengths and bond and torsion angles are presented. In each of these complexes, both the MN₄ chelate units and the N₄ units and all sixmembered metal rings were found to be non-coplanar.     

Monomere Dialkylmetallkomplexe des Typs R2M(NR′)2XR mit M = Al,Ga, In,TI; X = S,C und R,R′ = Alkyl und Silyl

Monomeric Dialkyl Metal Complexes of the R₂M(NR′)₂XR Type with M = Al, Ga, In, Tl; X = S, C and R, R′ = Alkyl and Silyl N,N′-Bis(trimethylsilyl)sulfurdiimide reacts with the trimethyl derivatives of aluminium, gallium, and indium within insertion. Hereby monomeric sulfinic acid imidamidates Me₂M(NSiMe₃)₂SMe (Me = CH₃) are formed. The lithium amidinates Li(NR′)₂CMe (R′ = i-C₃H₇ and SiMe₃) are formed likewise by insertion reactions with LiMe and the corresponding carbodiimides R′N?C?NR′ and were used in reactions with R₂MCl (M = Al to Tl) to synthesize dialkyl metal amidinates R₂M(NR′)₂CMe. The NMR (¹H and ¹³C) and the vibrational spectra (IR and Raman) are discussed and applied to describe the structure of these chelat complexes.     

Technetium Complexes with 2‐Mercapto‐methyltetrazolate

2‐Mercapto‐methyltetrazolate, Smetetraz^–, acts as monoanionic, monodentate ligand in a number of technetium compounds. Anionic Tc^V complexes of the types [TcO(Smetetraz)₄]^– and [TcN(Smetetraz)₄]^2– are formed when (Bu₄N)[Tc^VOCl₄] or (Bu₄N)[Tc^VINCl₄], respectively, react with Na(Smetetraz). Reduction of the metal takes place in the latter case. (Bu₄N)₂[TcN(Smetetraz)₄] crystallises in the monoclinic space group Pc (a = 9.701(5), b = 17.570(5), c = 16.821(10) Å, β = 96.50(3)°, Z = 2). The Tc atom is situated 0.580(3) Å above the basal plane of a square pyramid which is formed by the sulfur atoms and the nitrido ligand as its apex. The Tc–S bond lengths lie between 2.384(3) and 2.410(3) Å. [Tc(PPh₃)(Smetetraz)₃(CH₃CN)] is formed during the reaction of [TcCl₃(PPh₃)₂(CH₃CN)] with NaSmetetraz as blue needles with co‐crystallised solvent toluene (space group C2/c, a = 24.188(4), b = 14.373(1), c = 25.617(5) Å, β = 109.48(1)°, Z = 8). The metal atom is coordinated by PPh₃ and CH₃CN in the axial position of a trigonal bipyramid. All three aryl rings are on the sterically less strained side of the plane defined by the sulfur atoms. The Tc–S bond lengths range between 2.233(2) and 2.247(2) Å.     

High electrical conductivity for the partially oxidised d8 Ru–Ru bonded chain [Ru(bpy)(CO)2]n (bpy = 2,2′-bipyridine) and its wide range redox control

High, electrochemically controlled electrical conductivity (0.2–0.3 S cm^?1) was measured for the first time for the metal–metal bonded polymeric compound [Ru(bpy)(CO)₂]_n (bpy = 2,2′-bipyridine). The conductivity depended on the degree of partial oxidation of the initially zero-valent Ru to Ru^I in the chains and was found to increase by four orders of magnitude after 5% oxidative doping. Linear conductance vs. doping level dependence was found for low levels and the conductivity of films could repeatedly be switched on and off. The conduction process is ascribed to charge delocalisation on the Ru chains in analogy to that of other similar chains formed by stacking of planar transition metal d⁸ complexes.     

(Isocyano Group π-Hole)⋅⋅⋅[d -MII] Interactions of (Isocyanide)[MII] Complexes,in which Positively Charged Metal Centers (d8-M=Pt,Pd) Act as Nucleophiles

Inspection of the X-ray structures of the newly prepared trans-[M^II(CNXyl)₂(DAPT)₂]Cl(BF₄) (M=Pd, Pt; Xyl=2,6-Me₂C₆H₃; DAPT=4,6-diaminopyrimidine-2(1H)-thione) complexes and the appropriate Hirshfeld molecular surface analysis allowed the recognition of the previously unknown π-hole⋅⋅⋅metal interactions between a ligated isocyano group (acting as a π-hole donor) and the positively charged d⁸-Pt^II and d⁸-Pd^II metal centers (acting as nucleophiles); this is the first identification of π-hole⋅⋅⋅metal interactions with triple-bond species. Results of DFT calculations followed by the topological analysis of the electron density distribution within the framework of Bader's theory (quantum theory of atoms in molecules, QTAIM) confirmed the presence of these contacts. The electrostatic surface potential calculations indicated that π-hole⋅⋅⋅metal contacts are formed upon interaction between the electrophilic isocyano C atom (π-hole donor) and the nucleophilic d orbital of the metal centers, which act as π-hole acceptors. Available CCDC data were processed from the perspective of the π-hole⋅⋅⋅metal interactions with isocyanide ligands, and their analysis disclosed the role of metal nucleophilicity in the corresponding π-hole acceptor ability.     

The halogenation of toluene with sulphuryl chloride and dichlorine in the presence of transition metal complexes

A detailed study has been made of the halogenation of toluene in the presence of a range of transition metal complexes. Both side-chain and ring chlorination are observed, the favoured route depending on the metal complex. Side-chain halogenation, in the presence of [M(PPh₃)₄] and MCl₂(PPh₃)₂] (M = Pd, Pt), has been shown to proceed by a free radical chain reaction in which the metal complex acts solely as an initiator. In the presence of, [M₂(CO)₁₀] (M = Mn, Re), [Re₂(CO)₈-(PPh₃)₂], [Fe₂(CO)₄(η-cp)₂] and [Mo₂(CO)₆(η-cp)₂], ring chlorinated products are formed by a Friedel-Crafts mechanism.     

Hydrothermal Synthesis of Five New Coordination Polymers Based on Benzophenone‐2, 4′‐dicarboxylic Acid and N‐Donor Spacers

Five new coordination polymers, namely, [Ni₂(L)₂(4, 4′‐bipy)₃)] · H₂O]_n ( 1 ), [Ni₂(L)₂(O) (bpp)₂]_n ( 2 ), [Zn(L)(bib)_0.5]_n ( 3 ), [Zn(L)(PyBIm)]_n ( 4 ), and [Zn₃(L)₂(OH)(im)]_n ( 5 ) [H₂L = benzophenone‐2, 4′‐dicarboxylic acid, 4, 4′‐bipy = 4, 4′‐bipyridine, bpp = 1, 3‐bis(4‐pyridyl)propane, PyBIm = 2‐(4‐pyridyl)benzimidazole, and im = imidazole] were synthesized under hydrothermal conditions. Structure determination revealed that compound 1 is a 3D network and exhibits a 4‐connected metal‐organic framework with (4².6³.8) topology, whereas compounds 2 , 3 , 4 , and 5 are two‐dimensional layer structures. In compounds 2 – 4 , dinuclear metal clusters are formed through carboxylic groups. In compound 5 , trinuclear metal clusters are formed through μ₃‐OH and carboxylic groups. The carboxylic groups exhibit three coordination modes in compounds 1 – 5 : monodentately, bidentate‐chelating, and bis‐monodentately. Furthermore, the luminescent properties for compounds 3 , 4 , and 5 were investigated.     

Effects of metal salts on polymerization. Part III. Radical polymerizabilities and infrared spectra of vinylpyridines complexed with zinc and cadmium salts

Radical polymerization of 4-vinylpyridine (4-VP), 2-vinylpyridine (2-VP), and 2-methyl-5-vinylpyridine (MVP) was studied in concentrated DMF solutions of ZnCl₂, ZnBr₂, ZnI₂, Zn(CH₃COO)₂, and Cd(CH₂COO)₂ at 50°C. Polymerization of 4-VP and MVP was accelerated by the addition of the metal salts, while the polymerization of 2-VP was greatly retarded. The sequence of the accelerating effect of metal salts for 4-VP was in the following order: Cd(CH₃COO)₂ > ZnCl₂ > Zn(CH₃COO)₂ > ZnBr₂ > ZnI₂. This sequence is almost the same as that reported in a previous report for MVP. However, the order was reversed for the retarding effect on the polymerization of 2-VP. At the intermediate concentration of metal salts, polymerization of 4-VP proceeded heterogeneously, which was explained by considering crosslinking of poly-4-VP by the metal ion. Since a linear correlation between the rate R_p and the degree of polymerization was observed for the 4-VP–Zn(CH₃COO)₂ system, the accelerating effect was postulated to be due to the enhancement in k_p. Results of copolymerization of VP with styrene as M₂ in a concentrated solution of Zn(CH₃COO)₂ indicated the strong activation of 4-VP by complex formation (r₁ = 2.7 ± 0.5, r₂ = 0.08 ± 0.03), whereas the change in the monomer reactivity of MVP is smaller (r₁ = 2.0 ± 0.2, r₂ = 0.35 ± 0.05). The behavior of 2-VP was abnormal (r₁ = 3.35 ± 0.3, r₂ = 0.55 ± 0.15, then r₁r₂ > 1), which was attributed to the steric effect by complex formation. Solid complexes formed between pyridine, 4-VP, 2-VP, or MVP and zinc salts were prepared as samples for infrared spectroscopy. The shifts in infrared absorption bands of these amines were studied by comparing the infrared spectra of the amines before and after the complex formation, and the results were interpreted in terms of electronic as well as steric interactions of metal salts with ligands. Conjugation of the metal salt with the ligand π-orbitals was necessary to explain both infrared spectra and polymerization results.     

The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands

In recent years, it has become clear that the presence of redox-inactive Lewis acidic metal ions can decisively influence the reactivity of metal–dioxygen moieties that are formed in the course of O₂ activation, in molecular complexes, and metalloenzymes. Superoxide species are often formed as the primary intermediates but they are mostly too unstable for a thorough investigation. We report here a series of chromium(III) superoxide complexes [L₂Cr]M₂O₂(THF)_y (L=⁻OSiPh₂OSiPh₂O⁻, M⁺=Li⁺, Na⁺, K⁺ and y=4, 5), which could be accessed, studied spectroscopically and partly crystallized at low temperatures. They only differ in the two incorporated Lewis acidic alkali metal counterions (M⁺) and it could thus be shown that the nature of M⁺ determines considerably its interaction with the superoxide ligand. This interaction, in turn, has a significant influence on the stability and reactivity of these complexes towards substrates with OH groups. Furthermore, we show that stability and reactivity are also highly solvent dependent (THF versus nitriles), as donor solvents coordinate to the alkali metal ions and thus also influence their interaction with the superoxide moiety. Altogether, these results provide a comprehensive and detailed picture concerning the correlation between spectroscopic properties, structure, and behavior of such superoxides, that may be exemplary for other systems.     

Metal atoms and clusters in fullerene cages

Fullerenes containing metal atoms and clusters can be formed by the arc-vaporization method. The electronic structure of these metallofullerenes can be probed using magnetic resonance techniques. Electron paramagnetic resonance (EPR) spectra of LaC₈₂, YC₈₂, ScC₈₂ and Sc₃C₈₂ have been obtained. Metallofullerenes containing a single metal atom (MC₈₂ with M = La, Y, or Sc), have small hyperfine couplings and g-values close to 2, implying that they can be described as + 3 metal cations within — 3 fullerene radical anion cages. In the La and Y cases, additional EPR active MC₈₂ species have been found. The EPR spectrum of Sc₃C₈₂ shows that the metal atoms are equivalent, suggesting that they may form a triangular molecule. No EPR spectrum is found for Y₂C₈₂ or for Sc₂C_2n species (with 2n = 82,84,86), suggesting that they are diamagnetic. Sc NMR spectra of a solution containing Sc₂C_2n species have been obtained which confirm the diamagnetism of the discandium metallofullerenes.     

New Transition Metal Clusters with Ligands from Main Groups Five and Six

In both physics and chemistry, increased attention is being paid to metal clusters. One reason for this attitude is furnished by the surprising results that have been obtained from studies of the preparation, structural characterization and physical and chemical properties of the clusters. Whereas investigations of cluster reactivity are at present generally limited to three- or four-membered clusters, successful syntheses of clusters with many more metal atoms have recently been designed. These substances occupy an intermediate position between solid state chemistry and the chemistry of metal complexes. This review presents a versatile method for synthesizing metal clusters: the reaction of complexes of transition metal halides with silylated compounds such as E(SiMe₃)₂ (E = S, Se, Te) and E′R(SiMe₃)₂ (R = Ph, Me, Et; E′ = P, As, Sb). Although some of the compounds thus formed have already been prepared by other routes, the method affords ready access to both small and large transition metal clusters with unusual structures and valence electron concentrations; a variety of reactions in the ligand sphere are also possible.     

Hydrogenation of α,β-unsaturated substrates by tris(2-phridyl)amine (tpN) or tris(2-pyridyl)phosphine (tpP)/[Ir(COE)2Cl]2 catalyst systems

This work describes the homogeneous hydrogenation of different α,β-unsaturated substrates by using as catalyst systems the complex [Ir(COE)₂Cl]₂ stabilized by tris(2-pyridyl)amine (tpN) or tris(2-pyridyl)phosphine (tpP) formed in situ under the following reaction conditions: pH₂ = 34 atm; T=373 K; substrate/catalyst ratio = 100, [ligand]/[metal]: 2,1; toluene (50 mL); R.P.M.: 430; t = 6 h. The activities varies from low to moderate range, where both ligands proved to be catalyst systems able to hydrogenate C=C and C=O bonds.     

The Catalytic Methods of Synthesis of the Phosphorus Esters with Tertiary Polyfluoroalkyl Groups

Abstract

The phosphorylation of tertiary alcohols can be performed only in some exceptional cases. We established, that phosphorylation of tertiary fluoroalkanols H(CF₂) _nCMe₂OH (I, n = 2,4) with aryl- and polyfluoroalkyl-phosphorodicnlor-idates or aryl- and alkylphosphonic dichlorides in the presence of metal of metal salt catalysts yields chloroan-hydrides (II) and (III). When benzyl phosphorochloridates (IV) are used as phosphorylating agents, either products of phosphorylation or products of alkylation are formed depending on the nature of the substituent in the aromatic ring.