The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

Synthesis and Crystal Structure of Cucurbit[6]uril Adduct of Hydrogen-bonded Cluster Complex [Mo3(μ3-Se)(μ2-O)3(H2O)6Cl3]+

Reaction of [MoOCl₅]²⁻ with in situ generated H₂Se under hydrothermal conditions (4M HCl, 140 °C) leads to reduction of Mo(V) to Mo(IV) with the formation of a triangular cluster Mo₃(μ₃-Se)(μ-O)₃⁴⁺ in high yield. It is present in HCl solutions as aqua chlorocomplex [Mo₃(μ₃-Se)(μ-O)₃(H₂O)₆Cl₃]⁺ which was isolated and structurally characterized as supramolecular adduct with cucurbit[6]uril (CB[6]), {[Mo₃(μ₃-Se)(μ-O)₃(H₂O)₆Cl₃]₂CB[6]}Cl₂·15H₂O. Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday     

Luminescent Properties of Hexanuclear Molybdenum(II) Chloride Clusters Containing Thiolate Ligands

The emission spectra of a series of molybdenum(II) chloride clusters containing thiolate ligands, [Mo₆(μ₃-Cl)₈(SR)₆]²⁻ (R = Et, Bu, Ph, Bn), have been recorded. These complexes all show a broad emission at ~700 nm after excitation at 337, 400 and 410 nm. Determination of the excited state lifetimes and quantum yields of these complexes in acetonitrile reveals that (Bu₄N)₂[Mo₆(μ₃-Cl)₈(SPh)₆] displays the longest excited state lifetime of this series (26 μs at 296 K).

Crystal structure and fluorescence of supramolecular compound [Cd3Cl6C6N2O8H22]n

A novel trinuclear supramolecular compound of [Cd₃Cl₆C₆N₂O₈H₂₂] _n has been synthesized under alanine with cadmium chloride to the reaction in aqueous solution conditions, and characterized by elemental analyses, FT-IR spectroscopy, X-ray diffraction, DTA-TG. Its crystal structure was determined from single crystal X-ray diffraction. The title compound crystallizes in monoclinic system with space group P2₁/n. The crystal structure of the compound is characterized by forming a trinuclear 3D supramolecular structure with three cadmium(II) ions, six chloride ions, two molecules D, L-alanine in salt, two coordinated water molecules and two crystal water molecules. Cd(1) is distorted octahedrally coordinated with two oxygen atoms (from the adjacent amino acid and water molecule) and four chloride ions; Cd(2) is smaller extent distorted octahedrally coordinated with two oxygen atoms (from the adjacent amino acids) and four chloride ions. Cd(1) and Cd(2) connected by the bridge bonds of μ₂-Cl, μ₃-Cl and the carboxyl oxygen into ID chain structure, which further connected by hydrogen bonds to form 3D supramolecular network. Fluorescence test showed that the compound has a good photoluminescence property, respectively.     

Interaction of [Mo6Cl14]2− with H2Se: Selective Preparation of [Mo6SeCl13]3−

Reaction of [Mo₆(μ₃-Cl)₈Cl₆]²⁻ with H₂Se, generated in situ from ZnSe and 4 M HCl under hydrothermal conditions lead to the substitution of one or two bridging chlorides, depending on the reagents ratio. With the Mo₆/ZnSe 1:3 molar ratio [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ forms selectively in high yield. Further substitution is more hindered, and even at 1:20 cluster-to-selenide molar ratio a mixture of [Mo₆(μ₃-SeCl₇)Cl₆]³⁻ and [Mo₆(μ₃-Se₂Cl₆)Cl₆]⁴⁻ is formed. The products were characterized by X-ray, Raman spectra and electrospray ionization mass spectrometry.     

Cu(N-N)2Cl2 and Cu(N-N-N)Cl2 and HgCl2 building blocks in the synthesis of coordination compounds—X-ray studies and magnetic properties

A series of complexes containing Cu(N-N)₂Cl₂ (N-N=bis(pyrazol-1-yl)methane (bpzm), bis(3,5dimethylpyrazol-1-yl)methane (bdmpzm), 2,2-dipyridylamine (dpa), 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) and 2,2′-bipyridine (bipy)), Cu(N-N-N)Cl₂ (N-N-N=2,2′:6′,2″-terpyridine (terpy)) and HgCl₂ building blocks have been synthesized and structurally characterized. Increase in structural dimensionality is observed for [Cu(bpzm)₂][HgCl₄], [Cu(dpa)₂][HgCl₃]₂ and [Cu(terpy)(μ-Cl)HgCl₃] compounds. No coordination polymers have formed in the case of bis(3,5dimethylpyrazol-1-yl)methane, 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine and 2,2′-bipyridine. The [Cu(bpzm)₂][HgCl₄] and [Cu(terpy)(μ-Cl)HgCl₃] complexes have been studied by magnetic measurements.     

Syntheses, Crystal Structures and Third-order Nonlinear Optical Properties of Coordination Polymers {[Et4N][Ag2I3]}n and [CuBr(C10H8N2S2)]n

Coordination polymers {[Et₄N][Ag₂I₃]}_n (1) and [CuBr(C₁₀H₈N₂S₂)]_n (2) were prepared by standard Schlenk techniques. Their X-ray measurements indicate that polymer (1) crystallizes in the orthorhombic space group Pnma, and polymer (2) crystallizes in the monoclinic space group P21/n. Complex (1) has a hanging ladder-like polymeric chain which can also be described as a helical chain bridged by Ag–Ag edges. Complex (2) exhibits a monoclinic crystal system with a slightly distorted tetrahedron. The nonlinear optical (NLO) properties of (1) and (2) were investigated by using Z-scan techniques with an 8 ns pulsed laser at 532 nm. These two coordination polymers exhibit NLO absorption and an effective self-focusing effect. The effective α₂ and n₂ values of cluster (1) are 3.04×10⁻¹¹ m W⁻¹ and 7.6×10⁻¹⁸ m² w⁻¹ and the effective α₂ and n₂ values of compound (2) are 1.08×10⁻¹¹ m W⁻¹ and 3.1×10⁻¹⁸ m² w⁻¹ when measured in CH₂Cl₂ solution.     

Chemistry of ruthenium in N2P2X2 (X = Cl, Br) coordination sphere: Synthesis, characterization and reactivities

Reaction of 2-(phenylazo)pyridine (pap) with [Ru(PPh₃)₃X₂] (X = Cl, Br) in dichloromethane solution affords [Ru(PPh₃)₂(pap)X₂]. These diamagnetic complexes exhibit a weakdd transition and two intense MLCT transitions in the visible region. In dichloromethane solution they display a one-electron reduction of pap near − 0.90 V vs SCE and a reversible ruthenium(II)-ruthenium(III) oxidation near 0.70 V vs SCE. The [Ru^III(PPh₃)₂(pap)Cl₂]⁺ complex cation, generated by coulometric oxidation of [Ru(PPh₃)₂(pap)Cl₂], shows two intense LMCT transitions in the visible region. It oxidizes N,N-dimethylaniline and [Ru^II(bpy)₂Cl₂] (bpy = 2,2′-bipyridine) to produce N,N,N′,N′-tetramethylbenzidine and [Ru^III(bpy)₂Cl₂]⁺ respectively. Reaction of [Ru(PPh₃)₂(pap)X₂] with Ag⁺ in ethanol produces [Ru(PPh₃)₂(pap)(EtOH)₂]²⁺ which upon further reaction with L (L = pap, bpy, acetylacetonate ion(acac⁻) and oxalate ion (ox²⁻)) gives complexes of type [Ru(PPh₃)₂(pap)(L)]ⁿ⁺ (n = 0, 1, 2). All these diamagnetic complexes show a weakdd transition and several intense MLCT transitions in the visible region. The ruthenium(II)-ruthenium(III) oxidation potential decreases in the order (of L): pap > bpy > acac⁻ > ox²⁻. Reductions of the coordinated pap and bpy are also observed.     

CO2 fixation by [WIVO(S2C2(CN)2)2]2?: functional model for the tungsten-formate dehydrogenase of Clostridium thermoaceticum

(NEt₄)₂[W^IVO(S₂C₂(CN)₂)₂] (1), isolated by reaction of Na₂ WO₄, Na₂S₂C₂(CN)₂ (Na₂mnt) in acidified (pH5.5) aqueous medium in the presence of excess of sodium dithionite and NEt₄Br, reduces CO₂/HCO ₃ ⁻ (pH 7.5) to yield HCOO⁻ and (NEt₄)₂[W^VIO₂(S₂C₂(CN)₂)₂] (2) mimicking tungsten-formate dehydrogenase (W-FDH) activity. (1) reacts with Na₂MoO₄ in acidic medium to produce [Mo^IvO(S₂C₂(CN)₂)₂]²⁻ implicating the displacement of tungsten by molybdenum from the cofactor complex in W-FDH.     

Theoretical Study of the Metal–Metal Interaction in Dipalladium(I) Complexes

Correlated ab initio calculations have been performed on three dipalladium(I) complexes. These compounds differ both by the metal–metal interaction and by the metal–ligand interaction. The [Pd₂Cl₂(μ −H₂PCH₂PH₂)₂] complex exhibits a σ overlap between the two binding metallic orbitals and has no bridging ligand. In [Pd₂Cl₄(μ −CO)₂]²⁻, the leading interaction between the two palladium involves a π overlap between the metallic orbitals and goes through the two bridging CO ligands. In [Pd₂Cl₂(μ −CO)(μ −H₂PCH₂ PH₂)₂], a single CO ligand bridges the two palladium atoms which interact through a hybrid σ–δ overlap. The three compounds also differ by the metal–metal distances. Surprisingly enough, while the palladium atoms are formally d ⁹ in all these complexes, none of them is paramagnetic. We propose here a detailed analysis of the electronic structures of these compounds and rationalize their chemical structures as well as the role of back-donation in the CO bridged compounds. Finally, since highly correlated treatments are used to describe these complexes, a detailed study of the role of both non-dynamical and dynamical correlations is performed. Concerning the [Pd₂Cl₄(μ −CO)₂]²⁻ complex, this analysis has revealed that the complex is not bound at the lowest correlated levels of calculation and therefore dynamical correlation is alone responsible for its binding energy.     

Crystal structure of trinuclear mixed-valence CoIII-CoII-CoIII complex {CoIII(μ-Sal)2Mepn)(N3)(μ1,1-N3)}2CoII(H2O)2

Trinuclear mixed-valence Co(III)-Co(II)-Co(III) complex {Co^III(μ-Sal₂MePn)(N₃)(μ_1,1-N₃)}₂Co^II(H₂O)₂ (I) was synthesized by the reaction of Co(NO₃)₂ · 6H₂O with the Schiff base ligand H₂Sal₂MePn condensed from 2,2-dimethylpropylenediamine with salicylaldehyde and characterized by elemental analyses and FT-IR spectroscopy. The molecular structure of I has been determined from single-crystal X-ray diffraction analysis. In this structure, the N₃⁻ anions show both terminal and μ_1,1-bridging modes. The terminal Co(III) centers exhibit uniform arrangements of the Schiff-base ligand and N₃⁻ anions.     

Formation and structural characterization of mercury complexes from Te(R)CH2SiMe3 (R = Ph, CH2SiMe3) and HgCl2

The reaction of HgCl₂ and Te(R)CH₂SiMe₃ [R = CH₂SiMe₃ (1), Ph (2)] in ethanol yielded a mononuclear complex [HgCl₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 3a; R = CH₂SiMe₃, 3b). The recrystallization of 3a or 3b from CH₂Cl₂ produced a dinuclear complex [Hg₂Cl₂(μ-Cl)₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 4a; R = CH₂SiMe₃, 4b). When 3a was dissolved in CH₂Cl₂, the solvent quickly removed, and the solid recrystallized from EtOH, a stable ionic [HgCl{Te(Ph)CH₂SiMe₃}₃]Cl·2EtOH (5a·2EtOH) was obtained. Crystals of [HgCl₂{Te(CH₂SiMe)₂}]·2HgCl₂·CH₂Cl₂ (6b·2HgCl₂·CH₂Cl₂) were obtained from the CH₂Cl₂ solution of 3b upon prolonged standing. The complex formation was monitored by ¹²⁵Te-, and ¹⁹⁹Hg NMR spectroscopy, and the crystal structures of the complexes were determined by single crystal X-ray crystallography.     

Heterometallic clusters with the {MoNbI8} core: The synthesis and crystal structures of (Ph4P)2[Mo5NbI8Cl6] and (4-MePyH)5[Mo5NbI8Cl6]Cl2

Heterometallic chloride complexes [Mo₅NbI₈Cl₆] ⁿ⁻ (n = 2, 3) are synthesized. The crystal structures of their salts are determined: for (Ph₄P)₂[Mo₅NbI₈Cl₆] (I), triclinic crystal system, spacegroup P [`1]\bar 1, a = 10.9886(6), b = 11.4604(5), c = 13.4343(7) ?, α = 66.124(2), β = 86.892(2), γ = 86.490(2)°, Z = 1, V = 1543.35(13) ?³; and for (4-MePyH)₅[Mo₅NbI₈Cl₆]Cl₂ (II), monoclinic crystal system, space group C2/m, a = 16.4937(4), b = 14.7335(3), c = 11.6534(3) ?, β = 99.8750(10)°, Z = 2, V = 2789.94(11) ? The geometric parameters of compounds I and II and the conditions for the formation of the complexes with the charges −2 and −3 are discussed.     

X-ray study of Hg2Cl2Br2 and HgCl2HgBr2 reactions in solid state

The reactions (I) Hg₂Cl₂(s) + Br₂(g) and (II) HgCl₂(s) + HgBr₂(s) have been investigated by an X-ray method. Both the reactions yield two forms of the mixed halide HgClBr, designated as α-HgClBr and β-HgClBr. The cell parameters of the two are as follows:α-HgClBr: $\text{a = 6.196}\text{A}\text{?}$, $\text{b = 13.12}\text{A}\text{?}$, $\text{c = 4.37}\text{A}\text{?}$, z = 4, ? = 5.91 g/cm³. The powder pattern and cell parameters are similar to that of HgCl₂. Therefore it is probable that the chlorine atoms, in the linear halogenHghalogen molecules of HgCl₂ structure have been replaced by bromines, and since the radius of the bromine atom is larger than that of chlorine, the lattice is larger in this case.β-HgClBr: $\text{a = 6.78}\text{A}\text{?}$, $\text{b = 13.175}\text{A}\text{?}$, $\text{c = 4.17}\text{A}\text{?}$, z = 4, ? = 5.40. These parameters are the same as those reported in the literature for β-Hg(ClBr)₂, and its X-ray powder pattern is similar to HgCl₂. Therefore this phase also has linear halogenHghalogen molecules but the distribution of Cl and Br atoms is perhaps random.Heating the products (I) and (II) up to the melting point increases the amount of α phase and decreases the β phase, whereas crystallization increases the β phase. DTA study has supported the X-ray findings.     

Interconverting WW Triple Bonds and W4 Clusters: Structures of W4(OPrn)16 and [Li2W2(OPrn)8(DME)]2*

Alcoholysis of W₂(NMe₂)₆ with excess n-propanol in hexane yields the tetranuclear cluster, W₄(OPrⁿ, I. Reduction of I with two equivalents of Li₂COT in THF gives a small yield of Li₂W₂(OPrⁿ)₈. Single crystals were isolated by cooling the product mixture in DME and were shown to be [Li₂W₂(OPrⁿ)₈(DME)]₂, II, which consists of a unique “dimer of dimers” structure. In this reaction sequence, W₄¹⁶⁺ cluster formation is followed by four electron reduction to reform the (W≡W)⁶⁺ unit. Better yields of the lithium salt can be obtained by the addition of LiOPrⁿ/HOPrⁿ solutions to W₂(OBu^t)₆ in which case Li₂W₂(OPrⁿ)₈ has been obtained as a 1:1 adduct with LiOPr. This identity of this salt was confirmed by solution NMR spectroscopy. In the alternative reaction, the (W≡W)⁶⁺ center remains intact from reactant to product. No attempt has been made to separate the product from excess LiOPr. DFT (ADF 2004.01) molecular orbital calculations on the model cluster W₄(OH)₁₆ are used to help elucidate the disruption of the W₄ cluster upon four electron reduction. The molecular structures of compounds I and II are reported.*Dedicated to Professor F. A Cotton on the occasion of his 75th birthday.     

A re-interpretation of the crystal structure of ‘(NH4)2(NH3)[Ni(NH3)2Cl4]’ in terms of (NH4)2−2z[Ni(NH3)2]z[Ni(NH3)2Cl4]

A re-interpretation and re-evaluation of single-crystal X-ray diffraction data of a previously reported ‘(NH₄)₂(NH₃)[Ni(NH₃)₂Cl₄]’ (J. Solid State Chem. 162 (2001) 254) give a new formula (NH₄)_2−2z[Ni(NH₃)₂]_z[Ni(NH₃)₂Cl₄] with z=0.152. This new formula results from defects in an idealized ‘(NH₄)₂[Ni(NH₃)₂Cl₄]’ basic structure, where two adjacent NH₄⁺ cations are replaced by one Ni(NH₃)₂²⁺ unit. Cl⁻ anions from the basic structure complete the coordination sphere of the new Ni²⁺ to [Ni(NH₃)₂Cl₄]²⁻.     

Reaction of neodymium diiodide with methanol in acetonitrile. Structure of the cluster [Nd4(μ2-I)1.1(μ3-I)(μ2-OMe)4.9(μ4-O)(MeCN)12]I3

The reaction of neodymium diiodide NdI₂ with excess methanol in acetonitrile produced the tetranuclear neodymium cluster [Nd₄(μ₂-I)_1.1(μ₃-I)(μ₂-OMe)_4.9(μ₄-O)(MeCN)₁₂]I₃ (1). In the latter, the isomorphic substitution of one methoxy group by an I⁻ anion with site occupancies (%) of 90 and 10, respectively, was observed. Due to the isomorphic substitution in the crystal, cluster 1 can be considered as a superposition of two complexes, [Nd₄(μ₂-I)(μ₃-I)(μ₂-OMe)₅(μ₄-O)(MeCN)₁₂]I₃ and [Nd₄(μ₂-I)₂(μ₃-I)(μ₂-OMe)₄(μ₄-O)(MeCN)₁₂]I₃. The characteristic feature of cluster 1 is that the center of the Nd₄ cage is occupied by the μ₄-coordinated O²⁻ anion, which is indicative of the partial O-C bond cleavage in methanol. The reaction of NdI₂ with an equimolar amount of MeOH in an acetonitrile solution produced methoxide NdI₂(OMe)(MeCN)₄ in 49% yield. Dedicated to Professor W. J. Evans on the occasion of his 60th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1894–1897, October, 2007.     

Synthesis of heteroligand complex Nd(Phen){( iso -C4H9)2PS2}2(NO3). Crystal structure of [Nd(Phen){( iso -C4H9)2PS2}3] and luminescent properties of these compounds

The heteroligand complex Nd(Phen){(iso-C₄H₉)₂PS₂}₂(NO₃) (I) was synthesized and its IR spectrum was analyzed. The anions (iso-C₄H₉)₂PS_2/− and N_3/− act as bidentate cyclic ligands. The single crystals of [Nd(Phen){iso-C₄H₉)₂PS₂}₃] (II) were obtained on evaporation of a solution of complex I in a mixture CH₂Cl₂-hexane and were studied by X-ray diffraction. Crystals II are triclinic: a = 10.5509(5); b = 14.7432(8), c = 16.8503(10) ?; α = 102.882(2)°, β = 97.211(2)°, γ= 108.087(2)°, V = 2374(2) ?³, Z = 2, ρ(calcd.) = 1.332 g/cm³, space group . The coordination polyhedron of the Nd atom in a separate mononuclear molecule II is a distorted dodecahedron N₂S₆. The molecules are bound by weak van der Waals and π-π interactions. The photoluminescence spectra of complexes I, II were measured and interpreted. Original Russian Text ? S.V. Larionov, V.L. Varand, R.F. Klevtsova, T.G. Leonova, L.A. Glinskaya, E.M. Uskov, 2008, published in Koordinatsionnaya Khimiya, 2008, Vol. 34, No. 12, pp. 944–950.     

From Cluster to Cluster: Structural Transformation Reactions Among Tungsten Chloride Clusters

Reactions between tungsten halides are discussed along the series of compounds WCl₆ → WCl₄ → W₆Cl₁₂ ↔ W₆Cl₁₈ → [W₆CCl₁₈]ⁿ⁻ ← [W₃Cl₁₃]^u−, focusing on the two closely related tungsten chloride compounds whose structures compromise the well-known octahedro W₆Cl₁₈ cluster and the carbon-centered triprismo W₆CCl₁₈ cluster. Both clusters can be regarded as being built by merging two trigonal [W₃Cl₁₃]^u− units in different ways. Syntheses, structural transformation reactions, and concepts regarding electronic structures are reported.     

Synthesis, Characterization, and Fluxional Behaviour of Binuclear Palladium Complexes with a Half-A-Frame Structure

 Partial removal of chloride anions from the dimer [Pd(η³-2-CH₃*C₃H₄)(μ-Cl)]₂ with AgTf(Tf = CF₃SO₃) followed by addition of dppm affords [Pd₂(η³-Me*C₃H₄)₂(μ-Cl)(μ-dppm)]Tf (1). The substitution of Cl⁻ by X⁻ (X = pz, SC₆F₅, S _py ) using the appropriate salts yields the new derivatives [Pd₂(η³-Me*C₃H₄)₂(μ-X)(μ-dppm)]Tf (2–4). All complexes exhibit a dinuclear half-A-frame structure with two isomers present in solution. The isomers differ in the relative orientation of the two allyl groups (cis or trans). The isomer interconversion was studied by variable temperature ¹H NMR spectroscopy. The molecular structures of 2 and 4 were solved by X-ray diffraction studies. A distorted boat conformation of the seven- or six-membered metallacycle was found in both cases.