Cluster self-organization of Li- and TR-Containing silicate systems: Suprapolyhedral precursors and self-assembly of LiY<Superscript>[7]</Superscript>SiO<Subscript>4</Subscript> and LiTR<Superscript>[6]</Superscript>SiO<Subscript>4</Subscript> (TR = Y,Sc, Tm) dimorphic crystal structures

The combinatorial and topologic analysis (the TOPOS 4.0 program package, the coordination sequences method) is carried out for silicates LiY^[7]SiO₄ (a synthetic phase (SIN), space group P2₁/b) and LiTR^[6]SiO₄ (TR = Y, Sc, Tm; the olivine structure type (OLI), space group Pnma). The framework of these silicates is built of polyhedral structural units YO₇ + SiO₄ and YO₆(ScO₆, TmO₆) + SiO₄, respectively. The framework structures TRTO₄, built of Y,O- and Si,O-polyhedra in SIN and OLI, respectively, are represented as three-dimensional (3D) Y,Si-nets with distal oxygen atoms. The crystal-forming 2D Y,Si-net is the four-nodal net Y(1) (43333) + Y(2) (4334334) + Si(1) (434) + Si(2) (3343) for SIN and the two-nodal net Y 443333 + Si 4433 for OLI. In the 2D Y,Si, nets, equivalent chains of four-nodal precursor clusters Y-Si-Y-Si with three shared bonds are identified. In the dimorphic crystals structures of LiTRTO₄, polyhedral precursor clusters Li₂TR₂T₂ are linked into a ring with two Li atoms lying one above the other below the center of the ring, thus retaining the center of symmetry\(\bar 1\). Precursor clusters Li₂TR₂T₂ through the matrix self-assembly mechanism control the evolution of high-level crystal-forming clusters. Cluster coordination numbers in layers are equal to six.     

Cluster self-organization of germanate systems: Suprapolyhedral precursor clusters and self-assembly of K2Nd4Ge4O13(OH)4, K2YbGe4O10(OH), K2Sc2Ge2O7(OH)2, and KScGe2O6(PYR)

Geometric and topological analysis of all known types of K,TR germanates (TR = La-Lu, Y, Sc, In) is carried out with the use of computer techniques (the TOPOS 4.0 program package). Framework structures are represented as three-dimensional (3D) K,TR,Ge networks (graphs) with oxygen atoms removed. The following crystal-forming 2D TR,Ge networks are determined: for K₂Nd₄Ge₄O₁₃(OH)₄, this is TR 4 3 3 4 3 3 + T 4 3 4 3; for K₂YbGe₄O₁₀(OH), this is TR 6 6 3 6 + T 1 6 8 6 + T 2 3 6 8; for K₂Sc₂Ge₂O₇(OH)₂, this is TR 6 4 6 4 + T 6 4 6; and for KScGe₂O₆, TR 6 6 3 6 3 4 + T 1 6 3 6 + T 2 6 4 3. The full 3D reconstruction of the self-assembly mechanism of crystal structures is performed as follows: precursor cluster—primary chain—microlayer-microframework (supraprecursor). In K₂Nd₄Ge₄O₁₃(OH)₄, K₂Sc₂Ge₂O₇(OH)₂, and KScGe₂O₆, an invariant type of cyclic six-polyhedral precursor cluster is identified; this precursor clusters is built of TR octahedra, which are stabilized by atoms K. For K₂Nd₄Ge₄O₁₃(OH)₄, the type of cyclic four-polyhedral precursor cluster of tetrahedron-linked TR octatopes is identified. The cluster coordination number in a layer is six (the maximum possible value) only for anhydrous germanate KScGe₂O₆ (an analogue of pyroxene, PYR); in the other OH-containing germanates, this number is four. The mechanism of formation of Ge radicals in the form of groups Ge₂O₇ and Ge₄O₁₃, a chain GeO₃, and a tubular assembly of linked cyclic groups Ge₈O₂₀ is considered.     

Scandium terminal imido complex induced intramolecular C–N bond cleavage and transformation

<正>1 X-ray crystallography Suitable single crystal of 2 was sealed in a thin-walled glass capillary, and data collection was performed at 293(2) K on a Bruker SMART diffractometer with graphite-monochromated Mo Kα radiation(λ = 0.71073 ). Suitable single crystals of 3and 4 were mounted under nitrogen atmosphere on a glass fiber, and data collection was performed at 133(2) K on a Bruker APEX2 diffractometer with graphite-monochromated Mo Kα radiation(λ = 0.71073 ). The SMART program package was used to determine the unit cell parameters. The absorption correction was applied using SADABS. The structures were solved     

Five-, six- and eight-membered ring organosilicon chalcogenides of the types Z2(SiMe2)2E (Z = Me2Si, H2C; E = S, Se, Te), Z(SiMe2E)2MR2 (Z = Me2Si, H2C, O; E = S, Se, Te; M = Si, Ge, Sn, R = Me, Ph) and (SiMe2ZSiMe2E)2 (Z = Me2Si, H2C; E = S, Se)

Reactions of ClMe₂Si–Z–SiMe₂Cl (Z = SiMe₂ (1a), CH₂ (1c), O (1e)) with Li₂E (E = S, Se) yielded eight-membered ring compounds (SiMe₂ZSiMe₂E)₂ (3a–d) as well as acyclic oligomers (SiMe₂ZSiMe₂E)_x of different chain lengths. If 1:1 molar mixtures of 1a, 1c or 1e and a diorganodichlorosilane, -germane or -stannane (R₂MCl₂) are reacted with Li₂E (E = S, Se, Te), six-membered ring compounds Z(SiMe₂E)₂MR₂ (4a–7g) are formed exclusively. Five-membered rings Z₂(SiMe₂)₂E (Z = SiMe₂ (8a–c), CH₂ (9a–c); E = S, Se, Te) are obtained starting from the tetrasilane ClMe₂Si–(SiMe₂)₂–SiMe₂Cl (1b) or the disilylethane ClMe₂Si–(CH₂)₂–SiMe₂Cl (1d) by treatment with Li₂E. All products were characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ⁷⁷Se, ¹²⁵Te, including coupling constants) and the effects of the different ring sizes towards NMR chemical shifts are discussed.     

Hydride Dynamics in Triosmium and Triruthenium Carbonyl Clusters: Synthesis,Reactivity and Dynamics of a Trihydrido Quinoline-4-Carboxaldehyde Triosmium Cluster

An overview of the dynamical processes involving the hydrido ligand in triosmium and triruthenium carbonyl clusters is presented. The relationship between the mechanisms of hydride motions and the other ligands in the cluster are discussed for mono- di- and trihydrido-clusters. In addition, the reactivity of the electron deficient 46e^? cluster, (μ-H)(μ₃-η²-C₉H₅N-4-CHO)Os₃(CO)₉ (1) with hydrogen is reported. The reaction gives two isomeric trihydrido clusters, H(μ-H)₂(μ₃-η²-C₉H₅N-4-CHO)Os₃(CO)₈ (2) and (μ-H)₃(μ₃-η²-C₉H₅N-4-CHO)Os₃(CO)₈ (2′) in low yield along with trace amounts of other hydrido clusters. Reaction of the inseparable mixture of 2 and 2′ with triphenylphosphine at ambient temperatures gives two related addition products H(μ-H)₂(μ-η²-C₉H₅N-4-CHO)Os₃(CO)₈PPh₃ (3) and (μ-H)₃(μ-η²-C₉H₅N-4-CHO)Os₃(CO)₈PPh₃ (3′) in a 5:1 ratio. These results contrast with the previously reported trihydrido-derivatives of triosmium μ₃-η²-imidoyl clusters where only analogues of 2 and 3 are obtained. Clusters 2 and 2′ are rigid on the NMR time scale while 3 exhibits dynamical behavior in the temperature range of ?50 to +25 °C. Cluster 3′ is stereochemically rigid in this temperature range. The dynamical behavior of 3 involves the exchange of the terminal and bridging hydrides coupled with tripodal motion of the phosphine substituted osmium atom, a process virtually identical to previously reported trihydrides of the μ₃-η²-imidoyl triosmium clusters.     

Silylated gallium and indium chalcogenide ring systems as potential precursors to ME (E=O, S) materials

The reaction of R₃M (M=Ga, In) with HESiR′₃ (E=O, S; R′₃=Ph₃, ⁱPr₃, Et₃, ^tBuMe₂) leads to the formation of (Me₂GaOSiPh₃)₂ (1); (Me₂GaOSi^tBuMe₂)₂ (2); (Me₂GaOSiEt₃)₂ (3); (Me₂InOSiPh₃)₂ (4); (Me₂InOSi^tBuMe₂)₂ (5); (Me₂InOSiEt₃)₂ (6); (Me₂GaSSiPh₃)₂ (7); (Et₂GaSSiPh₃)₂ (8); (Me₂GaSSiⁱPr₃)₂ (9); (Et₂GaSSiⁱPr₃)₂ (10); (Me₂InSSiPh₃)₃ (11); (Me₂InSSiⁱPr₃)_n (12), in high yields at room temperature. The compounds have been characterized by multinuclear NMR and in most cases by X-ray crystallography. The molecular structures of (1), (4), (7) and (8) have been determined. Compounds (3), (6) and (10) are liquids at room temperature. In the solid state, (1), (4), (7) and (9) are dimers with central core of the dimer being composed of a M₂E₂ four-membered ring. VT-NMR studies of (7) show facile redistribution between four- and six-membered rings in solution. The thermal decomposition of (1)–(12) was examined by TGA and range from 200 to 350°C. Bulk pyrolysis of (1) and (2) led to the formation of Ga₂O₃; (4) and (5) In metal; (7)–(10) GaS and (11)–(12) InS powders, respectively.      

Di- and tetranuclear heterometallic CuII-LnIII complexes (Ln = Gd and Dy): Synthesis, structure and magnetic properties

Four 3d-4f heterometallic complexes, [CuⅡ LnⅢ (bpt) 2 (NO 3 ) 3 (MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-1,2,4- triazole), [CuⅡ 2 LnⅢ 2 (μ-OH) 2 (bpt) 4 Cl 4 (H 2 O) 2 ]·6H 2 O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal conditions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuⅡ -LnⅢ dinuclear unit. The intramolecular Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH- groups into the zig-zag tetranuclear {CuⅡ 2 LnⅢ 2 } structures with the Ln(Ⅲ) Ln(Ⅲ) distances of 3.742 and 3.684 for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CuⅡ-LnⅢ interactions occur in 1 (J CuGd = 0.21 cm-1 ) and 2. The antiferromagnetic interaction occurs in complex 3 with J CuGd = 0.82 cm-1 and J GdGd = 0.065 cm-1 , while dominant ferromagnetic interaction occurs in complex 4.     

Neutral and monocationic dinuclear (carbonyl)(cyclopentadienyl)(phenylchalcogenate) iron complexes of the general formulas [(RC5H4)Fe(CO)EPh]2 and [(RC5H4)Fe(CO)EPh]2PF6 (E = S or Te; R = H or Me): Synthesis, molecular structures, and EPR spectra

Heating of the compounds (RC₅H₄)Fe(CO)₂TePh (R = H (I) and Me (II)) in heptane afforded the dinuclear complexes [(RC₅H₄)Fe(CO)TePh]₂ (III and IV, respectively). By oxidation with Fc⁺PF ₆ ^? , these complexes were transformed into the paramagnetic cationic complexes [(RC₅H₄)Fe(CO)TePh]₂PF₆ (V and VI, respectively). Structures III–V and [(C₅H₅)Fe(CO)SPh]₂PF₆ (VII) were characterized by X-ray diffraction.     

Synthesis and spectral properties of lutetium complexes with unsymmetrical phthalocyanines and sandwich complexes based thereon containing tetraanthraquinonoporphyrazine fragments

Joint condensation of 4,5-bis(4-hexadecyloxyphenoxy)phthalonitrile (A) and tetrachlorophthalonitrile (B) in boiling hexan-1-ol in the presence of lithium hexan-1-olate and subsequent reaction with LuCl₃ · 6 H₂O gave single-decker lutetium complexes with unsymmetrical phthalocyanines (AABB, ABAB). Reactions of the latter with 9,10-dioxo-9.10-dihydroanthraquinone-2,3-dicarbonitrile afforded mixed-ligand double-decker lutetium complexes containing tetraanthraquinonoporphyrazine as one of the ligands. Spectral properties of the synthesized complexes were studied, and all complexes were found to exhibit red fluorescence.     

Synthesis and Stereochemical/Electrochemical Analyses of Cuboctahedral-Based Pd23(CO) x (PR3)10 Clusters (x=20 with R3=Bu n 3, Me2Ph; x=20, 21, 22 with R3=Et3): Geometrically Analogous Pd23(PEt3)10 Fragments with Variable Carbonyl Ligations and Resulting Implications

This research was an outgrowth of previous reactions with [Pd₁₃Ni₁₃(CO)₃₄]^4? which produced a tetragonal crystal form of Pd₂₃(CO)₂₀(PEt₃)₁₀ (1) that has the same cuboctahedral-based Pd₂₃ framework with an identical number of PEt₃ ligands but two fewer CO ligands than the monoclinic crystal form of Pd₂₃(CO)₂₂(PEt₃)₁₀ (3) originally reported from reactions with Pd₁₀(CO)₁₂(PEt₃)₆. A subsequent investigation presented herein to establish whether the carbonyl capacity is influenced by the nature of the phosphine ligands has led to syntheses of Pd₂₃(CO) _x (PR₃)₁₀ [R₃=Et₃ (1), Bu ⁿ ₃ (4), and Me₂Ph (5)] with 20 CO ligands (x=20) from corresponding Pd₁₀(CO)₁₂(PR₃)₆ precursors either by deligation with Pd(OAc)₂, CF₃CO₂H, Ni(1,5-COD)₂, [NMe₄]₂[Ni₆(CO)₁₂], or HCO₂H or by spontaneous enlargement; yields varied from 15 to 79%. Although attempts to obtain the original Pd₂₃(CO)₂₂(PEt₃)₁₀ (3) were unsuccessful, a highly significant outcome was the isolation (one time) of another monoclinic crystal form possessing the triethylphosphine Pd₂₃(CO) _x (PEt₃)₁₀ cluster with 21 COs (2). Both the compositions and atomic arrangements for each of five Pd₂₃ clusters [1a (solvated); 1b (unsolvated); 2, 4, and 5] were unambiguously established from low-temperature single-crystal CCD X-ray crystallographic determinations in accordance with their nearly identical IR carbonyl frequencies. Solution ³¹P{¹H} NMR spectra of 1 and 4 at room temperature displayed three distinct signals with expected integral ratios of 2/4/4 that are consistent with the solid-state structures of Pd₂₃(CO)₂₀(PR₃)₁₀ [R₃=Et₃ (1), Bu ⁿ ₃ (4)] remaining intact in solution. The metal-core geometries of all of these Pd₂₃(CO) _x (PR₃)₁₀ clusters, including the thermodynamically stable ones with 20 CO ligands and the kinetic products with additional CO ligands (x=21, 22), are essentially the same. The common Pd₂₃ core may be best described as possessing a centered hexacapped cuboctahedral Pd₁₉ kernel (alternatively denoted as a centered ν₂ Pd₁₉ octahedron) with four edge-connected exopolyhedral wingtip Pd(exo) atoms that reduce the pseudo metal-core symmetry from O_h to D_2h. The 10 PR₃ ligands are linked to the six tetracapped Pd(cap) and four edge-capped wingtip Pd(exo) atoms; the latter four Pd(exo) atoms are each composed of four trigonal-planar Pd(μ₂-CO)₂(PR₃) units. These crystallographic results provide compelling geometrical evidence for a heretofore unknown stereochemical example involving variable carbonyl ligation (x=20, 21, 22) of a close-packed nanosized Pd _n (CO) _x (PR₃) _y cluster (in this case with identical PEt₃ ligands) without significant changes being induced in either the overall metal-core architecture or steric dispositions of the same number of PR₃ ligands. These experimental findings have particular relevance to the long-standing Muetterties cluster/surface science analogy in showing that the different number (as well as different modes) of carbonyl ligations observed in these large metal carbonyl clusters are directly related to pressure-induced dissociative/nondissociative migratory coverages in CO chemisorptions on metal surfaces. The observed expanded capacity of CO coordination on the same Pd₂₃ polyhedron without notable changes in geometry is no doubt a consequence of its virtually nanosized metal-core architecture; distances between outermost centrosymmetrically related pairs of Pd(cap) and Pd(exo) atoms in the Pd₂₃ framework are 0.8 and 0.9 nm, respectively. An electrochemical (CV) study revealed that 1 undergoes one quasi-reversible two-electron reduction to 1 ^2? (E_1/2=?0.91 V) and two consecutive quasi-reversible one-electron oxidations to 1/1 ⁺ at E_1/2=0.08 V and 1 ⁺/1 ²⁺ at E_1/2=0.32 V (THF; Ag/AgCl as reference electrode). A stereochemical/electronic analysis with the isostructural Au₂Pd₂₁(CO)₂₀(PEt₃)₁₀ analogue (9) and resulting implications are given.     

Molecular geometry and electronic structures of stable organic derivatives of divalent germanium and tin [(\operatorname{Me} _3 \operatorname{Si} )_2 \operatorname{N} {\kern 1pt} ---{\kern 1pt} Me_2 ]_n (M = Ge, n = 1; M = Sn, n = 2): a theoretical study

The molecular geometry and electronic structure of stable organic derivatives of divalent germanium and tin, [(Me₃Si)₂N-M-OCH₂CH₂NMe₂]_n (M = Ge (4), n = 1; M = Sn (5), n =2) and their isomers with broken (4a, 5a) and closed (4b, 5b) intramolecular coordination bonds M←NMe₂, were studied by the density functional (PBE/TZ2P/SBK-JC) and NBO methods. Factors responsible for stability of their dimers 4c and 5c were established. Dimerization of 5b in the gas phase is a thermodynamically favorable process (ΔG ⁰ = ?2.1 kcal mol^?1) while that of 4b is thermally forbidden (ΔG ⁰ = 10.1 kcal mol^?1), which is consistent with experimental data. The M←NMe₂ coordination bond energies, ΔE ⁰, were found to be ?5.3 and ?8.6 kcal mol^?1 for M = Ge and Sn, respectively. NBO analysis showed that the metal atoms M in molecules 4 and 5 are weakly hybridized. The lone electron pairs of the M atoms have strong s-character while vacant orbitals of these atoms, LP* M, are represented exclusively by the metal np_z-AOs. The strongest orbital interactions between subunits in dimers 4c and 5c involve electron density donation from the lone electron pairs of oxygen atoms (LP O) to the LP* M orbitals.     

Lanthanide Cluster Organic Frameworks Derived from Pyridine-2,6-dicarboxylate and Oxalate: Syntheses,Structures and Luminescence

Two novel cluster organic frameworks derived from pyridine-2,6-dicarboxylate (PDA) and oxalate (ox^2?) have been hydrothermally made: [Eu₃(SO₄)(PDA)₃(ox)_0.5(H₂O)₅]·4H₂O (1) and Er(PDA)(ox)_0.5(H₂O) (2). Compound 1 possesses one-dimensional chain structure constructed from the alternate linkage of tetranuclear [Eu₄(SO₄)₂]⁸⁺ (Eu₄) and dinuclear [Eu₂(ox)]⁴⁺ (Eu₂) clusters. Compound 2 is a two-dimensional layer based on dimeric [Er₂(COO)₂]²⁺ (Er₂) cluster units. Interestingly, such layer can be intuitively viewed as the linkages of helical chains and oxalate. In these two compounds, all anions are bivalent, and the ratio of trivalent lanthanide ions to these dianions is 2:3. Furthermore, compound 1 exhibits strong red luminescence upon 276 nm excitation.     

Ligand substitution in HC(O)CCo3(CO)9 with 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd): Diphosphine ligand fluxionality, decarbonylation of the formyl moiety and competitive P-Ph bond cleavage reactivity

The reaction of the formyl-capped cluster HC(O)CCo₃(CO)₉ (1) with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) in the presence of added Me₃NO leads to the production of the disubstituted cluster HC(O)CCo₃(CO)₇(bpcd) (2). Thermolysis of 2 in toluene at 60 °C gives the methylidyne-capped cluster HCCo₃(CO)₇(bpcd) (4) and the phosphido-bridged cluster Co₃(CO)₇[μ₂,η²,η¹-P(Ph)CC(PPh₂)C(O)CH₂C(O)] (5). Cluster 4 has been independently prepared from HCCo₃(CO)₉ and bpcd and shown to serve as the precursor to 5. The new clusters 2, 4, and 5 have been isolated and characterized in solution by IR and NMR (¹H and ³¹P) spectroscopies and their solid-state structures have been established by X-ray diffraction analyses. Both clusters 2 and 4 contain 48e- and exhibit triangular Co₃ cores with a chelating and bridging bpcd ligand in the solid state, respectively. The structure of 5 provides unequivocal support for the loss of the methylidyne capping ligand and P-Ph bond cleavage attendant in the activation of 4 and confirms the presence of the face capping seven-electron μ₂,η²,η¹-P(Ph)CC(PPh₂)C(O)CH₂C(O) ligand in the final product. The fluxionality displayed by the bpcd ligand in clusters 2 and 4 and the decarbonylation behavior of the formyl moiety in the former cluster are discussed relative to related alkylidyne-capped Co₃ derivatives.     

The electronic structure of 5-methylhexa-1,2,4-triene-1,3-diyl, the first representative of highly delocalized triplet ethynylvinylcarbenes, from ESR spectroscopy data and quantum chemical calculations

The ESR spectrum of the first representative of highly conjugated triplet ethynylvinylcarbenes, 5-methylhexa-1,2,4-triene-1,3-diyl (1), was recorded in solid argon matrix. The zero-field splitting (ZFS) parameters of carbene 1 (D = 0.5054±0.0006 cm^?1 and E = 0.0045±0.0002 cm^?1) determined from the experimental ESR spectrum are in between the corresponding parameters of ethynylcarbene C3H2 (2) and vinylcarbene C₃H₄ (3): D(3) < D(1) < D(2) and E(2) < E(1) < E(3). Quantum chemical calculations of the ZFS parameters of 1, 2, and 3 have been carried out for the first time using two DFT-based approaches, RODFT and UDFT. An analysis of the experimental and theoretical ZFS parameters shows that carbene 1 is characterized by a greater extent of delocalization of the spin density of unpaired electrons than carbenes 2 and 3. The characteristic structural fragments of carbene 1 possess the principal features of the electronic structure of both ethynylcarbene (2) and vinylcarbene (3), respectively. Magnetic spin-spin interactions are identical in carbenes 1 and 2. The dominant contribution to D in 1 and 2 results from the one-center spin-spin interactions on carbon atoms in the propynylidene group, which are subjected to strong spin polarization.     

Synthesis, characterization and catalytic activity of three palladium(II) complexes containing Schiff base ligands

Three new Pd(II) complexes of Schiff base ligands, namely, [Pd₄(L¹)₄] (1), [Pd₂(L²)₂Cl₂] (2) and [Pd(L³)₂Cl₂] (3) [HL ¹ ?=?N-(benzylidene)-2-aminophenol; L ² ?=?N-(2,4-dichlorobenzylidene)-2,6-diethylbenzenamine, L ³ ?=?4-(2,4-dichlorobenzylide-neamino)phenol] have been synthesized using solvothermal methods and characterized by elemental analysis, spectroscopy and single crystal X-ray diffraction. The crystal structures of the free ligands were also determined. The ??-oxygen-bridged tetranuclear cyclometallated Pd(II) complex (1) contains four nearly planar units, in which Pd^II is four-coordinate. Complex 2 is a ??-chloro-bridged dinuclear cyclometallated Pd(II) complex, whereas complex 3 is mononuclear. The Heck reactions of bromobenzene with acrylic acid catalyzed by complexes 1?C3 have also been studied.     

Copper(II), iron(III) and cobalt(III) complexes of the pendent-arm cyclam derivative 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane

The interaction of Cu(II), Fe(III) and Co(III) with 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane (L ³ ) incorporating a pendent amine group has led to isolation of the new octahedral complexes [Cu(HL ³ )(ClO₄)₂]Cl·H₂O (1), [Fe(L ³ )Cl](S₂O₆)·H₂O (2), [Co(L ³ )Cl](ClO₄)_1.5Cl_0.5·0.25H₂O (3), [Co(HL ³ )Cl₂](ClO₄)₂·H₂O (4) and [Co(L ³ )Cl]₂(S₂O₄)(ClO₄)₂ (5). In (1) the copper ion occupies the macrocyclic cavity of protonated (–NH₃ ⁺) L ³ which is present in its trans-III configuration; weakly bound ClO₄ ^? ligands occupy the axial positions. The X-ray structure of (2) showed that Fe(III) occupies the N₄-macrocyclic cavity of L ³ in a trans-III configuration, with the pendent amine group binding in an axial position. The remaining axial position is occupied by a Cl^? ligand. Chromatography of the product obtained from the reaction of Na₃[Co(CO₃)₃] with L ³ yielded three fractions. Fraction 1 yielded crystals (3) composed of three crystallographically independent species incorporating cations of type [Co(L ³ )Cl]²⁺ with very similar structures; in each case the macrocyclic ring nitrogens of L ³ are bound to the Co(III) in an asymmetric cis-fashion. Fraction 2 yielded the trans-III octahedral cationic complex (4) incorporating L ³ in its protonated form. The Co(III) complex (5) from fraction 3 shows a different coordination arrangement to the products from fractions 1 or 2. The macrocyclic ring coordinates in its trans-III form, but the axial sites in this case are occupied by the pendent-NH₂ group and a Cl^? ligand.     

Aromatic stability energy studies on five-membered heterocyclic C4H4M (M = O, S, Se, Te, NH, PH, AsH and SbH): DFT calculations

Energetic, geometric and magnetic criteria were applied to examine the stability and/or aromatic character for the cyclic molecules C ₄ H ₄ M (M = O, S, Se, Te, NH, PH, AsH and SbH) at B3LYP/6-311++G^** and MP2/6-311++G^** levels of theory. The isodesmic reactions and nuclear independent chemical shifts (NICS) calculations were utilized to examine the molecules for energetic and magnetic criteria, respectively. The isodesmic reaction energies reveal that thiophene (C ₄ H ₄ S, ?23.269 kcal/mol) and pyrrole (C ₄ H ₄ NH, ?20.804 kcal/mol) have the greatest aromatic stabilization energies and tellurophene (C ₄ H ₄ Te, ?15.114 kcal/mol) and stibole (C ₄ H ₄ SbH, ?1.169 kcal/mol) have the lowest aromatic stabilization energies in their corresponding groups at MP2/6-311++G^**. The NICS calculations confirmed the results obtained through isodesmic reaction energies.     

Syntheses and characterization of a new class of vanadia precursors of oxime-modified oxovanadium(V) isopropoxide,crystal and molecular structure of [VO{ONC10H16}3]

Modification of [VO(OPrⁱ)₃] with oximes in different molar ratios, yielded new class of vanadia precursors, [VO{OPrⁱ}_3?n{L}_n] {where, n = 1–3 and LH = C₉H₁₆C=NOH (1–3) and (CH₃)₂C=NOH (4–6)}.All the products are yellow in colour. (1) and (2) are liquid/viscous liquid, while others are solids. Molecular weight measurements of all these derivatives and the ESI-mass spectral studies of (1), (2), (3) and (5) indicate their monomeric nature. ¹H and ¹³C{¹H} NMR spectra suggest that the oximato moieties are monodentate in solution which was further confirmed by the ⁵¹V NMR signals, appeared in the region expected for tetra-coordinated oxo-vanadium atoms. On ageing, a disproportionation reaction occurs in (1) and some crystals appeared. Single crystal X-ray diffraction analyses of the crystals obtained from (1) as well as from (3) were found to be the same and indicate the presence of side-on {dihapto η ²-(N, O)} binding modes of the oximato ligands, leading to the formation of seven coordination environment around the vanadium atom. Thermogravimetric curve of (1) exhibits multi-step decomposition with the formation of V₂O₅ as the final product at ~850 °C. Sol–gel transformation of (3) yielded (a) VO₂ sintered at 300 °C and (b) V₂O₅ at 600 °C. Similarly, sol–gel transformations of (1) and (2) yielded V₂O₅ (c) and (d) at 600 °C, respectively. Formation of monoclinic phase in (a) and orthorhombic phase in (b), (c) and (d) were confirmed by powder XRD patterns.     

Synthesis,characterization, and thermal behavior of palladium(II) complexes containing 4-iodopyrazole

The mononuclear pyrazolyl complexes [PdCl₂(HIPz)₂] (1), [PdBr₂(HIPz)₂] (2), [PdI₂(HIPz)₂] (3), [Pd(SCN)₂(HIPz)₂] (4), and [Pd(NHCOIPz)₂] (5) have been prepared. Compound 1 was obtained from the displacement of acetonitrile from [PdCl₂(CH₃CN)₂] precursor by the 4-iodopyrazole (HIPz) ligand, whereas 2–5 were synthesized by substitution of the chlorido in 1 by the respective anionic group. The compounds were characterized by elemental analysis, infrared spectroscopy, and ¹H NMR spectroscopy. The thermal behavior of 1–5 has been studied by TG and DTA. The thermal stability of [PdX₂(HIPz)₂] compounds varies according to the trends X = Cl^? < I^? ? SCN^?< Br^?. No stable intermediates were isolated during the thermal decompositions due to the overlap of the degradation processes. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Derivatives of Bis(diphenylphosphino)maleic Anhydride as Ligands in Polynuclear Gold(I) Complexes

Based on the new binuclear gold(I) complex [(AuCl)₂(L1)] (1) (L1?=?2,3-bis(diphenylphosphino)maleic anhydride) four new polynuclear compounds were synthesized by reactions of 1 with E(SiMe₃)₂ (E?=?S, Se). During the formation of these new compounds the initial ligand L1 undergoes various transformations (e.g. substitution, hydration or hydrogenation) leading to the new ligands: trans-2,3-bis(diphenylphosphino)succinic anhydride (L2), 2-diphenylphosphino-3-mercapto-maleic anhydride anion (L3), 2-diphenylphosphino-3-selenolato-maleic anhydride anion (L4) and 2,3-bis(diphenylphosphino)succinic acid (L5). In case of using the sulfur species S(SiMe₃)₂ a pentanuclear cluster, [Au₅(PPh₂)₃(L3)₂] (2), and a 24-nuclear cluster, [Au₂₄S₆(PPh₂)₄(L3)₈] (3), could be obtained. With Se(SiMe₃)₂ the binuclear complex, [(AuCl)₂(L2)] (4), and the dodecanuclear cluster, [Au₁₂Se₄(L4)₄(L5)₂] (5), were yielded.