Bimetallic single-source precursors [M(NH3)4][Co(C2O4)2(H2O)2]·2H2O (M = Pd, Pt) for the one run synthesis of CoPd and CoPt magnetic nanoalloys

All the steps of the proposed technique, from the synthesis of single-source precursors to the preparation of CoPd and CoPt nanoalloys, are described. The double complex salts (DCS) [M(NH₃)₄][Co(C₂O₄)₂(H₂O)₂]·2H₂O (M = Pd, Pt), which were synthesized by mixing solutions containing [M(NH₃)₄]²⁺ cations and [Co(C₂O₄)₂(H₂O)₂]²⁻ anions, have been used as precursors. The salts obtained were characterized by IR spectroscopy, thermal analysis, XRD and single crystal X-ray diffraction. The prepared compounds crystallize in the monoclinic (space group I2/m, M = Pd) and orthorhombic (space group I222, M = Pt) crystal systems. Thermal decomposition of the salts in helium or hydrogen atmosphere at 200-600 °C results in the formation of nanoalloys powders (random solid solution Co_0.50Pd_0.50 and chemically ordered CoPt). The size of the bimetallic particles varied from 5 to 20 nm. Order-disorder structural transformations in Co_0.50Pt_0.50 nanoalloys were studied. The magnetic properties of both chemically disordered Co_0.50Pd_0.50 and ordered CoPt clusters have also been measured.     

In depth investigation of the synthesis, structural, and spectroscopic characterization of a high pH binary Co(II)-N,N-bis(phosphonomethyl)glycine species. Association with aqueous speciation studies of binary Co(II)-(carboxy)phosphonate systems

Cobalt is an abundant metal ion present in the abiotic and biological world. The chemical reactivity of Co(II) is exemplified through complex interactions with variable molecular mass ligands, including amino acids, peptides, variable nature organic ligands, and/or phospho(nate)-derivatives thereof. Poised to gain insight into the chemical reactivity of Co(II) toward the family of mixed (carboxy)phosphonate-containing ligands, pH-specific aqueous reactions were carried out between Co(II) and N,N-bis(phosphonomethyl)-glycine (NTA2P), leading to a new pH-structural variant species (NH₄)₃[Co(C₄H₆O₈NP₂)(H₂O)₂]·4H₂O (1) at pH 8. Compound 1 was characterized analytically, spectroscopically (FT-IR, UV-Vis, EPR), and magnetically. X-ray crystallography reveals a mononuclear complex of Co(II) in an NO₅ octahedral environment. The solid state magnetic and EPR data on 1 suggest the presence of a high-spin Co(II) in a distorted octahedral geometry, with a ground state of an effective spin S = 1/2. The solution UV-Vis and EPR data suggest retention of the integrity of 1, consistent with the magnetization measurements. Detailed aqueous speciation studies on binary Co(II)-carboxylate (NTA) and all Co(II)-(carboxy)phosphonate (NTA_xP; x = 1-3) systems reveal the aqueous distributions of all species involved in the respective systems and project a mononuclear species not unlike that of 1 in the Co(II)-NTA2P system. The structural and chemical attributes of the title complex reflect the (a) pH-dependent chemical reactivity in the binary Co(II)-NTA2P system, and (b) structure-activity correlations in the aqueous media linking both high and low pH-structural variants. To this end, fundamental structural properties influence the reactivity of Co(II) toward phosphonate and mixed carboxyphosphonate ligands and are ultimately exemplified as a function of phosphonate-containing moieties in NTA derivatives. The variably configured species in such binary Co(II)-ligand systems define the pH dependence and nature of interactions between the two reagents, and could serve further as precursors in the design and discovery of new Co(II)-organophosphonate materials of specific structural lattice, spectroscopic, and magnetic properties.     

Iron(II) and cobalt(II) complexes bearing 8-(1-aryliminoethylidene) quinaldines: Synthesis, characterization and ethylene dimerization behavior

The series of bidentate N^N iron(II) and cobalt(II) complexes containing 8-(1-aryliminoethylidene) quinaldine derived ligands, 8-[2,6-(R¹)₂-4-R²-C₆H₂NC (Me)]-2-Me-C₁₀H₅N, were synthesized and characterized by elemental and spectroscopic techniques. The molecular structures of Co1 (R¹ = Me, R² = H), Co3 (R¹ = ⁱPr, R² = H) and Co4 (R¹ = R² = Me) were confirmed as the distorted tetrahedral by single crystal X-ray diffraction. On treatment with modified methylaluminoxane (MMAO), these complexes exhibited good catalytic activities of up to 5.71 × 10⁵ g mol⁻¹(Fe) h⁻¹ for the ethylene dimerization at 30 °C under 10 atm of ethylene, in which iron pre-catalysts produced butenes with a high selectivity for α-butene. The correlation between metal complexes, catalytic activities and the product formed were investigated under various reaction parameters.     

Synthesis and properties of novel ortho-metalated cobalt(I) and iron(II) complexes through Csp2-H bond activation of dibenzylphenylphosphine

Dibenzylphenylphosphine in the reaction with CoMe(PMe₃)₄ afforded complex [(Me₃P)₃Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (1) by C_sp2-H activation via ortho-metalation with P atom as anchoring group. An unexpected dinitrogen iron(II) complex [(Me₃P)₂(N₂)Fe((ortho-C₆H₄)₂∩P(C₆H₅))] (2) stabilized by two five-membered chelate rings as [CPC]-pincer ligand was formed through the reaction of dibenzylphenylphosphine with FeMe₂(PMe₃)₄ via double C_sp2-H activation. The reactions of complexes 1 and 2 with carbon monoxide delivered carbonyl complexes [(Me₃P)(CO)₂Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (3) and [(Me₃P)₂(CO)Fe((ortho-C₆H₄)₂∩P(C₆H₅))] (4). An iodo methyl cobalt(III) complex [(Me₃P)₂(Me)(I)Co((ortho-C₆H₄)∩P(C₆H₅)(CH₂C₆H₅))] (5) was isolated through the reaction of 1 with iodomethane. The structures of 1, 2, 3, 4 and 5 were determined by X-ray diffraction.     

Silylated Co/SBA-15 catalysts for Fischer-Tropsch synthesis

A series of silylated Co/SBA-15 catalysts were prepared via the reaction of surface Si-OH of SBA-15 with hexamethyldisilazane (HMDS) under anhydrous, vapor-phase conditions, and then characterized by FT-IR, N₂ physisorption, TG, XRD, and TPR-MS. The results showed that organic modification led to a silylated SBA-15 surface composed of stable hydrophobic Si-(CH₃)₃ species even after calcinations and H₂ reduction at 673 K. Furthermore, the hydrophobic surface strongly influenced both metal dispersion and reducibility. Compared with non-silylated Co/SBA, Co/S-SBA (impregnation after silylation) showed a high activity, due to the better cobalt reducibility on the hydrophobic support. However, S-Co/SBA (silylation after impregnation) had the lowest FT activity among all the catalysts, due to the lower cobalt reducibility along with the steric hindrance of grafted -Si(CH₃)₃ for the re-adsorption of α-olefins.     

Supramolecular Hydrogen‐Bonded Frameworks from a New Bisphosphonic Acid and Transition Metal Ions

The reaction of 2‐morpholinoethylimino‐bis(methylenephosphonic acid) (H₄L) with cobalt(II), nickel(II) acetate, and cadmium(II) chloride in ethanol/water mixed solvents afforded three new crystal‐engineered supramolecular metal phosphonates, Co(H₃L)₂ · 2H₂O ( 1 ), Ni(H₃L)₂ · 2H₂O ( 2 ), and [Cd₂Cl₄(H₂O)₆]_0.5[H₄L] ( 3 ) by using a layering technique. The cobalt(II) ions in complex 1 are hexacoordinated by four phosphonate oxygen atoms and two imino nitrogen atoms. The mononuclear units of complex 1 are connected through hydrogen bonds to form a three dimensional supramolecular network. The structure of compound 2 is analogous to that of 1 except that the cobalt(II) ion in compound 1 is replaced by nickel(II) in compound 2 . In the molecular structure of compound 3 , cadmium is coordinated to three chloride ions and three aqua oxygen atoms to form a novel neutral dinuclear complex. Several hydrogen bonds connect the dinuclear complex and the neutral form of the ligand to build a supramolecular three dimensional structure.     

Isomorphous Catena Transition Metal Squarates [MII(C4O4)(dmso)2(OH2)2] (M = Co,Mn) and Magnetic Investigation into their Solid Solution M = CoxMn1–x

The crystal structures of two new isomorphous transition metal squarato complexes [M^II(C₄O₄)(dmso)₂(OH₂)₂] [M^II = Co^II (3d⁷), Mn^II (3d⁵); dmso = dimethylsulfoxide] and their magnetic properties are reported. The compounds feature two symmetrically independent chains, in which 1,3‐bridging squarato ligands connect cations in distorted octahedral surroundings of pseudo‐symmetry D_4h. From an equimolar solution of CoCl₂ · 6H₂O and MnCl₂ · 2H₂O a mixed‐metal coordination polymer crystallizes; it represents a solid solution and adopts the same structure as the corresponding monometallic compounds. The results of the diffraction experiment unambiguously proof the presence of both Co^II and Mn^II cations in either independent site albeit no precise ratio between the metal cations involved may be deduced from these findings. The difference in the magnetic properties between Co^II and Mn^II cations in the given ligand field has allowed us to establish their ratio in the solid solution more reliably than by X‐ray diffraction: Accounting for ligand field potential and spin‐orbit coupling of Co^II and regarding Mn^II as a pure spin system, the calculations yielded a fraction of 73 % Co^II in the mixed‐metal polymer. With respect to superexchange effects only weak antiferromagnetic interactions have been detected for the three coordination polymers.     

Alternating copolymerization of cyclohexene oxide and carbon dioxide under cobalt porphyrin catalyst

Cobalt porphyrin complexes（TPPCo^ⅢX）（TPP = 5,10,15,20-tetraphenyl-porphyrin;X = halide） in combination with bis（triphenylphosphine） iminium chloride（PPNCl） were used for the copolymerization of cyclohexene oxide and CO₂. The highest turnover frequency of 67.2 h^-1 was achieved after 13 h at 20℃,and the obtained poly（1,2-cyclohexylene carbonate）（PCHC） showed number average molecular weight（M_n） of 10×10³.Though the obtained PCHC showed atactic structure,the m-centered tetrads content reached 58.1%at CO₂ pressure of 1.0 MPa,and decreased to 51.9%at CO₂ pressure of 6.0 MPa,indicating that it was inclined to form atactic polymer at high CO₂ pressure.     

Syntheses, electrochemical and spectroelectrochemical properties of novel ball-type and mononuclear Co(II) phthalocyanines substituted at the peripheral and non-peripheral positions with binaphthol groups

Mononuclear cobalt phthalocyanine (CoPc) substituted at the non-peripheral 8 and peripheral positions 9 with 1,1′-binaphthyl-8,8′-diol and ball-type dinuclear Co₂Pc₂ substituted at the non-peripheral 10 and peripheral 11 positions with the same substituent are reported. The complexes with 1,1′-binaphthol-bridges were prepared from the corresponding phthalonitriles 4-7. The effects of the position of substituent on spectral, electrochemical and spectroelectrochemical properties of these complexes were also explored. The mononuclear complexes 8 and 9 exhibited one metal reduction, one ring reduction and one ring oxidation. The redox properties of the ball-type complexes 10 and 11 exhibited two reduction processes assigned to [(Co^IPc⁻²)₂]²⁻/[(Co^IPc⁻³)₂]⁴⁻ (I), (Co^IIPc⁻²)₂/[(Co^IPc⁻²)₂]²⁻ (II) and one oxidation process assigned to [(Co^IIIPc⁻²)₂]²⁺/Co^IIPc⁻²)₂ (III). The ball-type complexes are much easier to oxidize and more difficult to reduce than the corresponding monomers 8 and 9.