Hexanuclear cobalt carbonyl carbide clusters: the interplay between octahedral and trigonal prismatic structures

The six-vertex cobalt carbonyl clusters [Co6C(CO)n](2-) (n = 12, 13, 14, 15, 16) with an interstitial carbon atom have been studied by density functional theory (DFT). These DFT studies indicate that the experimentally known structure of [Co6C(CO)15](2-) consisting of a Co6 trigonal prism with each of its edges bridged by carbonyl groups is a particularly stable structure lying more than 20 kcal/mol below any other [Co6C(CO)15](2-) structure. Addition of a CO group to this [Co6C(CO)15](2-) structure gives the lowest energy [Co6C(CO)16](2-) structure, also a Co6 trigonal prism with one of the vertical edges bridged by two CO groups and the remaining eight edges each bridged by a single CO group. However, this [Co6C(CO)16](2-) structure is thermodynamically unstable with respect to CO loss reverting to the stable trigonal prismatic [Co6C(CO)15](2-). This suggests that 15 carbonyl groups is the maximum that can be attached to a Co6C skeleton in a stable compound. The lowest energy structure of [Co6C(CO)14](2-) has a highly distorted octahedral Co6 skeleton and is thermodynamically unstable with respect to disproportionation to [Co6C(CO)15](2-) and [Co6C(CO)13](2-). The lowest energy [Co6C(CO)13](2-) structure is very similar to a known stable structure with an octahedral Co6 skeleton. The lowest energy [Co6C(CO)12](2-) structure is a relatively symmetrical D3d structure containing a carbon-centered Co6 puckered hexagon in the chair form.     

Synthesis and structural and magnetic characterization of cobalt(II) phosphonate cage compounds

Reaction of cobalt salts with phosphonic acids in the presence of 6-chloro-2-hydroxypyridine as a co-ligand, normally in its deprotonated form, leads to a series of new polymetallic cobalt cages. The most common structural type is a {Co(14)} cage which resembles a fragment of cobalt hydroxide. Variation of the phosphonate present and the cobalt salt leads to {Co(6)}, {Co(8)}, {Co(10)}, {Co(11)}, {Co(12)}, {Co(13)}, and {Co(20)} cages, all of which have been characterized by X-ray crystallography. Magnetic studies of these cages show a general decline in the product chi(m)T with T, but for {Co(6)}, {Co(8)}, and {Co(12)} there are maxima at low temperature, which suggests nondiamagnetic ground states. Investigation of the dynamic behavior of the magnetization of these complexes shows that the octanuclear cage displays slow relaxation of magnetization.     

Boronyl ligand as a member of the isoelectronic series BO(-) → CO → NO(+): viable cobalt carbonyl boronyl derivatives?

Recently the first boronyl (oxoboryl) complex [(c-C(6)H(11))(3)P](2)Pt(BO)Br was synthesized. The boronyl ligand in this complex is a member of the isoelectronic series BO(-) → CO → NO(+). The cobalt carbonyl boronyls Co(BO)(CO)(4) and Co(2)(BO)(2)(CO)(7), with cobalt in the formal d(8) +1 oxidation state, are thus isoelectronic with the familiar homoleptic iron carbonyls Fe(CO)(5) and Fe(2)(CO)(9). Density functional theory predicts Co(BO)(CO)(4) to have a trigonal bipyramidal structure with the BO group in an axial position. The tricarbonyl Co(BO)(CO)(3) is predicted to have a distorted square planar structure, similar to those of other 16-electron complexes of d(8) transition metals. Higher energy Co(BO)(CO)(n) (n = 3, 2) structures may be derived by removal of one (for n = 3) or two (for n = 2) CO groups from a trigonal bipyramidal Co(BO)(CO)(4) structure. Structures with a CO group bridging 17-electron Co(CO)(4) and Co(BO)(2)(CO)(3) units and no Co-Co bond are found for Co(2)(BO)(2)(CO)(8). However, Co(2)(BO)(2)(CO)(8) is not viable because of the predicted exothermic loss of CO to give Co(2)(BO)(2)(CO)(7). The lowest lying Co(2)(BO)(2)(CO)(7) structure is a triply bridged (2BO + CO) structure closely related to the experimental Fe(2)(CO)(9) structure. However, other relatively low energy Co(2)(BO)(2)(CO)(7) structures are found, either with a single CO bridge, similar to the experimental Os(2)(CO)(8)(μ-CO) structure; or with 17-electron Co(CO)(4) and Co(BO)(2)(CO)(3) units joined by a single Co-Co bond with or without semibridging carbonyl groups. Both triplet and singlet Co(2)(BO)(2)(CO)(6) structures are found. The lowest lying triplet Co(2)(BO)(2)(CO)(6) structures have a Co(CO)(3)(BO)(2) unit coordinated to a Co(CO)(3) unit through the oxygen atoms of the boronyl groups with a non-bonding ～4.3 ? Co···Co distance. The lowest lying singlet Co(2)(BO)(2)(CO)(6) structures have either two three-electron donor bridging η(2)-μ-BO groups and no Co···Co bond or one such three-electron donor BO group and a formal Co-Co single bond.     

N‐Doped Sub‐3 nm Co Nanoparticles as Highly Efficient and Durable Aerobic Oxidative Coupling Catalysts

A nano‐coating associated with sulfuric acid leaching protocol was developed to prepare N‐doped sub‐3 nm Co‐based nanoparticle catalyst (Co?N/C) using melamine–formaldehyde resin as the N‐containing precursor, active carbon as the support, and Co(NO₃)₂ as the Co‐containing precursor. By thermal treatment under nitrogen atmosphere at 800 °C and leached with sulfuric acid solution, a stable and highly dispersive Co?N coordination structure was uniformly dispersed on the formed Co?N/C catalyst with a Co loading of 0.47 wt % and Co nanoparticle size of 2.55 nm. The Co?N/C catalyst was characterized with XRD, XPS, Raman, SEM, TEM, ICP, and elemental analysis. The Co?N/C catalyst showed extremely high catalytic efficiency with a TON of 257 for the aerobic oxidative coupling of aldehydes with methanol to directly synthesize methyl esters with molecular oxygen as the final oxidant. The Co?N/C catalyst also showed broad substrate range and stable recyclability. After recycling for 7 times, no obvious deactivation was detected. It was confirmed that the sub‐3 nm Co?N coordination structure formed between metallic Co nanoparticles and pyridinic nitrogen doping into graphitic layers functions as the active site to activate molecular oxygen for the β‐H elimination from generated hemiacetal intermediates to produce methyl esters. The nano‐coating associated with acid leaching protocol provides a novel strategy to prepare highly efficient non‐precious metal‐based catalysts.     

Maleate-fumarate conversion and other novel aspects of the reaction of a Co(II) maleate with pyridine and bipyridine

Reaction of a molecular Co(II) maleate, [Co(Hmal)2(H2O)4], with pyridine yields a Co(II) fumarate, [Co(fum)(H2O)4], with a chain structure and a chiral pyridylsuccinic acid zwitter ion, (-)OOC-CH(N+C5H5)-CH2-COOH, in almost quantitative yields, while the reaction of 4,4'-bipyridine (bipy) with the Co(II) maleate, on the other hand, almost quantitatively generates a polylmeric Co(II) maleate, [Co(mal)(bipy)]n.(n/2)H2O along with the adduct of fumaric acid with bipyridine.     

Determination of coenzyme Q10, alpha-tocopherol and cholesterol in biological samples by coupled-column liquid chromatography with coulometric and ultraviolet detection

Coenzyme (Co) Q10, Co Q10H2, alpha-tocopherol and cholesterol were dissociated from lipoproteins in plasma by treatment with 1-propanol. The supernatant obtained was injected directly for determination of Co Q10 and Co Q10H2. Precolumn reduction with borohydride was used for determination of total Co Q10 simultaneously with alpha-tocopherol and cholesterol. Total Co Q10 in freeze-dried myocardial biopsies was determined after extraction with 1-propanol and oxidation of Co Q10H2 with ferric chloride. The chromatographic system comprised two reversed-phase columns and a three-electrode coulometric detector and a UV detector coupled in series. A pre-fractionation on the first column protected the coulometric detector from contamination and reduced the time for analysis by eliminating strongly retained solutes. The coulometric electrodes were operated in the oxidation-reduction-oxidation mode, and the last electrode was used for detection of alpha-tocopherol, Co Q10 and Co Q10H2, while cholesterol was detected by UV at 215 nm. The fast isolation procedure made it possible to determine the reduced and oxidized forms of Co Q10 in plasma. Quantitative recoveries were obtained for all the analytes studied and normal levels were determined with a coefficient of variation of 2-3%.     

Theoretical analysis of mechanistic pathways for hydrogen evolution catalyzed by cobaloximes

The mechanistic pathways for hydrogen evolution catalyzed by cobalt complexes with supporting diglyoxime ligands are analyzed with computational methods. The cobaloximes studied are Co(dmgBF(2))(2) (dmg = dimethylglyoxime) and Co(dpgBF(2))(2) (dpg = diphenylglyoxime) in acetonitrile. The reduction potentials and pK(a) values are calculated with density functional theory in conjunction with isodesmic reactions, incorporating the possibility of axial solvent ligand loss during the reduction process. The solvent reorganization energies for electron transfer between the cobalt complex and a metal electrode and the inner-sphere reorganization energies accounting for intramolecular rearrangements and the possibility of ligand loss are also calculated. The relative reduction potentials agree quantitatively with the available experimental values. The pK(a)s and reorganization energies agree qualitatively with estimates based on experimental data. The calculations suggest that a peak measured at ca. -1.0 V vs SCE in cyclic voltammetry experiments for Co(dmgBF(2))(2) is more likely to correspond to the Co(II)H/Co(I)H reduction potential than the Co(III)H/Co(II)H reduction potential. The calculations also predict pK(a) values of Co-hydride complexes and reduction potentials for both cobaloximes that have not been determined experimentally. The results are consistent with a mechanism in which the Co(III) and Co(II) complexes have two axial solvent ligands and the Co(I) complex has a single axial ligand along the reaction pathway. Analysis of the free energy diagrams generated for six different monometallic and bimetallic hydrogen production pathways identified the most favorable pathways for Co(dmgBF(2))(2) and tosic acid. The thermodynamically favored monometallic pathway passes through a Co(III)H intermediate, and Co(II)H reacts with the acid to produce H(2). The thermodynamically favored bimetallic pathways also pass through the Co(III)H intermediate, but the pathways in which two Co(III)H or two Co(II)H complexes react to produce H(2) are not thermodynamically distinguishable with these methods. On the basis of the electrostatic work term associated with bringing the two cobalt complexes together in solution, the preferred bimetallic pathway involves the reaction of two Co(III)H complexes to produce H(2). This mechanistic insight is important for designing more effective catalysts for solar energy conversion.     

固相法制备纳米Co3O4催化剂及其催化甲苯完全氧化性能

采用环境友好的固相法制备了高活性甲苯氧化Co3O4催化剂,通过与传统沉淀法和柠檬酸络合-燃烧法制备的Co3O4催化剂比较,固相合成法制备的Co3O4-SR催化剂在催化甲苯完全氧化反应中表现了很好的活性和稳定性,甲苯转化率为95%时的反应温度T95为230℃,反应60 h活性没有下降.通过XRD,Raman,FT-IR,XPS等手段对Co3O4催化剂的结构和表面性能进行了表征,结果表明固相法制备的Co3O4催化剂具有较多的表面缺陷,催化剂表面Co—O键较弱,具有较强的活化氧的能力,表现出突出的甲苯完全氧化的催化活性.     

TPR/TPO characterization of cobalt–silicon mixed oxide nanocomposites prepared by sol–gel

Cobalt–silicon mixed oxides with Co/Si ratio of 10/90 (10Co), 20/80 (20Co) and 30/70 (30Co) were prepared by a modified sol–gel method. The materials treated in air at 400 and 600 °C were characterized by SEM and TPR/TPO techniques. TPR measurements showed that in all samples only a fraction of Co was present as Co₃O₄ and as amorphous silicate and was reducible by H₂ within 800 °C, while a part was not reducible under TPR conditions. The fraction of Co not reducible decreased with increasing Co content. A TPO/TPR cycle gave rise to an increase of the fraction of not reducible Co.     

Co-P非晶态合金电子性质和局域结构的理论研究

In order to study the electron property and the microlocal structure of Co-P amorphous alloy,a series of single-P（ConP）and two-P（ConP2）cluster models were chosen according to the experiment fact of the possible presence of direct P-P contact and short-range-ordering in the amorphous alloy. ConP and ConP2 cluster models were calculated with the DFT method and calculations showed that P（phosphor）accepted electron from Co（cobalt）in single-P（Co2P（2）,Co3P（1）and Co4P（2））cluster models,which agrees well with the Pauli electronegative rule,and a very strong interaction between Co and P resulted in formation stable clusters Co2P（2）,Co3P（1）and Co4P（2）. However,two-P（ConP2）cluster models and single-P cluster Co5P（1）were unstable,and it was impossible to present direct P-P contact in two-P（ConP2）cluster models. It could be concluded that the clusters Co2P（2）,Co3P（1）and Co4P（2） is more reasonable to represent the local structure of Co-P amorphous alloy.     

Structural and magnetic studies of original tetranuclear CoII-LnIII complexes (LnIII = Gd, Tb, Y)

The syntheses, structural determinations and magnetic studies of tetranuclear Co(II)-Ln(III) complexes (Ln = Y, Gd, Tb) involving orthovanillin as main ligand are described. The structural studies demonstrate that centrosymmetric tetranuclear Co(2)-Ln(2) complex molecules with a defect-dicubane central core are obtained, with hexacoordinate Co ions in deformed octahedral environments and nine-coordinate lanthanide ions. The Co ions are linked by two hydroxo bridges and each Co ion is also involved in a double phenoxo-hydroxo bridge with the two Ln ions, so that each hydroxo group is triply linked to the two Co and one Gd ions. The four metal ions are coplanar. A ferromagnetic Co-Ln interaction operates in the Co(2)-Ln(2) complexes (Ln = Gd, Tb), along with a D zero-field splitting term for the cobalt ion and a weak ferromagnetic Co-Co interaction. The SMM behaviour of the Co(2)-Gd(2) complex is confirmed by observation of hysteresis loops, as a consequence of the slowing down of relaxation for this tetranuclear complex. The Co(2)-Tb(2) complex does not behave as a SMM, what could result from a subtractive combination of the Tb and Co anisotropies and an increased transverse anisotropy, leading to large tunnel splittings and quantum tunneling of magnetization.     

Poly­[di­aqua­cobalt(II)‐di‐μ4‐benzene‐1,2,4‐tri­carboxyl­ato‐bis­[1,10‐phenanthrolinecobalt(II)]]

In the polymeric title compound, [Co₃(btc)₂(phen)₂(H₂O)₂]_n [btc is the benzene‐1,2,4‐tri­carboxyl­ate trianion (C₉H₃O₆) and phen is 1,10‐phenanthroline (C₁₂H₈N₂)], there are two different Co centres, Co1 and Co2. The Co1 centre has a deformed trigonal–bipyramidal geometry, while the Co2 centre lies on an inversion centre and has distorted octahedral geometry. Moreover, the 1,2‐di­carboxyl­ate groups of one btc ligand bridge the two adjacent Co2 centres, and each Co2 centre is coordinated by four carboxyl­ate O atoms from four different btc ligands, forming a novel kind of intersecting double‐chain structure, with a Co⋯Co separation of 7.755 Å, along the a axis. On the other hand, the two Co1 centres are bridged by two btc ligands and chelated by phen mol­ecules, respectively, producing a binuclear unit with a Co⋯Co separation of 8.406 Å, and these binuclear units are linked by btc bridges and Co2 centres to extend hybrid chains of Co1 and Co2 along the [101] direction. Furthermore, each btc ligand acts as a pentadentate bridge, linking the Co2 double‐chain structures and the hybrid chains of Co1 and Co2 to yield a two‐dimensional network, and this leads to the formation of very different kinds of voids.     

Reducing power of three-coordinate cobalt(I)

Carbon monoxide adds easily to (PNP)Co, PNP = N(SiMe2CH2PtBu2)2, to give (PNP)Co(CO), whose nuco value of 1885 cm-1 suggests much back-donation, and thus an easily oxidized Co(I) in (PNP)Co. However, Co(III) is inaccessible from (PNP)Co by oxidation with I2, the products being first (PNP)CoI, then the zwitterion [ItBu2PCH2SiMe2NSiMe2CH2PtBu2]CoI2. The potential two-electron oxidant N2CH(SiMe3) reacts with (PNP)Co to form a 1:1 "adduct", whose crystal structure is most consistent with oxidation of Co(I), but not fully to Co(III).     

Co3O4/CeO2的氧化还原性能及反应条件对其CO氧化活性的影响

采用沉淀氧化法制备了Co₃O₄/CeO₂催化剂。运用XRD、BET和TPR表征手段,考察了不同钴铈比及焙烧温度对钴铈复合氧化物物理及化学性能的影响,并分别在干、湿条件下进行了一氧化碳氧化反应研究。结果表明,与纯的Co₃O₄相比,在不同比例的Co₃O₄/CeO₂均经723 K焙烧的各种催化剂中,钴铈原子比为9∶1的复合氧化物粒径较小,比表面积较大,说明适当比例铈的添加能使Co₃O₄具有较小的粒径。此氧化物经538 K温度焙烧制得的钴铈比为9∶1的复合氧化物中Co₃O₄平均粒径为7.2 nm, BET比表面积为167.6 m²/g。经TPR考察发现其具有最优的氧化还原性能。     

Multinuclear cobalt–salen complexes with phenylene linker for epoxide polymerizations

Di‐ and trinuclear cobalt (Co)–salen complexes with a benzene ring as a rigid linker were explored for epoxide polymerizations. The dinuclear Co–salen complex with a 1,2‐phenylene linker showed higher catalytic activity than the dinuclear Co–salen complex with a 1,3‐phenylene linker and the trinuclear Co–salen complex with a 1,3,5‐benzenetriyl linker for the copolymerization of propylene oxide (PO) with carbon dioxide. A combination of the absolute configuration of the two Co–salen moieties was found to affect its catalytic activity. The optimized dinuclear Co–salen complex with a heterochiral combination demonstrated highest activity and maintained its catalytic activity under a low catalyst concentration. The heterochiral dinuclear Co–salen complex also showed high activity for the copolymerization of PO with cyclic anhydride. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2150–2159     

Aminotroponiminates as ligands for potential metal-based nitric oxide sensors

A family of new fluorescently labeled ligands, HRDATI, was prepared to develop transition-metal-based NO sensing strategies. The ligands are composed of aminotroponiminates (ATIs) with a dansyl fluorophore on one of the imine nitrogen atoms and an alkyl substituent, either i-Pr (8), t-Bu (9), or Bz (10), on the other. Bis(chelate) Co2+ ([Co(i-PrDATI)2] (12), [Co(t-BuDATI)2] (14), [Co(BzDATI)2] (15)) and Zn2+ ([Zn(i-PrDATI)2] (13)) complexes were prepared and characterized by X-ray crystallography. The bis(ATI) complex [Co(i-Pr2ATI)2] (11) was also prepared and its X-ray crystal structure determined. Cyclic voltammetry reveals reversible redox waves at -2.57 and -0.045 V (vs Cp2Fe/Cp2Fe+) in THF for the Co2+/Co+ and Co3+/Co2+ couples, respectively, of 11. Only a Co2+/Co+ wave at -2.09 V is observed for 12. When excited at 350 nm, the HRDATI ligands and the diamagnetic Zn2+ complex 13 fluoresce around 500 nm, whereas the paramagnetic Co2+ complexes quench the fluorescence. These air-stable cobalt compounds react with nitric oxide to dissociate a DATI ligand and form neutral dinitrosyl complexes, [Co(NO)2(RDATI)]. The release of the fluorophore-containing ligand is accompanied by an increase in fluorescence intensity, thus providing a strategy for fluorescent NO sensing. Linking two DATI moieties via a tetramethylene chain affords the ligand H2DATI-4 (18). The Co2+ complex [Co(DATI-4)] (19) reacts more readily with NO than the bis(DATI) compounds and also displays an increase in fluorescence intensity upon NO binding.     

Isomorphic coordination polymers of cobalt(II), zinc(II) with a flexible ligand of cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid and their molecular alloys: crystal structures, thermal decomposition mechanisms and magnetic properties

Three new isomorphic coordination polymers of Co(2+), Zn(2+) ions with flexible multicarboxylic acid ligand of the cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid (H(4)L), [Co(4)L(2)(H(2)O)(8)]·3H(2)O (1), [Zn(4)L(2)(H(2)O)(8)]·3H(2)O (2) and [Co(0.8)Zn(3.2)L(2)(H(2)O)(8)]·3H(2)O (3), have been synthesized under hydrothermal conditions and by means of controlling the pH of the reaction mixtures (with an initial pH of 6.0 for 1, 4.0 for 2, and 5.0 for 3, respectively). In the crystal of 1, two crystallographically different Co(2+) ions (Co1 and Co2) form a negatively-charged coordination polymeric chain, which contains a centrosymmetric, linear, trinuclear Co(2+) cluster (Co(3)L(2)) subunit; another crystallographically independent Co(2+) ion (Co3) coordinated to six water molecules acts as a counter ions to link the neighboring coordination polymeric chains via intermolecular H-bond interactions. The Co(2+) ions in 1 were completely and partially replaced by Zn(2+) ions to give 2 and 3, respectively. Complex 3 shows a novel molecular alloy nature, due to the random distributions of the Co(2+) and Zn(2+) ions. Three isomorphic complexes exhibit distinct thermal decomposition mechanisms. The deprotonated cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylic acid ligands decompose at 420-750 °C to give the residue CoO in 1, ZnO + C in 2 and CoO + ZnO in 3. Complex 1 shows a complicated magnetic behavior with co-existence of antiferromagnetic exchange interactions between neighboring Co(2+) ions as well as strong spin-orbital coupling interactions for each Co(2+) ion; complex 3 exhibits a magnetically isolated high-spin Co(2+) ion behavior with strong spin-orbital coupling interactions.     

Co掺杂SAPO-5分子筛制备及其催化氧气氧化环己烷反应性能(英文)

环己醇和环己酮(KA油)是制备尼龙所需材料己二酸和己内酰胺的重要中间体,也可用作油漆、农药和染料等的溶剂以及染色和褪光丝的均化剂等.工业上制取KA油的方法主要为苯酚加氢法、环己烯水合法和环己烷氧化法,其中环己烷氧化法最为普遍,是非常重要的工业过程.为获得适宜的KA油选择性,工业上普遍采用Co盐为催化剂,将环己烷氧化单程转化率控制在5.0%以下,从而使得产物选择性达到70%以上.该环己烷氧化制KA油过程不仅生产效率较低,而且所用均相催化剂因分离困难而不能重复使用.因此,当前关于环己烷氧化反应催化剂的研究均是围绕多相催化剂进行.氧气选择性氧化环己烷反应因具有更高的原子经济性而逐渐成为环己烷氧化法制KA油研究中最具挑战性的课题.该反应是自由基机理,而Co~(2+),Cr~(3+),Mn~(2+)和Ce~(2+)等金属离子可以促进自由基链反应,因此含有这些金属的多相催化剂被广泛用于该反应.另一方面,AlPO-n系列分子筛由于具有特殊的孔结构和一定的表面酸性,在催化反应中显示出较大的应用潜力.如果进行杂原子掺杂,通过改变分子筛骨架的电荷平衡,可以有效提高其表面酸性.例如磷酸硅铝分子筛(SAPO-5)具有中等强度的酸性和良好的择形性,因而作为固体酸催化剂广泛用于乙醇脱水、甲醇制烯烃、丙烯聚合和苯乙烯环氧化等反应,表现出较高的选择性和良好的稳定性.本文以传统均相Co盐催化剂的多相化为出发点,制备了Co掺杂SAPO-5与分子筛催化剂(Co-SAPO-5),考察了Co掺杂量对催化剂结构、表面性质以及氧气选择性氧化环己烷反应性能的影响.结果表明,一部分Co进入分子筛骨架,同时有少量Co以氧化钻形式高度分散在SAPO-5表面.Co掺杂对SAOP-5催化剂比表面积没有显著影响,但可使其孔体积减小.相反,Co掺杂可以提高SAOP-5分子筛表面B酸性位数量和总酸量.活性测试结果表明,环己烷转化率随着Co-SAPO-5催化剂中Co含量的增加而增加,但KA油选择性在转化率高于6.3%时急剧下降.还考察了反应温度、反应时间、初始氧气压力和催化剂用量对Co-SAPO-5分子筛催化剂性能的影响,得到了最优反应条件.以Co-SAPO-5-0.2(Co/Si摩尔比为0.2)分子筛为催化剂时,KA油总收率最高可达7.8%.另外,Co-SAPO-5催化剂在环己烷氧化反应中显示出很好的稳定性,Co-SAPO-5-0.2催化剂套用6次后活性几乎没有变化.     

Monitoring transport phenomena of paramagnetic metal-ion complexes inside catalyst bodies with magnetic resonance imaging

An indirect magnetic resonance imaging (MRI) method has been developed to determine in a noninvasive manner the distribution of paramagnetic Co2+ complexes inside Co/Al2O3 catalyst extrudates after impregnation with Co2+/citrate solutions of different pH and citrate concentrations. UV/Vis/NIR microspectroscopic measurements were carried out simultaneously to obtain complementary information on the nature of the Co2+ complexes. In this way, it could be confirmed that the actual distribution of Co2+ inside the extrudates could be derived from the MRI images. By combining these space- and time-resolved techniques, information was obtained on both the strength and the mode of interaction between [Co(H2O)6]2+ and different Co2+ citrate complexes with the Al2O(3) support. Complexation of Co2+ by citrate was found to lead to a stronger interaction of Co with the support surface and formation of an eggshell distribution of Co2+ complexes after impregnation. By addition of free citrate and by changing the pH of the impregnation solution, it was possible to obtain the rather uncommon egg-yolk and egg-white distributions of Co2+ inside the extrudates after impregnation. In other words, by carefully altering the chemical composition and pH of the impregnation solution, the macrodistribution of Co2+ complexes inside catalyst extrudates could be fine-tuned from eggshell over egg white and egg yolk to uniform.     

Carboxylate and alkyl carbonate coordination at the hydrophobic binding site of redox-active dicobalt amine thiophenolate complexes

A series of new dicobalt complexes of the permethylated macrocyclic hexaamine dithiophenolate ligand H(2)L(Me) have been prepared and investigated in the context of ligand binding and oxidation state changes. The octadentate ligand is an effective dinucleating ligand that supports the formation of bioctahedral complexes with a central N(3)Co(mu-SR)(2)(mu-X)CoN(3) core structure, leaving a free bridging position X for the coordination of the substrates. The acetato- and cinnamato-bridged complexes [(L(Me))Co(II)(2)(mu-O(2)CMe)](+) (2) and [(L(Me))Co(II)(2)(mu-O(2)CCH=CHPh)](+) (5) were prepared by reaction of the mu-Cl complex [(L(Me))Co(II)(2)(mu-Cl)](+) (1) with the corresponding sodium carboxylates in methanol. The electrochemical properties of these and of the methyl carbonate complex [(L(Me))Co(II)(2)(mu-O(2)COMe)](+) (8) were also investigated. All complexes undergo two stepwise oxidations at ca. E(1)(1/2) = +0.22 and at E(2)(1/2) = ca. +0.60 V vs SCE, affording the mixed-valent complexes [(L(Me))Co(II)Co(III)(mu-O(2)CR)](2+) (3, 6, 9) and the fully oxidized Co(III)Co(III) forms [(L(Me))Co(III)(2)(mu-O(2)CR)](3+) (4, 7, 10), respectively. Compounds 3, 6, 9 and 4, 7, 10 refer to acetato-, cinnamato-, and methylcarbonato species, respectively. The Co(II)Co(III) compounds were prepared by comproportionation of the respective Co(II)(2) and Co(III)(2) compounds. The Co(III)Co(III) species were prepared by bromine oxidation of the Co(II)Co(II) forms. The crystal structures of complexes 2.BPh(4).MeCN, 3.(I(3))(2), 5.BPh(4).2MeCN, 6.(ClO(4))(2).EtOH, 7.(ClO(4))(3).MeCN.(H(2)O)(3), and 9.(ClO(4))(2).(MeOH)(2).H(2)O were determined by single-crystal X-ray crystallography at 210 K. The oxidations occur without gross structural changes of the parent complexes. The Co(II)Co(III) complexes are composed of high-spin Co(II) (d(7)) and low-spin Co(III) (d(6)) ions. The Co(III)Co(III) complexes are diamagnetic. The oxidation reactions affect the binding mode of the substrates. In the Co(II)(2) and Co(II)Co(III) forms the carboxylates bridge the two Co(2+) ions in a symmetric mu-1,3 fashion with uniform C-O bond distances, whereas asymmetric bridging modes, with one short C=O and one long C-O distance, are adopted in the fully oxidized species. This is consistent with the observed shifts in vibrational frequencies for nu(as)(C-O) and nu(s)(C-O) across the series.