M(CO)4~(2+)(M=Ni,Pd,Pt)的几何结构与自旋态的理论研究

对标题化合物的几何结构和可能的自旋态在密度泛函DFT-BP86和从头算的水平上进行了研究.计算结果表明:作为16电子配合物阳离子,Pd(CO)_4~(2+)和Pt(CO)~(2+)都以低自旋态平面四边形构型存在,这与实验事实相符,计算得到的键长Pd-C和Pt-C相对趋势也与实验数据一致.而对于Ni(CO)_4~(2+)阳离子计算,在低自旋态平面四边形构型和高自旋态的(扭曲)四面体之间无法给出明确的答案,因为CCSD(T)//BP86和CCSD(T)//MP2水平下得到的两种结构之间的能量差几乎可以忽略.     

CO在Pt(111)和Pt-M(111)(M=Ni,Mg)表面吸附的理论研究

采用密度泛函理论与周期性平板模型相结合的方法,对CO在Pt(111)表面top,fcc,hcp和bridge 4个吸附位和Pt-M(111)(M=Ni,Mg)表面h-top,M-top,Pt(M)Pt-bridge,Pt(M)M-bridge,Pt(Pt)M-bridge,M(Pt)M-bridge,Pt1M2-hcp...     

Synthesis, Electrochemistry and Crystal Structure of the [Ni36Pt4(CO)45]6− and [Ni37Pt4(CO)46]6− Hexaanions

The [Ni₃₆Pt₄(CO)₄₅]^6- and [Ni₃₇Pt₄(CO)₄₆]^6- clusters have been obtained in mixture upon reaction in acetonitrile of [Ni₆(CO)₁₂]^2- salts with K₂PtCl₄ in a 2.5:1 molar ratio. The two hexaanions were indistinguishable by spectroscopic techniques. Crystallization of their trimethylbenzylammonium salts led to crystals of composition 0.5[NMe₃CH₂Ph]₆[Ni₃₆Pt₄(CO)₄₅]-0.5[NMe₃CH₂Ph]₆[Ni₃₇Pt₄(CO)₄₆]·C₃H₈O, hexagonal,space group P6₃ (No. 173), a=17.853(9), c=27.127(13) Å, Z=2; final R=0.057. The metal core of the [Ni₃₆Pt₄(CO)₄₅]^6- anion consists of a Pt₄ tetrahedron fully encapsulated in a shell of 36 Ni atoms belonging to a very distorted and incomplete ₅ tetrahedron. The [Ni₃₇Pt₄(CO)₄₆]^6- hexaanion derives from the former by capping the unique triangular face of the metal polyhedron with an additional Ni(CO) fragment. The [Ni₃₆Pt₄(CO)₄₅]^6--[Ni₃₇Pt₄(CO)₄₆]^6- mixture is rapidly degraded to the known [Ni₉Pt₃(CO)₂₁]^4- cluster by exposure to carbon monoxide. Its reaction with protic acids initially affords the corresponding [H_6-nNi₃₆Pt₄(CO)₄₅]^n--[H_6-nNi₃₇Pt₄(CO)₄₆]^n- (n=5, 4) derivatives, and eventually leads to rearrangement to the known [H_6-n Ni₃₈Pt₆(CO)₄₈]^n- species. Both [Ni₃₆Pt₄(CO)₄₅]^6--[Ni₃₇Pt₄(CO)₄₆]^6- and [HNi₃₆Pt₄(CO)₄₅]^5--[HNi₃₇Pt₄(CO)₄₆]^5- mixtures have been chemically and electrochemically reduced to their corresponding [Ni₃₆Pt₄(CO)₄₅]^n--[Ni₃₇Pt₄(CO)₄₆]^n- (n=7–9) and [HNi₃₆Pt₄(CO)₄₅]^n--[HNi₃₇Pt₄(CO)₄₆]^n- (n=6–8) mixtures.     

Pt–M (M=Fe,Co, Ni and Cu) electrocatalysts synthesized by an aqueous route for proton exchange membrane fuel cells

Nanostructured Pt–M (M=Fe, Co, Ni, and Cu) alloy catalysts synthesized by a low temperature (70 °C) reduction procedure with sodium formate in aqueous medium have been investigated for oxygen reduction in sulfuric acid and as cathodes in single proton exchange membrane fuel cells (PEMFC). The Pt–M alloy catalysts show improved catalytic activity towards oxygen reduction compared to pure platinum. Among the various alloy catalysts investigated, the Pt–Co catalyst shows the best performance with the maximum catalytic activity and minimum polarization occurring at a Pt:Co atomic ratio of around 1:7. While mild heat treatments at moderate temperatures (200 °C) improve the catalytic activity due to a cleaning of the surface oxides, annealing at elevated temperatures (900 °C) degrade the activity due to an increase in particle size.     

金基二元合金团簇Au_(12)M(M=Cu,Pt,Ni)催化水煤气变换反应的理论研究

利用密度泛函理论(DFT)对Au12M(M=Cu,Pt,Ni)3种合金团簇的结构稳定性、热力学稳定性和反应活性进行研究,并对金基二元合金团簇催化水煤气变换反应(WGSR)的反应机理进行探讨.研究发现,Au12Ni合金团簇的稳定性及电子活性最优.考察了WGSR在金基二元合金团簇上的氧化还原机理和羧基机理,表明Au12Cu合金团簇上WGSR按照氧化还原机理A进行,水解离后产生的OH*会继续解离为O*和H*(*代表吸附物质);Au12Pt及Au12Ni合金团簇上按照氧化还原机理B进行,2个OH*发生歧化反应.比较3种团簇上的最佳反应路径发现,Au12Cu团簇对WGSR表现出较好的催化活性.     

Infrared spectroscopic studies of some piperidine metal(II) clathrates: M(C5H11N)2Ni(CN)4·G (M = Co,Ni; G = m-xylene,p-xylene or o-xylene; M = Ni; G = dioxane)

IR spectra of M(C₅H₁₁N)₂Ni(CN)₄·G (M=Co, Ni; G=o-, m- or p-xylene; M=Ni; G=dioxane) are reported. These clathrates are analogues to the previously reported classical Hofmann-type clathrates.     

噻吩在M(111)(M=Pd,Pt,Au)表面的吸附(英文)

采用密度泛函理论(DFT),选取DMol3程序模块,对噻吩在M(111)(M=Pd,Pt,Au)表面上的吸附行为进行了探讨.通过对噻吩在不同底物金属上的吸附能、吸附构型、Mulliken电荷布居、差分电荷密度以及态密度的分析发现,噻吩在Pd(111)面上的吸附能最大,Pt(111)面次之,Au(111)面最小.吸附后,噻吩在Au(111)面上的构型几乎保持不变,最终通过S端倾斜吸附于top位;噻吩在Pd(111)及Pt(111)面上发生了折叠与变形,环中氢原子向上翘起,最终通过环平面平行吸附于hollow位.此外,噻吩环吸附后芳香性遭到了破坏,环中碳原子发生sp3杂化,同时电子逐渐由噻吩向M(111)面发生转移,M(111)面上的部分电子也反馈给了噻吩环中的空轨道,这种协同作用最终导致了噻吩分子稳定吸附于M(111)面.     

单原子催化剂M1/FeOx(M=Pt,Fe)的理论研究:CO氧化反应

负载型纳米贵金属催化剂是用于多相催化反应的重要的催化剂之一,也是各国催化科学与技术研发的重点,其工业应用也越来越广泛.理论和实验的研究结果均表明,当载体表面的金属粒子尺寸减小至亚纳米级乃至更小的低配位、不饱和的原子团簇时,它们常常成为诱发催化反应的活性中心,呈现更高的催化活性和选择性.将负载的金属尺寸由纳米量级减小至分散的金属团簇甚至单原子而使每个原子成为反应的活性位点已成为研究的重点.最近,由张涛等首次合成的单原子催化剂(SAC)Pt1/FeOx引起了国内外催化及表面科学工作者的极大关注.单原子催化剂作为连接均相催化剂和多相催化剂的桥梁,不仅具有非均相催化剂的稳定、易于与反应体系分离、易表征等优点,而且具有均相催化剂活性中心结构均一、活性中心原子利用率百分之百等优点.一方面,单原子催化剂给多相催化领域注入了新的活力,另一方面也更有利于运用量子与计算化学的研究方法建立与实验相匹配的理论模型并从原子水平上进一步理解多相催化反应的微观作用机理.实验和理论的研究结果表明,其它单原子催化剂如Ir1/FeOx,Au1/FeOx和Ni1/FeOx催化CO氧化反应表现出不同的活性.然而,底物FeOx中的Fe同样是第VIII族中的3d过渡金属,却在低温下对CO氧化反应没有催化活性.我们围绕这一问题,重点研究了底物FeOx在负载单原子Pt1前后催化CO氧化的反应机理和活性,解释了单原子催化剂Pt1/FeOx相比于底物FeOx为何具有如此高的催化活性的原因.我们采用Vienna Ab-initio Simulation Package(VASP)从头算模拟软件和密度泛函理论(DFT)的广义梯度近似(GGA)进行了理论计算.其中,选择PBE泛函描述体系的交换关联相互作用,用投影缀加波(PAW)赝势基组方法描述体系中的电子和离子实之间的相互作用,对Fe原子采用了DFT+U方法进行d电子强相关校正,并使用Dimer计算方法搜寻反应过渡态.研究结果表明,底物FeOx中氧空位的再生伴随第二个CO2分子从催化剂表面脱附的过程需要较高的活化势垒(1.09 eV),这一过程是整个CO氧化反应的决速步.与此相比较,Pt1/FeOx催化剂中,由于Pt原子代替了表面Fe原子,导致电子结构及性质的显著变化,有利于CO的活化、氧化和CO2的脱附.我们从电子能量态密度(DOS)和Bader电荷分析及模型分子团簇的轨道相互作用的角度进一步分析了两种催化剂存在差异的本质;揭示了单原子催化剂Pt1/FeOx中Pt1和底物FeOx之间的相互作用的机理及催化剂表面Pt单原子在催化反应过程中的关键作用.     

噻吩在M(111)(M=Pd,Pt, Au)表面的吸附

采用密度泛函理论(DFT), 选取DMol³程序模块, 对噻吩在M(111) (M=Pd, Pt, Au)表面上的吸附行为进行了探讨. 通过对噻吩在不同底物金属上的吸附能、吸附构型、Mulliken 电荷布居、差分电荷密度以及态密度的分析发现, 噻吩在Pd(111)面上的吸附能最大, Pt(111)面次之, Au(111)面最小. 吸附后, 噻吩在Au(111)面上的构型几乎保持不变, 最终通过S端倾斜吸附于top 位; 噻吩在Pd(111)及Pt(111)面上发生了折叠与变形, 环中氢原子向上翘起, 最终通过环平面平行吸附于hollow 位. 此外, 噻吩环吸附后芳香性遭到了破坏, 环中碳原子发生sp³杂化, 同时电子逐渐由噻吩向M(111)面发生转移, M(111)面上的部分电子也反馈给了噻吩环中的空轨道, 这种协同作用最终导致了噻吩分子稳定吸附于M(111)面.     

Intermediates-induced CO2 Reduction Reaction Activity at Single-Atom M−N2 (M=Fe,Co, Ni) Sites

Single-atom M−N₂ (M=Fe, Co, Ni) catalysts exhibit high activity for CO₂ reduction reaction (CO₂RR). However, the CO₂RR mechanism and the origin of activity at the single-atom sites remain unclear, which hinders the development of single-atom M−N₂ catalysts. Here, using density functional theory calculations, we reveal intermediates-induced CO₂RR activity at the single-atom M−N₂ sites. At the M−N₂ sites, the asymmetric *O*CO configuration tends to split into *CO and *OH intermediates. Intermediates become part of the active moiety to form M−(CO)N₂ or M-(OH)N₂ sites, which optimizes the adsorption of intermediates on the M sites. The maximum free energy differences along the optimal CO₂RR pathway are 0.30, 0.54, and 0.28 eV for Fe−(OH)N₂, Co−(CO)N₂, and Ni−(OH)N₂ sites respectively, which is lower than those of Fe−N₂ (1.03 eV), Co−N₂ (1.24 eV) and Ni−N₂ (0.73 eV) sites. The intermediate modification can shift the d-band center of the spin-up (minority) state downward by regulating the charge distribution at the M sites, leading to less charge being accepted by the intermediates from the M sites. This work provides new insights into the understanding of the activity of single-atom M−N₂ sites.     

双金属合金团簇M12Ni(M=Pt,Sn,Cu)催化甲烷干法重整反应的理论研究

利用密度泛函理论(DFT)研究了M₁₂Ni(M=Pt, Sn, Cu) 3种双金属合金团簇的电子活性和结构稳定性, 并探讨了甲烷干法重整反应(DRM)在M₁₂Ni双金属团簇表面的反应能量变化情况. 经比较发现甲烷脱氢和二氧化碳活化过程在Pt₁₂Ni团簇表面进行需克服的活化能垒最低, 反应最易进行. Sn₁₂Ni团簇上生成碳需要较高的活化能, 说明Sn₁₂Ni团簇能够有效抑制焦碳的生成, 一定程度上克服了碳沉积导致的催化剂失活现象, 并且Sn₁₂Ni团簇在C ^*和CH ^*氧化过程中表现出最佳的催化活性. Cu₁₂Ni团簇仅在甲烷脱氢过程中表现出较为优异的催化活性.     

Redox chemistry and magnetism of LaSrM(0.5)Ru(0.5)O(4±δ) (M = Co, Ni and Zn) Ruddlesden-Popper phases

The n = 1 Ruddlesden-Popper (RP) phases LaSrM(0.5)Ru(0.5)O(4±δ) (M = Co, Ni and Zn) have been prepared by solid state reactions and structurally characterized by powder X-ray and electron diffraction. All the samples adopt the tetragonal I4/mmm space group with random M and Ru cation occupation on the B-sites. The potential causes of no cation ordering are discussed. A combined analysis of the tolerance factors, the distortion of the octahedral coordination of M and Ru cations and the magnetic interactions between M and Ru cations provide a better understanding for forming a phase with 3D cation ordering on the B-sites in the n = 1 RP phases. The investigation of XPS spectra suggests that the transition element species exist as mixed ion pairs, Ru((4-δ)+)-Ru(4+)? Co(2+)-Co(3+) in LaSrCo(0.5)Ru(0.5)O(4), and Ru(4+)-Ru((4+δ)+)? Ni(+)-Ni(2+) in LaSrNi(0.5)Ru(0.5)O(4), which is consistent with cation disorder over the B sites. LaSrCo(0.5)Ru(0.5)O(4) shows a weakly ferromagnetic behaviour below 50 K; LaSrNi(0.5)Ru(0.5)O(4) is evidenced by the presence of long-range magnetic ordering at a Néel temperature of 125 K, and LaSrZn(0.5)Ru(0.5)O(4) exhibits a paramagnetic behaviour down to 5 K. Due to atomic disorder, Ru4d, O2p covalent coupling is weakened, strengthening the intraatomic spin-spin coupling among the π* electrons. Charge transfer between Ru and Co or Ru and Ni, as well as the increasing overlap of both nearest-neighbour and next-nearest-neighbour Ru 4d electrons due to atomic disorder, favour the formation of ferromagnetic interactions. Although antiferromagnetism is dominant, particularly in LaSrNi(0.5)Ru(0.5)O(4), ferromagnetic interactions are stronger in the title compounds than in the related La(2)MRuO(6) (M = Co, Ni) double perovskites where the B-site cations are ordered.     

Conversion of E4 (E4=P4, As4, AsP3) by Ni(0) and Ni(I) Synthons – A Comparative Study

The reactivity of white phosphorus and yellow arsenic towards two different nickel nacnac complexes is investigated. The nickel complexes [(L¹Ni)₂tol] ( 1 , L¹=[{N(C₆H₃ⁱPr₂-2,6)C(Me)}₂CH]⁻) and [K₂][(L¹Ni)₂(μ,η^{1 : 1}-N₂)] ( 6 ) were reacted with P₄, As₄ and the interpnictogen compound AsP₃, respectively, yielding the homobimetallic complexes [(L¹Ni)₂(μ-η²,κ¹:η²,κ¹-E₄)] (E=P ( 2 a ), As ( 2 b ), AsP₃ ( 2 c )), [(L¹Ni)₂(μ,η^{3 : 3}-E₃)] (E=P ( 3 a ), As ( 3 b )) and [K@18-c-6(thf)₂][L¹Ni(η^{1 : 1}-E₄)] (E=P ( 7 a ), As ( 7 b )), respectively. Heating of 2 a , 2 b or 2 c also leads to the formation of 3 a or 3 b . Furthermore, the reactivity of these compounds towards reduction agents was investigated, leading to [K₂][(L¹Ni)₂(μ,η^{2 : 2}-P₄)] ( 4 ) and [K@18-c-6(thf)₃][(L¹Ni)₂(μ,η^{3 : 3}-E₃)] (E=P ( 5 a ), As ( 5 b )), respectively. Compound 4 shows an unusual planarization of the initial Ni₂P₄-prism. All products were comprehensively characterized by crystallographic and spectroscopic methods.     

钛,锆和铪羰基化合物M(CO)_n(M=Ti,Zr,Hf;n=4～7)的理论研究

利用密度泛函方法对标题化合物的平衡几何、热化学及振动频率进行了理论预测,发现这3种金属原子都有相似的M(CO)n(n=4～7)结构.全局最低构型对M(CO)7都是单态C3v戴帽八面体7S-1,对M(CO)6都是三重态D3d畸变八面体6T(而对应的单重态M(CO)5仅比它低不到21 kJ·mol-1).对M(CO)n(n=5,4)都是三重态6S-1,其构型分别为从6T中移去1个或2个CO基的衍生物5T和4T.此外,五重态的D3h的三角双锥M(CO)5和单态的Td四面体M(CO)4以及能量更高的含有C和O同时与金属成键的独特配位CO基的M(CO)6和M(CO)3也被发现.最后,给出M(CO)7→M(CO)6+CO反应的离解能.并讨论了金属18价电子的Ti(CO)7存在的可能性.     

Interactions of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1)

The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.     

Formation of M(4)Se(4) cuboids (M = As, Sb, Bi) via secondary pnictogen-chalcogen interactions in the co-crystals MX(3)·Se[double bond, length as m-dash]P(p-FC(6)H(4))(3) (M = As, X = Br; M = Sb, X = Cl; M = Bi, X = Cl, Br)

The reactions of the group 15 trihalides, MX(3) (M = As, Sb, Bi; X = Cl, Br), with the phosphine selenide SeP(p-FC(6)H(4))(3) result in the formation of co-crystals of formula MX(3)·SeP(p-FC(6)H(4))(3). No reaction was observed with MI(3) (M = As, Sb, Bi). The structures of MX(3)·SeP(p-FC(6)H(4))(3) (M = As, X = Br 2; M = Sb, X = Cl 3; M = Bi, X = Cl 5; M = Bi, X = Br 6) have been established, and are isomorphous, crystallising in the cubic I23 space group. All the structures feature a primary MX(3) unit, which has three weak secondary MSe interactions to SeP(p-FC(6)H(4))(3) molecules. However, each of these SeP(p-FC(6)H(4))(3) molecules bridges three MX(3) molecules, resulting in the generation of an M(4)Se(4) (M = As, Sb, Bi) distorted cuboid linked by the pnictogen-chalcogen interactions. Four opposing corners of the cuboid are occupied by the M atom (M = As, Sb, Bi) of an MX(3) pyramid, and the other four by the selenium atom of the phosphine selenide.     

Reaction of bis(o-phosphinophenyl)silane with M(PPh3)4 (M = Ni, Pd, Pt): synthesis and structural analysis of η2-(Si-H) metal(0) and pentacoordinate silyl metal(II) hydride complexes of the Ni triad bearing a PSiP-pincer ligand

Reactions of bis(o-(diphenylphosphino)phenyl)methylsilane with M(PPh(3))(4) (M = Ni, Pd, Pt) were investigated. When M = Ni or Pd, synthesis and isolation of η(2)-(Si-H) complexes of mononuclear Ni(0) and Pd(0) were achieved for the first time as frozen intermediates for oxidative addition of the Si-H bond. Structural analysis by X-ray and NMR spectroscopy disclosed that their η(2)-(Si-H) structures were maintained in both solid and solution states and coordination of the Si-H bond to the metal center was relatively weak. On the other hand, reaction with a platinum(0) complex afforded two kinds of pentacoordinate silyl platinum(II) hydride complexes having a PSiP-pincer ligand, which underwent unique thermal isomerization from a square-pyramidal cis-H-Pt-Si to a trigonal-bipyramidal trans-H-Pt-Si isomer. Mechanistic investigations revealed that this isomerization proceeded via an intramolecular rearrangement process probably through a turnstile rotation.     

Infrared Spectroscopic Study of the Hofmann-daon-Type Clathrates : M(1,8-diaminooctane)Ni(CN)4⋅G (M=Co, Ni or Cd; G=Aromatic Guest Molecules)

Infrared spectra of M(1,8-diaminooctane)Ni(CN)4G (M= Co, Ni or Cd; G=benzene, chlorobenzene, toluene, p-xylene, naphthalene or biphenyl) compounds are reported. The 1,8-diaminooctane molecules in the host permit the inclusion of bulky guest molecules. The spectral features suggest that the compounds are similar in structure to the Hofmann-type clathrates.