Synthesen und Kristallstrukturen neuer heterobimetallischer Tantal‐Münzmetall‐Chalkogenido‐Cluster

Syntheses and Crystal Structures of Novel Heterobimetallic Tantalum Coin Metal Chalcogenido Clusters In the presence of phosphine the thiotantalats (Et₄N)₄[Ta₆S₁₇] · 3MeCN reacts with copper to give a number of new heterobimetallic tantalum copper chalcogenide clusters. These clusters show metal chalcogenide units some of which here already known from the chemistry of vanadium and niobium. New Ta—M‐chalcogenide clusters could also be synthesised by reaction of TaCl₅ and silylated chalcogen reagents with copper or silver salts in presence of phosphine. Such examples are: [Ta₂Cu₂S₄Cl₂(PMe₃)₆] · DMF ( 1 ), (Et₄N)[Ta₃Cu₅S₈Cl₅(PMe₃)₆] · 2MeCN ( 2 ), (Et₄N)[Ta₉Cu₁₀S₂₄Cl₈(PMe₃)₁₄] · 2MeCN ( 3 ), [Ta₄Cu₁₂Cl₈S₁₂(PMe₃)₁₂] ( 4 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(PPh₃)₆] · 5MeCN ( 5 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(PPh₂Me)₆] · 2MeCN ( 6 ), (Et₄N)[Ta₂Cu₆S₆Cl₅(P^tBu₂Cl)₆] · MeCN ( 7 ) [Ta₂Cu₂S₄Br₄(PPh₃)₂(MeCN)₂] · MeCN ( 8 ), [Cu(PMe₃)₄]₂[Ta₂Cu₆S₆(SCN)₆(PMe₃)₆] · 4MeCN ( 9 ), [TaCu₅S₄Cl₂(dppm)₄] · DMF ( 10 ), [Ta₂Cu₂Se₄(SCN)₂(PMe₃)₆] ( 11 ), [Cu(PMe₃)₄]₂[Ta₂Cu₆Se₆(SCN)₆(PMe₃)₆] · 4MeCN ( 12 ), [TaCu₄Se₄(PⁿPr₃)₆][TaCl₆] ( 13 ), [Ta₂Ag₂Se₄Cl₂(PMe₃)₆] · MeCN ( 14 ), _∞[TaAg₃Se₄(PMe₃)₃] ( 15 ). The structures of these compounds were obtained by X‐ray single crystal structure analysis.     

直链小碳簇Cn(n=3～6)微正则解离速率常数的RRKM理论计算(Ⅰ)

用从头计算法研究小碳簇的解离通道及其动力学.以MP2/6-31G^*精度优化直链C₃,C₄,C₅,C₆及其过渡态的结构,并对它们进行振动分析.在此基础上计算了各解离通道的能垒,并根据RRKM理论估算各个通道的微正则解离速率.计算结果表明,这些小碳簇的解离主要表现为均裂方式.     

First-Known High-Nuclearity Copper–Nickel Carbonyl Cluster: [CuxNi35−x(CO)40]5− (with x=3 or 5) Containing an Unprecedented 35-Atom Three-Layer hcp Triangular Stacking Metal-Core Geometry

Reactions of [Ni₆(CO)₁₂]^2- (1) with CuBr₂ have given rise in small yields (10%) to the first example of a close-packed copper-nickel carbonyl cluster; its formulation as [Cu_xNi_35-x(CO)₄₀]^5- (with x=3 or 5) is based upon a low-temperature CCD X-ray crystallographic determination coupled with an elemental analysis and X-ray fluorescence measurements. This air-unstable black pentaanion (2) together with one co-crystallized bromide anion, six [NMe₄]⁺ counterions, and one solvated acetone molecule comprise the crystallographic independent part in a monoclinic unit cell of P2₁/n symmetry (with Z=4). The geometrically unprecedented 35-atom hcp M(A)₂M(B)₃Ni₃₀ polyhedron of pseudo-D_3h symmetry consists of a central 15-atom equilateral ₄M(B)₃Ni₁₂ triangle that is capped on both sides by two symmetry-related 10-atom equilateral ₃M(A)Ni₉ triangles. The 35-atom M(A)₂M(B)₃Ni₃₀ core is encapsulated by 40 COs, whose connectivities, due to an extra CO ligand on one of the three triangular sides, reduce the pseudo D_3h symmetry of the metal core to C_s. An elemental analysis via AA and X-ray fluorescence measurements resulted in Cu/Ni ratios of 3.2/31.8 and 3.7/31.3, respectively, that are consistent with the metal core being either Cu₅Ni₃₀ (i.e., M(A)=M(B)=Cu) or Cu₃Ni₃₂ (i.e., M(A)=Ni; M(B)=Cu). Several attempts to determine the actual stoichiometry of the metal core by use of electrospray FT/MS/ICR measurements were unsuccessful. The maximum metal-core diameter of 2 is ca. 0.41 nm parallel and 0.85 nm perpendicular to the principal 3-fold axis.     

Model studies of the chemisorption of hydrogen and oxygen on the Au (1 0 0) surface

 The convergence of chemisorption energy for hydrogen and oxygen on gold clusters is studied. Two theoretical approaches have been employed; wavefunction methods at the self-consistent-field second–order M?ller–Plesset level and density functional theory and the two methods are compared. Relativistic effective core potentials exploited in the former approach were developed in this work. Received: 25 October 1999 / Accepted: 21 February 2001 / Published online: 11 October 2001     

Hydrido-Carbonyl Rhenium Clusters with a Square Geometry of the Metal Core. Synthesis and X-Ray Characterization of the Novel [Re4(μ-H)3(CO)16]− Anion

Three and tetranuclear ring clusters have been obtained by treatment of [Re₂(CO)₈(THF)₂] with carbonyl-rhenates containing two terminal hydrides. The reaction with [ReH₂(CO)₄]^- provided a selective route to the previously known [Re₃(-H)₂(CO)₁₂]^- triangular cluster anion 1. The reaction with [Re₂H₂(-H)(CO)₈]^- gave the novel [Re₄(-H)₃(CO)₁₆]^- anion 2, containing a rare example of a puckered-square metal cluster. Protonation of 1 is known to afford the neutral [Re₃(-H)₃(CO)₁₂] species 3. Analogously the reaction of 2 with a strong acid afforded the previously known square metal clusters [Re₄(-H)₄(CO)₁₆] 4. The reaction could not be reversed by treatment with bases. Photolysis of 4 gave the unsaturated complex [Re₂(-H)₂(CO)₈] 5: this is the reverse of the dimerization reaction, that in THF at room temperature produces 4 from 5. Thermal treatment (reflux in cyclohexane for 24 h) left 4 almost unchanged. A single crystal X-ray analysis of [NEt₄]2 showed a s/e/s/s (e=eclipsed, s=staggered) conformation of the Re(CO)₄ units, leading to a puckered geometry of the ring, at variance with the square-planar geometry of 4 (all eclipsed). Two of the three hydrides of 2 have been located as bridging the Re–Re edges from inside the metal ring, as previously observed in 4. Density functional computations indicated a puckered conformation as the most stable for both 2 and 4, with very low activation energies for ring inversion (6.6 and 2.2 kcal·mol^-1, respectively), but ruled out solid state fluxionality for 4, whose observed planar geometry must be attributed to packing stabilization.     

Theoretical study of silicon–sulfur clusters (SiS2)n (n = 1–6)

 The possible geometrical structures and relative stability of (SiS₂) _n (n=1–6) silicon–sulfur clusters are explored by means of density functional theory quantum chemical calculations. The effects of polarization functions and electron correlation are included in these calculations. The electronic structures and vibrational spectra of the most stable geometrical structures of (SiS₂) _n are analyzed by the same method. As a result, the regularity of the (SiS₂) _n cluster growth is obtained, and the calculation may used for predicting the formation mechanism of the (SiS₂) _n cluster. Received: 17 November 1999 / Accepted: 3 November 2000 / Published online: 3 May 2001     

Application of the Spherical Harmonic Model to the ν(CO) Vibrational Spectra of Some Fe(CO)4 and M(CO)5 (M=Cr, W) Transition Metal Cluster Carbonyl Species

When the Fe(CO)₄ and M(CO)₅ (M=Cr, W) groups are co-ordinated in C_3v and C_4v fashion, respectively, in transition metal carbonyl cluster species they contain two sets of non-symmetry related carbonyl groups. In the application of the spherical harmonic model (SHM) to the interpretation of the infrared spectra of these compounds it proves necessary first to treat these as for a normal, isolated, M(CO)₄ or M(CO)₅ group and then apply the SHM. This recognition gives insights into the general application of the SHM.     

Synthesis,molecular structures,and thermal decomposition of heterometallic (π-cyclooctadiene)platinum-bis(tricarbonyliron-μ3-chalcogenides)[Fe—Fe], (π-C8H12)Pt(μ3-X)2Fe2(CO)6, where X = S,Se, or Te

Transmetallation of the Fe₃(₃-X)₂(CO)₉ clusters (X = S, Se, or Te) under the action of (-C₈H₁₂)PtCl₂ afforded new heterometallic clusters (-C₈H₁₂)Pt(₃-X)₂Fe₂(CO)₆ (2—4, respectively), which were characterized by X-ray diffraction analysis. The (-C₈H₁₂)Pt fragment in these clusters is bound to two ₃-bridging chalcogen atoms X. The iron atoms are linked to each other. The coordination environment about the Pt atom is planar-square; the Pt...Fe distance is larger than 3.2 . In the synthesis of cluster 4, a new Pt complex was also obtained for which the structure (CO)₂Pt(-Te)₂Pt(CO)₂ (5) was proposed. According to the results of differential scanning calorimetry, thermal decomposition of complex 5 gave rise only to PtTe, whereas complexes 1—4 gave products with the empirical formula Fe₂PtX₂C₂O₂. The influence of the steric effects on the geometry of the clusters is discussed.     

Development of non‐bonded interaction parameters between graphene and water using particle swarm optimization

New Lennard‐Jones parameters have been developed to describe the interactions between atomistic model of graphene, represented by REBO potential, and five commonly used all‐atom water models, namely SPC, SPC/E, SPC/Fw, SPC/Fd, and TIP3P/Fs by employing particle swarm optimization (PSO) method. These new parameters were optimized to reproduce the macroscopic contact angle of water on a graphene sheet. The calculated line tension was in the order of 10⁻¹¹ J/m for the droplets of all water models. Our molecular dynamics simulations indicate the preferential orientation of water molecules near graphene–water interface with one O H bond pointing toward the graphene surface. Detailed analysis of simulation trajectories reveals the presence of water molecules with ≤∼1, ∼2, and ∼4 hydrogen bonds at the surface of air–water interface, graphene–water interface, and bulk region of the water droplet, respectively. Presence of water molecules with ≤∼1 and ∼2 hydrogen bonds suggest the existence of water clusters of different sizes at these interfaces. The trends observed in the libration, bending, and stretching bands of the vibrational spectra are closely associated with these structural features of water. The inhomogeneity in hydrogen bond network of water at the air–water and graphene–water interface is manifested by broadening of the peaks in the libration band for water present at these interfaces. The stretching band for the molecules in water droplet shows a blue shift as compared to the pure bulk water, which conjecture the presence of weaker hydrogen bond network in a droplet. © 2017 Wiley Periodicals, Inc.