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An explanation of the high stability of a cage based on D(sub 5h) C(sub 50) fullerene, D(sub 5h) C(sub 50)Cl(sub 10) is provided. The possible connectivity patterns to form dimers and oligomers are evaluated and the formation of fullerene solids based on C(sub 50) is discussed.

A series of new complexes of a general motif [R2E(μ-N,S)2TM–L] (E: metalloid group 14 element; TM: group 10 metal; R: Cl, Ph, pyS, OH, (N,N,O)-chelating ligands; N,S: 1-methylimidazole-2-thiolate (methimazolyl, mt−), pyridine-2-thiolate (pyS−); L: PPh3, PCy3, pyS) was synthesised and characterised by single-crystal X-ray diffraction, multi-nuclear NMR spectroscopy (1H, 13C, 31P, 119Sn), 119Sn Mössbauer spectroscopy and quantum chemical calculations. The E–TM bonding situation in these compounds can be described with various resonance structures which comprise E(ii)→TM(ii), E(iii)–TM(i) and E(iv)←TM(0) features. Thus, in these complexes the atoms of the group 14 based ligand sites reveal L-, X- and Z-type ligand characteristics. A systematic comparison between structural and spectroscopic parameters as well as the results from NLMO analyses of structurally related compounds provided information about the differences in the E–TM bonding situation upon alteration of the metal atoms or ligand patterns. Under investigation are the structurally related compounds [Cl2Sn(μ-pyS)2TM–PPh3] (1: TM = Pd; 2: TM = Ni; 3: TM = Pt), [Cl2Ge(μ-pyS)2Pd–PPh3] (4) and, for in silico analysis, [Cl2Si(μ-pyS)2Pd–PPh3] (5), which indicate a pronounced shift of the E–TM bond electron pair towards TM for TM = Pt. Further complexes serve as representatives of these compounds with different bridging ligands {[Cl2Sn(μ-mt)2Pd–PPh3] (8)}, different trans-E–TM-bound ligands {[Cl2Sn(μ-pyS)2Pd–PCy3] (9), [Cl2Sn(μ-pyS)2Pd]4 (10)} and with different substituents at Sn (including penta- and hexacoordinated tin compounds), i.e., [R2Sn(μ-pyS)2Pd–PPh3] with R = Ph (6) and pyS (7), [(O,N,N)Sn(μ-pyS)2Pd–PPh3] (11) and (12) having two different (O,N,N) tridentate ligands, and [(μ-OH)ClSn(μ-pyS)2Pd–PPh3]2 (13). The latter series indicates a shift of the E–TM (= Sn–Pd) bond electron pair towards Pd upon transition from penta- to hexacoordinated tin compounds. [ABSTRACT FROM AUTHOR]

The reaction of 1-methyl-3-trimethylsilylimidazoline-2-thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N, S-bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel-shaped complexes of the type ClSi(μ-mt)4SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN4)SiSi(S4Cl), (ClN3S)SiSi(S3NCl), and (ClN2S2)SiSi(S2N2Cl) skeletons as so-called (4,0), (3,1), and cis-(2,2) paddlewheels) were detected in solution by using 29Si NMR spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X-ray diffraction studies. In accord with time-dependent NMR spectroscopy, computational analyses proved the cis-(2,2) isomer with a (ClN2S2)SiSi(S2N2Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two SiSi-bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms. [ABSTRACT FROM AUTHOR]

The interaction of molecular nitrogen with selected polycyclic aromatic hydrocarbons (PAHs), i.e., benzene, naphthalene, anthracene, pentacene, coronene, and triphenylene, is investigated. The energetically most favorable orientation of N2 is parallel to the PAH, with a distance of 3.2 Å, independent on shape and size of the investigated PAHs. An interaction energy of 10–17 kJ mol-1, depending on PAH size, shape and adsorption position, is calculated using Møller–Plesset perturbation theory. A value of 17.7 kJ mol-1 is obtained by extrapolation to infinite graphene. Hence, N2 is physisorbed 2–3 times stronger than H2 on PAHs. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [ABSTRACT FROM AUTHOR]

Reactions of tin(IV) complexes of the type Sn(PyS)2X2 (X = Cl, PyS, Ph; PyS = pyridine-2-thiolate) with Pd(PPh3)4 provide easy access to novel heterometallic complexes with Pd-Sn bonds. Electronic characteristics of this connection were analysed by X-ray crystallography, 119Sn Mossbauer spectroscopy and quantum chemical analyses. [ABSTRACT FROM AUTHOR]

The metal-organic framework, MFU-4, possessing small cavities and apertures, is exploited for quantum sieving of hydrogen isotopes. Quantum mechanically, a molecule confined in a small cavity shows an increase in effective size depending on the particle mass, which leads to a faster deuterium adsorption from a H(2)/D(2) isotope mixture., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The reaction of the methimazolyl (mt, i.e., 2-mercapto-1-methylimidazolide) substituted silane Si(mt)(4) with SnCl(2) and GeCl(2) in dioxane affords the paddlewheel-shaped complexes [ClSi(μ-mt)(4)MCl] (M=Sn (1) and Ge (2), respectively). These compounds represent the first crystallographically characterized hexacoordinate silicon complexes comprising a Sn or Ge atom in the Si coordination sphere. An attempt to synthesize the related silicon compound 3 [ClSi(μ-mt)(4)SiCl] instead afforded the trisilane [ClSi(μ-mt)(4)Si-SiCl(3)] (3a), which provides the first crystallographic evidence for the feasibility of oligosilanes with adjacent hexacoordinate Si atoms. One of the hexacoordinate Si atoms of 3a features the unprecedented (Si(2)S(4))Si skeleton. Natural bonding orbital (NBO) analyses of compounds 1, 2, 3a (and the target compound 3) revealed characteristics of M(II)→Si(IV) (for 2 and 3) or M(I)→Si(IV) (for 3a) dative bonding in the systems with M=Si and Ge, whereas compound 1 exhibits a covalent Sn(III)-Si(III) bond.

The geometrical properties of recently synthesised C60 intercalated in graphite have been confirmed by density-functional-based computer simulations. The capability of this material to store molecular hydrogen by physisorption is evaluated. While the material can sieve H2 from heavier molecular gases, our free energy calculations indicate that further tuning of the system by reducing the amount of intercalated fullerene cages is necessary to achieve H2 loadings which are interesting for technical applications.

Mechanical and electronic properties of hypothetical carbon nanostructures, on the basis of C28 building blocks, hyperdiamond and hyperlonsdaleite, have been investigated with DFT based methods. The low mass density and large internal surface suggest applications as catalyst, nanosieve and gas storage material. We estimate the active volume accessible by H2. Special emphasis is given to the possibility to tune their properties by endo- and exohedral intercalation with Zn, Ti and K. While endohedral intercalation with Zn does not affect the overall structure, endohedral Ti intercalation has different consequences on the structural stability of the two allotropes. Exohedral intercalation with K leads to an ionic fullerite phase with metallic conductivity.

The performance of density functional theory (DFT) (VWN-LDA, PBE-GGA, and B3LYP hybrid functionals), density-functional-based tight binding (DFTB), and ab initio methods [HF, MP2, CCSD, and CCSD(T)] for the treatment of London dispersion is investigated. Although highly correlated ab initio methods are capable of describing this phenomenon, if they are used with rather large basis sets, DFT methods are found to be inadequate for the description of H2/PAH (polycyclic aromatic hydrocarbon) interactions. As an alternative approach, an a posteriori addition of a van der Waals term to DFTB is proposed. This method provides results for H2/PAH interactions in close agreement with MP2 and higher-level ab initio methods. Bulk properties of graphite also compare well with the experimental data.