Icosahedral WAu12: A Predicted Closed-Shell Species, Stabilized by Aurophilic Attraction and Relativity and in Accord with the 18-Electron Rule This work was supported by The Academy of Finland. The computations were carried out at CSC, Espoo, Finland.

Pyykkö, Pekka; Runeberg, Nino

doi:10.1002/1521-3773(20020617)41:12<2174::aid-anie2174>3.0.co;2-8

Cited by 352 publications

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“…If two TMs form a cluster, the OS might become ambiguous. An example is the icosahedral WAu 12 predicted on the basis of the 18-electron rule [103] and later detected [104]. There is no rule that convincingly predicts the WAu bond order, and hence OS cannot be determined à priori.…”

Section: Tm Clustersmentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

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Section: Tm Clustersmentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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“…[1][2][3][4][5][6][7] In this work the existence of uranium-tetraauride, UAu 4 , and group-4-tetragold single molecules, MAu 4 , where M ) Ti, Zr, Hf, and Th is predicted. In such species gold carries a formal charge of (-1) and acts as a ligand to the metallic center.…”

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confidence: 99%

When Does Gold Behave as a Halogen? Predicted Uranium Tetraauride and Other MAu₄Tetrahedral Species, (M = Ti, Zr, Hf, Th)

Gagliardi

2003

J. Am. Chem. Soc.

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Stable gold clusters are the subject of both experimental and theoretical studies, because of their potential use as building blocks of new materials and catalytic properties. [1][2][3][4][5][6][7] In this work the existence of uranium-tetraauride, UAu 4 , and group-4-tetragold single molecules, MAu 4 , where M ) Ti, Zr, Hf, and Th is predicted. In such species gold carries a formal charge of (-1) and acts as a ligand to the metallic center. Only a few Au (-1) compounds are known in bulk and in the gas phase. Cesium auride in bulk was discussed in a recent mini-review by Pyykkö. 8 Goodman 9 mentioned other auride species, such as RbAu. The compound BaAu 2 was made in 1938. 10 CsAu ammonia (1/1), CsAu‚NH 3 , was recently studied. 11 Elements such as Cs and Ba are expected to form ionic compounds with all elements in the periodic table, and the fact that they bind to Au is not an indication that Au is a good ligand. The situation is different if Au, behaving like a halogen, forms tetrahedral complexes with group 4 elements, and also with Th and U. The present quantum chemical calculations show that these molecules are stable, with all real frequencies and some covalent bond character. (For the main group tetraaurides at HF level the same was true for groups 13-15. 12 ) In this work all species were studied using second-order perturbation theory, MBPT2, and density functional theory, DFT, with the B3LYP exchange-correlation functional. The open shell species UAu 4 , was also studied using the complete active space (CAS) SCF method 13 with dynamic correlation added by multiconfigurational second-order perturbation theory (MS-CASPT2). 14 For Ti a basis set of 6-31 g* type (5s4p2d1f) was used. For Au and M ) Zr, Hf, Th, U the energy-adjusted Stuttgart ECPs were used to take into account relativistic effects. 15 The number of valence electrons is 19 for Au, 12 for Zr and Hf, 30 for Th, and 32 for U. The basis sets accompanying the ECPs 6s5p3d for Au, Zr, and Hf, and 8s7p6d4f for Th and U, were used. 16 Some calculations were repeated with larger basis sets, namely the gold valence basis set was increased by three f functions, 6s5p3d3f, the Zr and Hf valence basis set were increased with one f function, 6s5p3d1f, and the Th and U valence basis were increased with one g function, 8s7p6d4f1g. The first set of calculations will be indicated as BS1-calculations and the second set as BS2-calculations. Equilibrium geometries and harmonic frequencies were computed for all species at the DFT and MBPT2 level of theory. For UAu 4 , the MS-CASPT2 equilibrium geometry was also computed. The programs MOLCAS-5.2 17 and Gaussian98 18 were employed.All molecules were found to be local minima in T d symmetry in their singlet ground state, with the exception of UAu 4 which has a triplet ground state and a slightly distorted symmetry from T d (see below). The calculations were repeated with lowered D 2d symmetry but the molecules maintained the tetrahedral structure. The results for the closed shell species will be presented first, and ...

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“…8-13͒ and the core-shell clusters I h -W@Au 12 and I h -Mo@Au 12 . 14,15 These small-sized double magic clusters possess 40 and 18 valence electrons, respectively. Clusters with both closed electronic shell and the tetrahedral symmetry may be considered as the "nearly double magic" clusters.…”

Section: Introductionmentioning

confidence: 99%

“…[40][41][42][43][44][45][46][47][48] In particular, the medium-sized clusters Cu 55 and Ag 55 are geometric magic-number clusters with the icosahedral symmetry, whereas the icosahedral cluster Au 55 is not the global minimum. [46][47][48][49] The bimetallic double magic cluster, I h -W@Au 12 , was first predicted by Pyykkö and Runeberg 14 and later experimentally produced and detected by Li et al 15 This core-shell metal cluster has a very large HOMO-LUMO gap ⌬ HL = 1.68 eV. The central "impurity" atom can be used to finetuning electronic properties of core-shell clusters.…”

Section: Introductionmentioning

confidence: 99%