Tin atom

For comparison, we applied also a simplified LCAO-DFT method to get the conductivity by means of the Kubo-Greenwood formula. This method is a hybrid between ab initio and empirical methods and is described in detail in Ref. [12]. It allows a faster computation of the electronic properties and the consideration of larger supercells than the Car-Parrinello method. Within this scheme it is also possible to split the total DOS into fractions referring to the sodium and tin atoms, respectively, i.e. to get the partial densities-of-states. 

An essential result of the simulations is that the Zintl anions Sn for the equimolar case do not survive in the liquid. They form (dynamical) networks. For the liquid with 80% of sodium, the suggested octet compounds SnNa4 do not exist, and only isolated tin atoms or tin dimers appear. 

Disc T>2 after many revolutions Increasing -velocity of tin. atoms... 

Tin phthalocyanines can be prepared using tin(II)110 or -(IV)154 chlorides. The reaction can be performed in 1-chloro-1 10,1 37,1 55 or 1-bromonaphthalene,154 starting from phthalonitrile110137154,155 or phthalic anhydride. In the second case, urea and ammonium molyb-date(VI) arc added.137 The central tin atom can also be introduced into metal-free phthalocyanine by the reaction with tin(IV) chloride in dimethylformamide.141 Treatment of PcSnCl2 with disodium phthalocyanine in refluxing 1-chloronaphthalenc forms a sandwich-like bis-(phthalocyanine) Pc2Sn.154... 

The mode of the diastcrcofacial selectivity is completely reversed in the case of reactions with A -methyl A-acyliminium precursors 4176. Now the nitrogen atom of the A-acyliminium ion is not able to chelate with the tin atom and the lower diastereoselectivity is explained by the less rigid nonchelation-controlled transition state 5. An electronic effect, such as n-iz attraction between the electron-deficient carbonyl group of the acyliminium ion and the electron-rich phenyl group of the phcnylthio substituent R, may account for the somewhat higher diastereoselectivity in the case of arylthio substituents R. 

IR spectra of these complexes suggest that the ligands are coordinated by the oxygen atom. The magnetic non-equivalence of the methylene groups due to flanking by the sulphur is influenced seriously by the oxygen coordination to the tin atom. 

AuSn has the nickel arsenide structure, B8, with abnormally small axial ratio (c/a = 1.278, instead of the normal value 1.633). Each tin atom is surrounded by six gold atoms, at the corners of a trigonal prism, with Au-Sn = 2.847 A. and each gold atom is surrounded by six tin atoms, at the corners of a flattened octahedron, and two gold atoms, at 2.756 A., in the opposed directions through the centers of the two large faces of the octahedron. 

It is found that chromium atoms, manganese atoms, and tin atoms exist in metals in two forms, a small, high-valent form and a larger, low-valent form. The two kinds of manganese atoms coexist in a-manganese and in /3-manganese. 

White tin, to which the valency 2-44 has been assigned (Pauling 1938), does not contain bivalent Sn B alone, but also some Sn A. It seems likely that these two kinds of tin atoms occur in the ratio 3 1, leading to the average valency 2-5, a value in essential agreement with that suggested before. 

For example, tin, with v = 2-5, crystallizes with a unique atomic arrangement, in which each atom has six ligates, four at 3-016 A and two at 3-175 A. These distances have been used (1947) in assigning the bond numbers 0-48 and 0-26 to these bonds. It is clear that these bond numbers can be taken as and and that the choice of the structure and the value of its axial ratio (which determines the relative lengths of the two kinds of bonds) are the result of the effort of the tin atom to use its valency 2-5 in the formation of stable bonds with simple fractional bond numbers. 

The species [organohn(IV)] (n — 1-3) are considered to be Lewis acids of different strength, depending on the groups bound to the tin atom. As a consequence, they promptly hydrolyze in aqueous solution, as first demonstrated by Tobias. Later studies on the interactions of [MeiSndV)] " with hgands containing different donor atoms ( O, N, S, etc.) necessitated determination of the hydrolysis constants the evaluation of such complex formation constants was based on the data obtained earlier from independent measurements. Some data are compared in Table 1. 

The disproportionation reactions of organotin compounds may also be regarded as alkylations by organometallic compiounds, as they involve transfer of an alkyl group from one tin atom to another. An ingenious application of this has been described in which a,ct>-distannanes are caused to disproportionate into the corresponding tetraalkyltins and 1,1-dialkyIstannacycloalkanes (65). 

A single-crystal. X-ray diffraction analysis of the structure has recently been performed that shows that the compound is, in fact, a tin-tin bonded dimer, having an Sn-Sn bond length of 276 pm, similar to that in hexaphenylditin this was interpreted in terms of overlap of a filled spaPy orbital with the vacant p orbitals on the other tin atom resulting in a "bent, weak, Sn-Sn double bond (332). 

If the ligand X2 in a pentacoordinate triorganotin compound is potentially bidentate, such as the anion of l,3-diphenyl-l,3-propanedione or ofiV-benzoyl-N-phenylhydroxylamine, the tin atom is constrained to a cis-RsSnXj type of geometry, e.g., the triphenylstannyl derivatives of... 

It is quite probable that, in the monoorganostannatranes, RSnlOCHjjCHjljN, the tin atom also occupies a trigonal, bipyramidal geometry, but with the organic group forced into an axial site (195,... 

Dimethyltin dichloride has a similar chain structure (375). In diethyltin diiodide (374), dimethyltin diisothiocyanate (376, 377), and di-chloro bis(chloromethyl)stannane (378), however, the distorted, trans-RgSnX geometry of each tin atom is completed by two bridging bonds involving the halogen or pseudohalogen atoms on the same, neighboring molecule. 

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