Atomic bridge

Tartar emetic was the subject of controversy for many years, and a variety of iacorrect stmctures were proposed. In 1966, x-ray crystallography showed that tartar emetic contains two antimony(III) atoms bridged by two tetranegative D-tartrate residues acting as double bidentate ligands to form dipotassium bis[D-p.-(2,3-dihydroxybutanedioato)]diantimonate [28300-74-5] (41). 

Fullerene epoxide, C )0, is formed by the UV irradiation of an oxygenated benzene solution of Cfio The O atom bridges a 6 6 bond of the closed fullerene structure. The same compound is also formed as one of the products of the reaction of Cgo with dimethyldioxirane, Mc2COO (see later). ... 

Progress in molecular recognition of functionalized calixarenes with hetero-atomic bridges as synthetic receptors 99MI43. 

Eacli of tlie four organic moieties bridges between an equatorial and an axial copper atom tlirougli its C( 1) atom, while tlie nitrogen atom in tlie substituent is coordinated to an adjacent equatorial copper atom. Hie two bromine atoms bridge, at opposite sites, between two equatorial copper atoms. Tliis structural ariange-menl has tlie consequence tliat tlie aggregate incorporates two distinct types of... 

Maltose, a decomposition product of starch, is a dimer of two glucose molecules. These are combined head-to-tail carbon atom 1 of one molecule is joined through an oxygen atom to carbon atom 4 of the second molecule. To form maltose, the two OH groups on these carbon atoms react, condensing out H20 and leaving the O atom bridge. 

Yokoyama, Y. and Hall, H. K. Ring-Opening Polymerization of Atom-Bridged and Bond-Bridged Bicyclic Ethers, Acetals and Orthoesters. Vol. 42, pp. 107—138. 

Studies of the bonding of carbon monoxide to the metal surfaces produced structures in which the carbon atom is linked to one, two, or three metal atoms. The existence of bonds to two or three atoms (bridged bonds) has been questioned on the basis of theoretical calculations. None of these bondings, however, clarify the mechanism to any extent. 

In the gas phase, BeCl2 forms a dimer by forming chlorine-atom bridges like those in the AICI dimer. Draw the Lewis structure for the BeCl2 dimer and assign formal charges. 

It contains a Hg atom bridging two Co atoms. Similarly, [Tj -Cp(CO)3MoMoHg]4 forms by reduction of [Mo(CO)3Cp-Tj ]2 by Na/Hg in the presence of 2-chlorobutene and THF. The central metal atoms are arranged in a cubane structure... 

By ab initio MO and density functional theoretical (DPT) calculations it has been shown that the branched isomers of the sulfanes are local minima on the particular potential energy hypersurface. In the case of disulfane the thiosulfoxide isomer H2S=S of Cg symmetry is by 138 kj mol less stable than the chain-like molecule of C2 symmetry at the QCISD(T)/6-31+G // MP2/6-31G level of theory at 0 K [49]. At the MP2/6-311G //MP2/6-3110 level the energy difference is 143 kJ mol" and the activation energy for the isomerization is 210 kJ mol at 0 K [50]. Somewhat smaller values (117/195 kJ mor ) have been calculated with the more elaborate CCSD(T)/ ANO-L method [50]. The high barrier of ca. 80 kJ mol" for the isomerization of the pyramidal H2S=S back to the screw-like disulfane structure means that the thiosulfoxide, once it has been formed, will not decompose in an unimolecular reaction at low temperature, e.g., in a matrix-isolation experiment. The transition state structure is characterized by a hydrogen atom bridging the two sulfur atoms. 

The Lewis acid activates the acid chloride by forming an adduct with a chlorine atom bridge between carbon and aluminum. This chlorine bridge is similar to the one found in AI2 Clg ... 

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