Krypton-carbon bonds

Radon forms a series of clathrate compounds (inclusion compounds) similar to those of argon, krypton, and xenon. These can be prepared by mixing trace amounts of radon with macro amounts of host substances and allowing the mixtures to crystallize. No chemical bonds are formed the radon is merely trapped in the lattice of surrounding atoms it therefore escapes when the host crystal melts or dissolves. Compounds prepared in this manner include radon hydrate, Rn 6H20 (Nikitin, 1936) radon-phenol clathrate, Rn 3C H 0H (Nikitin and Kovalskaya, 1952) radon-p-chlorophenol clathrate, Rn 3p-ClC H 0H (Nikitin and Ioffe, 1952) and radon-p-cresol clathrate, Rn bp-CH C H OH (Trofimov and Kazankin, 1966). Radon has also been reported to co-crystallize with sulfur dioxide, carbon dioxide, hydrogen chloride, and hydrogen sulfide (Nikitin, 1939). 

The bonding between the metal and the cyclopentadiene rings involves the it electrons of the two rings, all carbons being equally bonded to the central ferrous ion. The latter, in accepting a share of 12 tt electrons from two cyclo-pentadienyl anions, achieves the 18 outer-shell electron configuration1 of the inert gas, krypton. Analysis of the structure of crystalline ferrocene shows... 

In the carbonyls, each molecule of carbon monoxide donates two electrons to the central atom. Cobalt has 27 extra nuclear electrons, and if two electrons are contributed by each of four carbon monoxide molecules, the cobalt would have an E.A.N. of 35. One more electron is needed to attain the rare gas structure of krypton and this is secured by the sharing of one electron pair between two cobalt monomers. The existence of a metal to metal bond in dicobalt octacarbonyl has been postulated by Ewens (34) and cryoscopic measurements have established without doubt the dimeric structure [Co(CO)4]2 for dicobalt octacarbonyl. 

Tin, element 50, has 14 electrons outside of the krypton shell, and nine stable orbitals Ad, 5s, 5p). The five Ad orbitals, which are more stable than the 55 and 5p orbitals, are occupied by five unshared electron pairs. The remaining four electrons may separately occupy the four tetrahedral 5s5p - orbitals, and be used in forming four bonds, tetrahedrally directed. In fact, gray tin, one of the two allotropic forms of the element, has the diamond structure. The tin atoms in gray tin are quadrivalent, as are the carbon atoms in diamond. They have no metallic orbital, and gray tin is not a metal, but is a metalloid. 

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