Unit trigonal

Multiple bonds are treated as a single unit m the VSEPR model Formaldehyde is a trigonal planar molecule m which the electrons of the double bond and those of the two single bonds are maximally separated A linear arrangement of atoms m carbon diox ide allows the electrons m one double bond to be as far away as possible from the elec Irons m the other double bond... 

Gep2 is formed as a volatile white solid (mp 110°) by the action of Gep4 on powdered Ge at 150-300° it has a unique structure in which trigonal pyramidal [GePsI units share 2 P atoms to form infinite spiral chains (Pig. 10.2). Pale-yellow GeCl2 can be prepared similarly at 300° or by thermal decomposition of GeHCls at 70°. Typical reactions are summarized in the scheme ... 

The HP may then be removed by adding MgO to precipitate MgF2 and the colourless deliquescent solid Xe03 obtained by evaporation. The aqueous solution known as xenic acid is quite stable if all oxidizable material is excluded, but the solid is a most dangerous explosive (reported to be comparable to TNT) which is easily detonated. The X-ray analysis, made even more difficult by the tendency of the crystals to disintegrate in an X-ray beam, shows the solid to consist of trigonal pyramidal Xe03 units, with the xenon atom at the apex (cf. the isoelectronic iodate ion 103 p. 863). 

B-type, also eonsisting of LnOy units but now of three types, two are eapped trigonal prisms and one is a eapped oetahedron favoured by the middle lanthanides. 

Filgueiras and coworkers222 prepared the complex of a disulphoxide with triphenyltin chloride. The complex is a 2 1 adduct with two Ph3SnCl units whose Sn atoms occupy the centre of the two trigonal bipyramids, as shown in Scheme 17. 

When more d orbitals are available, six stronger equivalent eigenfunctions with their maxima directed towards the comers of a trigonal prism of unit axial ratio can be formed1). The bond-strength of these is 2.985, nearly equal to the maximum 3.000 possible for dsp orbitals. 

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