Stannic and plumbic compounds

Bond arrangements found are tetrahedral, trigonal bipyramidal, and octahedral for completely shared valence groups of 8, 10, and 12 electrons respectively. Higher coordination numbers are exhibited by Sn(iv), 7, and 8, and by Pb(iv), 8, in certain complexes formed by chelating ligands, most or all of the bonds being formed to 0 atoms. 

Tetrahedral coordination. The simplest examples are molecules MX4 and MX4 jY f, a number of which have been shown to be tetrahedral either in the vapour or crystalline states  

Some compounds (CH3)3SnX and (CH3)2SnX2 show a clear-cut change from a tetrahedral monomer to a polymeric structure with 5- or 6-coordination of Sn (see later). 

Monomeric Sn R2 compounds generally polymerize to Sn compounds, either linear (for example, H[Sn(C6H5)2] H) or cyclic molecules. An example of the latter is [Sn(CfiHs)2] 6 Fig- 26.10(a), which has been studied in the crystalline 

Stereochemistry of Sn(lV) (a) cyclic lSn(C6H5)2]j molecule (phenyl groups omitted), (b) infinite chains in (C H3)3SnCN, (c) Sn04.2 POQ3, (d) SnQ4. 2 SeOClj. 

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