Complex or Co-ordination Compounds and Ions

The general nature of complexes has been discussed (pp. 131-137) and particular complexes have been considered elsewhere here is a more systematic review of the subject. 

Two or more compounds capable of independent existence often combine  

These products differ widely in their behaviour, particularly in water and, though there is no general agreement on what constitutes a complex or coordination compound the following definition is sufficient for the present purpose a complex molecule or ion is one in which an atom (A) is attached to other atoms (B) or groups of atoms (C) to a number in excess of the charge or oxidation number of the atom (A). 

In solid KgPtClg there are octahedral PtClg ions. In KMgFg there are no discrete complex ions the compound has the perovskite structure (p. I5I). There is thus no simple way of defining a complex in terms of solid structure. 

Not all complexes contain complex ions. The well-known nickel dimethyl-glyoxime, bis(dimethylglyoximato)nickel(II), [Ni(C4H702N2)2], (p- 543, Fig. 288 (c)) and bis(acetylacetonato)copper(II) (p. 522) are uncharged molecules, 

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