Applications of Monodentate Complexes

Many students have prepared coordination compounds in prior chemistry courses but often have not fully understood or even identified them as such. For example, in the Group I qualitative-analysis scheme, lead(II), mercury(I), and silver(I) are isolated as the white precipitates PbCl2, Hg2Cl2, and AgCl, respectively. To separate the silver from the other two cations, aqueous ammonia is added to form the linear diamminesilver(I) complex, [Ag(NH3)2], as shown in Equation (6.1)  

Since neither lead(II) chloride nor mercury(I) chloride react similarly, the silver is successfully separated from the other two metals. 

Copper(II) is sometimes included in the Group I qualitative-analysis scheme. 

Its chloride is soluble, but it does form a tetraammine complex, as shown in 

This square planar complex absorbs visible light to produce a characteristic deep-blue color that can be used to indicate the presence of copper ions. 

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