The structures of oxy-salts

Crystalline oxy-salts provide many examples of (4 -h 1)- and (4 + 2)-coordination in 3D structures. 

In Cu(N03)2. 2 H20 the four strong bonds from Cu define groups Cu(N03)2(H20)2 (Fig. 25.12(d)) and as in the anhydrous nitrate there are two kjnds of non-equivalent NOJ ions. Here both types of NOJ ion are behaving as pseudo-bidentate ligands, and a second bond from 0 of one NO J links the square coplanar groups into infinite chains. The environment of Cu(ii) is very similar to that in the nitromethane complex, namely, Cu-4 0, 1-97 A, 1 0, 2-39 A, and 2 0, 

We noted in Chapter 18 the behaviour of NOJ as a monodentate, symmetrical bidentate, and bridging ligand. We summarize in Fig. 25.13 the types of NOJ ligand observed in the compounds of Fig. 25.12. There appears to be a correlation 

In the dihydrate of cupric succinate one-half of the water is present as isolated molecules of water of crystallization and the remainder is present in dimeric complexes like those of Cu2(ac)4(H20)2. The succinate ions form not only the bridges in the dimers but also link these units into infinite chains (Fig. 25.14(c)). 

In the trihydrate of cupric benzoate there are chains CUX2B of the type illustrated in Fig. 25.16(c), p. 903, in which X is H2O and B is the benzoate group, —0C(CgHs)0- the remaining H2O and CgHsCOO ions are accommodated between the chains. 

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