The structural chemistry of nickel

The following bond arrangements have been established by structural studies of finite ions or molecules  

Much confusion in the literature on this subject has been due to the placing of too much reliance on magnetic data of dubious quality and to incorrect deductions of coordination numbers from chemical formulae. There are regrettably few examples of compounds of which both thorough magnetic and structural studies have been made. The following facts have been established  

Trigonal bipyramidal NiCl3(H20)[N(C2H4)3NCH3] Octahedral Ni(pyr)4(C104)2 

3-34 A, while the latter consist of octahedral molecules, (d). The compounds studied were the 3,5-dimethylpyridine compound, (c), and the 3,4-dimethyl-pyridine compound, (d). The compounds containing the bidentate ligand meso-stilbene diamine, CgHs. CH(NH2)—CH(NH2). C Hs, are still more interesting. The blue and yellow forms are interconvertible in solution, and while the hydrated blue form (/n = 3-16 BM) of the dichloroacetate contains octahedral ions, (e), the yellow form (ju = 2-58 BM) contains planar ions of type (f) and octahedral 

Ni(ii) forming 4 coplanar bonds. Planar diamagnetic complexes include the Ni(CN)4 ion, which has been studied in the and other salts (Ni-C, 1-85 A), and molecules such as (a) and (b). The numerous complexes with bidentate ligands include the thio-oxalate ion, (c), molecules of the types (d) ) and (e), and the glyoximes, (0 notable for the short intramolecular hydrogen bonds. Many divalent metals form phthalocyanins, M(ii) replacing 2 H in C32H18N8 (Fig. 27.9). 

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