Lewis-like structures for the d-block elements

1 Common empirical formulas of transition-metal compounds 

The development of G. N. Lewis s octet rule for the s/p-block elements was strongly influenced by the stoichiometric ratios of atoms found in the common compounds and elemental forms (CH4, CCI4, CO2, CI2, etc.). Let us therefore begin analogously by examining the formulas of the common neutral binary chloride, oxide, and alkyl compounds of transition metals. (Here we substitute alkyl groups for hydrogen because only a small number of binary metal hydrides have been well characterized.) 

In many instances several different compositions of the binary oxide and chloride compounds are available. In each case we designate as most common the particular compound that is least expensive and available in the largest quantities from common suppliers,4 as summarized in Table 4.1. Included with each entry is the number (eu) of unpaired electrons determined from magnetic-susceptibility measurements. 

From Table 4.1a remarkably simple regularity becomes apparent. If Gm denotes the group number, n the stoichiometric ML coordination number, If the valency of the ligand, and eu the number of unpaired electrons, one can recognize that the relationship 

If we now assume, following Lewis, that each monovalent bond coordination is associated with an electron pair, we can write the total number (ebf) of valence bond-pair electrons as 

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