The oxygen chemistry of some transition elements

For a discussion of certain aspects of their oxygen chemistry it is convenient to group together the six elements Ti, V, Nb, Mo, W, and Re. The following 

As far as is known the oxygen chemistry of Cr is based exclusively on tetrahedral coordination. Cr is present in some, if not all, of the black oxides intermediate in composition between CrOj and Cr03 (p. 947) which are obviously metallic oxides more akin to those of Mo and W. Not much is known of the structural chemistry of oxy-compounds of Mn apart from the fact that the permanganate ion MnOJ is tetrahedral. We have already referred to MujOt. Both Mo and W form tetrahedral oxy-ions but their complex oxy-chemistry is largely based on octahedral coordination, which appears even in the pyro -salts Na2Mo207 and Na2W207 (p. 431), Some finite oxy-ions of V, Nb, Mo, and W are described in 

Chapter 11, Comparatively little is yet known of the complex oxy-chemistry of Re and still less in the case of Tc, white that of Ta has yet to be developed, but from what we know of these elements it would seem justifiable to group together Ti, V, Nb, Mo, W, and Re for a discussion of their complex oxy-chemlstry. 

In Chapter 13 we discuss complex oxides of these elements, including the bronzes . 

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