Variable oxidation state of transition metal ions
Thermodynamics proposes, kinetics disposes.  The most stable form can have a high activation energy barrier surrounding it.  The medium matters.  Hard Lewis bases (water) stabilize high oxidation states (Cu(II), tungstate).  Soft Lewis bases (acetonitrile) stabilize low oxidation states (Cu(II); $\ce{W(CO)6}$ and http://www.google.com/patents/EP1995347A1?cl=en).

$\ce{Ti^{+4}}$ is the basement, especially with oxygen.  Now rationlalize titanium suboxide Magnéli phases.  They are spectacular as inert electrodes under extreme conditions, re Ebonex.

DOI:10.1016/j.electacta.2010.05.011 
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