Electrochemical and infrared spectral data for a number of octahedral systems of the type LM(CO)₅ (M=Cr, Mo) and W; L=pyridine and quinoline), L₂M(CO)₄ (M=Cr, Mo, and W; L₂ =ethylenediamine, (pyridine)₂, and bipyridyl), (LM(CO)₄)₂ (M=Cr, Mo, and W; L=As(CH₃)₂ and P(CH₃)₂) and (LFe(CO)₃)₂ (L=SCH₃ , P(CH₃)₂ , and As(CH₃)₂) before and after electrochemical reduction are presented. Force constants are calculated using the Cotton-Kraihanzel force field and the results discussed in terms of sigma and pi-bonding. Infrared spectral data before and after electroche~ical reduction are also reported for a number of iron-olefin complexes of low symmetry. / M.S.