Compounds of the type Fe(CO)₄(GeR₃)₂ containing two different methylgermyl substituents have been prepared and characterised. The preparation was via the exchange reaction Fe(CO)₄(GeR₃)₂ + [Mn(CO)₅]⁻ → [Fe(CO)₄(GeR₃)]⁻ + Mn(CO)₅(GeR₃) [Fe(CO)₄(GeR₃)]⁻ + GeXR’₃ → Fe(CO)₄(GeR₃)(GeR’₃) The compounds characterised were Fe(CO)₄(GeMeH₂) (GeH₃) Fe(CO)₄(GeMe₂H) (GeH₃), Fe(CO)₄ (GeMe₂H) (GeMeH₂), Fe(CO)₄(GeMe₃) (GeH₃) Fe(CO)₄(GeMe₃)(GeMeH₂) and Fe(CO)₄(GeMe₃)(GeMe₂H). Of these, the species Fe(CO)₄(GeMeH₂) (GeH₃) were characterised fully by infrared, proton nmr and mass spectroscopic studies. The self-reaction 2Fe(CO)₄(GeR₃)₂ → [Fe(CO)₄(GeR₂)]₂ + 2GeR₄ has also been examined in some detail. The methylgermane was eliminated in preference to GeH₄ and species of the type [Fe(CO)₄(GeH₃)]₂-GeR₂ were also identified in two cases. Halogenation of Fe(CO)₄(GeMeH₃) (GeH₃) and Fe(CO)₄(GeMe₂H) (GeH3) was followed by ¹H nmr studies. CCℓ₄ results in the substitution of Ge-H, while HCℓ cleaves Fe-Ge bonds. While Fe(CO)₄(GeMe₂H) (GeMeH₂), Fe(CO)₄(GeMe₃) (GeMeH₂) and Fe(CO)₄(GeMe₃) (GeMe₂H) have been prepared, spectroscopic identification of these species is rather tenuous as these samples were found always to be contaminated with either the symmetrically substituted species Fe(CO)₄(GeR₃)₂ and/or products from the self-reaction. Mn(CO)₅(GeR₃) species obtained in the above syntheses react with Co₂(CO)₈ to yield the species [Co₃ (CO)₉][Mn(CO)₅]Ge, [Co₂(CO)₇[Mn(CO)₅]GeMe and possibly [Co(CO)₄][Mn(CO)₅]GeMe₂. These species were characterised by their infrared and mass spectroscopic properties.