[Mn(CO)₅GeH₃] reacts smoothly with Co₂(CO)₈ to form the [(CO)₅MnGeCo₃(CO)₉], which is also produced by the reaction of Mn(CO)₅⁻ with [(CO)₄CoGeCo₃(CO)₉]. [Mn(CO)₅GeMeH₂] similarly reacts with Co₂(CO)₈ to give [{Mn(CO)₅} {Co₂(CO)₇}GeMe]. The products were characterised spectroscopically and the ESR spectrum of the radical ion of the title compound is presented.