The reactions of C(NMe2)4 (1) with Mn2(CO)10 or Co2(CO)8 in THF yield[C(NMe2)3][Co(CO)4] (3) and [C(NMe2)3][Mn(CO)5] (4), respectively. The compounds Co(CO)4NMe2 (5) and Mn(CO)5NMe2 (6) could not be found. With CH2Cl2 4 is quantitatively converted into [C(NMe2)3][Mn(CO)4Cl2] (7) as shown by IR and 13C NMR investigations. 3 and 4 were characterized by an X-ray structure determination. 3: Space group Pnma, Z = 4, a = 7.435(2), b = 10.79(2), c = 20.299(5)Å. 4: Space group C2/c, Z = 4, a = 11.378(2), b = 10.165(1), c = 14.533(1) Å; β = 103.37(1)°. The compounds form independent ions with no bonding interactions between cation and anion; the central CN3 unit of the [C(NMe2)3]+ cation in 3 and 4 is disordered.