The reaction of anhydrous CoCl2 with depe [1,2-bis(diethylphosphino)ethane] yields [CoCl2(depe)2]1, which reacts with Na[BPh4] in ethanol to give five-co-ordinate [CoCl(depe)2][BPh4]2. Both complexes have been studied by EPR spectroscopy. Complex 1 reacts with NaBH4 in ethanol yielding [CoH2(depe)2]+, isolable as the tetraphenylborate salt 3. This compound is stereochemically non-rigid in solution, having a cis configuration at low temperatures. The spin–lattice relaxation times (T1) for the hydrides of 3 suggest a classical formulation for this complex. The monohydride [CoH(depe)2]4 is obtained by deprotonation of 3 using KOBut. Complex 3 reacts with CO and CS2 with reductive elimination of H2, yielding [Co(CO)(depe)2][BPh4]5 and [Co(η2-CS2)(depe)2][BPh4]6, respectively, both stereochemically non-rigid in solution. The reaction of 6 with alkyl halides leads to CS2 elimination, and formation of [CoX(depe)2][BPh4] derivatives (X = Br 7 or I 8). Complex 6 reacts with activated alk-1-ynes eliminating CS2 and undergoing an oxidative addition of the alkyne, yielding the hydridoalkynyl complexes [CoH(CCR)(depe)2][BPh4](R = Ph 9 or CO2Et 10). A mechanistic study of the reaction between 6 and HCCCO2Et has been carried out, and the X-ray crystal structure of 10 determined.