(Co-4), and (R,R)-(BINAP)Co(CO)2H (Co-5) was prepared using the procedure developed for Co-2 and exhibited poor performance for the reductive hydroformylation of 1octene with little preference for formation of 1-nonanol. Monitoring the catalytic reactions by 31 P NMR spectroscopy established sequestration of a significant amount of bis(phosphine)cobalt as the carbonyl-bridged dimers. Based on these observations, a bis(phosphine) ligand was targeted that would disfavor dimer formation by virtue of large alkyl substituents. Accordingly, addition of two equivalents of dicyclohexylphosphinoethane (dcype) to a toluene solution of Co2(CO)8 under 4 atm hydrogen gas at 60 °C afforded the bis(phosphine)cobalt carbonyl hydride, (dcype)Co(CO)2H (Co-2, %Vbur = 53.7) in 89% isolated yield. Single-crystals suitable for X-ray diffraction were obtained from a concentrated diethyl ether solution at -35 ºC (Table ) and confirmed a five-coordinate, idealized trigonal bipyramidal structure. In benzene-d6, a resonance was observed at  -11.2 and assigned to the Co-H. Likewise, a diagnostic, exposure of Co-2 to a blue Kessil lamp and 1-4 atm of syngas did not result in H2 loss and formation of the bridging carbonyl dimer, [(dcype)Co(CO)2]2 suggesting that bimolecular release of dihydrogen is inhibited by the large cyclohexyl substituents.