Hydrolysis of lanthanide dicarbides. Rates of reaction with water

Article abstract of DOI:10.1016/0022-5088(91)90064-B

The kinetics of the reaction between liquid water and nine lanthanide dicarbides and YC₂ have been investigated by monitoring the gas evolved into a constant volume apparatus. The ratio of volume of gas-evolved to that predicted was found to be consistent at 0.51 for wholly trivalent dicarbides, but rose to 0.66 for the light lanthanides containing Ln^IV components. Only linear kinetics were observed with the linear reaction rate constant K_L in the range 0.44 cm cm^-2 min^-1 for LuC₂ to 6.9 cm cm^-2 min^-1 for CeC₂. Over the limited temperature range 283-303.5 K it was possible to estimate activation energies for four of the dicarbides and the values ranged from 48.5 kj mol^-1 for the heavy, hard carbides to 150 kJ mol^-1 for the light, soft, Ln^IV-containing members. The variation of K_L and E across the series is discussed in terms of M-C₂ bond energies, 4f-band electron density and the hardness of these dicarbides.