Carbon and Oxygen Isotope Exchange between CO and Ni(CO)4

Abstract

The single stage factor α of the carbon and oxygen isotope exchanges between liquid Ni(CO)4 and gaseous CO, according to the reactions Ni(C12O)4+C13O⇌Ni(C12O)3C13O+C12Oand Ni(CO16)4+CO18⇌Ni(CO16)3CO18+CO18,respectively, has been determined: For the carbon exchange,α=1.020±0.002 at−10∘ and α=1.010±0.002 at+10∘.For the oxygen exchange,α=1.005±0.002 at−10∘ and α=1.000±0.002 at +10∘.These data are in good agreement with values calculated from spectroscopic data for Ni(CO)4 and CO. From the isotope fractionation measured in a packed countercurrent column, the activation energy E for the exchange was estimated. The value of E=12 kcal/mole agrees with the results obtained from kinetic data for the thermal decomposition of Ni(CO)4 and the exchange of Ni(CO)4 with labeled CO. The rate of the thermal decomposition of Ni(CO)4 is assumed to be the rate determining step in the exchange.