22) In Tables II and III and throughout the paper when compounds in those tables are referred to, an arabic number is used to indicate the olefin, the arabic number followed by a lower case "a" indicates the Ni(r-BuNC)2 complex of that olefin and "b" indicates the Ni(PPh3)2 complex of that olefin; i.e., 20 is acrylonitrile, 20a is Ni(r-BuNC)(CH2CHCN) and 20b is Ni(PPh3)2(CH2CHCN). ( 23) For an ethylene complex, the symmetry would be and vNC' and i^c2 would be Aj and Bi. Substitution reduces the symmetry to C2 (trans