“…17,18,[30][31][32] If the first step of such reaction is the nucleophilic attack of the metal atom to an alkyl halide, 17,18,22,32 it should be favored by the previous coordination of a Lewis base, as discussed above. A rate-enhancing effect of an added Lewis base on the oxidative addition reaction of alkyl halide over square planar complexes of Rh(I) [23][24][25][26] and Ir(I) 27 has in fact been detected experimentally. Even if pentacoordinate intermediate species have not been detected in most cases, these have been postulated as reaction intermediates because kinetic experiments have shown that pentacoordinate complexes are better nucleophiles than tetracoordinate ones.…”