Synthetic and Mechanistic Studies of the Addition of 4-Chloroaniline to Tricarbonyl (1-5-η-dienyl)iron(II) cations (dienyl= C6H7, 2-MeOC6H6 or C7H9)

Article abstract of DOI:10.1016/0022-328X(87)85042-8

A kinetic study of the reactions between the organometallic complexes <(Fe(CO)3(1-5-η-dienyl)>BF4 (1, dienyl= C6H7, 2-MeOC6H6 or C7H9) and 4-chloroaniline in CH3CN reveal the general two-term expression k_obs= k_a<4-ClC6H4NH2>+k_b, which is consistent with an equilibrium process.The observed rate sequence C6H7>2-MeOC6H6>C7H9 and the low ΔH_a^<> and large negative ΔS_a^<*> values are in accordance with direct addition to the dienyl rings of 1.On the other hand, the much higher ΔH_b^<*> values are consistent with bond cleavage in dissociation.The values ΔS_b^<*> are negative, indicating the presence of an ordered transition state through which the starting dienyl complexes are reformed via some internal S_N² process.