The kinetics of base hydrolysis of trans-dichlorotetrakis(alkylamine)-rhodium(III) ions

Abstract

The observed pseudo-first-order rate constants for the base hydrolysis of the series of complexes trans-[Rh(NH₂R)₄Cl₂]⁺(R = H, Me, Et, or Prⁿ) have been found to depend on hydroxide ion according to K_obs.=k₁+k₂[OH^–]. The k₁ term is believed to be the aquation pathway which is operative in the bromide interchanges of these complexes, whereas the k₂ term corresponds to the S_N1 (c.b.)(conjugate base) mechanism. Values of the activation parameters for the base hydrolysis have also been determined and are discussed in relation to the results for similar rhodium(III), cobalt(III), and chromium(III) complexes. It is concluded that in complexes of this type rhodium(III) is less able to participate in π bonding than are cobalt(III) and chromium(III).