Affiliation:
1. Department of Chemistry, University of Lucknow, Lucknow, India
Abstract
The kinetics of the formation of the light orange–coloured complex [Ru(CN)5D-PA]3− are studied spectrophotometrically through substitution of a coordinated H2O molecule in aquapentacyanoruthenate(II) [Ru(CN)5OH2]3− by interaction with D-penicillamine [D-PA] in aqueous medium at 490 nm (λmax of [Ru(CN)5D-PA]3−). The reaction is monitored under pseudo-first-order conditions, taking [D-PA] in excess over [Ru(CN)5OH23−]. The effects of various reaction parameters on the rate of the reaction are investigated. Experimental observations reveal that the variation in [D-PA] obeyed the first-order rate law while it is found to be invariant with [Ru(CN)5OH23−] in the whole experimental range. With ionic strength variation, as the reaction advances a decrease in the reaction rate is noticed. The product stoichiometry is assigned as 1:1. The ease of substitution at an H2O molecule in [Ru(CN)5OH23−] is considered on the basis of the electronic effect generated through interactions of the M–OH2 bond. A provisional mechanism based on the calculated results is proposed based on the slowest step of the reaction.