Formation and kinetics of decomposition of monoaquobis(ethylenediamine)(pyridylmethyl)chromium(III) complexes

Abstract

Monoaquobis(ethy1enediamine) (pyridylmethyl)chromium(lll) complexes, 2-NC5H4CH2Cr(en)2(H20)2+ and 3-NC5H,CH2Cr(en)2(Ha20)2+, are prepared by the reduction of the corresponding picolyl chlorides by the c ~I I ( e n ) ~~+ ion. The decomposition of these ions is studied in 0.01 -1 .OM-perchloric acid and in acetate buffers of pH 1-7.Spectral changes show that these complexes undergo aquation before carbon-chromium bond cleavage. Product studies as well as kinetic data and activation parameters obtained indicate that the 2and 3-ions decompose via the penta-aquo-derivative. 2-NC,H,CH,Cr(H,O) 62+, and the trisaquo-derivative, 3-NC,H,CH,Cr(en) (H20)32+ respectively. Acetate-ion catalysis is also observed for the decomposition of these ions.