1H N.m.r. Chemical shifts and hydrogen exchange rates oftrans-[Co(en)2XY]n+ complexes in liquid ammonia

Summary ¹H n.m.r. spectra of coordinated ethylenediamine HN< hydrogens for 23trans-Co(en)₂XY]ⁿ⁺ complexes and¹H-²H exchange rates for some selected compounds are reported in the solvent liquid ammonia. Assignments are presented for asymmetric complexes. These are based on the chemical shift order of the symmetric complexes. The assignments are confirmed by independent experimental findings including the effect of specific ion-association and the observed exchange rates. The exchange rates follow the relation k_obsd=k⁰+k¹ N²H₄ClO₄]^–1, illustrative of general base-catalysis; in this case rate-determining proton abstraction by N²H₃ and N²H ₂ ^– , respectively. Chemical shifts and exchange rates in liquid ammonia follow the published order of the aqueous parameters.