Abstract
The reduction of Os(NH3)5(OTf)3 in D20 or H20 over zinc amalgam gives rise to a species that retains the ability
to form (NH3)50sn adducts with the -acidic ligands acetone, 7V,iV-dimethyluracil (DMU), and acetonitrile for
periods of hours in the absence of reducing agent. The i?2-DMU complex was shown not to be in equilibrium with
free DMU, in contrast to a previous report. Kinetic trapping studies are described that demonstrate the following:
(1) an “active” source of (NH3)50sn other than the aquo complex is formed and decomposes by a first-order process
with a half-life of about 3 hat room temperature in D20; (2) the rate of the decomposition process increases markedly
at lower pH; and (3) the decomposition rate in H20 is about twice that in D20. No direct spectroscopic or
electrochemical evidence of species having osmium-hydrogen bonds was observed at neutral pH.
