Abstract
A useful precursor dj-[0s(NH3)4(CF3S03)2](CF3S03) (1) has been synthesized by oxidation of the dinitrogen
complex cis-[Os(NH3)4(N2)2]Cl2 in CF3SO3H. While the reduction of 1 in aqueous solution leads to the * 12-
dihydrogen complexes1 in high yield, in acetone, and at room temperature, however, when reduced by Mg or Zn/Hg,
1 reacts rapidly with a variety of unsaturated ligands. In the presence of norbornadiene and 1,5-cyclooctadiene,
the corresponding ?/-diene tetraammine complexes were obtained in recovered yields of 30% and 80%, respectively.
Traces of acid left in 1 lead to much reduced yields of these and of other species we have prepared, owing to the
formation of the diacetone alcohol complex as a side product in which the ligand bonds to Os(II) center in rj’-fHO-)
and t?2-(0=C-) fashion. In the absence of a competing ligand, this chelate complex is the major product of the
reaction. In the presence of the arenes, benzene, phenol and naphthalene, reduction of 1 was found to lead to the
?;6-arene triammine complexes, the reaction yields as determined by NMR being 64%, 68%, and 95%.
