Abstract
Treatment of [0s(NH3)5(C3H5)20](0Tf)2 in methanol with triflic acid produces [Os(NH3)5(tj3-C3Hs)](OTf)3 in good yield. The
cation in solution was characterized by NMR spectroscopy. In cyclic voltammetry, no redox activity is revealed within the
solvent window, +1.5 to -1.5 V vs NHE. The complex readily undergoes addition at a terminal carbon by a variety of neutral
and negatively charged nucleophiles. Complexes of cyclic allyls are generated when either the complex of anisóle or of 1,4-di-
methoxybenzene is hydrogenated in acidic methanol. As is true of the benzene analogue, hydrogenation does not proceed beyond
two molecules of H2/molecule of ligand. In the reduction of the complex of 1,4-dimethoxybenzene, elimination of methanol leads
to the ij2-benzene complex as the reaction product. A proton is eliminated from [Os(NH3)5(tj3-C6H9)]3+, yielding [Os(NH3)5-
( 2-1,3-cyclohexadiene)]2+, and the reaction is governed by an equilibrium quotient of 0.3 M in methanol. This equilibrium quotient,
together with that for the addition of CH30" to coordinated allyl, leads to an estimate of 2 X 1015 for the equilibrium quotient
for elimination of CH3OH from [Os(NH3)5(?;2-3-methoxycyclohexene)]2+, to be compared to ca. 0.1 for the free organic ligand.
The comparison shows that the affinity of [Os(NH3)5]2+ for the carbon/carbon double bond in a conjugated diene is very much
greater than for the carbon/carbon double bond of 3-methoxycyclohexene.
