Transformations of Alkynes at a Cyclotriphosphato Ruthenium Complex

Photolysis of the cyclotriphosphato complex (PPN)­[Ru­(P3O9)­(η6-C6H6)] (2) with bpy (2,2′-bipyridyl) in alcohols
generated a violet solution of (PPN)­[Ru­(P3O9)­(bpy)­(ROH)] (3) with a labile alcohol
ligand. Complexes 3 were readily oxidized during recrystallization
to give the Ru­(III) alkoxo complexes (PPN)­[Ru­(OR)­(P3O9)­(bpy)] (4). Treatment of 3 with internal alkynes led to selective formation of η2-alkyne complexes (PPN)­[Ru­(P3O9)­(bpy)­(η2-RCCR′)]
(7), which did not undergo vinylidene rearrangement under
heating and photoirradiation conditions in contrast to its dppe analogues.
On the other hand, diphenylacetylene complex 7c (R =
R′ = Ph) gave the α-ketocarbene complex (PPN)­[Ru­(P3O9)­(bpy)­(CPhCOPh)] (8) on reaction with m-CPBA. This observation provides
a very rare example for the direct and controlled oxidation of a coordinated
alkyne ligand. Reactions of 3 with the terminal alkynes
in alcohols and in DMF afforded the alkoxycarbene complexes (PPN)­[Ru­(P­3O9)­(bpy)­{C­(OR)­CH2CR′}] (9) and the carbonyl complex (PPN)­[Ru­(P3O9)­(CO)­(bpy)] (12), respectively,
presumably by way of vinylidene intermediates.