Protonation of Cp(CO)(PPh3)RuCCPh: Formation of cationic phenylacetylene and phenylvinylidene complexes and subsequent reaction with ethylene oxide to form the net cycloadduct

Article abstract of DOI:10.1016/0022-328X(95)05692-I

Protonation of the alkynyl complex Cp(CO)(PPh3)RuC<*>CPh (1) at low temperature affords quantitatively the vinylidene complex ⁺ (3), which upon warming to room temperature forms an equilibrium with the η²-phenylacetylene complex 2-HC<*>CPh)>⁺ (4), with the latter predominating.Subsequent reaction with ethylene oxide yields the cyclic oxacarbene complex (5), which can be regarded as the result of a net <3+2> cycloaddition reaction between 3 and ethylene oxide.Deprotonation of 5 affords the corresponding neutral cyclic vinyl complex (6), which can in turn be protonated to regenerate 5 in a diastereoselective manner.The structures of complexes 5 and 6 were determined by X-ray crystallography.Keywords: Ruthenium; Cyclopentadienyl; Vinylidene complex; Acetylene complex; Isomerism; Carbene complex