Formation of Vinylidenes from Internal Alkynes at a Cyclotriphosphato Ruthenium Complex

摘要

Terminal alkynes are readily converted into the corresponding vinylidenes at transition-metal complexes, and this tautomerization is now recognized as a key reaction in many metal-promoted or -catalyzed transformations of alkynes. Alkynes with a heteroatom substituent are also known to undergo similar rearrangement. In contrast isomerization of internal alkynes with two carbon substituents to vinylidenes has not been developed. In the course of our study on transition-metal complexes with a cyclophosphato ligand, we have revealed that this class of organometallic compounds exhibit unique structural and chemical properties based on the circular array of P-O groups as an effective σ-donor set. Now we have found that the reaction of the ruthenium cyclotriphosphato (P3O_9~(3-) )-methanol complex (PPN)[Ru(P3O9)(CH3OH)(dppe)] (1) with internal alkynes leads to the vinylidene complexes via the 1.2-migration of an alkyl, aryl, or acyl group.