Intramolecular Diels-Alder Reactions in Ruthenium Vinylidene Complexes Containing Anthracenyl Groups

An intramolecular Diels-Alder (IMDA) reaction was observed at room temperature between an allyl group and a chloroanthracenyl group that were both bonded to the vinylidene ligand of the cationic ruthenium complex [Ru]dCdC(CH2CHdCH2)CH(CH2CHdCH2)(C14H8Cl) (6; [Ru] ) Cp(PPh3)3Ru). The vinylidene ligand functions as a mediator to bring the allyl and the chloroanthracenyl groups in proximity for the reaction to take place. For the two allyl groups in 6, only the one at C underwent the reaction. In the analogous triethylphosphine complex 6′, more electron-donating triethylphosphine ligands lower the rate of the IMDA reaction. For this IMDA reaction in several vinylidene complexes, each with a nonchlorinated anthracenyl ligand, the rate of the reaction is accelerated by the presence of an unsaturated functional group at Cγ of the vinylidene ligand, particularly by a terminal alkynyl substituent. The solidstate structures of two IMDA reaction products have been determined by single-crystal X-ray diffraction analysis.