Synthesis of ruthenium vinylidene complexes with dppe ligand and their cyclopropenation reaction

A number of cationic ruthenium vinylidene complexes [Ru]=C=C(Ph)CH2R+ ([Ru]=(eta(5)-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2, 5a, R = CN; 5b, R = C6F5; 5c, R = Ph; 5d, R = p-C6H4CN; 5e, R = p-C6H4CF3; 5f, R = 1-C10H7; 5g, R = CO2CH3) are prepared from electrophilic addition of organic halides to the acetylide complex [Ru]-C=CPh at the boiling point of CHCl3. Complex 5g', prepared at room temperature, displays similar spectroscopic property as that of 5g but is easily hydrolyzed to give [Ru]COCH2Ph (6). Cyclopropanation of the organic vinylidene moiety of 5a-5f is accomplished in acetone by deprotonation of 5 with n-Bu4NOH yielding the neutral cyclopropenyl complexes [Ru]-C=C(Ph)CHR (7a, R = CN; 7b, R = C6F5; 7c, R = Ph; 7d, R = p-C6H4CN; 7e, R = p-C6H4CF3; 7f, R = 1-H-10(7)). Protonation of 7b-7f regenerates the corresponding vinylidene complexes. In the presence of allyl iodide, opening of the three-membered ring of 7a, followed by a subsequent oxidative coupling reaction, gives a dimeric dicationic product {[Ru]=C=C(Ph)-CHCN}(2)(+2) (9a). In the processes of preparing the starting material Cp(dppe)RuCl for the acethylide complex, two dppe complexes Ru(dppe)(2)Cl-2 (2) and [Cp(dppe)RuCl](2) (3) are isolated. Molecular structures of complexes 2, 3, 6, and 7b have been confirmed by X-ray diffraction analysis. (C) 1998 Elsevier Science S.A.