Cyclopropenation and related reactions of ruthenium vinylidene complexes

Facile deprotonation of a number of cationic ruthenium vinylidene complexes, followed by cyclopropenation,is accomplished in acetone. The deprotonation of [Ru]=C=(Ph)CH(2)R(+), ([Ru] = (eta(5)-C5H5)(PPh(3))(2)Ru) by n-Bu(4)-NOH induces a novel cyclization reaction and yields the neutral cyclopropenyl complexes [Ru]-C=C(Ph)CHR (3b,R=CN; 3c, R=Ph; 3d, R=CH=CH2; 3e, R=CH=CMe(2)). Complex [Ru]-C=C(C6H9)CHCN+ (3k) is similarly prepared. Protonation of 3b-3e regenerates the corresponding vinylidene complexes. Deprotonation of [Ru]=C=C(Ph)CH(2)COOMe(+) (2h) by n-Bu(4)NOH induces a different type of cyclization and yields the neutral furan complex [Ru]-C=C(Ph)CH=C(O)OMe (4h). The cyclopropenyl complex containing a methoxy substituent cannot be prepared from [Ru]=C=C(Ph)CH2OCH3+ (2i), but F- of n-Bu(4)NF attacks the C-alpha of 2i to produce the unstable vinyl complex [Ru]C(F)=C(Ph)CH2OCH3 (5). Complex [Ru]-C=C(Ph)C(CN)OCH3 (9b) was indirectly prepared from the addition of TCNQ to 3b, giving [Ru]=C=C(Ph)CH(CN)TCNQ (6b) followed by methanolysis. Unlike 3, complex 9b is not converted to vinylidene complex, instead, removal of the methoxy substituent by acid gives the cationic cyclopropenlium complex [Ru]-C=C(Ph)C(CN)(+) (10b). Complex [Ru]-C=C(Ph)C(COOMe)(+) (10h) is similarly prepared from 4h via a TCNQ complex 6h followed by a methoxy-substituted complex 9h. In the presence of allyl iodide, opening of the three-membered ring of 3b, followed by a subsequent oxidative coupling reaction, gives a dimeric dicationic product {[Ru]=C=C(Ph)-CHCN}(2+)(2) (11). Proton abstraction of 11 by n-Bu(4)-NF gives the biscyclopropenyl complex {[Ru]-C=C(Ph)CCN}(2) (12). Molecular structures of complexes 3b, 3f, 4h, 6b, 9b, and 11 have been confirmed by X-ray diffraction analysis.