Selective C-C bond activation of 2-aryl-1-methylenecyclopropanes promoted by Ir(I) and Rh(I) hydrido complexes. Mechanism of ring-opening isomerization of the strained molecules

[IrH(CO)(PPh3)(3)] promotes ring opening of 2-phenyl-l-methylenecyclopropane at room temperature to produce the Ir complex with a chelating 2-phenyl-3-butenyl ligand, [Ir{eta(2)-CH2CH(Ph)CH=CH2-kappa C-1}(CO)(PPh3)(2)] (1). The reaction of excess 2-phenyl-l-methylenecyclopropane with [IrH(CO)(PPh3)(3)] at 50 degrees C yields [Ir{eta(2)-(o-C6H4)CH(Me)CH= CH2-kappa C-1)(CO)(PPh3)(2)] (2), accompanied by the formation of 1-phenyl-1,3-butadiene and 2-phenyl-1.3-butadiene. 2,2-Diphenyl-l-methylenecyclopropane reacts with [IrH(CO)(PPh3)(2)] to afford [Ir{eta(2)-CH2-CPh2CH=CH2-kappa C-1}(CO)-(PPh3)(2)] (3) at 50 degrees C and [Ir{eta(2)-(o-C6H4)CMe(Ph)CH=CH2-kappa C-1)(CO)(PPh3)(2)] (4) at 100 degrees C. Heating a solution of 3 at 100 degrees C also forms 4 quantitatively. X-ray crystallography of 3 reveals a penta-coordinated structure around the Ir center bonded to a chelating 2,2-diphenyl-3-butenyl ligand. The reactions of 2,2-diphenyl-l-methylenecyclopropane and of 2,2-di(4-fluorophenyt)-1-methylenecyclopropane with [RhH(CO)(PPh3)(3)] at room temperature yield [Rh{eta(2)- CH2CAr2CH=CH2-kappa C-1}(CO)(PPh3)(2)] (5a: Ar = Ph, 5b: Ar = C6H4-F-4). The reactions at 50 degrees C cause ring opening of the substrate and orthometalation of the phenyl group to afford [Rh{eta(2)-(o-C6H4)CMe(Ph)CH=CH2-kappa C-1}-(CO)(PPh3)(2)](6a) and [Rh{eta(2)-(o-C6H3-F-4)CMe(C6H4-F-4)CH=CH2-kappa C-1}(CO)(PPh3)(2)](6b), respectively. Formation of 1,1-diaryl-1,3-butadiene is observed during the reaction. Heating a solution of 5a at 50 degrees C produces 1,1-diphenyl-1,3-butadiene and an allylrhodium complex, 8, rather than 6a, although the reaction of excess 2,2-diphenyt-1-methylenecyclopropane with 5a at 50 degrees C affords 6a in 60 %. The mechanisms of the above reactions are discussed based on the products and reaction rates. Coordination of P(OMe)(3) to the Rh center of 5a causes insertion of the CO ligand into the Rh-C bond to afford [Rh{eta(2)-CO-CH2CPh2CH=CH2-kappa C-1}(P(OMe)(3))(3)] (7).