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
作者:Yasushi Nishihara、Chikako Yoda、Masumi Itazaki、Kohtaro Osakada
DOI:10.1246/bcsj.78.1469
日期:2005.8
[IrH(CO)(PPh3)3] promotes ring opening of 2-phenyl-1-methylenecyclopropane at room temperature to produce the Ir complex with a chelating 2-phenyl-3-butenyl ligand, [Irη2-CH2CH(Ph)CH=CH2-κC1}(CO)(PPh3)2] (1). The reaction of excess 2-phenyl-1-methylenecyclopropane with [IrH(CO)(PPh3)3] at 50 °C yields [Irη2-(o-C6H4)CH(Me)CH=CH2-κC1}(CO)(PPh3)2] (2), accompanied by the formation of 1-phenyl-1,3-butadiene and 2-phenyl-1,3-butadiene. 2,2-Diphenyl-1-methylenecyclopropane reacts with [IrH(CO)(PPh3)3] to afford [Irη2-CH2CPh2CH=CH2-κC1}(CO)(PPh3)2] (3) at 50 °C and [Irη2-(o-C6H4)CMe(Ph)CH=CH2-κC1}(CO)(PPh3)2] (4) at 100 °C. Heating a solution of 3 at 100 °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-1-methylenecyclopropane and of 2,2-di(4-fluorophenyl)-1-methylenecyclopropane with [RhH(CO)(PPh3)3] at room temperature yield [Rhη2-CH2CAr2CH=CH2-κC1}(CO)(PPh3)2] (5a: Ar = Ph, 5b: Ar = C6H4-F-4). The reactions at 50 °C cause ring opening of the substrate and orthometalation of the phenyl group to afford [Rhη2-(o-C6H4)CMe(Ph)CH=CH2-κC1}(CO)(PPh3)2] (6a) and [Rhη2-(o-C6H3-F-4)CMe(C6H4-F-4)CH=CH2-κC1}(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 °C produces 1,1-diphenyl-1,3-butadiene and an allylrhodium complex, 8, rather than 6a, although the reaction of excess 2,2-diphenyl-1-methylenecyclopropane with 5a at 50 °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 [Rhη2-CO-CH2CPh2CH=CH2-κC1}(P(OMe)3)3] (7).
[IrH(CO)(PPh3)3] 可促进 2-苯基-1-亚甲基环丙烷在室温下开环,生成带有 2-苯基-3-丁烯基螯合配体的 Ir 复合物 [Irη2-CH2CH(Ph)CH=CH2-κC1}(CO)(PPh3)2] (1)。过量的 2-苯基-1-亚甲基环丙烷与[IrH(CO)(PPh3)3]在 50 °C下反应生成[Irη2-(o-C6H4)CH(Me)CH=CH2-κC1}(CO)(PPh3)2](2),同时生成 1-苯基-1,3-丁二烯和 2-苯基-1,3-丁二烯。2,2-二苯基-1-亚甲基环丙烷与[IrH(CO)(PPh3)3]反应,在 50 °C 时生成[Irη2-CH2CPh2CH=CH2-κC1}(CO)(PPh3)2](3),在 100 °C 时生成[Irη2-(o-C6H4)CMe(Ph)CH=CH2-κC1}(CO)(PPh3)2](4)。在 100 °C 下加热 3 的溶液也能定量生成 4。3 的 X 射线晶体学显示,围绕与 2,2-二苯基-3-丁烯基螯合配体成键的 Ir 中心,存在五配位结构。室温下,2,2-二苯基-1-亚甲基环丙烷和 2,2-二(4-氟苯基)-1-亚甲基环丙烷与[RhH(CO)(PPh3)3]反应生成[Rhη2-CH2CAr2CH=CH2-κC1}(CO)(PPh3)2](5a:Ar = Ph,5b:Ar = C6H4-F-4)。在 50 °C下反应会导致底物开环和苯基正金属化,分别生成[Rhη2-(o-C6H4)CMe(Ph)CH=CH2-κC1}(CO)(PPh3)2](6a)和[Rhη2-(o-C6H3-F-4)CMe(C6H4-F-4)CH=CH2-κC1}(CO)(PPh3)2](6b)。在反应过程中观察到 1,1-二芳基-1,3-丁二烯的形成。在 50 °C下加热 5a 的溶液会生成 1,1-二苯基-1,3-丁二烯和烯丙基铑络合物 8,而不是 6a,不过在 50 °C下将过量的 2,2-二苯基-1-亚甲基环丙烷与 5a 反应会生成 60%的 6a。根据产物和反应速率对上述反应的机理进行了讨论。P(OMe)3 与 5a 的 Rh 中心配位,导致 CO 配体插入 Rh-C 键,生成 [Rhη2-CO-CH2CPh2CH=CH2-κC1}(P(OMe)3)3] (7)。