名称:
A Four-Electron π-Alkyne Complex as Precursor for Allenylidene Derivatives: Preparation, Structure, and Reactivity of [Os(η5-C5H5)(CCCPh2)L(PiPr3)]PF6 (L = CO, PHPh2)
摘要:
The pi-alkyne complex [Os(eta(5)-C5H5){eta(2)-HCdropCC(OH)Ph-2}((PPr3)-Pr-i)]PF6 (1), where the alkyne acts as a four-electron donor ligand, reacts with CO to give initially the two-electron pi-alkyne derivative [Os(eta(5)-C5H5){ eta(2)-HCdropCC(OH)Ph2}(CO)((PPr3)-Pr-i)]PF6 (2). In dichloromethane, complex 2 isomerizes into the hydroxyvinylidene [Os(eta(5)-C5H5){=C=CHC(OH)Ph-2}(CO)((PPr3)-Pr-i)]PF6 (3), which dehydrates to afford the allenylidene [Os(eta(5)-C5H5)(=C=C=CPh2)(CO)((PPr3)-Pr-i)]PF6 (4). Complex 1 also reacts with PHPh2. In this case, the reaction initially gives the hydridehydroxyalkynyl intermediate [OsH(eta(5)-C5H5){CdropCC(OH)Ph-2}(PHPh2)((PPr3)-Pr-i)]PF6 (5). Similar to 2, in dichloromethane, complex 5 isomerizes into the hydroxyvinylidene [Os(eta(5)-C5H5){= C=CHC(OH)Ph-2}(PHPh2)((PPr3)-Pr-i)]PF6 (6), which dehydrates to afford [Os(eta(5)-C5H5)(=C=C= CPh2)(PHPh2)((PPr3)-Pr-i)]PF6 (7). In the presence of HPF6, complex 4 isomerizes into [Os(eta(5)-C5H5)(3-phenyl-1-indenylidene)(CO)((PPr3)-Pr-i)]PF6 (8). Under the same conditions, compound 7 affords the dicationic alkenylcarbyne derivative [Os(eta(5)-C5H5)(dropC-CH=CPh2)(PHPh2)((PPr3)-Pr-i)](PF6)(2) (9). The allenylidene ligand of 4 undergoes the addition of carbodiimides to give iminiumazetidinylidenemethyl derivatives. The reaction with N,N'-dicyclohexylcarbodiimide affords [Os(eta(5)-C5H5){CH=CC(Ph)(2)N(Cy)=C=N=C(CH2)(4)CH2}(CO)((PPr3)-Pr-i)]PF6 (10), whereas the reaction with N,N'-diisopropylcarbodiimide leads to [Os(eta(5)-C5H5){CH=CC(Ph)(2)N(Pr-i) =C=N=C(CH3)(2)}(CO)((PPr3)-Pr-i)]PF6 (11). Complex 4 also reacts with methanol and aniline. The addition of methanol to the allenylidene 4 gives [Os(eta(5)-C5H5){C(OCH3)CH=CPh2}(CO)((PPr3)-Pr-i)]PF6 (12), which undergoes deprotonation at the CH=CPh2 group to afford Os(eta(5)-C5H5){C(OCH3)=C=CPh2}(CO)((PPr3)-Pr-i) (13). The addition of aniline leads to [Os(eta(5)-C5H5){C(CH=CPh2)=NHPh}(CO)((PPr3)-Pr-i)]PF6 (14). Treatment of 14 with NaOCH3 gives Os(eta(5)-C5H5){C(CH=CPh2)=NPh}(CO)((PPr3)-Pr-i) (15). Complexes 4, 7, and 8 have been characterized by X-ray diffraction analysis.