Chemistry of Metal-Metal-Bonded Early-Late Heterobimetallics:Cooperative Reactions of Functional Groups at a Persistent Organometallic Zr-Rh Framework

摘要

The reaction of(C_5H_4-PPh_2)_2Zr(CH_3)_2(5a)with HRh(CO)(PPh_3)_3(6)leads to methane evolution and the formation of the early- late heterobimetallic complex [(mu-C_5H_4- PPh_2)_2-(H_3C-Zr-Rh(CO)PPh_3)](7a),which was characterized by X-ray diffraction(d(Zr-Rh)= 2.863(1)A).The analogous dialkylphosphino-substituted complexes(C_5H_4-PR_2)_2Zr(CH_3)_2(5b,R=isopropyl;5c,R=cyclohexyl)react with the hydrido-rhodium reagent 6 to initially form the analogous bimetallic(Zr-Rh)complexes 7b,c,respectively.However,these complexes are not stable at ambient temperature in toluene solution,due to an equilibration with the products [(mu-C_5H_4-PR_2)_2(mu-CH_3-Zr-Rh(PPh_3))](11)and [(mu-C_5H_4-PR_2)_2(H_3C-Zr-Rh-(CO)_2](10).Treatment of the initially formed complexes 7b,c with carbon monoxide rapidly leads to the formation of the H_3C(Zr-Rh)-dicarbonyl complexes 10b,c.The product l0c was characterized by X-ray crystal structure analysis.The systems 7b,c are not stable in dichloromethane.They react readily with the solvent by abstraction of two chlorine atoms to yield the compounds [(mu-C_5H_4-PR_2)_2(mu-O=C(CH_3))(Cl-Zr-Rh-Cl)](12b,c).Both products were characterized by X-ray diffraction.A cooperative action of the involved metals is assumed to account for the observed reactions at the intact heterobimetallic Zr-Rh framework.