Substituent effect on reactions of ReH5(PMe2Ph)(3) with propargyl alcohols

摘要

Reactions of the rhenium polyhydride ReH5(PMe2Ph)(3) with propargyl alcohols in the presence of HCl can produce gamma-hydroxycarbyne, vinylcarbyne and eta(2)-vinyl complexes, the relative amounts of which are dependent on the substituents of the propargyl alcohols. The reaction with the bis-alkyl substituted propargyl alcohol HC CC(OH)Me-2 produced only the vinylcarbyne complex ReCl2(=CCH=CMe2)(PMe2Ph)(3). The reaction with the bis-alkynyl substituted propargyl alcohol HC=CC(OH)(C=CSiMe3)(2) produced only the eta(2)-vinyl complex ReCl2{eta(2)-CH2=CC(OH)(C=CSiMe3)(2)}(PMe2Ph)(3). The reactions with the bis-(o-functionalized aryl) substituted propargyl alcohols HC CC(OH)Ar-2 (Ar = o-C6H4Br, o,o'-C6H3Cl2) produced only the gamma-hydroxycarbyne complexes Re{ CCH2C(OH)Ar-2}Cl-2(PMe2Ph)(3). The reactions with the monoaryl substituted propargyl alcohol HC CC(OH)Ph(C CSiMe3) produced a mixture of the vinylcarbyne Re{ CCH CPh(C CSiMe3)} Cl-2(PMe2Ph)(3), the gamma-hydroxycarbyne Re{ CCH2C(OH)Ph(C=CSiMe3)}Cl-2(PMe2Ph)(3) and the eta(2)-vinyl complex Re{eta(2)-CH2=CC(OH)Ph(C CSiMe3)}Cl-2(PMe2Ph)(3). The selectivity for the products can be related to the steric and electronic effect of the substituents of propargyl alcohols. In general, formation of eta(2)-vinyl complexes is favored over carbyne complexes when the substituents are sterically less demanding. Formation of gamma-hydroxycarbyne complexes is favored over vinylcarbyne complexes when the substituents are electron withdrawing.