Selective Isomerization of Terminal Alkenes to ( Z )-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex

Positional and stereochemical selectivity in the isomerization of terminal alkenes to internal alkenes is observed using the cis -Mo(CO) 4 (PPh 3 ) 2 precatalyst. A p -toluenesulfonic acid (TsOH) cocatalyst is essential for catalyst activity. Various functionalized terminal alkenes have been converted to the corresponding 2-alkenes, generally favoring the Z isomer with selectivity as high as 8:1 Z: E at high conversion. Interrogation of the catalyst initiation mechanism by 31 P NMR reveals that cis -Mo(CO) 4 (PPh 3 ) 2 reacts with TsOH at elevated temperatures to yield a phosphine-ligated Mo hydride (MoH) species. Catalysis may proceed via 2,1-insertion of a terminal alkene into a MoH group and stereoselective β-hydride elimination to yield the ( Z )-2-alkene.