Synthesis and structural characterization of (pyrazolyl)alkenyl Fischer carbene complexes of chromium and tungsten

Reactions of 1-alkynyl Fischer carbene complexes (CO)5MC(OEt)(CCPh) (M = Cr, W) with substituted pyrazoles afforded (pyrazolyl)alkenyl Fischer carbene complexes with an exclusive (E)-configuration in mild to excellent yields.