Homogeneous and Solid-Gas Hydrogenation of Alkynes in the Presence of the Clusters Fe 3 (CO) 9 (ε- R C 2 R 1 ) { R = R 1 =Ph, Et; R =Me, R 1 =Ph}: Characterization of New Metallacyclic Derivatives

Abstract

The clusters Fe3(CO)9(RC2R1) (R=R1=Ph, Et; R=Me, R1=Ph), complexes 1a, 1b, 1c, containing an alkyne bound in perpendicular fashion with respect to a cluster edge, catalyze the hydrogenation of some acetylenes either under homogeneous and solid–gas conditions. We hypothesize that cluster catalysis occurs and that the catalytic activity is related to the coordinating ability of the alkynic substrates. Competition between hydrogenation and formation of metallacyclic byproducts occurs. The new metallacyclic derivatives Fe3(CO)6(e-CO)2{(RC2R1)(R2C2R3)}, Fe2(CO)6{(RC2R1)(R2C2R3)} {R=R1=Et, R2=R3=H, Ph; R2=Me, R3=Et, Ph; R2=H, R3=But. R=R1=Ph, R2=Me, R3=Et, Ph} (complexes 2, 3) were found both in the homogeneous reaction mixtures and after the solid–gas reactions. The formation of these products lowers the catalytic activity.