Development and mechanistic investigation of the dehydrogenation of alcohols with an iron(iii) salen catalyst

The iron(iii) salen complex (R,R)-N,N '-bis(salicylidene)-1,2-cyclohexanediamineiron(iii) chloride has been developed as a catalyst for the acceptorless dehydrogenation of alcohols. The complex catalyzes the direct synthesis of imines in good yields from different primary alcohols and amines with the liberation of hydrogen gas. The mechanism has been investigated experimentally with labelled substrates and theoretically with density functional theory calculations. In contrast to the corresponding manganese(iii) salen-catalyzed dehydrogenation, it has not been possible to identify a homogeneous catalytic pathway with the iron complex. Instead, poisoning experiments with trimethylphosphine and mercury indicated that the catalytically active species are heterogeneous small iron particles.

Automated summary

The iron(iii) salen complex (R,R)-N,N'-bis(salicylidene)-1,2-cyclohexanediamineiron(iii) chloride is a catalyst for the acceptorless dehydrogenation of alcohols, leading to the synthesis of imines and hydrogen gas liberation. Experimental and theoretical studies have revealed that the catalytic mechanism involves heterogeneous small iron particles, in contrast to the homogeneous catalytic pathway observed with the corresponding manganese(iii) salen complex.