Rare-Earth Metal Allyl and Hydrido Complexes Supported by an (NNNN)-Type Macrocyclic Ligand: Synthesis, Structure, and Reactivity toward Biomass-Derived Furanics

The preparation and characterization of a series of neutral rare‐earth metal complexes [Ln(Me3TACD)(η3‐C3H5)2] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane anion (Me3TACD−) are reported. Upon treatment of the neutral allyl complexes [Ln(Me3TACD)(η3‐C3H5)2] with Brønsted acids, monocationic allyl complexes [Ln(Me3TACD)(η3‐C3H5)(thf)2][B(C6X5)4] (Ln=La, Ce, Nd, X=H, F) were isolated and characterized. Hydrogenolysis gave the hydride complexes [Ln(Me3TACD)H2]n (Ln=Y, n=3; La, n=4; Sm). X‐ray crystallography showed the lanthanum hydride to be tetranuclear. Reactivity studies of [Ln(Me3TACD)R2]n (R=η3‐C3H5, n=0; R=H, n=3,4) towards furan derivatives includes hydrosilylation and deoxygenation under ring‐opening conditions. Rare catalysts: Hydrosilylation of furfural and deoxygenation of furan under ring‐opening conditions was catalyzed by neutral complexes [Ln(Me3TACD)(η3‐C3H5)2] (Ln=Y, La, Ce, Pr, Nd, Sm) supported by the 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane Me3TACD− ion. Monocationic allyl [Ln(Me3TACD)(η3‐C3H5)(thf)2][B(C6X5)4] (Ln=La, Ce, Nd, X=H, F) and hydrido complexes [Ln(Me3TACD)H2]n (Ln=Y, La, Sm, n=3,4) were synthesized from the bis(allyl) precursors and characterized (see picture).