Hydrido and Allyl/Hydrido Complexes of Early Lanthanides Supported by an NNNN‐Type Macrocyclic Ligand

Hydrogenation of the neutral bis(allyl) complexes of the early lanthanides [Ln(Me 3 TACD)(η 3 ‐C 3 H 5 ) 2 ] [(Me 3 TACD)H = 1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane, Me 3 [12]aneN 4 ] with phenylsilane gave the tetranuclear octahydrido complexes [Ln(Me 3 TACD)(μ‐H) 2 ] 4 [Ln = Ce ( 1 ‐Ce), Pr ( 2 ‐Pr)] or the dinuclear allyl/hydrido complexes [Ln(Me 3 TACD)(η 3 ‐C 3 H 5 )(μ‐H)] 2 [Ln = Nd ( 3 ‐Nd), Sm ( 4 ‐Sm)], which were isolated and characterized. The structures of 1 ‐Ce and 2 ‐Pr are constructed of a tetrahedral Ln 4 H 8 core. Single‐crystal X‐ray diffraction analyses of 3 ‐Nd and 4 ‐Sm revealed a C 2 symmetric planar Ln 2 H 2 core. The experimental structures agreed with the results of DFT calculations, which predict that the nuclearity of the dihydrido complexes depend on the ionic radius of the metal. Compounds 1 ‐Ce, 2 ‐Pr, 3 ‐Nd and 4 ‐Sm were tested as catalysts in the copolymerization of cyclohexene oxide with CO 2 to give highly carbonate‐linked copolymers with moderate activities.