Over the last two decades, terminal imido complexes of early transition metals, which contain the M = N double bond, have attracted intensive interest and have been extensively studied. [1] The research on such complexes has revealed rich reactivities and applications in the group transfer and catalytic reactions. In contrast, the chemistry of rare-earthmetal terminal imido complexes remains unexplored. Owing to a relative mismatch in LUMO/HOMO orbital energies between the d 0 rare-earth-metal ions and the imido groups, the Ln=N (Ln = rare-earth metal) bonds are highly polar and reactive. [2] The rare-earth-metal terminal imido species once formed can easily assemble into more stable m or m n (n = 3, 4) bridged bimetallic or multimetallic species, [3,4] or undergo reactions with solvents by C À H bond activation. [5] Meanwhile, the chemistry of the rare-earth-metal terminal imido complexes is of great interest, as the highly polar and reactive Ln= N bonds should lead to rich reactivity. Recently, we have synthesized and characterized the first rare-earth-metal terminal imido complex, a scandium terminal imido complex. [6] Herein, we uncover reactions of the scandium terminal imido complex with a series of unsaturated substrates that show interesting reactivity and lead to novel products.
When a C 6 D 6 solution of the scandium terminal imido complex, [MeC(NAr)CHC(Me)(NCH 2 CH 2 N(Me)CH 2 CH 2 NMe 2 )Sc = NAr] (Ar = 2,6-(iPr) 2 C 6 H 3 ) (1), [7,8] was exposed to CO 2 (1.0 atm) at room temperature, the solution changed from red to pale yellow in 30 minutes. Monitoring of the reaction by 1 H NMR spectroscopy revealed that 1 was almost completely converted into a new complex 2. A subsequent scaled-up reaction provided 2 as colorless crystals in 53 % isolated yield. 2 was characterized by NMR spectroscopy, elemental analysis, and X-ray crystallography, confirming that 2 is a scandium dicarboxylate (Scheme 1). Rare-earth-metal carboxylates are common, but to our knowledge, this type of rare-earth-metal dicarboxylate complexes has not been
[*] J.