Solution Synthesis, Structure, and CO2 Reduction Reactivity of a Scandium(II) Complex, {Sc[N(SiMe3)2]3}

• Published in: Angewandte Chemie International Edition Vol. 56; no. 8; pp. 2050 - 2053
• Main Authors: Woen, David H., Chen, Guo P., Ziller, Joseph W., Boyle, Timothy J., Furche, Filipp, Evans, William J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 13.02.2017
• Edition: International ed. in English
• Subjects: Anions; Carbon dioxide; Cesium; Crystallography; Lanthanides; Line spectra; low-valent metals; Metals; Nuclei; Oxalic acid; Oxidation; Rare earth elements; rare earths; reduction; Reduction (metal working); Salts; Scandium; Valence
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201611758

The first crystallographically characterizable complex of Sc2+, [Sc(NR2)3]− (R=SiMe3), has been obtained by LnA3/M reactions (Ln=rare earth metal; A=anionic ligand; M=alkali metal) involving reduction of Sc(NR2)3 with K in the presence of 2.2.2‐cryptand (crypt) and 18‐crown‐6 (18‐c‐6) and with Cs in the presence of crypt. Dark maroon [K(crypt)]+, [K(18‐c‐6)]+, and [Cs(crypt)]+ salts of the [Sc(NR2)3]− anion are formed, respectively. The formation of this oxidation state of Sc is also indicated by the eight‐line EPR spectra arising from the I=7/2 45Sc nucleus. The Sc(NR2)3 reduction differs from Ln(NR2)3 reactions (Ln=Y and lanthanides) in that it occurs under N2 without formation of isolable reduced dinitrogen species. [K(18‐c‐6)][Sc(NR2)3] reacts with CO2 to produce an oxalate complex, {K2(18‐c‐6)3}{[(R2N)3Sc]2(μ‐C2O4‐κ1O:κ1O′′)}, and a CO2− radical anion complex, [(R2N)3Sc(μ‐OCO‐κ1O:κ1O′)K(18‐c‐6)]n. Scandium's crowning: The first crystallographically characterizable complex of scandium in the +2 oxidation state was isolated from the reduction of Sc(NR2)3 (R=SiMe3). The low oxidation state was characterized by EPR and UV/Vis spectroscopy and DFT calculations. Reactivity studies with CO2 resulted in the isolation of both an oxalate complex and a rare CO2− species.