Scandium has been declared one of the ‘nationally critical materials’ due to its widespread utility in commercial applications and difficulty in establishing a reliable supply chain. While Sc(0) is often thought to be ‘rare’, it is more abundant than boron; however, it is never found as the main component of naturally occurring minerals. Therefore, scandium is typically isolated as a by-product of other processes, such as mining tailings of other metals or rare earth refining. Our efforts have focused on the isolation of Sc(0) or Sc2O3 via recycling methods. For this study we have investigated the recovery of Sc(0) from a support by developing the fundamental chemistry of this understudied element. The exploration of the hydrogen halide acidification of Sc(0) led to isolation of [Sc(H2O)n]3[X] (X = Cl (n = 6), Br, I (n = 7)) at low temperature and [(H2O)nSc(μ-OH)]2[X] (X = Cl, Br, I) at ambient or elevated temperatures. Dehydration by literature routes (SO2Cl/THF) produced monohydrated complexes [(THF)5Sc(H2O)]3[X] (X = Cl, Br]; whereas, modification of this route (SO2Cl/DME/THF) led to dry salts: [(solv)ScCl3] (solv = THF, DMF, MeCN), [ScX2(MeOH)4][X], and [Sc(DMSO)6]3[X]. Conversion to scandium amide derivatives, [Sc(NR2)3] (R = Me, Pri, N(SiMe3)2], was facile following established metathesis routes. The amide complexes were then used to prepare a series of scandium alkoxides via an alcoholysis (ortho-isopropylphenol, dimethylphenol, diisopropylphenyl, di-tert-butylphenol, dimethyl-tert-butylphenol, tert-butyldimethylsilanol) of the amide. These compounds were fully characterized using 45Sc solution and solid state NMR spectroscopy and single crystal X-ray diffraction. In addition, the synthesis and characterization of these compounds, the various attempts and subsequent results to reduce these precursors to Sc(0) (both chemically and electrochemically) will be presented. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04- 94AL85000.

Fundamental coordination chemistry for the recycle efforts of scandium

251st National Meeting (2016)

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