SUPPLEMENTARY INFORMATION

Synthesis and characterization of a series of mixed-cation borohydrides of scandium: [Cat][Sc(BH4)4], [Cat]=[Me4N], [n-Bu4N], and [Ph4P]

A. Starobrata, T. Jarońb*#, W. Grochalab

a Faculty of Physics, University of Warsaw, Pasteura 5, 02093 Warsaw, Poland

b Centre of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw, Poland

# current corresponding address: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC 20015, USA

*e-mail:

Figure S1. Powder X-ray diffraction (PXD) pattern of [Bu4N][Sc(BH4)4] – compound 2: (a) as synthesized; (b), (c), (d) various batches of product purified via extraction with dichloromethane (DCM) and filtration of LiCl by-product. Note that in case of (d) ca. 1.65 wt% LiCl remains in the sample as it is not completely filtered off by the fritted glass funnel due to a very small grain size. All unmarked diffraction peaks originate from the target compound 2.

Figure S2. The FTIR spectra of (a) [Me4N][Sc(BH4)4] – 1, (b)[Bu4N][Sc(BH4)4] – 2, (c)[Ph4P][Sc(BH4)4] – 3, (d) [Bu4N][Y(BH4)4] – [S1]and (e) Li[Sc(BH4)4] – as prepared, in mixture with 3 equivalents of LiCl.

Table S1. The most significant IR wavenumbers for [Me4N][Sc(BH4)4] – 1, [Bu4N][Sc(BH4)4]– 2, [Ph4P][Sc(BH4)4] – 3, [Bu4N][Y(BH4)4] – TBAYB and Li[Sc(BH4)4]. Relative intensity of absorption bands: vs – very strong, s – strong, m – medium, w – weak, vw– very weak.

1 / 2 / 3 / TBAYB / Li[Sc(BH4)4]
3023 vw
2960 vw
2924 vw
2488 s
2292 w
2234 vs
2152 m
1629 vw
1484 vs
1355 m
1286 m
1262 m
1182 vs
1110 s
949 s
910 w
710 vw / 2999 w
2964 vs
2936 m
2900 w
2876 m
2734 vw
2494 s
2360 w
2229 vs
2150 w
1472 vs
1401 w
1382 m
1360 w
1322 w
1267 w
1180 vs
1100 s
1057 w
1032 m
992 vw
926 w
895 w
885 w
798 vw
736 m / 3079 w
3069 vw
3054 vw
3025 vw
3010 vw
2996 vw
2461 m
2227 m
2138 w
1989 vw
1967 vw
1920 vw
1898 vw
1814 vw
1768 vw
1671 vw
1588 w
1576 vw
1482 m
1442 m
1435 vs
1387 w
1339 w
1311 w
1257 w
1189 m
1176 s
1109 vs
1027 w
999 m
975 w
924 vw
847 vw
750 m
723 vs
688 vs
616 vw
537 s
526 vs / 2964 vs
2936 s
2876 s
2477 s
2439 s
2391 s
2291 m
2220 vs
2162 s
2054 w
1483 s
1472 s
1383 m
1362 w
1347 w
1313 m
1285 m
1193 vs
1100 m
1066 w
1030 m
925 vw
882 w
799 vw
738 w / 2466 s
2390 w
2294 s
2259 s
2240 s
1631 vw
1325 s
1194 vs
1112 m
904 w
699 w

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Figure S3. Rietveld refinement of as-prepared [Me4N][Sc(BH4)4] – compound 1. Measured and calculated powder diffraction (PXD) pattern have been plotted in black and red color, respectively. Positions of Bragg reflections has been marked in blue – upper set corresponds to LiCl and bottom set corresponds to compound1. The difference curve has been plotted in the bottom. Profile parameters: wRp = 0.94%, GOF = 1.81, cwRp = 4.85%, R(obs)[Me4N][Sc(BH4)4] = 4.40%, R(obs)LiCl = 0.89%.

Figure S4. Rietveld refinement of one of the batches of purified [Bu4N][Sc(BH4)4] – compound 2. Measured and calculated powder diffraction (PXD) pattern have been plotted in black and red color, respectively. Positions of Bragg reflections has been marked in blue – upper set corresponds to LiCl and bottom set corresponds to compound 1. The difference curve has been plotted in the bottom. Profile parameters: wRp = 1.01%, GOF = 1.55, cwRp = 5.20%, R(obs)[Bu4N][Sc(BH4)4] = 4.78%, R(obs)LiCl = 2.27%. The refined phase amounts are 98.4(15) wt% of [Bu4N][Sc(BH4)4] and 1.65(7) wt% of LiCl.

Figure S5. Rietveld refinement of one of the batches of purified [Ph4P][Sc(BH4)4] – compound 3. Measured and calculated powder diffraction (PXD) pattern have been plotted in black and red color, respectively. Positions of Bragg reflections has been marked in blue. The difference curve has been plotted in the bottom. Profile parameters: wRp = 2.92%, GOF = 3.39, cwRp = 10.44%, R(obs)[Ph4P][Sc(BH4)4] = 6.85%. The fit quality is lowered by the peaks from unknown impurities, which are clearly visible in the difference pattern.

Table S2. Comparison of geometries of [(n–Bu)4N]+ cation in several structurally characterized derivatives. Selected distances are given in [Å] and bond angles in [o]. Cat.–an. – distance between cation and central atom of anion. Type of coordination of [(n–Bu)4N]+ by anions is described. T – temperature, RT – room temperature, CN – coordination number.

Anion / [Sc(BH4)4]– / BH4– / [Y(BH4)4]– / FeCl4– / PF6– / HSO4– / I– / [(n–Bu)4B]–
T /K / RT / RT / 100 K / RT / 110 K / 120 K / 100 K / RT
Space group / Pnna / P2/c / P21/c / Pnna / P21/c / P21/c / C2/c / I41/a

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Reference / This work / [S[i]] / [S1] / [S[ii]] / [S[iii]] / [S[iv]] / [S[v]] / [S[vi]]
Bond lengths
C–N min. / 1.48(2) / 1.483(14) / 1.516(3) / 1.507(3) / 1.515(2) / 1.505(5) / 1.517(2) / 1.519(3)
C–N max. / 1.51(2) / 1.546(12) / 1.529(3) / 1.524(3) / 1.529(2) / 1.532(5) / 1.522(2) / 1.519(3)
C–C min. / 1.40(6) / 1.46(3) / 1.516(2) / 1.440(6) / 1.516(3) / 1.349(8) / 1.516(2) / 1.456(7)
C–C max. / 1.52(2) / 1.551(13) / 1.533(3) / 1.523(5) / 1.531(2) / 1.657(9) / 1.525(3) / 1.511(4)
Bond angles
C–N–C min. / 106.2(9) / 91.8(9) / 108.5(2) / 108.5(2) / 108.4(1) / 105.0(3) / 108.6(1) / 105.0(1)
C–N–C max. / 113.1(19) / 119.2(13) / 111.1(2) / 111.6(2) / 111.2(1) / 112.2(3) / 111.1(1) / 111.8(1)
N–C–C min. / 117.9(15) / 111.7(7) / 115.4(2) / 117.1(2) / 114.6(1) / 114.5(3) / 114.9(1) / 115.9(2)
N–C–C max. / 118.0(16) / 117.2(10) / 116.4(2) / 117.7(2) / 116.8(1) / 117.2(3) / 115.4(1) / 115.9(2)
C–C–C min. / 112.5(14) / 102.1(11) / 108.6(2) / 109.7(3) / 109.6(1) / 103.8(4) / 109.8(1) / 112.8(3)
C–C–C max. / 125(10) / 121.4(12) / 113.4(2) / 116.2(3) / 114.4(1) / 135.7(6) / 111.3(2) / 117.8(4)
Cation–anion packing
Cat.–an. min. / 4.973(15) / 4.404(18) / 5.735(2) / 5.7858(4) / 5.111(1) / 4.596(3) / 5.048(1) / 5.2901(1)
Cat.–an. coordination / Trigonal bipyramid / Trigonal + tetrahedral / Tetrahedral / Trigonal bipyramid / Trigonal pyramid / Trigonal + tetrahedral / Square / Linear
Cat.–an. CN [30] / 5 / 3; 4 / 4 / 5 / 4 / 3; 4 / 4 / 2

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Figure S6. The coordination of [Me4N]+ cation by six [Sc(BH4)4]- anions in the crystal structure of the compound 1.

Figure S7. The coordination of [Bu4N]+ cation by five [Sc(BH4)4]- anions in the crystal structure of the compound 2.

Figure S8. The cation-anion network in the crystal structure of the compound 2 (Sc – violet balls, N – blue balls).

Figure S9. The cation-anion network in the crystal structure of the compound 3 (Sc – violet balls, P – red balls). Note the distorted NaCl-type network.

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Figure S10. The time-resolved mass spectrum of the volatile products evolved during thermal decomposition of [Bu4N][Sc(BH4)4] – 2.The main decomposition products are H2 (M/Z=2) and various fragments of [Bu4N]+ cations.


Figure S11. The time-resolved mass spectrum of the volatile products evolved during thermal decomposition of [Ph4P][Sc(BH4)4] – 3. The main decomposition products are H2 (M/Z=2) and various fragments of [Bu4N]+ cations (the other M/Z).

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Supplementary references

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[i][S] T. Jaroń, W. Wegner, M. K. Cyrański, Ł. Dobrzycki, W. Grochala, J. Solid State Chem., 191 (2012) 279.

[ii][S] M. T. Hay, S. J. Geib, Acta Cryst., E61 (2005) m190.

[iii][S] Z. Stein, I. Goldberg, Acta Cryst. E, 61 (2005) o272.

[iv][S] M. E. Light, P. A. Gale, M. B. Hursthouse, Acta Cryst. E, 57 (2001) o705.

[v][S] W. Prukała, B. Marciniec, M. Kubicki, Acta Cryst. E, 63 (2007) o1464.

[vi][S] B. Kaitner, V. Stilinović, Acta Cryst. A, 66 (2010) 441.