The scandium(III) cations in the structures of pentaaqua(biuret-
2O,
O')scandium(III) trichloride monohydrate, [Sc(C
2H
5N
3O
2)(H
2O)
5]Cl
3·H
2O, (I), and tetrakis(biuret-
2O,
O')scandium(III) trinitrate, [Sc(C
2H
5N
3O
2)
4](NO
3)
3, (II), are found to adopt very different coordinations with the same biuret ligand. The roles of hydrogen bonding and the counter-ion in the establishment of the structures are described. In (I), the Sc
3+ cation adopts a fairly regular pentagonal bipyramidal coordination geometry arising from one
O,
O'-bidentate biuret molecule and five water molecules. A dense network of N-H
Cl, O-H
O and O-H
Cl hydrogen bonds help to establish the packing, resulting in dimeric associations of two cations and two water molecules. In (II), the Sc
3+ cation (site symmetry 2) adopts a slightly squashed square-antiprismatic geometry arising from four
O,
O'-bidentate biuret molecules. A network of N-H
O hydrogen bonds help to establish the packing, which features [010] chains of cations. One of the nitrate ions is disordered about an inversion centre. Both structures form three-dimensional hydrogen-bond networks.
Supporting information
CCDC references: 690177; 690178
To prepare (I), 0.1 M aqueous solutions of ScCl3 (10 ml) and biuret
(10 ml) were mixed and a small quantity of dilute hydrochloric acid was added,
resulting in a colourles soluton. Colourless blocks of (I) grew over several
days as the water slowly evaporated. Compound (II) was prepared in the same
way, with 0.1 M Sc(NO3)3 replacing the scandium chloride solution.
Large colourless slabs of (II) grew as the water evaporated.
N-bound H atoms were positioned geometrically (N—H = 0.88 Å) and refined as
riding [Uiso(H) = 1.2Ueq(N)]. Water H atoms were located in
difference maps and refined as riding in their as-found relative positions
[Uiso(H) = 1.2Ueq(O)].
For both compounds, data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997), and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).
(vii).
-->
(I) pentaaqua(biuret-
κ2O,O')scandium(III) trichloride monohydrate,
top
Crystal data top
[Sc(C2H5N3O2)(H2O)5]Cl3·H2O | F(000) = 744 |
Mr = 362.50 | Dx = 1.662 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 3458 reflections |
a = 15.2430 (7) Å | θ = 2.9–27.5° |
b = 7.5653 (5) Å | µ = 1.09 mm−1 |
c = 14.1276 (9) Å | T = 120 K |
β = 117.247 (4)° | Block, colourless |
V = 1448.39 (15) Å3 | 0.40 × 0.20 × 0.15 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD diffractometer | 3308 independent reflections |
Radiation source: fine-focus sealed tube | 2988 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.025 |
ω and ϕ scans | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | h = −19→19 |
Tmin = 0.670, Tmax = 0.854 | k = −9→9 |
17376 measured reflections | l = −18→17 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difmap (O-H) and geom (N-H) |
R[F2 > 2σ(F2)] = 0.023 | H-atom parameters constrained |
wR(F2) = 0.060 | w = 1/[σ2(Fo2) + (0.0242P)2 + 1.028P] where P = (Fo2 + 2Fc2)/3 |
S = 1.06 | (Δ/σ)max = 0.001 |
3308 reflections | Δρmax = 0.41 e Å−3 |
155 parameters | Δρmin = −0.50 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0036 (5) |
Crystal data top
[Sc(C2H5N3O2)(H2O)5]Cl3·H2O | V = 1448.39 (15) Å3 |
Mr = 362.50 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 15.2430 (7) Å | µ = 1.09 mm−1 |
b = 7.5653 (5) Å | T = 120 K |
c = 14.1276 (9) Å | 0.40 × 0.20 × 0.15 mm |
β = 117.247 (4)° | |
Data collection top
Nonius KappaCCD diffractometer | 3308 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | 2988 reflections with I > 2σ(I) |
Tmin = 0.670, Tmax = 0.854 | Rint = 0.025 |
17376 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.023 | 0 restraints |
wR(F2) = 0.060 | H-atom parameters constrained |
S = 1.06 | Δρmax = 0.41 e Å−3 |
3308 reflections | Δρmin = −0.50 e Å−3 |
155 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Sc1 | 0.279407 (18) | 0.52397 (3) | 0.76641 (2) | 0.00972 (8) | |
C1 | 0.19226 (10) | 0.55210 (19) | 0.51566 (11) | 0.0132 (3) | |
C2 | 0.08651 (10) | 0.69220 (19) | 0.57832 (11) | 0.0130 (3) | |
N1 | 0.20169 (10) | 0.50241 (19) | 0.43149 (10) | 0.0212 (3) | |
H1 | 0.2575 | 0.4559 | 0.4393 | 0.025* | |
H2 | 0.1521 | 0.5157 | 0.3674 | 0.025* | |
N2 | 0.10344 (9) | 0.62660 (16) | 0.49725 (9) | 0.0132 (2) | |
H3 | 0.0559 | 0.6325 | 0.4315 | 0.016* | |
N3 | 0.00641 (9) | 0.79154 (17) | 0.54877 (10) | 0.0179 (3) | |
H4 | −0.0096 | 0.8331 | 0.5970 | 0.021* | |
H5 | −0.0307 | 0.8158 | 0.4810 | 0.021* | |
O1 | 0.26138 (7) | 0.53469 (15) | 0.60730 (8) | 0.0157 (2) | |
O2 | 0.14031 (7) | 0.65574 (14) | 0.67355 (8) | 0.0157 (2) | |
O3 | 0.19635 (8) | 0.53287 (15) | 0.85603 (8) | 0.0183 (2) | |
H6 | 0.2139 | 0.5018 | 0.9181 | 0.022* | |
H7 | 0.1315 | 0.5607 | 0.8266 | 0.022* | |
O4 | 0.38819 (7) | 0.49064 (13) | 0.92988 (8) | 0.0136 (2) | |
H8 | 0.3972 | 0.3901 | 0.9647 | 0.016* | |
H9 | 0.4009 | 0.5714 | 0.9765 | 0.016* | |
O5 | 0.40281 (7) | 0.39425 (15) | 0.76046 (8) | 0.0177 (2) | |
H10 | 0.4028 | 0.3662 | 0.6989 | 0.021* | |
H11 | 0.4533 | 0.3494 | 0.8111 | 0.021* | |
O6 | 0.34154 (8) | 0.78173 (14) | 0.79497 (8) | 0.0171 (2) | |
H12 | 0.3178 | 0.8561 | 0.7442 | 0.020* | |
H13 | 0.4041 | 0.7995 | 0.8333 | 0.020* | |
O7 | 0.21979 (8) | 0.26624 (15) | 0.73430 (9) | 0.0207 (2) | |
H14 | 0.2274 | 0.1888 | 0.6938 | 0.025* | |
H15 | 0.1590 | 0.2357 | 0.7302 | 0.025* | |
Cl1 | 0.24740 (3) | 0.00162 (5) | 0.59188 (3) | 0.01852 (10) | |
Cl2 | 0.02112 (2) | 0.14336 (5) | 0.70783 (3) | 0.01652 (9) | |
Cl3 | 0.43907 (2) | 0.35199 (5) | 0.55806 (3) | 0.01596 (9) | |
O8 | 0.57430 (8) | 0.26397 (14) | 0.91828 (8) | 0.0166 (2) | |
H16 | 0.5662 | 0.1510 | 0.9339 | 0.020* | |
H17 | 0.6246 | 0.2645 | 0.9025 | 0.020* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Sc1 | 0.00743 (13) | 0.01241 (14) | 0.00796 (13) | 0.00051 (9) | 0.00235 (10) | −0.00001 (9) |
C1 | 0.0127 (7) | 0.0137 (7) | 0.0117 (6) | −0.0012 (5) | 0.0042 (5) | −0.0002 (5) |
C2 | 0.0111 (6) | 0.0129 (7) | 0.0134 (6) | −0.0013 (5) | 0.0040 (5) | 0.0008 (5) |
N1 | 0.0151 (6) | 0.0353 (8) | 0.0092 (6) | 0.0038 (5) | 0.0020 (5) | −0.0042 (5) |
N2 | 0.0101 (6) | 0.0164 (6) | 0.0087 (5) | 0.0016 (5) | 0.0005 (5) | 0.0002 (5) |
N3 | 0.0127 (6) | 0.0222 (7) | 0.0147 (6) | 0.0057 (5) | 0.0029 (5) | 0.0014 (5) |
O1 | 0.0115 (5) | 0.0244 (6) | 0.0089 (5) | 0.0043 (4) | 0.0028 (4) | 0.0002 (4) |
O2 | 0.0121 (5) | 0.0224 (5) | 0.0119 (5) | 0.0059 (4) | 0.0049 (4) | 0.0046 (4) |
O3 | 0.0118 (5) | 0.0338 (6) | 0.0094 (5) | 0.0062 (4) | 0.0047 (4) | 0.0043 (4) |
O4 | 0.0127 (5) | 0.0151 (5) | 0.0089 (5) | 0.0013 (4) | 0.0016 (4) | 0.0004 (4) |
O5 | 0.0119 (5) | 0.0298 (6) | 0.0103 (5) | 0.0083 (4) | 0.0041 (4) | 0.0021 (4) |
O6 | 0.0143 (5) | 0.0151 (5) | 0.0153 (5) | −0.0015 (4) | 0.0012 (4) | 0.0019 (4) |
O7 | 0.0185 (6) | 0.0178 (5) | 0.0321 (6) | −0.0063 (4) | 0.0171 (5) | −0.0097 (5) |
Cl1 | 0.0262 (2) | 0.01783 (18) | 0.01257 (17) | −0.00048 (14) | 0.00978 (15) | −0.00053 (13) |
Cl2 | 0.00969 (17) | 0.02252 (19) | 0.01462 (17) | −0.00057 (13) | 0.00321 (13) | 0.00427 (13) |
Cl3 | 0.01396 (17) | 0.01700 (18) | 0.01731 (17) | 0.00036 (13) | 0.00749 (14) | −0.00218 (13) |
O8 | 0.0146 (5) | 0.0177 (5) | 0.0171 (5) | 0.0029 (4) | 0.0070 (4) | 0.0008 (4) |
Geometric parameters (Å, º) top
Sc1—O7 | 2.1109 (11) | N2—H3 | 0.8800 |
Sc1—O6 | 2.1242 (11) | N3—H4 | 0.8800 |
Sc1—O1 | 2.1377 (10) | N3—H5 | 0.8800 |
Sc1—O4 | 2.1541 (10) | O3—H6 | 0.8256 |
Sc1—O5 | 2.1572 (10) | O3—H7 | 0.9042 |
Sc1—O2 | 2.1595 (10) | O4—H8 | 0.8815 |
Sc1—O3 | 2.1629 (10) | O4—H9 | 0.8528 |
C1—O1 | 1.2468 (17) | O5—H10 | 0.8948 |
C1—N1 | 1.3162 (19) | O5—H11 | 0.8460 |
C1—N2 | 1.3770 (19) | O6—H12 | 0.8514 |
C2—O2 | 1.2444 (17) | O6—H13 | 0.8645 |
C2—N3 | 1.3278 (19) | O7—H14 | 0.8634 |
C2—N2 | 1.3766 (18) | O7—H15 | 0.9307 |
N1—H1 | 0.8800 | O8—H16 | 0.9051 |
N1—H2 | 0.8800 | O8—H17 | 0.8910 |
| | | |
O7—Sc1—O6 | 177.98 (4) | C1—N1—H1 | 120.0 |
O7—Sc1—O1 | 88.49 (4) | C1—N1—H2 | 120.0 |
O6—Sc1—O1 | 89.79 (4) | H1—N1—H2 | 120.0 |
O7—Sc1—O4 | 99.59 (4) | C2—N2—C1 | 122.21 (12) |
O6—Sc1—O4 | 81.17 (4) | C2—N2—H3 | 118.9 |
O1—Sc1—O4 | 142.85 (4) | C1—N2—H3 | 118.9 |
O7—Sc1—O5 | 82.45 (4) | C2—N3—H4 | 120.0 |
O6—Sc1—O5 | 95.98 (4) | C2—N3—H5 | 120.0 |
O1—Sc1—O5 | 70.78 (4) | H4—N3—H5 | 120.0 |
O4—Sc1—O5 | 74.43 (4) | C1—O1—Sc1 | 137.45 (10) |
O7—Sc1—O2 | 95.14 (4) | C2—O2—Sc1 | 137.47 (9) |
O6—Sc1—O2 | 85.41 (4) | Sc1—O3—H6 | 128.4 |
O1—Sc1—O2 | 74.09 (4) | Sc1—O3—H7 | 123.2 |
O4—Sc1—O2 | 139.92 (4) | H6—O3—H7 | 108.0 |
O5—Sc1—O2 | 144.83 (4) | Sc1—O4—H8 | 123.1 |
O7—Sc1—O3 | 81.07 (4) | Sc1—O4—H9 | 122.3 |
O6—Sc1—O3 | 100.94 (4) | H8—O4—H9 | 105.4 |
O1—Sc1—O3 | 141.86 (4) | Sc1—O5—H10 | 122.3 |
O4—Sc1—O3 | 75.26 (4) | Sc1—O5—H11 | 128.4 |
O5—Sc1—O3 | 142.33 (4) | H10—O5—H11 | 108.8 |
O2—Sc1—O3 | 70.50 (4) | Sc1—O6—H12 | 117.8 |
O1—C1—N1 | 121.21 (13) | Sc1—O6—H13 | 122.0 |
O1—C1—N2 | 121.98 (13) | H12—O6—H13 | 110.3 |
N1—C1—N2 | 116.80 (13) | Sc1—O7—H14 | 126.5 |
O2—C2—N3 | 121.42 (13) | Sc1—O7—H15 | 124.1 |
O2—C2—N2 | 122.54 (13) | H14—O7—H15 | 102.8 |
N3—C2—N2 | 115.98 (12) | H16—O8—H17 | 107.1 |
| | | |
O2—C2—N2—C1 | −15.9 (2) | O2—Sc1—O1—C1 | −21.41 (14) |
N3—C2—N2—C1 | 166.85 (13) | O3—Sc1—O1—C1 | 0.93 (18) |
O1—C1—N2—C2 | 2.4 (2) | N3—C2—O2—Sc1 | −174.13 (10) |
N1—C1—N2—C2 | −176.50 (13) | N2—C2—O2—Sc1 | 8.8 (2) |
N1—C1—O1—Sc1 | −159.81 (12) | O7—Sc1—O2—C2 | −81.51 (15) |
N2—C1—O1—Sc1 | 21.4 (2) | O6—Sc1—O2—C2 | 96.53 (15) |
O7—Sc1—O1—C1 | 74.37 (15) | O1—Sc1—O2—C2 | 5.44 (14) |
O6—Sc1—O1—C1 | −106.69 (15) | O4—Sc1—O2—C2 | 166.98 (13) |
O4—Sc1—O1—C1 | 178.33 (13) | O5—Sc1—O2—C2 | 2.66 (18) |
O5—Sc1—O1—C1 | 156.90 (15) | O3—Sc1—O2—C2 | −160.15 (15) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl3 | 0.88 | 2.62 | 3.4148 (14) | 152 |
N1—H2···Cl2i | 0.88 | 2.53 | 3.2883 (14) | 145 |
N2—H3···Cl2ii | 0.88 | 2.45 | 3.1609 (12) | 138 |
N3—H4···Cl2iii | 0.88 | 2.74 | 3.4239 (14) | 136 |
N3—H5···Cl2ii | 0.88 | 2.75 | 3.4882 (14) | 142 |
O3—H6···Cl1iv | 0.83 | 2.27 | 3.0662 (11) | 163 |
O3—H7···Cl2v | 0.90 | 2.24 | 3.1245 (11) | 167 |
O4—H8···Cl3iv | 0.88 | 2.18 | 3.0519 (11) | 173 |
O4—H9···O8vi | 0.85 | 1.84 | 2.6929 (15) | 176 |
O5—H10···Cl3 | 0.89 | 2.30 | 3.1671 (11) | 164 |
O5—H11···O8 | 0.85 | 1.89 | 2.7274 (14) | 174 |
O6—H12···Cl1iii | 0.85 | 2.21 | 3.0477 (11) | 169 |
O6—H13···Cl3vii | 0.86 | 2.21 | 3.0691 (11) | 175 |
O7—H14···Cl1 | 0.86 | 2.14 | 3.0014 (11) | 179 |
O7—H15···Cl2 | 0.93 | 2.10 | 3.0229 (11) | 173 |
O8—H16···Cl3viii | 0.91 | 2.27 | 3.1512 (11) | 165 |
O8—H17···O1viii | 0.89 | 2.51 | 3.2003 (15) | 135 |
O8—H17···Cl1vii | 0.89 | 2.62 | 3.3161 (11) | 135 |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x, −y+1, −z+1; (iii) x, y+1, z; (iv) x, −y+1/2, z+1/2; (v) −x, y+1/2, −z+3/2; (vi) −x+1, −y+1, −z+2; (vii) −x+1, y+1/2, −z+3/2; (viii) −x+1, y−1/2, −z+3/2. |
(II) tetrakis(biuret-
κ2O,O')scandium(III) trinitrate
top
Crystal data top
[Sc(C2H5N3O2)4](NO3)3 | F(000) = 1320 |
Mr = 643.36 | Dx = 1.899 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 2691 reflections |
a = 19.2409 (13) Å | θ = 2.9–27.5° |
b = 7.0167 (4) Å | µ = 0.45 mm−1 |
c = 17.4653 (13) Å | T = 120 K |
β = 107.344 (4)° | Cut slab, colourless |
V = 2250.7 (3) Å3 | 0.18 × 0.12 × 0.10 mm |
Z = 4 | |
Data collection top
Nonius KappaCCD diffractometer | 2581 independent reflections |
Radiation source: fine-focus sealed tube | 1704 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.070 |
ω and ϕ scans | θmax = 27.6°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | h = −24→22 |
Tmin = 0.924, Tmax = 0.957 | k = −9→9 |
12063 measured reflections | l = −22→22 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.051 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0547P)2 + 1.5264P] where P = (Fo2 + 2Fc2)/3 |
2581 reflections | (Δ/σ)max < 0.001 |
204 parameters | Δρmax = 0.61 e Å−3 |
3 restraints | Δρmin = −0.39 e Å−3 |
Crystal data top
[Sc(C2H5N3O2)4](NO3)3 | V = 2250.7 (3) Å3 |
Mr = 643.36 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 19.2409 (13) Å | µ = 0.45 mm−1 |
b = 7.0167 (4) Å | T = 120 K |
c = 17.4653 (13) Å | 0.18 × 0.12 × 0.10 mm |
β = 107.344 (4)° | |
Data collection top
Nonius KappaCCD diffractometer | 2581 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2003) | 1704 reflections with I > 2σ(I) |
Tmin = 0.924, Tmax = 0.957 | Rint = 0.070 |
12063 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.051 | 3 restraints |
wR(F2) = 0.122 | H-atom parameters constrained |
S = 1.05 | Δρmax = 0.61 e Å−3 |
2581 reflections | Δρmin = −0.39 e Å−3 |
204 parameters | |
Special details top
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell e.s.d.'s are taken
into account individually in the estimation of e.s.d.'s in distances, angles
and torsion angles; correlations between e.s.d.'s in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s.
planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor
wR and goodness of fit S are based on F2, conventional
R-factors R are based on F, with F set to zero for
negative F2. The threshold expression of F2 >
σ(F2) is used only for calculating R-factors(gt) etc.
and is not relevant to the choice of reflections for refinement.
R-factors based on F2 are statistically about twice as large
as those based on F, and R- factors based on ALL data will be
even larger. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
Sc1 | 0.5000 | 0.21789 (10) | 0.2500 | 0.0146 (2) | |
C1 | 0.43962 (14) | 0.2257 (4) | 0.05573 (17) | 0.0173 (6) | |
C2 | 0.47271 (14) | 0.5311 (4) | 0.12188 (17) | 0.0185 (6) | |
N1 | 0.41501 (12) | 0.1514 (3) | −0.01718 (14) | 0.0235 (6) | |
H1A | 0.4143 | 0.0270 | −0.0236 | 0.028* | |
H1B | 0.3993 | 0.2266 | −0.0591 | 0.028* | |
N2 | 0.43599 (12) | 0.4213 (3) | 0.05769 (14) | 0.0192 (5) | |
H2 | 0.4083 | 0.4798 | 0.0149 | 0.023* | |
N3 | 0.46016 (14) | 0.7161 (3) | 0.11584 (15) | 0.0280 (6) | |
H3A | 0.4841 | 0.7929 | 0.1546 | 0.034* | |
H3B | 0.4279 | 0.7628 | 0.0731 | 0.034* | |
O1 | 0.46269 (9) | 0.1276 (2) | 0.11798 (11) | 0.0190 (5) | |
O2 | 0.51830 (9) | 0.4598 (2) | 0.18200 (11) | 0.0182 (5) | |
C3 | 0.32898 (14) | 0.2222 (4) | 0.16901 (17) | 0.0194 (6) | |
C4 | 0.37035 (14) | −0.0829 (4) | 0.23231 (17) | 0.0181 (6) | |
N4 | 0.27434 (13) | 0.3026 (3) | 0.11449 (16) | 0.0347 (7) | |
H4A | 0.2776 | 0.4221 | 0.1006 | 0.042* | |
H4B | 0.2346 | 0.2369 | 0.0919 | 0.042* | |
N5 | 0.31777 (11) | 0.0361 (3) | 0.18679 (14) | 0.0207 (6) | |
H5 | 0.2735 | −0.0101 | 0.1674 | 0.025* | |
N6 | 0.34883 (12) | −0.2563 (3) | 0.24458 (14) | 0.0225 (6) | |
H6A | 0.3805 | −0.3390 | 0.2730 | 0.027* | |
H6B | 0.3028 | −0.2889 | 0.2243 | 0.027* | |
O3 | 0.38606 (9) | 0.3086 (2) | 0.20247 (11) | 0.0188 (5) | |
O4 | 0.43567 (9) | −0.0317 (2) | 0.26038 (11) | 0.0192 (5) | |
N7 | 0.64799 (12) | 0.3132 (3) | 0.11046 (14) | 0.0206 (6) | |
O5 | 0.69109 (11) | 0.1984 (3) | 0.15281 (13) | 0.0314 (6) | |
O6 | 0.59093 (9) | 0.2591 (3) | 0.05913 (11) | 0.0206 (5) | |
O7 | 0.66153 (10) | 0.4909 (3) | 0.11766 (13) | 0.0298 (5) | |
N8 | 0.2577 (5) | 0.7663 (12) | −0.0042 (9) | 0.018 (2) | 0.50 |
O8 | 0.3025 (2) | 0.8926 (6) | 0.0297 (3) | 0.0311 (11) | 0.50 |
O9 | 0.2753 (3) | 0.5946 (6) | 0.0073 (3) | 0.0358 (12) | 0.50 |
O10 | 0.1959 (2) | 0.8131 (7) | −0.0484 (3) | 0.0298 (11) | 0.50 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Sc1 | 0.0117 (4) | 0.0115 (4) | 0.0184 (4) | 0.000 | 0.0012 (3) | 0.000 |
C1 | 0.0148 (13) | 0.0161 (13) | 0.0202 (16) | −0.0012 (11) | 0.0037 (11) | −0.0024 (12) |
C2 | 0.0191 (14) | 0.0183 (14) | 0.0188 (16) | −0.0039 (11) | 0.0066 (12) | 0.0005 (12) |
N1 | 0.0311 (14) | 0.0141 (11) | 0.0222 (15) | 0.0009 (10) | 0.0034 (11) | −0.0024 (10) |
N2 | 0.0228 (12) | 0.0133 (11) | 0.0168 (13) | −0.0007 (10) | −0.0009 (10) | 0.0003 (10) |
N3 | 0.0428 (16) | 0.0124 (12) | 0.0194 (14) | 0.0006 (11) | −0.0052 (12) | −0.0009 (10) |
O1 | 0.0201 (10) | 0.0122 (9) | 0.0218 (12) | −0.0008 (8) | 0.0019 (8) | 0.0017 (8) |
O2 | 0.0183 (10) | 0.0141 (9) | 0.0197 (11) | −0.0016 (8) | 0.0019 (8) | 0.0002 (8) |
C3 | 0.0152 (14) | 0.0205 (14) | 0.0218 (16) | −0.0006 (12) | 0.0046 (12) | −0.0021 (13) |
C4 | 0.0186 (14) | 0.0165 (14) | 0.0163 (15) | −0.0025 (12) | 0.0007 (12) | −0.0007 (12) |
N4 | 0.0198 (13) | 0.0256 (13) | 0.0452 (18) | −0.0024 (11) | −0.0111 (12) | 0.0075 (12) |
N5 | 0.0127 (11) | 0.0199 (12) | 0.0239 (14) | −0.0046 (10) | −0.0032 (10) | 0.0023 (10) |
N6 | 0.0200 (12) | 0.0172 (12) | 0.0274 (15) | −0.0064 (10) | 0.0025 (11) | 0.0063 (11) |
O3 | 0.0150 (9) | 0.0161 (9) | 0.0226 (11) | −0.0018 (8) | 0.0015 (8) | −0.0002 (8) |
O4 | 0.0161 (9) | 0.0138 (9) | 0.0232 (11) | −0.0010 (8) | −0.0011 (8) | 0.0023 (8) |
N7 | 0.0189 (12) | 0.0219 (14) | 0.0216 (14) | −0.0010 (10) | 0.0072 (11) | 0.0008 (11) |
O5 | 0.0237 (11) | 0.0312 (12) | 0.0325 (13) | 0.0072 (9) | −0.0021 (10) | 0.0098 (10) |
O6 | 0.0142 (9) | 0.0223 (10) | 0.0222 (11) | −0.0036 (8) | 0.0004 (8) | −0.0040 (9) |
O7 | 0.0280 (11) | 0.0170 (11) | 0.0413 (14) | −0.0079 (9) | 0.0054 (10) | −0.0032 (10) |
N8 | 0.020 (4) | 0.023 (4) | 0.017 (3) | 0.001 (3) | 0.013 (4) | 0.005 (3) |
O8 | 0.025 (2) | 0.035 (3) | 0.031 (3) | −0.004 (2) | 0.0048 (19) | −0.009 (2) |
O9 | 0.055 (3) | 0.018 (2) | 0.040 (3) | 0.015 (3) | 0.022 (3) | 0.009 (2) |
O10 | 0.020 (2) | 0.028 (3) | 0.037 (3) | 0.003 (2) | 0.002 (2) | 0.001 (2) |
Geometric parameters (Å, º) top
Sc1—O2i | 2.1600 (18) | N3—H3B | 0.8800 |
Sc1—O2 | 2.1600 (18) | C3—O3 | 1.238 (3) |
Sc1—O4 | 2.1830 (18) | C3—N4 | 1.316 (3) |
Sc1—O4i | 2.1830 (18) | C3—N5 | 1.374 (3) |
Sc1—O3i | 2.1945 (17) | C4—O4 | 1.258 (3) |
Sc1—O3 | 2.1945 (17) | C4—N6 | 1.323 (3) |
Sc1—O1 | 2.2905 (18) | C4—N5 | 1.368 (3) |
Sc1—O1i | 2.2905 (18) | N4—H4A | 0.8800 |
C1—O1 | 1.251 (3) | N4—H4B | 0.8800 |
C1—N1 | 1.326 (3) | N5—H5 | 0.8800 |
C1—N2 | 1.375 (3) | N6—H6A | 0.8800 |
C2—O2 | 1.254 (3) | N6—H6B | 0.8800 |
C2—N3 | 1.319 (3) | N7—O5 | 1.232 (3) |
C2—N2 | 1.370 (3) | N7—O6 | 1.251 (3) |
N1—H1A | 0.8800 | N7—O7 | 1.272 (3) |
N1—H1B | 0.8800 | N8—O9 | 1.252 (8) |
N2—H2 | 0.8800 | N8—O10 | 1.253 (8) |
N3—H3A | 0.8800 | N8—O8 | 1.255 (8) |
| | | |
O2i—Sc1—O2 | 76.39 (10) | C1—N1—H1A | 120.0 |
O2i—Sc1—O4 | 113.28 (7) | C1—N1—H1B | 120.0 |
O2—Sc1—O4 | 149.94 (7) | H1A—N1—H1B | 120.0 |
O2i—Sc1—O4i | 149.94 (7) | C2—N2—C1 | 124.3 (2) |
O2—Sc1—O4i | 113.28 (7) | C2—N2—H2 | 117.8 |
O4—Sc1—O4i | 73.32 (10) | C1—N2—H2 | 117.8 |
O2i—Sc1—O3i | 82.66 (7) | C2—N3—H3A | 120.0 |
O2—Sc1—O3i | 70.84 (7) | C2—N3—H3B | 120.0 |
O4—Sc1—O3i | 136.76 (7) | H3A—N3—H3B | 120.0 |
O4i—Sc1—O3i | 74.74 (6) | C1—O1—Sc1 | 130.26 (16) |
O2i—Sc1—O3 | 70.84 (7) | C2—O2—Sc1 | 125.85 (16) |
O2—Sc1—O3 | 82.66 (7) | O3—C3—N4 | 122.5 (3) |
O4—Sc1—O3 | 74.74 (6) | O3—C3—N5 | 122.4 (2) |
O4i—Sc1—O3 | 136.76 (7) | N4—C3—N5 | 115.2 (2) |
O3i—Sc1—O3 | 146.28 (10) | O4—C4—N6 | 121.6 (2) |
O2i—Sc1—O1 | 135.83 (7) | O4—C4—N5 | 122.1 (2) |
O2—Sc1—O1 | 73.58 (7) | N6—C4—N5 | 116.2 (2) |
O4—Sc1—O1 | 81.17 (7) | C3—N4—H4A | 120.0 |
O4i—Sc1—O1 | 73.14 (7) | C3—N4—H4B | 120.0 |
O3i—Sc1—O1 | 116.04 (7) | H4A—N4—H4B | 120.0 |
O3—Sc1—O1 | 73.82 (7) | C4—N5—C3 | 124.9 (2) |
O2i—Sc1—O1i | 73.58 (7) | C4—N5—H5 | 117.5 |
O2—Sc1—O1i | 135.83 (7) | C3—N5—H5 | 117.5 |
O4—Sc1—O1i | 73.14 (7) | C4—N6—H6A | 120.0 |
O4i—Sc1—O1i | 81.17 (7) | C4—N6—H6B | 120.0 |
O3i—Sc1—O1i | 73.82 (7) | H6A—N6—H6B | 120.0 |
O3—Sc1—O1i | 116.04 (7) | C3—O3—Sc1 | 133.03 (17) |
O1—Sc1—O1i | 147.90 (9) | C4—O4—Sc1 | 136.25 (17) |
O1—C1—N1 | 123.4 (2) | O5—N7—O6 | 121.4 (2) |
O1—C1—N2 | 122.3 (2) | O5—N7—O7 | 120.0 (2) |
N1—C1—N2 | 114.2 (2) | O6—N7—O7 | 118.6 (2) |
O2—C2—N3 | 121.7 (2) | O9—N8—O10 | 120.9 (7) |
O2—C2—N2 | 121.5 (2) | O10—N8—O8 | 119.9 (7) |
N3—C2—N2 | 116.8 (2) | O9—N8—O8 | 119.3 (8) |
| | | |
O2—C2—N2—C1 | 6.6 (4) | O4—C4—N5—C3 | −2.3 (5) |
N3—C2—N2—C1 | −176.3 (3) | N6—C4—N5—C3 | 178.4 (3) |
O1—C1—N2—C2 | 17.3 (4) | O3—C3—N5—C4 | −10.8 (5) |
N1—C1—N2—C2 | −164.3 (3) | N4—C3—N5—C4 | 169.9 (3) |
N1—C1—O1—Sc1 | −175.09 (18) | N4—C3—O3—Sc1 | −148.2 (2) |
N2—C1—O1—Sc1 | 3.2 (4) | N5—C3—O3—Sc1 | 32.6 (4) |
O2i—Sc1—O1—C1 | 22.3 (3) | O2i—Sc1—O3—C3 | −150.5 (3) |
O2—Sc1—O1—C1 | −26.7 (2) | O2—Sc1—O3—C3 | 131.4 (3) |
O4—Sc1—O1—C1 | 136.8 (2) | O4—Sc1—O3—C3 | −28.6 (3) |
O4i—Sc1—O1—C1 | −148.1 (2) | O4i—Sc1—O3—C3 | 15.0 (3) |
O3i—Sc1—O1—C1 | −85.1 (2) | O3i—Sc1—O3—C3 | 169.3 (3) |
O3—Sc1—O1—C1 | 60.2 (2) | O1—Sc1—O3—C3 | 56.4 (3) |
O1i—Sc1—O1—C1 | 173.7 (2) | O1i—Sc1—O3—C3 | −90.7 (3) |
N3—C2—O2—Sc1 | 131.2 (2) | N6—C4—O4—Sc1 | 173.42 (19) |
N2—C2—O2—Sc1 | −51.9 (3) | N5—C4—O4—Sc1 | −5.9 (4) |
O2i—Sc1—O2—C2 | −97.0 (2) | O2i—Sc1—O4—C4 | 75.9 (3) |
O4—Sc1—O2—C2 | 16.1 (3) | O2—Sc1—O4—C4 | −27.5 (3) |
O4i—Sc1—O2—C2 | 113.0 (2) | O4i—Sc1—O4—C4 | −135.3 (3) |
O3i—Sc1—O2—C2 | 176.1 (2) | O3i—Sc1—O4—C4 | −179.3 (2) |
O3—Sc1—O2—C2 | −25.1 (2) | O3—Sc1—O4—C4 | 15.1 (3) |
O1—Sc1—O2—C2 | 50.2 (2) | O1—Sc1—O4—C4 | −60.4 (3) |
O1i—Sc1—O2—C2 | −145.2 (2) | O1i—Sc1—O4—C4 | 139.1 (3) |
Symmetry code: (i) −x+1, y, −z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6ii | 0.88 | 2.09 | 2.966 (3) | 171 |
N1—H1B···O7iii | 0.88 | 2.37 | 3.163 (3) | 150 |
N2—H2···O6iii | 0.88 | 2.24 | 2.971 (3) | 140 |
N2—H2···O7iii | 0.88 | 2.31 | 3.139 (3) | 156 |
N3—H3A···O4iv | 0.88 | 2.18 | 3.040 (3) | 167 |
N3—H3B···O6iii | 0.88 | 2.23 | 2.923 (3) | 135 |
N3—H3B···O10v | 0.88 | 2.35 | 2.887 (5) | 119 |
N3—H3B···O8 | 0.88 | 2.48 | 3.206 (5) | 141 |
N4—H4A···O9 | 0.88 | 2.02 | 2.779 (5) | 144 |
N4—H4A···O10v | 0.88 | 2.20 | 3.054 (5) | 165 |
N4—H4B···O7vi | 0.88 | 2.35 | 3.094 (3) | 142 |
N5—H5···O7vi | 0.88 | 2.07 | 2.904 (3) | 158 |
N6—H6A···O2vii | 0.88 | 2.34 | 3.193 (3) | 162 |
N6—H6B···O5vi | 0.88 | 2.14 | 2.997 (3) | 164 |
Symmetry codes: (ii) −x+1, −y, −z; (iii) −x+1, −y+1, −z; (iv) −x+1, y+1, −z+1/2; (v) −x+1/2, −y+3/2, −z; (vi) x−1/2, y−1/2, z; (vii) −x+1, y−1, −z+1/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | [Sc(C2H5N3O2)(H2O)5]Cl3·H2O | [Sc(C2H5N3O2)4](NO3)3 |
Mr | 362.50 | 643.36 |
Crystal system, space group | Monoclinic, P21/c | Monoclinic, C2/c |
Temperature (K) | 120 | 120 |
a, b, c (Å) | 15.2430 (7), 7.5653 (5), 14.1276 (9) | 19.2409 (13), 7.0167 (4), 17.4653 (13) |
β (°) | 117.247 (4) | 107.344 (4) |
V (Å3) | 1448.39 (15) | 2250.7 (3) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 1.09 | 0.45 |
Crystal size (mm) | 0.40 × 0.20 × 0.15 | 0.18 × 0.12 × 0.10 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2003) | Multi-scan (SADABS; Bruker, 2003) |
Tmin, Tmax | 0.670, 0.854 | 0.924, 0.957 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 17376, 3308, 2988 | 12063, 2581, 1704 |
Rint | 0.025 | 0.070 |
(sin θ/λ)max (Å−1) | 0.650 | 0.651 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.023, 0.060, 1.06 | 0.051, 0.122, 1.05 |
No. of reflections | 3308 | 2581 |
No. of parameters | 155 | 204 |
No. of restraints | 0 | 3 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.41, −0.50 | 0.61, −0.39 |
Selected bond lengths (Å) for (I) topSc1—O7 | 2.1109 (11) | Sc1—O5 | 2.1572 (10) |
Sc1—O6 | 2.1242 (11) | Sc1—O2 | 2.1595 (10) |
Sc1—O1 | 2.1377 (10) | Sc1—O3 | 2.1629 (10) |
Sc1—O4 | 2.1541 (10) | | |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···Cl3 | 0.88 | 2.62 | 3.4148 (14) | 152 |
N1—H2···Cl2i | 0.88 | 2.53 | 3.2883 (14) | 145 |
N2—H3···Cl2ii | 0.88 | 2.45 | 3.1609 (12) | 138 |
N3—H4···Cl2iii | 0.88 | 2.74 | 3.4239 (14) | 136 |
N3—H5···Cl2ii | 0.88 | 2.75 | 3.4882 (14) | 142 |
O3—H6···Cl1iv | 0.83 | 2.27 | 3.0662 (11) | 163 |
O3—H7···Cl2v | 0.90 | 2.24 | 3.1245 (11) | 167 |
O4—H8···Cl3iv | 0.88 | 2.18 | 3.0519 (11) | 173 |
O4—H9···O8vi | 0.85 | 1.84 | 2.6929 (15) | 176 |
O5—H10···Cl3 | 0.89 | 2.30 | 3.1671 (11) | 164 |
O5—H11···O8 | 0.85 | 1.89 | 2.7274 (14) | 174 |
O6—H12···Cl1iii | 0.85 | 2.21 | 3.0477 (11) | 169 |
O6—H13···Cl3vii | 0.86 | 2.21 | 3.0691 (11) | 175 |
O7—H14···Cl1 | 0.86 | 2.14 | 3.0014 (11) | 179 |
O7—H15···Cl2 | 0.93 | 2.10 | 3.0229 (11) | 173 |
O8—H16···Cl3viii | 0.91 | 2.27 | 3.1512 (11) | 165 |
O8—H17···O1viii | 0.89 | 2.51 | 3.2003 (15) | 135 |
O8—H17···Cl1vii | 0.89 | 2.62 | 3.3161 (11) | 135 |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x, −y+1, −z+1; (iii) x, y+1, z; (iv) x, −y+1/2, z+1/2; (v) −x, y+1/2, −z+3/2; (vi) −x+1, −y+1, −z+2; (vii) −x+1, y+1/2, −z+3/2; (viii) −x+1, y−1/2, −z+3/2. |
Selected bond lengths (Å) for (II) topSc1—O2 | 2.1600 (18) | Sc1—O3 | 2.1945 (17) |
Sc1—O4 | 2.1830 (18) | Sc1—O1 | 2.2905 (18) |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6i | 0.88 | 2.09 | 2.966 (3) | 171 |
N1—H1B···O7ii | 0.88 | 2.37 | 3.163 (3) | 150 |
N2—H2···O6ii | 0.88 | 2.24 | 2.971 (3) | 140 |
N2—H2···O7ii | 0.88 | 2.31 | 3.139 (3) | 156 |
N3—H3A···O4iii | 0.88 | 2.18 | 3.040 (3) | 167 |
N3—H3B···O6ii | 0.88 | 2.23 | 2.923 (3) | 135 |
N3—H3B···O10iv | 0.88 | 2.35 | 2.887 (5) | 119 |
N3—H3B···O8 | 0.88 | 2.48 | 3.206 (5) | 141 |
N4—H4A···O9 | 0.88 | 2.02 | 2.779 (5) | 144 |
N4—H4A···O10iv | 0.88 | 2.20 | 3.054 (5) | 165 |
N4—H4B···O7v | 0.88 | 2.35 | 3.094 (3) | 142 |
N5—H5···O7v | 0.88 | 2.07 | 2.904 (3) | 158 |
N6—H6A···O2vi | 0.88 | 2.34 | 3.193 (3) | 162 |
N6—H6B···O5v | 0.88 | 2.14 | 2.997 (3) | 164 |
Symmetry codes: (i) −x+1, −y, −z; (ii) −x+1, −y+1, −z; (iii) −x+1, y+1, −z+1/2; (iv) −x+1/2, −y+3/2, −z; (v) x−1/2, y−1/2, z; (vi) −x+1, y−1, −z+1/2. |
Compared with other first-row transition elements, the coordination chemistry of Sc3+ has not been extensively investigated, perhaps in part owing to the historical high cost of scandium compounds. Even so, it is clearly defined as a relatively weak class-a acceptor and shows a preference for O-atom donor ligands (Greenwood & Earnshaw, 1997), although coordination to N atoms and halide ions has been observed (e.g. Ripert et al., 1999). Scandium(III) is notably flexible in its coordination preference; for example, it can adopt six- [e.g. Sc(H2O)6.Sc(CH3SO3)6; Lindquist-Reis et al., 2006], seven- [e.g. Sc(H2O)7.3Cl; Lim et al., 2000], eight- [Sc(H2O)8.3(CF3SO3); Abbasi et al., 2005] and nine-coordination [Sc(H2O)9.3(CF3SO3); Castellani et al., 1995] in its mononuclear aqua complexes.
Biuret (biur), H2N—CO—NH—CO—NH2 (or C2H5N3O2), has long been recognized as a ligand in coordination chemistry (Wiedemann, 1848). In low-pH or neutral conditions, biuret shows O,O'-bidentate coordination to metal cations [e.g. with Zn (Nardelli et al., 1963), Cu (Freeman & Smith, 1966) or Ni (Lawson & Harrison, 2005)]. When biuret is deprotonated in basic conditions, N,N'-bidentate coordination can arise [e.g. with Cu (Pajunen & Pajunen, 1982)]. In this paper, we describe the syntheses and structures of two new scandium–biuret complexes, Sc(biur)(H2O)5.3Cl.H2O, (I), and Sc(biur)4.3NO3, (II). In the former, the Sc3+ ion is seven-coordinate, and in the latter, eight coordinate.
Compound (I) is a hydrated molecular salt containing a new [Sc(biur)(H2O)5]3+ complex ion, three charge-balancing chloride ions and one uncoordinated water molecule. The Sc3+ ion in (I) is coordinated to seven O atoms (Fig. 1 and Table 1) in a slightly distorted pentagonal–bipyramidal arrangement. The O,O-bidenate biuret molecule occupies two of the equatorial positions, and a six-membered chelate ring results. The mean equatorial O—Sc—O bond angle is 73.0° and the axial O6—Sc1—O7 bond angle is 177.98 (4)°. The axial Sc—O bond lengths are slightly shorter than their equatorial equivalents. In [Sc(H2O)7]3+.3X- (X = Cl and Br; Lim et al., 2000) a very similar scandium geometry arises although the complete complex cation is generated by twofold symmetry in these cases.
It has been noted previously (Carugo et al., 1992) that the biuret molecule can be regarded as two planar amide fragments linked by an NH bridge. Here, the dihedral angle between the N1/C1/O1/N2 and N2/C2/O2/N3 units is 13.21 (9)°. The Sc3+ cation deviates from the N1/C1/O1/N2 and N2/C2/O2/N3 mean planes by -0.501 (3) and 0.157 (3) Å, respectively.
On progressing along the chain formed by atoms N1, C1, N2, C2 and N3 (Fig. 1), the C—N bond lengths in (I) show a short–long–long–short (slls) pattern, although all of them are intermediate between typical C—N single (1.47 Å) and C═N double (1.30 Å) bonds, consistent with a significant degree of electronic delocalization over the entire biuret molecule (Carugo et al., 1992). This slls bond-length alternation pattern is the most common one seen in biurets, although others are also possible (Harrison, 2007).
The component species in (I) are linked by a dense network of N—H···Cl, O—H···Cl and O—H···O hydrogen bonds (Table 2). Perhaps the most interesting of these are the O—H···O links, which result in [Sc(biur)(H2O)5.H2O]2 inversion dimers (Fig. 2) in which the graph-set motif (Bernstein et al., 1995) is R24(12). Of the other hydrogen bonds, atoms Cl1, Cl2 and Cl3 accept four, six and five, respectively.
The asymmetric unit of (II) contains one Sc3+ ion (site symmetry 2), two biuret molecules and two nitrate ions, one of which is disordered about an inversion centre. Crystal symmetry generates an [Sc(biur)4]3+ complex ion (Fig. 3), in which the ScIII ion adopts a squashed square–antiprismatic geometry (Table 3 and Fig. 4). The r.m.s. deviation from the mean plane of the four O atoms forming one square face [O1, O2, O3i and O4i; (i) 1 - x, y, 1/2 - z] is 0.004 Å and Sc1 is displaced from this plane by 1.190 (1) Å. Owing to crystal symmetry, the same values apply to the other four O atoms (O1i, O2i, O3 and O4). The dihedral angle between the two sets of O atoms is 1.20 (9)°.
Both biuret molecules in (II) exhibit the slls C—N bond-length pattern. The dihedral angle between the N1/C1/O1/N2 and N2/C2/O2/N3 fragments is 20.35 (9)°, indicating an unusually high degree of twisting, and that between N4/C3/O3/N5 and N5/C4/O4/N6 is 11.76 (18)°. The deviations of the Sc3+ ion from the mean planes of the biuret fragments are -0.139 (4) Å for N1/C1/O1/N2, -1.323 (4) Å for N2/C2/O2/N3, 0.848 (5) Å for N4/C3/O3/N5 and -0.171 (5) Å for N5/C4/O4/N6.
The structure of (II) is completed by two nitrate ions, one of which is disordered about an inversion centre. A network of N—H···O hydrogen bonds (Table 4) link the component species into a three-dimensional array. The most notable are the N3—H3A···O4iii [symmetry code (iii) -x + 1, y + 1, -z + 1/2] and N6—H6A···O2vi [symmetry code: (vi) -x + 1, y - 1, -z + 1/2] links, which lead to [010] chains of cations containing R22(8) loops (Fig. 5).
The complex ion containing Sm3+ equivalent to that seen in (II) has been described by Haddad (1987) in Sm(biur)3.(NO3)3, and indeed the overall structures of (II) and Sm(biur)3.(NO3)3 are isostructural but not isomorphous.
A short nitro-O6···C1 contact of 2.904 (3) Å occurs in the crystal structure of (II), which could be another example of a short through-space O···C electrostatic interaction (O'Leary & Wallis, 2007).