Tetra­aqua­bis(biuret-κ² O,O′)gadolinium(III) trichloride

Abstract

In the title compound, [Gd(C₂H₅N₃O₂)₂(H₂O)₄]Cl₃, which is isostrucutural with its yttrium analogue, the Gd³⁺ ion (site symmetry 2) is bonded to eight O atoms (arising from two O,O′-bidentate biuret mol­ecules and four water mol­ecules) in a distorted square-anti­prismatic arrangement. A network of N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds helps to establish the packing, leading to a three-dimensional network. One of the chloride ions has site symmetry 2.

Related literature

For related structures, see: Haddad (1987 ▶, 1988 ▶); Harrison (2008 ▶). For related literature, see: Bernstein et al. (1995 ▶). For valence-sum calculations, see: Brese & O’Keeffe (1991 ▶).

Experimental

Crystal data

• [Gd(C₂H₅N₃O₂)₂(H₂O)₄]Cl₃

• M _r = 541.84

• Monoclinic,

• a = 7.6501 (3) Å

• b = 13.2164 (5) Å

• c = 17.4557 (6) Å

• β = 100.961 (1)°

• V = 1732.69 (11) ų

• Z = 4

• Mo Kα radiation

• μ = 4.33 mm⁻¹

• T = 293 (2) K

• 0.47 × 0.34 × 0.06 mm

Data collection

• Bruker SMART1000 CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 1999 ▶) T _min = 0.235, T _max = 0.781

• 8649 measured reflections

• 3134 independent reflections

• 2902 reflections with I > 2σ(I)

• R _int = 0.025

Refinement

• R[F ² > 2σ(F ²)] = 0.033

• wR(F ²) = 0.088

• S = 1.06

• 3134 reflections

• 101 parameters

• H-atom parameters constrained

• Δρ_max = 2.99 e Å⁻³

• Δρ_min = −3.45 e Å⁻³

Data collection: SMART (Bruker, 1999 ▶); cell refinement: SAINT (Bruker, 1999 ▶); data reduction: SAINT; 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.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Gd1—O1	2.350 (2)
Gd1—O2	2.375 (2)
Gd1—O4	2.407 (3)
Gd1—O3	2.414 (2)

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1i	0.86	2.10	2.910 (4)	157
N1—H2⋯Cl1ii	0.86	2.40	3.194 (3)	154
N2—H3⋯Cl1ii	0.86	2.53	3.315 (3)	153
N3—H4⋯Cl1iii	0.86	2.54	3.363 (3)	161
N3—H5⋯Cl1iv	0.86	2.53	3.311 (3)	151
O3—H6⋯Cl1v	0.81	2.39	3.163 (2)	162
O3—H7⋯Cl2vi	0.79	2.28	3.059 (2)	167
O4—H8⋯Cl1	0.76	2.45	3.208 (2)	178
O4—H9⋯Cl2	0.80	2.41	3.127 (2)	150

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

supplementary crystallographic information

Comment

The title compound, (I), is isostructural with its recently described yttrium-containing analogue (Harrison, 2008).

The complete [Gd(biur)₂(H₂O)₄]³⁺ (biur = biuret, C₂H₅N₃O₂) complex ion in (I) is generated by crystallographic 2-fold symmetry, with the metal atom lying on the rotation axis. Two uncoordinated chloride ions, one of which has site symmetry 2, complete the structure (Fig. 1) of (I).

The resulting GdO₈ polyhedral geometry in (I) (Table 1) is a distorted square antiprism. The nominal square face formed by atoms O1, O2, O1ⁱ and O2ⁱ (i = -x, y, 3/2 - z) is reasonably regular, but the second face formed by the four water molecules (O3, O4, O3ⁱ and O4ⁱ) is much more distorted, and the diagonal O3···O3ⁱ O4···O4ⁱ distances of 4.322 (4)Å and 3.551 (4) Å, respectively, are very different. Gd1 deviates from the mean planes of O1/O2/O1ⁱ/O2ⁱ and O3/O4/O3ⁱ/O4ⁱ by 1.1542 (16)Å and 1.3501 (19) Å, respectively. The gadolinium bond valence sum of 2.90, calculated by the Brese & O'Keffe (1991) method, indicates that it is slightly underbonded in (I), whereas in [Y(biur)₂(H₂O)₄].3Cl (Harrison, 2008), the yttrium cation was distinctly overbonded with a BVS of 3.34 (expected value = 3.00 in both cases).

The dihedral angle betwen the N1/C1/O1/N2 and N2/C2/O2/N3 fragments of the biuret molecule is 21.2 (2)°, which is far larger than the equivalent value of 5.06 (10)° in [Y(biur)₂(H₂O)₄].3Cl (Harrison, 2008). The gadolinium cation in (I) deviates from the N1/C1/O1/N2 and N2/C2/O2/N3 mean planes by -0.834 (6)Å and 0.530 (6) Å, respectively, indicating that the six-membered chelate ring is non-planar.

The component species in (I) are linked by a dense array of N—H···O, N—H···Cl and O—H···Cl hydrogen bonds (Table 2) resulting in a three-dimensional network. Of note is the N—H···O hydrogen bond, which results in [100] chains of cations, linked by R²₂(8) loops (Bernstein et al., 1995), as also seen in the yttrium phase (Harrison, 2008).

For related rare-earth–biuret complexes, see: Haddad (1987 and 1988).

Experimental

0.1 M Aqueous solutions of GdCl₃ (10 ml) and biuret (10 ml) were mixed and a small quantity of dilute hydrochloric acid was added, to result in a colourless solution. Colourless blocks of (I) grew over several days as the water slowly evaporated.

Refinement

The crystal quality was rather poor, with smeared and split peaks evident in the diffraction pattern.

The N-bound hydrogen atoms were geometrically placed (N—H = 0.88 Å) and refined as riding with U_iso(H) = 1.2U_eq(N). The water H atoms were located in difference maps and refined as riding in their as-found relative positions with U_iso(H) = 1.2U_eq(O).

The highest difference peak and deepest difference hole are 0.71Å and 0.75Å from Gd1, respectively.

Figures

Fig. 1.

View of the molecular structure of (I) showing 50% displacement ellipsoids (arbitrary spheres for the H atoms). Symmetry code: (i) -x, y, 3/2 - z.

Crystal data

[Gd(C2H5N3O2)2(H2O)4]Cl3	F000 = 1052
Mr = 541.84	Dx = 2.077 Mg m−3
Monoclinic, C2/c	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 6423 reflections
a = 7.6501 (3) Å	θ = 2.4–32.5º
b = 13.2164 (5) Å	µ = 4.33 mm−1
c = 17.4557 (6) Å	T = 293 (2) K
β = 100.961 (1)º	Slab, colourless
V = 1732.69 (11) Å3	0.47 × 0.34 × 0.06 mm
Z = 4

Data collection

Bruker SMART1000 CCD diffractometer	3134 independent reflections
Radiation source: fine-focus sealed tube	2902 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.025
T = 293(2) K	θmax = 32.5º
ω scans	θmin = 2.4º
Absorption correction: multi-scan(SADABS; Bruker, 1999)	h = −11→9
Tmin = 0.235, Tmax = 0.781	k = −19→18
8649 measured reflections	l = −19→26

Refinement

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)] = 0.033	H-atom parameters constrained
wR(F2) = 0.088	w = 1/[σ2(Fo2) + (0.0654P)2] where P = (Fo2 + 2Fc2)/3
S = 1.06	(Δ/σ)max < 0.001
3134 reflections	Δρmax = 2.99 e Å−3
101 parameters	Δρmin = −3.45 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Gd1	0.0000	0.106486 (13)	0.7500	0.02252 (7)
Cl1	−0.04157 (10)	0.33393 (7)	0.50790 (4)	0.03672 (16)
Cl2	0.5000	0.30307 (10)	0.7500	0.0389 (2)
O1	0.2531 (3)	0.02702 (18)	0.71963 (13)	0.0310 (4)
O2	−0.0822 (3)	0.01130 (17)	0.63327 (12)	0.0305 (4)
N1	0.4595 (4)	−0.0112 (3)	0.64845 (18)	0.0434 (7)
H1	0.5423	0.0169	0.6820	0.052*
H2	0.4845	−0.0387	0.6072	0.052*
N2	0.1720 (3)	−0.0598 (2)	0.60404 (15)	0.0295 (5)
H3	0.2119	−0.0977	0.5712	0.035*
N3	−0.1037 (4)	−0.1127 (2)	0.5433 (2)	0.0371 (6)
H4	−0.2181	−0.1098	0.5337	0.044*
H5	−0.0497	−0.1552	0.5186	0.044*
C1	0.2950 (4)	−0.0121 (2)	0.66032 (16)	0.0269 (5)
C2	−0.0103 (4)	−0.0513 (2)	0.59616 (16)	0.0265 (5)
O3	−0.2462 (3)	0.18787 (18)	0.66543 (13)	0.0360 (5)
H6	−0.2805	0.1748	0.6199	0.043*
H7	−0.3244	0.2160	0.6810	0.043*
O4	0.1191 (3)	0.2294 (2)	0.67206 (16)	0.0502 (7)
H8	0.0833	0.2534	0.6327	0.060*
H9	0.2181	0.2507	0.6743	0.060*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Gd1	0.01907 (9)	0.02952 (10)	0.01740 (9)	0.000	−0.00047 (6)	0.000
Cl1	0.0337 (3)	0.0470 (4)	0.0268 (3)	0.0011 (3)	−0.0007 (2)	−0.0067 (3)
Cl2	0.0301 (4)	0.0496 (6)	0.0377 (5)	0.000	0.0081 (4)	0.000
O1	0.0217 (8)	0.0441 (12)	0.0257 (9)	0.0024 (8)	0.0006 (7)	−0.0071 (8)
O2	0.0251 (9)	0.0359 (10)	0.0275 (9)	0.0038 (8)	−0.0024 (7)	−0.0077 (8)
N1	0.0233 (11)	0.073 (2)	0.0345 (14)	−0.0075 (12)	0.0071 (10)	−0.0178 (14)
N2	0.0240 (10)	0.0363 (12)	0.0269 (11)	0.0004 (9)	0.0018 (8)	−0.0083 (9)
N3	0.0297 (13)	0.0416 (15)	0.0364 (15)	−0.0020 (9)	−0.0025 (11)	−0.0147 (11)
C1	0.0227 (11)	0.0322 (12)	0.0241 (11)	0.0010 (9)	0.0005 (9)	−0.0008 (9)
C2	0.0247 (11)	0.0296 (12)	0.0231 (11)	0.0000 (9)	−0.0010 (9)	−0.0016 (9)
O3	0.0337 (10)	0.0484 (13)	0.0228 (9)	0.0135 (9)	−0.0027 (7)	−0.0022 (9)
O4	0.0384 (13)	0.0637 (17)	0.0423 (14)	−0.0157 (12)	−0.0084 (10)	0.0257 (12)

Geometric parameters (Å, °)

Gd1—O1i	2.350 (2)	N1—H2	0.8600
Gd1—O1	2.350 (2)	N2—C1	1.377 (4)
Gd1—O2	2.375 (2)	N2—C2	1.380 (4)
Gd1—O2i	2.375 (2)	N2—H3	0.8600
Gd1—O4i	2.407 (3)	N3—C2	1.330 (4)
Gd1—O4	2.407 (3)	N3—H4	0.8600
Gd1—O3i	2.414 (2)	N3—H5	0.8600
Gd1—O3	2.414 (2)	O3—H6	0.8067
O1—C1	1.253 (4)	O3—H7	0.7949
O2—C2	1.242 (3)	O4—H8	0.7597
N1—C1	1.314 (4)	O4—H9	0.8018
N1—H1	0.8600
O1i—Gd1—O1	126.90 (12)	O4—Gd1—O3	71.88 (8)
O1i—Gd1—O2	82.06 (8)	O3i—Gd1—O3	127.08 (12)
O1—Gd1—O2	70.41 (7)	C1—O1—Gd1	136.27 (18)
O1i—Gd1—O2i	70.41 (7)	C2—O2—Gd1	136.83 (18)
O1—Gd1—O2i	82.06 (8)	C1—N1—H1	120.0
O2—Gd1—O2i	116.04 (11)	C1—N1—H2	120.0
O1i—Gd1—O4i	75.96 (10)	H1—N1—H2	120.0
O1—Gd1—O4i	147.78 (8)	C1—N2—C2	125.1 (3)
O2—Gd1—O4i	140.85 (7)	C1—N2—H3	117.4
O2i—Gd1—O4i	86.53 (9)	C2—N2—H3	117.4
O1i—Gd1—O4	147.78 (8)	C2—N3—H4	120.0
O1—Gd1—O4	75.96 (10)	C2—N3—H5	120.0
O2—Gd1—O4	86.53 (9)	H4—N3—H5	120.0
O2i—Gd1—O4	140.85 (8)	O1—C1—N1	122.0 (3)
O4i—Gd1—O4	95.10 (17)	O1—C1—N2	122.1 (3)
O1i—Gd1—O3i	129.93 (8)	N1—C1—N2	115.9 (3)
O1—Gd1—O3i	75.91 (8)	O2—C2—N3	122.4 (3)
O2—Gd1—O3i	144.00 (8)	O2—C2—N2	122.7 (2)
O2i—Gd1—O3i	70.30 (7)	N3—C2—N2	114.8 (3)
O4i—Gd1—O3i	71.88 (9)	Gd1—O3—H6	125.2
O4—Gd1—O3i	73.11 (8)	Gd1—O3—H7	123.3
O1i—Gd1—O3	75.91 (8)	H6—O3—H7	108.2
O1—Gd1—O3	129.93 (8)	Gd1—O4—H8	133.1
O2—Gd1—O3	70.30 (7)	Gd1—O4—H9	131.7
O2i—Gd1—O3	144.00 (8)	H8—O4—H9	94.1
O4i—Gd1—O3	73.11 (8)
O1i—Gd1—O1—C1	81.6 (3)	O4—Gd1—O2—C2	85.5 (3)
O2—Gd1—O1—C1	18.4 (3)	O3i—Gd1—O2—C2	30.9 (4)
O2i—Gd1—O1—C1	139.7 (3)	O3—Gd1—O2—C2	157.5 (3)
O4i—Gd1—O1—C1	−149.9 (3)	Gd1—O1—C1—N1	149.2 (3)
O4—Gd1—O1—C1	−72.9 (3)	Gd1—O1—C1—N2	−31.6 (5)
O3i—Gd1—O1—C1	−148.7 (3)	C2—N2—C1—O1	15.1 (5)
O3—Gd1—O1—C1	−21.8 (3)	C2—N2—C1—N1	−165.6 (3)
O1i—Gd1—O2—C2	−124.7 (3)	Gd1—O2—C2—N3	161.3 (2)
O1—Gd1—O2—C2	9.2 (3)	Gd1—O2—C2—N2	−21.7 (5)
O2i—Gd1—O2—C2	−61.1 (3)	C1—N2—C2—O2	9.9 (5)
O4i—Gd1—O2—C2	179.3 (3)	C1—N2—C2—N3	−172.8 (3)

Symmetry codes: (i) −x, y, −z+3/2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1ii	0.86	2.10	2.910 (4)	157
N1—H2···Cl1iii	0.86	2.40	3.194 (3)	154
N2—H3···Cl1iii	0.86	2.53	3.315 (3)	153
N3—H4···Cl1iv	0.86	2.54	3.363 (3)	161
N3—H5···Cl1v	0.86	2.53	3.311 (3)	151
O3—H6···Cl1vi	0.81	2.39	3.163 (2)	162
O3—H7···Cl2vii	0.79	2.28	3.059 (2)	167
O4—H8···Cl1	0.76	2.45	3.208 (2)	178
O4—H9···Cl2	0.80	2.41	3.127 (2)	150

Symmetry codes: (ii) −x+1, y, −z+3/2; (iii) x+1/2, y−1/2, z; (iv) x−1/2, y−1/2, z; (v) −x, −y, −z+1; (vi) −x−1/2, −y+1/2, −z+1; (vii) x−1, y, z.