Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109020885/em3026sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109020885/em3026Isup2.hkl |
CCDC reference: 742261
Single crystals of the title compound, in the form of blue–green blocks, were obtained from the hydrolysis of N(CN)2- ions under alkaline conditions. Copper(I) dicyanamide (0.10 g) (Wang et al., 1990) was dissolved in an aqueous ammonia solution (35%, 15 ml) containing 10 drops of hydrazine. This formed a deep-blue solution which, over the course of 10 min, turned through green to orange. After a few days, the solution had returned to the deep-blue colour, and after 10 months, a small number of crystals suitable for single-crystal X-ray diffraction had grown. Intense bands were observed in the IR spectrum recorded in Spectrosol over the range 4000–1300 cm-1: 3467, 3354, 3312, 3220 (ν N—H, O—H); 2174, 2137 (ν C≡N); 1657, 1650 (ν C—O); 1535, 1529 (δ NH2) and 1412 (ν C—N).
All H atoms were located in difference Fourier maps and restrained to ride on their parent atoms [O—H = N—H = 0.85 (1) Å]. For the H atoms attached to framework atoms O1 to O3, the fractional coordinates and isotropic displacement parameters were refined. For the remaining H atoms on the water molecules O5H2 and O6H2, and the amide fragment –N1H2, the fractional coordinates were refined, with Uiso(H) = 1.2Ueq(O) or 1.2Ueq(N), respectively.
In addition to the much studied layered double hydroxides (LDH), such as hydrotalcite, Mg6Al2(OH)16(CO3).4H2O, and related transition metal substituted phases (Rives, 2001; Evans & Slade, 2006), a second class of materials with structures derived from brucite, Mg(OH)2, namely the layered metal hydroxide salts (LHS), are gaining in scientific and technological importance (Arisaga et al., 2007). This results from their potential uses as anion-exchangers, catalysts and two-dimensional magnetic materials (Laget et al., 1998, 1999; Yamanaka et al., 1992). The LHS have the general formula M2+(OH)2x(Am-)x/m.nH2O, where M is a divalent metal and A is a counteranion. Examples include M2(OH)3(A) (M = Co, Ni, Cu; A = Cl-, NO3-, CH3COO-), Cd(OH)NO3.H2O and Zn5(OH)8(NO3)2.2H2O (Arisaga et al., 2007). Most pertinent to this work are the copper hydroxide salts, Cu2(OH)3(A), where A can be a simple anion as above, or a long-chain organic anion, such as an alkylsulfonate (n-CmH2m+1OSO2-; Park & Lee, 2005) or alkylcarboxylate (n-CmH2m+1COO-; Fujita & Awaga, 1996, 1997). Adjusting the alkyl chain length in the organic anions enables the magnetic behaviour of the layered materials to be tuned by changing the relative importance of the intra- and interlayer interactions.
Full structural studies of Cu2(OH)3(A), using single-crystal and powder X-ray diffraction, have been reported in a number of cases [A = NO2- (Schmidt et al., 1993), NO3- (Effenberger, 1983; Guillou et al., 1994), Cl- (Hawthorne, 1985), Br- (Ostwald et al., 1961) and CH3COO- (Maschiocci et al., 1997)]. These results, together with EXAFS studies of compounds with A = CH3COO- and Br- (Jiménez-López et al., 1993), provide evidence for the coordination of A to Cu atoms in the copper hydroxide layers. All reported structures exhibit a Cu2(OH)3Cl botallackite-type structure, in which the Cu atoms lie in 4+2 (O + A) and 4+1+1 (O + O + A) environments.
In this work, we report the structure of the title new inorganic–organic hybrid material, Cu2(OH)3[H2NC(═O)NCN].2H2O, in which cyanoureate ions and water molecules reside between the copper(II) hydroxide layers. The cyanoureate ions coordinate to Cu via the nitrile N atoms. Within the layers, there are three crystallographically distinct Cu atoms, two of which, Cu2 and Cu3, reside on special positions, 2a and 2c, respectively, while the third, Cu1, lies on a general position, 4e (Fig. 1). Each Cu atom has an elongated octahedral coordination, with four shorter Cu—O bonds (~2 Å) and two longer bonds (>2.3 Å), in accordance with the Jahn–Teller distortion of Cu in a +2 oxidation state (Table 1). In the cases of atoms Cu1 and Cu2, the longer bonds are to atom N3, and for Cu3, to atom O3. Each O atom within the layer (O1, O2 and O3) is coordinated to three Cu atoms and an H atom. All the H atoms in the structure were located in difference Fourier maps. The copper hydroxide layers lie parallel to the bc plane and stack along the a axis in an AA fashion. The CuII ions within the layers form a triangular array (Fig. 2), with the shortest Cu···Cu distances in the range 3.010 (3)–3.164 (3) Å, comparable with those found in other Cu2(OH)3A compounds known to exhibit intralayer magnetic interactions (Jiménez-López et al., 1993).
The interlayer space contains cyanoureate ions, formed by the hydrolysis of dicyanamide anions ([N(CN)2-] under basic conditions, together with water molecules. The bond lengths and angles within the cyanourea moiety are in good agreement with those observed for the anions in Ag+[H2NC(═O)NCN]- (Britton, 1987) and NH4+[H2NC(═O)NCN]- (Lotsch & Schnick, 2004). The cyanoureate ion is almost planar, with a cis arrangement of the N3/C2/N2 and O4 groups. This conformation enables atom O4 of the C1═O4 carbonyl group to form a hydrogen bond with the O1—H1 hydroxide group of the layer, as well as with the interlayer water molecules O5H2 and O6H2 (Table 2, Fig. 3). The other hydroxide groups, O2H2 and O3H3, also form hydrogen bonds with water molecules O6H2 and O5H2, respectively, which in turn interact with each other. Hydrogen-bonding interactions between the amide N1H2 and the central atom N2 of cyanoureate anions associated with adjacent layers serve to hold the layers together.
To the best of our knowledge, Cu2(OH)3[H2NC(═O)NCN].2H2O is the first example of a layered solid in which the cyanoureate ion acts a ligand coordinating to a metal centre. Compounds are known in which the cyanoureate ion links metal atoms into dimers, e.g. in [Cu2{NCNC(═ O)NH2}(R3Bm)](ClO4)3.4H2O (where R3Bm is an m-xylyl-linked cryptand; Escuer et al., 2004), and chains, e.g. in Ag+[H2NC(═O)NCN]- (Britton, 1987). Interestingly, coordination to the Cu atoms occurs through atom N3 of the nitrile group rather than through atom N2, which formally carries the negative charge of the ion. In this respect, the behaviour of the ligand resembles that of the dicyanamide ion (Batten & Murray, 2003), particularly as observed in the two polymorphs of silver dicyanamide (Britton & Chow, 1977; Britton, 1990).
Data collection: Xcalibur (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS (Betteridge et al., 2003).
[Cu2(C2H2N3O)(OH)3]·2H2O | F(000) = 592 |
Mr = 298.22 | Dx = 2.440 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 6870 reflections |
a = 12.4648 (5) Å | θ = 5–32° |
b = 6.3096 (2) Å | µ = 5.25 mm−1 |
c = 10.6032 (5) Å | T = 150 K |
β = 103.269 (4)° | Block, blue-green |
V = 811.66 (6) Å3 | 0.20 × 0.08 × 0.06 mm |
Z = 4 |
Oxford Diffraction Xcalibur area-detector diffractometer | 2688 independent reflections |
Radiation source: fine-focus sealed tube | 1731 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.028 |
ω/2θ scans | θmax = 32.6°, θmin = 3.4° |
Absorption correction: multi-scan DENZO/SCALEPACK (Otwinowski & Minor, 1997) | h = −18→18 |
Tmin = 0.67, Tmax = 0.73 | k = −9→8 |
6870 measured reflections | l = −10→15 |
Refinement on F | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.031 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.025 | Method, part 1, Chebychev polynomial (Watkin, 1994; Prince, 1982),
[weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)],
where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = robust weighting (Prince, 1982), W = [weight] * [1-(deltaF/6*sigmaF)2]2 Ai are: 35.5 -37.7 28.1 |
S = 1.11 | (Δ/σ)max = 0.001 |
1731 reflections | Δρmax = 0.96 e Å−3 |
151 parameters | Δρmin = −0.81 e Å−3 |
9 restraints |
[Cu2(C2H2N3O)(OH)3]·2H2O | V = 811.66 (6) Å3 |
Mr = 298.22 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 12.4648 (5) Å | µ = 5.25 mm−1 |
b = 6.3096 (2) Å | T = 150 K |
c = 10.6032 (5) Å | 0.20 × 0.08 × 0.06 mm |
β = 103.269 (4)° |
Oxford Diffraction Xcalibur area-detector diffractometer | 2688 independent reflections |
Absorption correction: multi-scan DENZO/SCALEPACK (Otwinowski & Minor, 1997) | 1731 reflections with I > 2σ(I) |
Tmin = 0.67, Tmax = 0.73 | Rint = 0.028 |
6870 measured reflections |
R[F2 > 2σ(F2)] = 0.031 | 9 restraints |
wR(F2) = 0.025 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.11 | Δρmax = 0.96 e Å−3 |
1731 reflections | Δρmin = −0.81 e Å−3 |
151 parameters |
x | y | z | Uiso*/Ueq | ||
Cu1 | 0.007607 (19) | 0.23275 (4) | 0.25437 (2) | 0.0061 | |
Cu2 | 0.0000 | 0.5000 | 0.5000 | 0.0056 | |
Cu3 | 0.0000 | 0.0000 | 0.5000 | 0.0053 | |
O1 | 0.08154 (11) | 0.2938 (2) | 0.61558 (15) | 0.0058 | |
O2 | 0.06983 (14) | −0.0258 (2) | 0.34803 (17) | 0.0066 | |
O3 | −0.06870 (12) | 0.2500 (2) | 0.39781 (15) | 0.0056 | |
O4 | 0.30960 (11) | 0.2882 (3) | 0.66427 (16) | 0.0155 | |
O5 | 0.29541 (14) | 0.8486 (3) | 0.64881 (18) | 0.0185 | |
O6 | 0.29652 (13) | 0.9384 (3) | 0.37316 (18) | 0.0199 | |
N1 | 0.48208 (16) | 0.3833 (4) | 0.6566 (2) | 0.0253 | |
N2 | 0.34458 (14) | 0.4518 (4) | 0.4811 (2) | 0.0154 | |
N3 | 0.14777 (17) | 0.4720 (3) | 0.3721 (2) | 0.0126 | |
C1 | 0.37405 (16) | 0.3694 (3) | 0.6025 (2) | 0.0133 | |
C2 | 0.23926 (17) | 0.4572 (4) | 0.4272 (2) | 0.0107 | |
H1 | 0.1498 (9) | 0.317 (5) | 0.637 (3) | 0.011 (6)* | |
H2 | 0.1390 (9) | −0.039 (5) | 0.361 (3) | 0.014 (7)* | |
H3 | −0.1375 (9) | 0.235 (5) | 0.375 (3) | 0.021 (8)* | |
H4 | 0.504 (2) | 0.311 (5) | 0.725 (2) | 0.0300* | |
H5 | 0.526 (2) | 0.433 (6) | 0.614 (3) | 0.0300* | |
H6 | 0.307 (2) | 0.829 (5) | 0.5742 (15) | 0.0240* | |
H7 | 0.296 (3) | 0.9814 (17) | 0.659 (4) | 0.0240* | |
H8 | 0.315 (3) | 1.053 (3) | 0.342 (3) | 0.0240* | |
H9 | 0.310 (3) | 0.845 (4) | 0.321 (3) | 0.0240* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.00884 (10) | 0.00598 (9) | 0.00393 (11) | 0.00157 (11) | 0.00209 (8) | 0.00160 (11) |
Cu2 | 0.0077 (2) | 0.0046 (2) | 0.0039 (2) | 0.00026 (8) | 0.00002 (15) | 0.00009 (9) |
Cu3 | 0.0080 (2) | 0.0048 (2) | 0.0034 (2) | 0.00099 (8) | 0.00181 (15) | 0.00063 (10) |
O1 | 0.0069 (5) | 0.0056 (6) | 0.0052 (6) | 0.0005 (5) | 0.0020 (4) | 0.0000 (5) |
O2 | 0.0081 (7) | 0.0078 (5) | 0.0042 (7) | 0.0007 (5) | 0.0021 (5) | −0.0002 (5) |
O3 | 0.0081 (5) | 0.0056 (6) | 0.0037 (6) | −0.0014 (5) | 0.0022 (4) | −0.0012 (5) |
O4 | 0.0124 (6) | 0.0200 (7) | 0.0145 (7) | −0.0008 (6) | 0.0040 (5) | 0.0035 (7) |
O5 | 0.0213 (8) | 0.0159 (7) | 0.0177 (9) | −0.0013 (6) | 0.0034 (6) | −0.0020 (7) |
O6 | 0.0191 (7) | 0.0188 (8) | 0.0227 (9) | 0.0017 (7) | 0.0064 (7) | 0.0032 (8) |
N1 | 0.0103 (8) | 0.0479 (13) | 0.0159 (10) | −0.0009 (8) | −0.0005 (7) | 0.0125 (9) |
N2 | 0.0090 (8) | 0.0242 (8) | 0.0131 (10) | −0.0039 (8) | 0.0028 (6) | 0.0023 (9) |
N3 | 0.0136 (9) | 0.0138 (7) | 0.0102 (9) | 0.0005 (7) | 0.0028 (7) | −0.0009 (7) |
C1 | 0.0109 (8) | 0.0161 (8) | 0.0127 (10) | 0.0001 (6) | 0.0027 (7) | 0.0032 (7) |
C2 | 0.0136 (9) | 0.0136 (7) | 0.0058 (9) | −0.0025 (8) | 0.0040 (7) | −0.0008 (8) |
Cu1—O1i | 1.9145 (17) | Cu3—O3 | 1.9923 (15) |
Cu1—O2 | 1.9736 (16) | Cu3—O3v | 1.9923 (15) |
Cu1—O2ii | 1.9877 (16) | O1—H1 | 0.841 (9) |
Cu1—O3 | 1.9733 (17) | O2—H2 | 0.846 (9) |
Cu1—N3 | 2.426 (2) | O3—H3 | 0.841 (9) |
Cu1—N3iii | 2.658 (2) | O4—C1 | 1.256 (3) |
Cu2—O1 | 1.9119 (14) | O5—H6 | 0.845 (10) |
Cu2—O1iv | 1.9119 (14) | O5—H7 | 0.844 (9) |
Cu2—O3 | 1.9925 (14) | O6—H8 | 0.850 (10) |
Cu2—O3iv | 1.9925 (14) | O6—H9 | 0.85 (3) |
Cu2—N3 | 2.532 (2) | N1—C1 | 1.340 (3) |
Cu2—N3iv | 2.532 (2) | N1—H4 | 0.846 (10) |
Cu3—O1 | 2.3238 (15) | N1—H5 | 0.85 (3) |
Cu3—O1v | 2.3238 (15) | N2—C1 | 1.359 (3) |
Cu3—O2 | 2.0061 (18) | N2—C2 | 1.307 (3) |
Cu3—O2v | 2.0061 (18) | N3—C2 | 1.159 (3) |
N3iii—Cu1—O2ii | 89.58 (6) | O1v—Cu3—O3 | 105.27 (6) |
N3iii—Cu1—O1i | 88.94 (6) | O2v—Cu3—O3 | 99.27 (6) |
O2ii—Cu1—O1i | 84.62 (7) | O3v—Cu3—O3 | 180 |
N3iii—Cu1—O2 | 84.20 (6) | O1—Cu3—O3 | 74.73 (6) |
O2ii—Cu1—O2 | 173.67 (5) | O2—Cu3—O3 | 80.73 (6) |
O1i—Cu1—O2 | 96.40 (7) | Cu3—O1—Cu1vi | 96.09 (6) |
N3iii—Cu1—O3 | 89.92 (6) | Cu3—O1—Cu2 | 95.80 (6) |
O2ii—Cu1—O3 | 96.85 (7) | Cu1vi—O1—Cu2 | 105.87 (7) |
O1i—Cu1—O3 | 178.14 (6) | Cu3—O1—H1 | 125 (2) |
O2—Cu1—O3 | 82.01 (7) | Cu1vi—O1—H1 | 116 (2) |
N3iii—Cu1—N3 | 179.15 (2) | Cu2—O1—H1 | 114 (2) |
O2ii—Cu1—N3 | 90.36 (7) | Cu3—O2—Cu1iii | 104.78 (8) |
O1i—Cu1—N3 | 91.90 (7) | Cu3—O2—Cu1 | 98.30 (7) |
O2—Cu1—N3 | 95.84 (7) | Cu1iii—O2—Cu1 | 105.85 (8) |
O3—Cu1—N3 | 89.24 (7) | Cu3—O2—H2 | 120 (2) |
N3iv—Cu2—O3iv | 85.88 (7) | Cu1iii—O2—H2 | 111 (2) |
N3iv—Cu2—O1iv | 87.18 (7) | Cu1—O2—H2 | 116 (2) |
O3iv—Cu2—O1iv | 84.76 (6) | Cu2—O3—Cu3 | 104.69 (6) |
N3iv—Cu2—O1 | 92.82 (7) | Cu2—O3—Cu1 | 103.87 (7) |
O3iv—Cu2—O1 | 95.24 (6) | Cu3—O3—Cu1 | 98.77 (7) |
O1iv—Cu2—O1 | 180 | Cu2—O3—H3 | 122 (2) |
N3iv—Cu2—O3 | 94.12 (7) | Cu3—O3—H3 | 111 (2) |
O3iv—Cu2—O3 | 180 | Cu1—O3—H3 | 114 (2) |
O1iv—Cu2—O3 | 95.24 (6) | H6—O5—H7 | 106 (3) |
O1—Cu2—O3 | 84.76 (6) | H8—O6—H9 | 103 (3) |
N3iv—Cu2—N3 | 180 | C1—N1—H4 | 115 (2) |
O3iv—Cu2—N3 | 94.12 (7) | C1—N1—H5 | 120 (2) |
O1iv—Cu2—N3 | 92.82 (7) | H4—N1—H5 | 122 (3) |
O1—Cu2—N3 | 87.18 (7) | C1—N2—C2 | 116.8 (2) |
O3—Cu2—N3 | 85.88 (7) | Cu1—N3—Cu2 | 78.03 (6) |
O1v—Cu3—O2v | 105.69 (6) | Cu1—N3—Cu1ii | 76.72 (6) |
O1v—Cu3—O3v | 74.73 (6) | Cu2—N3—Cu1ii | 72.03 (6) |
O2v—Cu3—O3v | 80.73 (6) | Cu1—N3—C2 | 135.90 (18) |
O1v—Cu3—O1 | 180 | Cu2—N3—C2 | 119.21 (19) |
O2v—Cu3—O1 | 74.31 (6) | Cu1ii—N3—C2 | 145.31 (18) |
O3v—Cu3—O1 | 105.27 (6) | N2—C1—N1 | 114.0 (2) |
O1v—Cu3—O2 | 74.31 (6) | N2—C1—O4 | 125.73 (18) |
O2v—Cu3—O2 | 180 | N1—C1—O4 | 120.3 (2) |
O3v—Cu3—O2 | 99.27 (6) | N2—C2—N3 | 174.7 (3) |
O1—Cu3—O2 | 105.69 (6) |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x, y+1/2, −z+1/2; (iii) −x, y−1/2, −z+1/2; (iv) −x, −y+1, −z+1; (v) −x, −y, −z+1; (vi) x, −y+1/2, z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4 | 0.84 (1) | 1.95 (1) | 2.770 (2) | 163 (3) |
O2—H2···O6vii | 0.85 (1) | 1.94 (1) | 2.786 (2) | 175 |
O3—H3···O5iv | 0.84 (1) | 2.00 (2) | 2.824 (2) | 167 |
N1—H5···N2viii | 0.85 (3) | 2.21 (3) | 3.055 (3) | 174 |
O5—H6···O6 | 0.85 (1) | 2.22 (2) | 2.980 (3) | 150 (3) |
O5—H7···O4ix | 0.84 (1) | 1.94 (1) | 2.782 (3) | 172 |
O6—H8···O4x | 0.85 (1) | 2.12 (3) | 2.842 (3) | 142 |
O6—H9···O5x | 0.85 (3) | 2.17 (3) | 2.987 (3) | 161 |
Symmetry codes: (iv) −x, −y+1, −z+1; (vii) x, y−1, z; (viii) −x+1, −y+1, −z+1; (ix) x, y+1, z; (x) x, −y+3/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | [Cu2(C2H2N3O)(OH)3]·2H2O |
Mr | 298.22 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 150 |
a, b, c (Å) | 12.4648 (5), 6.3096 (2), 10.6032 (5) |
β (°) | 103.269 (4) |
V (Å3) | 811.66 (6) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 5.25 |
Crystal size (mm) | 0.20 × 0.08 × 0.06 |
Data collection | |
Diffractometer | Oxford Diffraction Xcalibur area-detector |
Absorption correction | Multi-scan DENZO/SCALEPACK (Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.67, 0.73 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6870, 2688, 1731 |
Rint | 0.028 |
(sin θ/λ)max (Å−1) | 0.757 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.025, 1.11 |
No. of reflections | 1731 |
No. of parameters | 151 |
No. of restraints | 9 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.96, −0.81 |
Computer programs: Xcalibur (Oxford Diffraction, 2006), CrysAlis RED (Oxford Diffraction, 2006), SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), CAMERON (Watkin et al., 1996).
Cu1—O1i | 1.9145 (17) | Cu3—O1 | 2.3238 (15) |
Cu1—O2 | 1.9736 (16) | Cu3—O2 | 2.0061 (18) |
Cu1—O2ii | 1.9877 (16) | Cu3—O3 | 1.9923 (15) |
Cu1—O3 | 1.9733 (17) | O4—C1 | 1.256 (3) |
Cu1—N3 | 2.426 (2) | N1—C1 | 1.340 (3) |
Cu1—N3iii | 2.658 (2) | N2—C1 | 1.359 (3) |
Cu2—O1 | 1.9119 (14) | N2—C2 | 1.307 (3) |
Cu2—O3 | 1.9925 (14) | N3—C2 | 1.159 (3) |
Cu2—N3 | 2.532 (2) | ||
N3iii—Cu1—O2ii | 89.58 (6) | O2v—Cu3—O1 | 74.31 (6) |
N3iii—Cu1—O1i | 88.94 (6) | O3v—Cu3—O1 | 105.27 (6) |
O2ii—Cu1—O1i | 84.62 (7) | O2v—Cu3—O2 | 180 |
N3iii—Cu1—O2 | 84.20 (6) | O3v—Cu3—O2 | 99.27 (6) |
O2ii—Cu1—O2 | 173.67 (5) | O1—Cu3—O2 | 105.69 (6) |
O1i—Cu1—O2 | 96.40 (7) | O3v—Cu3—O3 | 180 |
N3iii—Cu1—O3 | 89.92 (6) | O1—Cu3—O3 | 74.73 (6) |
O2ii—Cu1—O3 | 96.85 (7) | O2—Cu3—O3 | 80.73 (6) |
O1i—Cu1—O3 | 178.14 (6) | Cu3—O1—Cu1vi | 96.09 (6) |
O2—Cu1—O3 | 82.01 (7) | Cu3—O1—Cu2 | 95.80 (6) |
N3iii—Cu1—N3 | 179.15 (2) | Cu1vi—O1—Cu2 | 105.87 (7) |
O2ii—Cu1—N3 | 90.36 (7) | Cu3—O2—Cu1iii | 104.78 (8) |
O1i—Cu1—N3 | 91.90 (7) | Cu3—O2—Cu1 | 98.30 (7) |
O2—Cu1—N3 | 95.84 (7) | Cu1iii—O2—Cu1 | 105.85 (8) |
O3—Cu1—N3 | 89.24 (7) | Cu2—O3—Cu3 | 104.69 (6) |
N3iv—Cu2—O1 | 92.82 (7) | Cu2—O3—Cu1 | 103.87 (7) |
O3iv—Cu2—O1 | 95.24 (6) | Cu3—O3—Cu1 | 98.77 (7) |
O1iv—Cu2—O1 | 180 | C1—N2—C2 | 116.8 (2) |
N3iv—Cu2—O3 | 94.12 (7) | Cu1—N3—C2 | 135.90 (18) |
O3iv—Cu2—O3 | 180 | Cu2—N3—C2 | 119.21 (19) |
O1—Cu2—O3 | 84.76 (6) | Cu1ii—N3—C2 | 145.31 (18) |
N3iv—Cu2—N3 | 180 | N2—C1—N1 | 114.0 (2) |
O1—Cu2—N3 | 87.18 (7) | N2—C1—O4 | 125.73 (18) |
O3—Cu2—N3 | 85.88 (7) | N1—C1—O4 | 120.3 (2) |
O1v—Cu3—O1 | 180 | N2—C2—N3 | 174.7 (3) |
Symmetry codes: (i) x, −y+1/2, z−1/2; (ii) −x, y+1/2, −z+1/2; (iii) −x, y−1/2, −z+1/2; (iv) −x, −y+1, −z+1; (v) −x, −y, −z+1; (vi) x, −y+1/2, z+1/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O4 | 0.841 (9) | 1.954 (14) | 2.770 (2) | 163 (3) |
O2—H2···O6vii | 0.846 (9) | 1.943 (14) | 2.786 (2) | 175 |
O3—H3···O5iv | 0.841 (9) | 1.997 (16) | 2.824 (2) | 167 |
N1—H5···N2viii | 0.85 (3) | 2.21 (3) | 3.055 (3) | 174 |
O5—H6···O6 | 0.845 (10) | 2.216 (18) | 2.980 (3) | 150 (3) |
O5—H7···O4ix | 0.844 (9) | 1.943 (11) | 2.782 (3) | 172 |
O6—H8···O4x | 0.849 (10) | 2.12 (3) | 2.842 (3) | 142 |
O6—H9···O5x | 0.850 (30) | 2.17 (3) | 2.987 (3) | 161 |
Symmetry codes: (iv) −x, −y+1, −z+1; (vii) x, y−1, z; (viii) −x+1, −y+1, −z+1; (ix) x, y+1, z; (x) x, −y+3/2, z−1/2. |
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In addition to the much studied layered double hydroxides (LDH), such as hydrotalcite, Mg6Al2(OH)16(CO3).4H2O, and related transition metal substituted phases (Rives, 2001; Evans & Slade, 2006), a second class of materials with structures derived from brucite, Mg(OH)2, namely the layered metal hydroxide salts (LHS), are gaining in scientific and technological importance (Arisaga et al., 2007). This results from their potential uses as anion-exchangers, catalysts and two-dimensional magnetic materials (Laget et al., 1998, 1999; Yamanaka et al., 1992). The LHS have the general formula M2+(OH)2x(Am-)x/m.nH2O, where M is a divalent metal and A is a counteranion. Examples include M2(OH)3(A) (M = Co, Ni, Cu; A = Cl-, NO3-, CH3COO-), Cd(OH)NO3.H2O and Zn5(OH)8(NO3)2.2H2O (Arisaga et al., 2007). Most pertinent to this work are the copper hydroxide salts, Cu2(OH)3(A), where A can be a simple anion as above, or a long-chain organic anion, such as an alkylsulfonate (n-CmH2m+1OSO2-; Park & Lee, 2005) or alkylcarboxylate (n-CmH2m+1COO-; Fujita & Awaga, 1996, 1997). Adjusting the alkyl chain length in the organic anions enables the magnetic behaviour of the layered materials to be tuned by changing the relative importance of the intra- and interlayer interactions.
Full structural studies of Cu2(OH)3(A), using single-crystal and powder X-ray diffraction, have been reported in a number of cases [A = NO2- (Schmidt et al., 1993), NO3- (Effenberger, 1983; Guillou et al., 1994), Cl- (Hawthorne, 1985), Br- (Ostwald et al., 1961) and CH3COO- (Maschiocci et al., 1997)]. These results, together with EXAFS studies of compounds with A = CH3COO- and Br- (Jiménez-López et al., 1993), provide evidence for the coordination of A to Cu atoms in the copper hydroxide layers. All reported structures exhibit a Cu2(OH)3Cl botallackite-type structure, in which the Cu atoms lie in 4+2 (O + A) and 4+1+1 (O + O + A) environments.
In this work, we report the structure of the title new inorganic–organic hybrid material, Cu2(OH)3[H2NC(═O)NCN].2H2O, in which cyanoureate ions and water molecules reside between the copper(II) hydroxide layers. The cyanoureate ions coordinate to Cu via the nitrile N atoms. Within the layers, there are three crystallographically distinct Cu atoms, two of which, Cu2 and Cu3, reside on special positions, 2a and 2c, respectively, while the third, Cu1, lies on a general position, 4e (Fig. 1). Each Cu atom has an elongated octahedral coordination, with four shorter Cu—O bonds (~2 Å) and two longer bonds (>2.3 Å), in accordance with the Jahn–Teller distortion of Cu in a +2 oxidation state (Table 1). In the cases of atoms Cu1 and Cu2, the longer bonds are to atom N3, and for Cu3, to atom O3. Each O atom within the layer (O1, O2 and O3) is coordinated to three Cu atoms and an H atom. All the H atoms in the structure were located in difference Fourier maps. The copper hydroxide layers lie parallel to the bc plane and stack along the a axis in an AA fashion. The CuII ions within the layers form a triangular array (Fig. 2), with the shortest Cu···Cu distances in the range 3.010 (3)–3.164 (3) Å, comparable with those found in other Cu2(OH)3A compounds known to exhibit intralayer magnetic interactions (Jiménez-López et al., 1993).
The interlayer space contains cyanoureate ions, formed by the hydrolysis of dicyanamide anions ([N(CN)2-] under basic conditions, together with water molecules. The bond lengths and angles within the cyanourea moiety are in good agreement with those observed for the anions in Ag+[H2NC(═O)NCN]- (Britton, 1987) and NH4+[H2NC(═O)NCN]- (Lotsch & Schnick, 2004). The cyanoureate ion is almost planar, with a cis arrangement of the N3/C2/N2 and O4 groups. This conformation enables atom O4 of the C1═O4 carbonyl group to form a hydrogen bond with the O1—H1 hydroxide group of the layer, as well as with the interlayer water molecules O5H2 and O6H2 (Table 2, Fig. 3). The other hydroxide groups, O2H2 and O3H3, also form hydrogen bonds with water molecules O6H2 and O5H2, respectively, which in turn interact with each other. Hydrogen-bonding interactions between the amide N1H2 and the central atom N2 of cyanoureate anions associated with adjacent layers serve to hold the layers together.
To the best of our knowledge, Cu2(OH)3[H2NC(═O)NCN].2H2O is the first example of a layered solid in which the cyanoureate ion acts a ligand coordinating to a metal centre. Compounds are known in which the cyanoureate ion links metal atoms into dimers, e.g. in [Cu2{NCNC(═ O)NH2}(R3Bm)](ClO4)3.4H2O (where R3Bm is an m-xylyl-linked cryptand; Escuer et al., 2004), and chains, e.g. in Ag+[H2NC(═O)NCN]- (Britton, 1987). Interestingly, coordination to the Cu atoms occurs through atom N3 of the nitrile group rather than through atom N2, which formally carries the negative charge of the ion. In this respect, the behaviour of the ligand resembles that of the dicyanamide ion (Batten & Murray, 2003), particularly as observed in the two polymorphs of silver dicyanamide (Britton & Chow, 1977; Britton, 1990).