Poly­[[(pyridazine-κN)copper(I)]-μ₃-thio­cyanato-κ³N:S:S]

In the crystal structure of the title compound, [Cu(NCS)(C₄H₄N₂)]_n, each Cu atom is coordinated by one N atom of one pyridazine ligand and by one N and two S atoms of three symmetry-related thio­cyanate anions within a distorted tetrahedron. Only one N atom of the pyridazine ligand is involved in Cu coordination. The Cu atoms are connected via the thio­cyanate anions, forming layers parallel to the ab plane.

S1. Comment

Recently, we have investigated coordination polymers based on copper(I) halides and pseudohalides and aromatic dinitrogen donor ligands (Näther et al., 2002; Näther & Jeß, 2002; Näther, Wriedt & Jeß, 2003; Näther, Jeß et al., 2003; Näther & Jeß, 2003; Näther, Greve et al., 2003). In these compounds, typical CuX substructures occur, which are mostly connected by donor ligands. However, in some cases the dinitrogen ligand does not bridge different Cu atoms. Frequently, for one particular copper(I) halide or pseudohalide, several compounds are found which differ in their ratio between the inorganic and organic parts. Therefore, e.g. 1:1, 2:1, 4:1 or 3:2 compounds are found.

We have found that most of the amine-rich coordination polymers can be transformed into amine-poor coordination polymers via a well directed thermal decomposition. Therefore, we have begun systematic investigations of the synthesis, structure and thermal properties of such compounds. In some of these investigations, we were particularly interested in copper(I) thiocyanate compounds with aromatic dinitrogen ligands such as pyrazine, pyrimidine and pyridazine. With pyrimidine and pyrazine, only the 2:1 compound catena[bis(µ₃-thiocyanato)(µ₂-pyrimidine)dicopper(I) (Barnett et al., 2000; Teichert & Sheldrick, 2000), the 1:1 compound catena[(µ₂-thiocyanato)(µ₂-pyrazine)copper(I) (Goher & Mautner, 1999) and the 2:1 compound catena[bis(µ₂-thiocyanato)(µ₂-pyrimidine)dicopper(I) (Blake et al., 1998, 1999) have been reported. However, with pyridazine as the ligand, no structures have been reported to date. Against this background, we present here the structure of the title compound, (I), with pyridazine as the ligand. \sch

In the structure of (I), the Cu atom is coordinated by one N atom of the pyridazine ligand, and one N atom and two S atoms of three symmetry-related thiocyanate ligands. Only one of the two pyridazine N atoms is involved in Cu coordination; the second N atom is not involved in any interaction.

As expected, the Cu—N bond length to the negatively charged thiocyanate anion is significantly shorter than that to the neutral pyridazine ligand. However, the bond lengths and angles around the Cu atom are comparable with those observed in other copper(I) thiocyanate coordination polymers with aromatic dinitrogen ligands (Barnett et al., 2000; Teichert & Sheldrick, 2000; Goher & Mautner, 1999; Blake et al., 1998, 1999), and the coordination polyhedron around the Cu atom can be described as a distorted tetrahedron.

In contrast with most other CuX coordination polymers (where X is Cl, Br, N, SCN or CN), compound (I) contains an unusual CuX substructure. The Cu atoms are connected via the S atoms of the thiocyanate anions into zigzag-like single chains which are elongated in the direction of the a axis. These Cu atoms are oriented in the direction of the lone pairs of the S atoms. These single chains are connected via the N atoms of the thiocyanate anions into layers which are parallel to the ab plane. As expected, the Cu atoms are oriented in the direction of the N—C—S vector. Only one of the two N atoms of the pyridazine ligand is involved in Cu coordination. It must be noted that a similar coordination network is also found in catena-[(µ₃-thiocyanato-N,S,S)pyridylcopper] and catena-[(µ₃-thiocyanato-N,S,S)pyridylsilver] (Krautscheid et al., 1998). These compounds are not isomorphous with (I), but the topology of the coordination network is similar. Concerning the notation of these compounds, they use the term catena, whereas we use poly because the compounds exhibit a layered structure.

In contrast with (I), in the 1:1 compound catena[(µ₂-thiocyanato)(µ₂-pyrazine)copper(I) (Goher & Mautner, 1999), which exhibits the same ratio between copper(I) thiocyanate and the N-donor ligand, a CuX substructure is found which is frequently observed in such coordination polymers with CuCl, CuBr or CuI. CuX single chains are observed which are connected into layers by the dinitrogen ligands. In this structure, the N-donor ligand acts as a bridging ligand and the S atoms of the thiocyanate anions are coordinated to only one Cu atom. This clearly shows the influence of the position of the N-donor atoms on the topology of the coordination network. It is interesting to note that this compound also crystallizes in the chiral space group P2₁. Because of the different stoichiometry, the structures of the amine-poor 2:1 compounds catena[bis(µ₃-thiocyanato)(µ₂-pyrimidine)dicopper(I) (Barnett et al., 2000) and catena[bis(µ₂-thiocyanato)(µ₂-pyrimidine)dicopper(I) (Blake et al., 1998, 1999) cannot be compared with that of (I).

Concerning the thermal behaviour of (I), we have found that no amine-poor coordination polymers can be observed on heating. If (I) is heated in a thermobalance starting at about 210° (C or K?), a mass loss is observed which corresponds to the loss of all of the amine ligands. The final product of this thermal decomposition reaction was identified as copper(I)thiocyanate by X-ray powder diffraction.

S2. Experimental

The title compound was prepared by the reaction of CuSCN (0.1 mmol) and pyridazine (0.1 mmol) in acetonitrile (4 ml) in a Teflon-lined steel autoclave at 373 K. After 3 d, the reaction mixture was cooled, and the product was filtered off and washed with ethanol and diethyl ether. The homogeneity of theproduct was checked by comparison of the experimental powder pattern with that calculated from the single-crystal data. In addition, the CHN content obtained by elemental analysis was in agreement with that calculated.

S3. Refinement

H atoms were positioned with idealized geometry (C—H distances of 0.93 Å) and refined with fixed isotropic displacement parameters [U_iso(H) = 1.2U_eqC(aromatic)] using the riding model. The absolute structure could not be determined using the Flack x test (Flack, 1983). Therefore, a twin refinement for racemic twinning was performed yielding a BASF parameter of 0.33 (2). However, if no twin refinement was performed, the reliability factors were different for a refinement using the current setting [wR₂ = 0.0722, R₁ for F_o > 4σ(F_o) = 0.0313] and for the inverse structure [wR₂ = 0.1006, R₁ for F_o > 4σ(F_o) = 0.0388].

Computing details

Data collection: DIF4 (Stoe & Cie, 1990); cell refinement: DIF4; data reduction: REDU4 (Stoe & Cie, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL (Bruker AXS 1998); software used to prepare material for publication: CIFTAB in SHELXL97.

Figures

	Fig. 1. A view of the copper coordination in (I), with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii [symmetry codes: (i) x + 1, −y, z; (ii) 1 − x, y + 1/2, 2 − z].
	Fig. 2. The crystal structure of (I), viewed along the crystallographic c axis.

Poly[[(pyridazine-κN)copper(I)]-µ₃-thiocyanato-κ³N:S:S]

Crystal data

[Cu(NCS)(C4H4N2)]	Dx = 1.980 Mg m^−3
Mr = 201.71	Melting point: decomposes at about 483 K to CuSCN K
Monoclinic, P21	Mo Kα radiation, λ = 0.71073 Å
a = 3.8338 (7) Å	Cell parameters from 104 reflections
b = 10.5755 (12) Å	θ = 15–20°
c = 8.3938 (12) Å	µ = 3.45 mm^−1
β = 96.182 (14)°	T = 293 K
V = 338.34 (9) Å^3	Block, yellow
Z = 2	0.12 × 0.09 × 0.08 mm
F(000) = 200

Data collection

Stoe AEDII diffractometer	1620 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.017
Graphite monochromator	θmax = 30.0°, θmin = 3.1°
ω scans	h = 0→5
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1998)	k = −14→13
Tmin = 0.698, Tmax = 0.757	l = −11→11
2193 measured reflections	4 standard reflections every 120 min
1943 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.028	H-atom parameters constrained
wR(F^2) = 0.062	w = 1/[σ^2(Fo^2) + (0.0262P)^2 + 0.0638P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max = 0.001
1943 reflections	Δρmax = 0.34 e Å^−3
93 parameters	Δρmin = −0.49 e Å^−3
1 restraint	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.021 (3)

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
Cu1	0.77947 (11)	0.47073 (4)	0.90923 (4)	0.04060 (13)
S1	0.31381 (18)	0.41702 (6)	1.07211 (8)	0.02963 (15)
C10	0.2772 (7)	0.2612 (2)	1.0848 (3)	0.0247 (5)
N3	0.2517 (7)	0.1528 (2)	1.0953 (3)	0.0339 (6)
N1	0.7599 (7)	0.3551 (2)	0.7181 (3)	0.0315 (5)
N2	0.8524 (8)	0.4036 (3)	0.5802 (3)	0.0408 (6)
C1	0.6837 (9)	0.2329 (3)	0.7261 (4)	0.0355 (6)
H1	0.6216	0.2008	0.8222	0.043*
C2	0.6927 (9)	0.1508 (3)	0.5972 (4)	0.0428 (7)
H2	0.6344	0.0659	0.6055	0.051*
C3	0.7897 (9)	0.1992 (4)	0.4587 (4)	0.0427 (8)
H3	0.8031	0.1486	0.3689	0.051*
C4	0.8671 (10)	0.3260 (3)	0.4567 (4)	0.0447 (8)
H4	0.9344	0.3598	0.3624	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0601 (2)	0.02068 (15)	0.04132 (19)	0.00176 (19)	0.00681 (15)	−0.00387 (17)
S1	0.0335 (3)	0.0179 (2)	0.0385 (3)	−0.0012 (3)	0.0087 (3)	−0.0010 (3)
C10	0.0243 (13)	0.0241 (13)	0.0264 (13)	−0.0003 (9)	0.0067 (11)	−0.0023 (9)
N3	0.0407 (14)	0.0233 (10)	0.0387 (13)	0.0008 (10)	0.0090 (11)	0.0021 (9)
N1	0.0416 (13)	0.0237 (10)	0.0297 (11)	−0.0006 (10)	0.0066 (10)	−0.0014 (9)
N2	0.0549 (16)	0.0341 (13)	0.0347 (13)	−0.0040 (13)	0.0099 (11)	0.0062 (10)
C1	0.0485 (18)	0.0265 (12)	0.0329 (15)	−0.0038 (12)	0.0112 (13)	−0.0001 (11)
C2	0.057 (2)	0.0295 (13)	0.0413 (16)	−0.0025 (13)	0.0031 (15)	−0.0072 (12)
C3	0.051 (2)	0.0454 (17)	0.0308 (14)	0.0099 (16)	0.0016 (14)	−0.0095 (16)
C4	0.055 (2)	0.052 (2)	0.0291 (14)	0.0062 (16)	0.0124 (14)	0.0058 (13)

Geometric parameters (Å, º)

Cu1—N3^i	1.930 (3)	N1—N2	1.348 (3)
Cu1—N1	2.012 (2)	N2—C4	1.328 (4)
Cu1—S1^ii	2.4053 (9)	C1—C2	1.391 (4)
Cu1—S1	2.4299 (9)	C1—H1	0.9300
S1—C10	1.658 (3)	C2—C3	1.358 (5)
S1—Cu1^iii	2.4053 (9)	C2—H2	0.9300
C10—N3	1.155 (4)	C3—C4	1.373 (5)
N3—Cu1^iv	1.930 (3)	C3—H3	0.9300
N1—C1	1.328 (3)	C4—H4	0.9300
N3^i—Cu1—N1	126.44 (10)	C4—N2—N1	118.2 (3)
N3^i—Cu1—S1^ii	107.10 (8)	N1—C1—C2	123.0 (3)
N1—Cu1—S1^ii	105.42 (8)	N1—C1—H1	118.5
N3^i—Cu1—S1	101.34 (8)	C2—C1—H1	118.5
N1—Cu1—S1	109.88 (8)	C3—C2—C1	117.5 (3)
S1^ii—Cu1—S1	104.91 (3)	C3—C2—H2	121.2
C10—S1—Cu1^iii	101.44 (9)	C1—C2—H2	121.2
C10—S1—Cu1	109.92 (9)	C2—C3—C4	117.2 (3)
Cu1^iii—S1—Cu1	104.91 (3)	C2—C3—H3	121.4
N3—C10—S1	179.3 (2)	C4—C3—H3	121.4
C10—N3—Cu1^iv	174.2 (2)	N2—C4—C3	124.5 (3)
C1—N1—N2	119.5 (2)	N2—C4—H4	117.8
C1—N1—Cu1	122.72 (19)	C3—C4—H4	117.8
N2—N1—Cu1	117.6 (2)

Symmetry codes: (i) −x+1, y+1/2, −z+2; (ii) x+1, y, z; (iii) x−1, y, z; (iv) −x+1, y−1/2, −z+2.