Bis(2-amino-2-thia­zolinium) tetra-μ-formato-κ⁸O:O′-bis[(formato-κO)copper(II)]

In the title dimeric compound, (C₃H₇N₂S)₂[Cu₂(CHO₂)₆], each Cu^II atom has a square-pyramidal coordination, with the nonbridging formate ion at the apical position. The complex anion is located on a crystallographic inversion centre, with a Cu...Cu separation of 2.6566 (4) Å. 2-Amino-2-thia­zolinium cations connect complex anions via hydrogen bonds to form a ribbon running along the a axis.

S1. Comment

2-Amino-2-thiazoline (C₃H₆N₂S, 2-amt) derivatives have been described as compounds with m-cholinergic activity (Ivanov et al., 2002). 2-Amino-2-thiazoline itself has been considered as a possible inducer of the reverse transformation of tumour cells (Brugarolas & Gosálvez, 1982). This ligand contains three donor atoms potentially available for coordination of metal ions, viz. the amine and heterocyclic N atoms and also the S atom. However, a search of the Cambridge Structural Database (CSD, Version 5.28, January 2007 update; Allen, 2002) identified only two structures with metal-coordinated 2-amt. This study was undertaken in order to check the possibilities of 2-amt coordination with copper(II) formate.

The title compound, (I), contains a dimeric copper(II) complex anion, [Cu₂(HCOO)₄(HCOO)₂]^2-, containing two Cu^II centres, with two protonated 2-amt molecules (Fig. 1). Since the anion is located on a crystallographic inversion centre, the asymmetric unit is composed of a half of the anionic complex and one 2-amtH⁺ cation. Each Cu^II atom has a (regular within the experimental error) five-coordinate square-pyramidal environment, with the basal plane defined by the O atoms of four bridging bidentate carboxylate groups of the formate ligands. The apical position is occupied by the O atom of the terminal formate group, coordinating in anti arrangement. The Cu^II atom deviates out of the mean plane formed by the four basal O atoms towards the apical atom O5 by 0.2076 (8) Å. The Cuⁱ···Cu—O5 [symmetry code: (i) -x + 1, -y, -z + 1] angle of 178.30 (5)° indicates only a very slight deviation from the expected value of 180° for idealized D_4h symmetry.

Each axial formate group links to two 2-amino-2-thiazolinium cations via an intermolecular N—H···O hydrogen bond. The first linkage forms eight-membered rings described by the R₂²(8) graph-set motif (Etter et al., 1990), in the manner observed in other 2-amino-2-thiazolinium carboxylate salts (Lynch et al., 1999; Lynch, 2004). The second linkage associates adjacent cations via carboxy atom O6 into C₂²(6) chains. The combination of these motifs results in the formation of a one-dimensional ribbon structure lying in the (021) plane and running along the a axis, as shown in Fig. 2. Selected bond distances and bond angles are listed in Table 1, and the hydrogen-bonding geometric details are summarized in Table 2.

The O—C distances in all formate groups are approximately equal and range from 1.232 (2) to 1.252 (3) Å, indicating the distinct delocalization of their π electrons (Borthwick, 1980). The planes of the two independent bridging formate groups are perpendicular within experimental error. The apical formate group is twisted by a dihedral angle of 40.2 (5)° with respect to the C1/O1/O3ⁱ mean plane. Rotation of the Cu₂(HCOO)₄ core is limited sterically by the adjacent unit, which gives the mutual [please clarify meaning] intermolecular C—H···O interactions. Other weak Csp²—H···O contacts stabilize the structure and extend it into a three-dimensional arrangement. The Cu···Cu distance of 2.6566 (4) Å is comparable to those found in other dimeric copper(II) carboxylates.

Related literature

For related literature, see: Allen (2002); Borthwick (1980); Brugarolas & Gosálvez (1982); Etter et al. (1990); Ivanov et al. (2002); Lynch (2004); Lynch et al. (1999).

S2. Experimental

The title complex was prepared by dissolving cupric formate [2 mmol, Cu(HCOO)₂·2H₂O] in 50 ml of water with 2-amino-2-thiazoline (2 mmol, C₃H₆N₂S). After heating to boiling, formic acid was added dropwise to clear the solution; it was subsequently filtered and allowed to cool. After a few days, green crystals were obtained.

S3. Refinement

All H atoms were initially located in a difference Fourier synthesis. The H atoms bonded to C atoms were positioned with idealized geometry, with C—H = 0.93 and 0.97 Å, and refined using a riding model. The amine H-atom positions and isotropic displacement parameters of all H atoms were refined freely.

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXTL (Sheldrick, 2001); molecular graphics: SHELXTL and Mercury (Macrae et al., 2006); software used to prepare material for publication: PLATON (Spek, 2003) and publCIF (Westrip, 2007).

Figures

	Fig. 1. A view of (I), with the atom-numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 40% probability level. Unlabelled atoms are related to labelled ones by the symmetry code (-x + 1, -y, -z + 1). Dotted lines indicate hydrogen bonds.
	Fig. 2. The packing of (I), showing a ribbon of hydrogen-bonded (dashed lines) cations and anions running along the a axis.

Bis(2-amino-2-thiazolinium) tetra-µ-formato-κ⁸O:O')bis[(formato-κO)copper(II)]

Crystal data

(C3H7N2S)2[Cu2(CHO2)6]	Z = 1
Mr = 603.56	F(000) = 306
Triclinic, P1	Dx = 1.817 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.5347 (5) Å	Cell parameters from 6467 reflections
b = 7.5170 (8) Å	θ = 2.9–29.9°
c = 12.4428 (5) Å	µ = 2.18 mm^−1
α = 80.022 (6)°	T = 294 K
β = 80.203 (5)°	Prism, green
γ = 67.250 (8)°	0.40 × 0.22 × 0.10 mm
V = 551.54 (8) Å^3

Data collection

Kuma KM-4 CCD diffractometer	2530 independent reflections
Radiation source: CX-Mo12x0.4-S Seifert Mo tube	2228 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
Detector resolution: 8.2356 pixels mm^-1	θmax = 27.5°, θmin = 3.0°
ω scans	h = −8→8
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2006)	k = −9→9
Tmin = 0.426, Tmax = 0.811	l = −16→15
8874 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: structure-invariant direct methods
R[F^2 > 2σ(F^2)] = 0.025	Hydrogen site location: difference Fourier map
wR(F^2) = 0.072	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0431P)^2 + 0.0951P] where P = (Fo^2 + 2Fc^2)/3
2530 reflections	(Δ/σ)max < 0.001
164 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.48 e Å^−3

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement on F² for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating -R-factor-obs 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	0.43825 (4)	0.05735 (3)	0.399449 (17)	0.03466 (10)
O1	0.6146 (3)	0.2223 (3)	0.38482 (13)	0.0542 (4)
O2	0.7156 (3)	−0.1575 (3)	0.35555 (13)	0.0561 (4)
O3	0.7146 (3)	0.1281 (3)	0.55571 (12)	0.0519 (4)
O4	0.8140 (3)	−0.2585 (2)	0.52600 (13)	0.0514 (4)
O5	0.3435 (2)	0.1403 (2)	0.23771 (11)	0.0450 (3)
O6	0.1141 (2)	0.1894 (2)	0.11452 (11)	0.0470 (4)
C1	0.7098 (4)	0.2250 (4)	0.46340 (19)	0.0518 (6)
H1	0.7863	0.3096	0.4515	0.075 (9)*
C2	0.8403 (4)	−0.2659 (4)	0.4247 (2)	0.0517 (5)
H2	0.9681	−0.3638	0.3979	0.056 (7)*
C3	0.1629 (3)	0.1569 (3)	0.20923 (16)	0.0416 (4)
H3	0.0536	0.1434	0.2650	0.072 (9)*
N1	0.4494 (3)	0.2550 (3)	−0.04469 (15)	0.0445 (4)
H4	0.368 (4)	0.223 (3)	−0.005 (2)	0.041 (7)*
S1	0.80449 (11)	0.32201 (10)	−0.11982 (5)	0.05678 (17)
N2	0.7045 (4)	0.1672 (3)	0.08106 (16)	0.0500 (5)
H21	0.614 (5)	0.145 (4)	0.128 (2)	0.059 (8)*
H22	0.825 (5)	0.161 (4)	0.093 (2)	0.056 (8)*
C4	0.6401 (3)	0.2381 (3)	−0.01633 (16)	0.0367 (4)
C5	0.3988 (4)	0.3500 (4)	−0.15356 (19)	0.0545 (6)
H5A	0.2825	0.4776	−0.1491	0.101 (12)*
H5B	0.3465	0.2741	−0.1901	0.085 (10)*
C6	0.6081 (5)	0.3680 (4)	−0.2167 (2)	0.0604 (6)
H6A	0.5757	0.4974	−0.2560	0.102 (12)*
H6B	0.6701	0.2747	−0.2698	0.090 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.03464 (14)	0.04886 (16)	0.02294 (12)	−0.01795 (11)	−0.01010 (9)	0.00222 (9)
O1	0.0605 (10)	0.0708 (11)	0.0433 (8)	−0.0418 (9)	−0.0186 (7)	0.0166 (7)
O2	0.0479 (9)	0.0711 (11)	0.0395 (8)	−0.0072 (8)	−0.0077 (7)	−0.0136 (7)
O3	0.0638 (10)	0.0714 (11)	0.0366 (8)	−0.0423 (9)	−0.0145 (7)	0.0017 (7)
O4	0.0414 (8)	0.0595 (10)	0.0441 (8)	−0.0065 (7)	−0.0118 (6)	−0.0045 (7)
O5	0.0419 (8)	0.0709 (10)	0.0264 (6)	−0.0265 (7)	−0.0126 (6)	0.0051 (6)
O6	0.0430 (8)	0.0726 (10)	0.0313 (7)	−0.0262 (8)	−0.0161 (6)	0.0018 (6)
C1	0.0542 (13)	0.0668 (15)	0.0496 (12)	−0.0410 (12)	−0.0129 (10)	0.0056 (11)
C2	0.0380 (11)	0.0586 (14)	0.0504 (13)	−0.0068 (10)	−0.0034 (9)	−0.0135 (10)
C3	0.0370 (10)	0.0584 (13)	0.0293 (9)	−0.0182 (9)	−0.0076 (8)	0.0001 (8)
N1	0.0382 (10)	0.0632 (12)	0.0349 (9)	−0.0204 (9)	−0.0081 (8)	−0.0053 (8)
S1	0.0583 (4)	0.0741 (4)	0.0459 (3)	−0.0387 (3)	−0.0035 (3)	0.0041 (3)
N2	0.0406 (10)	0.0787 (14)	0.0365 (9)	−0.0284 (10)	−0.0106 (8)	0.0001 (9)
C4	0.0373 (10)	0.0414 (10)	0.0331 (9)	−0.0154 (8)	−0.0040 (7)	−0.0071 (7)
C5	0.0618 (15)	0.0594 (14)	0.0436 (12)	−0.0183 (12)	−0.0235 (10)	−0.0021 (10)
C6	0.0819 (19)	0.0603 (15)	0.0381 (12)	−0.0266 (14)	−0.0133 (12)	0.0034 (10)

Geometric parameters (Å, º)

Cu1—O1	1.963 (2)	N1—C5	1.445 (3)
Cu1—O2	1.974 (2)	N2—C4	1.306 (3)
Cu1—O3^i	1.967 (2)	N1—H4	0.74 (3)
Cu1—O4^i	1.9753 (16)	N2—H21	0.80 (3)
Cu1—O5	2.1244 (14)	N2—H22	0.81 (3)
S1—C4	1.727 (2)	C1—H1	0.93
S1—C6	1.805 (3)	C2—H2	0.93
O1—C1	1.252 (3)	C3—H3	0.93
O2—C2	1.245 (3)	C5—C6	1.499 (4)
O3—C1	1.247 (3)	C5—H5A	0.97
O4—C2	1.251 (3)	C5—H5B	0.97
O5—C3	1.244 (3)	C6—H6A	0.97
O6—C3	1.232 (2)	C6—H6B	0.97
N1—C4	1.306 (3)
Cu···Cu^i	2.6566 (4)
O1—Cu1—O2	88.45 (9)	O2—C2—O4	127.6 (3)
O1—Cu1—O3^i	167.96 (7)	O5—C3—O6	126.57 (19)
O1—Cu1—O4^i	88.90 (8)	O3—C1—H1	116.00
O1—Cu1—O5	95.79 (6)	O1—C1—H1	116.00
O2—Cu1—O3^i	89.65 (9)	O4—C2—H2	116.00
O2—Cu1—O4^i	167.75 (7)	O2—C2—H2	116.00
O2—Cu1—O5	93.63 (6)	O6—C3—H3	117.00
O3^i—Cu1—O4^i	90.46 (8)	O5—C3—H3	117.00
O3^i—Cu1—O5	96.20 (6)	S1—C4—N1	113.90 (15)
O4^i—Cu1—O5	98.54 (6)	N1—C4—N2	124.5 (2)
C4—S1—C6	91.37 (12)	S1—C4—N2	121.63 (19)
Cu1—O1—C1	120.66 (17)	N1—C5—C6	108.0 (2)
Cu1—O2—C2	121.08 (16)	S1—C6—C5	107.86 (17)
Cu1^i—O3—C1	123.36 (18)	N1—C5—H5A	110.00
Cu1^i—O4—C2	123.37 (17)	N1—C5—H5B	110.00
Cu1—O5—C3	126.37 (13)	C6—C5—H5A	110.00
C4—N1—C5	116.9 (2)	C6—C5—H5B	110.00
C4—N1—H4	121 (2)	H5A—C5—H5B	108.00
C5—N1—H4	122 (2)	S1—C6—H6A	110.00
C4—N2—H22	119.3 (18)	S1—C6—H6B	110.00
H21—N2—H22	123 (3)	C5—C6—H6A	110.00
C4—N2—H21	117 (2)	C5—C6—H6B	110.00
O1—C1—O3	128.0 (3)	H6A—C6—H6B	108.00

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H4···O6	0.74 (3)	2.09 (3)	2.826 (2)	169 (2)
N2—H21···O5	0.80 (3)	2.05 (3)	2.841 (3)	169 (3)
N2—H22···O6^ii	0.81 (3)	2.05 (3)	2.849 (3)	171 (3)
C1—H1···O4^iii	0.93	2.55	3.244 (4)	132
C5—H5B···O2^iv	0.97	2.52	3.421 (3)	154
C6—H6A···O1^v	0.97	2.46	3.364 (3)	155
C6—H6B···O3^vi	0.97	2.53	3.447 (3)	159

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