Diaqua­bis(saccharinato-κN)copper(II)

In the title compound, [Cu(C₇H₄NO₃S)₂(H₂O)₂], the Cu^II atom lies on a crystallographic inversion centre and is in a square-planar coordination geometry. The saccharinate ligand is essentially planar and the crystal structure is stabilized by inter­molecular O—H...O and C—H...O inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.027
• wR factor = 0.080
• Data-to-parameter ratio = 25.6

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.74 mm
PLAT154_ALERT_1_C The su's on the Cell Angles are Equal  (x 10000)        100 Deg.
PLAT180_ALERT_3_C Check Cell Rounding: # of Values Ending with 0 =          4
PLAT222_ALERT_3_C Large Non-Solvent    H     Ueq(max)/Ueq(min) ...       3.64 Ratio
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          2

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Cu1         (2)       2.09

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

Saccharin (or O-sulphobenzoimide) is widely used as an artificial sweetening agent. The chemistry of saccharin has attracted attention because of its suspected carcinogenous nature (Suzuki & Suzuki, 1995; Zurlo & Squire, 1998). Saccharin, its derivatives and some metal saccharinates are found to be enzymatic inhibitors (Groutas et al., 1996). Saccharin itself does not coordinate metal ions, but its deprotonated form (saccharinate) interacts with trace elements in human body and readily forms complexes with a large number of metal ions (Baran, 2005). The saccharinate anion acts as a polyfunctional ligand and may bond to metals by means of its imino nitrogen, carbonyl oxygen, or sulfonyl oxygen atoms, exhibiting different coordination modes such as monodentate (through the N-or the carbonyl O-atom), bidentate (N, O), tridentate (N, O, O) or as bridging ligand (Baran & Yilmaz, 2006). Our current interest in the chemistry of copper complexes with saccharin is because of its potential as a chiral specific catalyst. Our investigation has resulted in the synthesis of a unique square planar copper-saccharin complex in which the N—Cu—N and O—Cu—O angles (from water) are uniquely 180°. We report herein the crystal structure of disaquabis(Saccharinato-κN)Copper(II).

The Cu^II atom of the title complex lies on an inversion centre and is coordinated in a square-planar mode by two saccharinate (sac) ligands and two water molecules (Fig. 1). All bond lengths and angles in normal ranges (Allen et al., 1987). The sac ligand is essentially planar with the maximum deviation is 0.035Å for atom S1.

The H atoms of the water molecules participate in both intra and intermolecular hydrogen bonding with the carbonyl and sulfonyl O atoms of the sac ligand (Table 1, Fig. 2). Intermolecular O1W-H1W1···O3ⁱⁱ interactions link molecules into one-dimensional chains along the b axis and these chains are stacked along the a axis by C4—H4A···O2ⁱⁱⁱ, C5- H5A···O1^iv interactions [symmetry codes as in Table 1] and Cu···O short contacts [Cu1···O1(1 + x, y, z) = 2.488 Å] (Fig. 3).

Related literature

For a related crystal structure, see: Yilmaz et al., (2001). For general background, see: Allen et al. (1987); Baran (2005); Baran & Yilmaz (2006); Groutas et al. (1996); Suzuki & Suzuki, (1995); Zurlo & Squire (1998).

S2. Experimental

To a solution of saccharin (0.732 g, 4 mmol) in 95% ethanol (20 ml), copper(II) nitrate (0.4832 g, 2 mmol) in ethanol (10 ml) was added, followed by triethylamine (0.5 ml, 3.6 mmol). The mixture was refluxed with stirring for 3 h. The resulting blue solution was filtered and left to evaporate slowly at room temperature. Blue needle-shaped single crystals suitable for X-ray diffraction were obtained after one week. Analysis found: C 36.21, H 2.28, N 6.67%; calculated: C 36.25, H 2.61, N 6.04%.

S3. Refinement

All C-bound H atoms were placed in calculated positions with C—H = 0.93Å and refined as riding, with U_iso(H) = 1.2U_eq(C). The H atoms for water molecules were located in a difference map and freely refined.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL (Sheldrick, 1998); molecular graphics: SHELXTL (Sheldrick, 1998); software used to prepare material for publication: SHELXTL (Sheldrick, 1998), PARST (Nardelli, 1995) and PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structure showing 50% probability displacement ellipsoids and the atomic numbering [symmetry code: A, -x - 1, -y, -z]
	Fig. 2. The crystal packing viewed along the a axis. Hydrogen bonds are shown as dashed lines.
	Fig. 3. Packing viewed along the b axis, showing an extended chain along the a axis. Dashed lines denote Cu···O short contacts.

Diaquabis(saccharinato-κN)copper(II)

Crystal data

[Cu(C7H4NO3S)2(H2O)2]	Z = 1
Mr = 463.92	F(000) = 235
Triclinic, P1	Dx = 1.970 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 4.9171 (1) Å	Cell parameters from 14734 reflections
b = 7.8826 (2) Å	θ = 2.7–37.5°
c = 10.5731 (3) Å	µ = 1.72 mm^−1
α = 96.167 (1)°	T = 100 K
β = 102.295 (1)°	Block, blue
γ = 99.211 (1)°	0.74 × 0.13 × 0.09 mm
V = 390.97 (2) Å^3

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	3411 independent reflections
Radiation source: fine-focus sealed tube	2975 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 8.33 pixels mm^-1	θmax = 35.0°, θmin = 2.7°
ω scans	h = −7→7
Absorption correction: multi-scan (SADABS; Bruker, 2005)	k = −12→12
Tmin = 0.362, Tmax = 0.861	l = −17→16
12980 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.080	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0421P)^2 + 0.1186P] where P = (Fo^2 + 2Fc^2)/3
3411 reflections	(Δ/σ)max < 0.001
133 parameters	Δρmax = 0.61 e Å^−3
0 restraints	Δρmin = −0.63 e Å^−3

Special details

Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.

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	−0.5000	0.0000	0.0000	0.00928 (6)
S1	−0.16480 (6)	0.00582 (4)	−0.23237 (3)	0.00896 (6)
O1	0.03679 (19)	−0.08789 (12)	−0.16235 (10)	0.01210 (16)
O2	−0.3837 (2)	−0.09943 (12)	−0.33636 (10)	0.01312 (17)
O3	−0.3156 (2)	0.40733 (12)	−0.07145 (10)	0.01392 (17)
O1W	−0.4091 (2)	−0.22110 (13)	−0.05806 (11)	0.01448 (18)
N1	−0.2966 (2)	0.11832 (13)	−0.12802 (11)	0.01013 (17)
C1	0.0086 (2)	0.18416 (15)	−0.28886 (12)	0.01025 (19)
C2	0.1765 (3)	0.18638 (16)	−0.37910 (12)	0.0119 (2)
H2A	0.2172	0.0850	−0.4181	0.014*
C3	0.2806 (3)	0.34929 (17)	−0.40792 (13)	0.0139 (2)
H3A	0.3928	0.3571	−0.4684	0.017*
C4	0.2201 (3)	0.50066 (17)	−0.34815 (13)	0.0143 (2)
H4A	0.2941	0.6075	−0.3688	0.017*
C5	0.0504 (3)	0.49440 (16)	−0.25788 (13)	0.0132 (2)
H5A	0.0091	0.5953	−0.2183	0.016*
C6	−0.0548 (2)	0.33242 (15)	−0.22911 (12)	0.01049 (19)
C7	−0.2353 (2)	0.29281 (16)	−0.13564 (12)	0.01059 (19)
H1W1	−0.467 (7)	−0.301 (4)	−0.018 (3)	0.051 (8)*
H2W1	−0.259 (5)	−0.232 (3)	−0.067 (2)	0.030 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.01117 (10)	0.00630 (9)	0.01183 (10)	0.00185 (6)	0.00573 (7)	0.00140 (7)
S1	0.01026 (12)	0.00659 (12)	0.01066 (13)	0.00134 (8)	0.00412 (9)	0.00103 (9)
O1	0.0129 (4)	0.0100 (4)	0.0151 (4)	0.0039 (3)	0.0049 (3)	0.0036 (3)
O2	0.0142 (4)	0.0107 (4)	0.0128 (4)	−0.0002 (3)	0.0029 (3)	−0.0009 (3)
O3	0.0180 (4)	0.0090 (4)	0.0169 (4)	0.0031 (3)	0.0087 (3)	0.0010 (3)
O1W	0.0173 (4)	0.0094 (4)	0.0205 (5)	0.0036 (3)	0.0114 (3)	0.0031 (3)
N1	0.0124 (4)	0.0076 (4)	0.0118 (4)	0.0023 (3)	0.0059 (3)	0.0007 (3)
C1	0.0114 (4)	0.0083 (5)	0.0112 (5)	0.0011 (3)	0.0034 (4)	0.0016 (4)
C2	0.0129 (5)	0.0108 (5)	0.0125 (5)	0.0019 (4)	0.0045 (4)	0.0017 (4)
C3	0.0150 (5)	0.0137 (5)	0.0137 (5)	0.0006 (4)	0.0058 (4)	0.0032 (4)
C4	0.0176 (5)	0.0111 (5)	0.0151 (5)	0.0004 (4)	0.0065 (4)	0.0034 (4)
C5	0.0153 (5)	0.0088 (5)	0.0158 (5)	0.0011 (4)	0.0054 (4)	0.0019 (4)
C6	0.0114 (5)	0.0085 (5)	0.0121 (5)	0.0017 (3)	0.0040 (4)	0.0015 (4)
C7	0.0115 (5)	0.0092 (5)	0.0116 (5)	0.0019 (3)	0.0036 (4)	0.0021 (4)

Geometric parameters (Å, º)

Cu1—O1W^i	1.9366 (10)	C1—C6	1.3800 (17)
Cu1—O1W	1.9366 (10)	C1—C2	1.3878 (17)
Cu1—N1^i	2.0618 (10)	C2—C3	1.3943 (17)
Cu1—N1	2.0619 (10)	C2—H2A	0.9300
S1—O2	1.4387 (10)	C3—C4	1.394 (2)
S1—O1	1.4546 (10)	C3—H3A	0.9300
S1—N1	1.6438 (11)	C4—C5	1.3949 (18)
S1—C1	1.7532 (12)	C4—H4A	0.9300
O3—C7	1.2363 (16)	C5—C6	1.3891 (17)
O1W—H1W1	0.84 (3)	C5—H5A	0.9300
O1W—H2W1	0.78 (3)	C6—C7	1.4875 (17)
N1—C7	1.3750 (16)
O1W^i—Cu1—O1W	180.0	C2—C1—S1	129.07 (10)
O1W^i—Cu1—N1^i	90.97 (4)	C1—C2—C3	116.20 (12)
O1W—Cu1—N1^i	89.03 (4)	C1—C2—H2A	121.9
O1W^i—Cu1—N1	89.03 (4)	C3—C2—H2A	121.9
O1W—Cu1—N1	90.97 (4)	C4—C3—C2	121.47 (12)
N1^i—Cu1—N1	179.999 (1)	C4—C3—H3A	119.3
O2—S1—O1	114.97 (6)	C2—C3—H3A	119.3
O2—S1—N1	111.85 (6)	C3—C4—C5	121.06 (11)
O1—S1—N1	109.84 (6)	C3—C4—H4A	119.5
O2—S1—C1	110.82 (6)	C5—C4—H4A	119.5
O1—S1—C1	111.27 (6)	C6—C5—C4	117.75 (12)
N1—S1—C1	96.63 (6)	C6—C5—H5A	121.1
Cu1—O1W—H1W1	113 (2)	C4—C5—H5A	121.1
Cu1—O1W—H2W1	123.5 (19)	C1—C6—C5	120.30 (11)
H1W1—O1W—H2W1	108 (3)	C1—C6—C7	112.00 (10)
C7—N1—S1	110.67 (8)	C5—C6—C7	127.70 (11)
C7—N1—Cu1	127.87 (8)	O3—C7—N1	124.73 (11)
S1—N1—Cu1	121.35 (6)	O3—C7—C6	122.43 (11)
C6—C1—C2	123.22 (11)	N1—C7—C6	112.83 (10)
C6—C1—S1	107.69 (9)
O2—S1—N1—C7	−111.62 (9)	C1—C2—C3—C4	0.51 (19)
O1—S1—N1—C7	119.47 (9)	C2—C3—C4—C5	−0.6 (2)
C1—S1—N1—C7	3.99 (9)	C3—C4—C5—C6	0.4 (2)
O2—S1—N1—Cu1	71.93 (8)	C2—C1—C6—C5	−0.06 (19)
O1—S1—N1—Cu1	−56.99 (8)	S1—C1—C6—C5	−178.70 (10)
C1—S1—N1—Cu1	−172.47 (7)	C2—C1—C6—C7	−179.28 (11)
O1W^i—Cu1—N1—C7	8.84 (10)	S1—C1—C6—C7	2.09 (13)
O1W—Cu1—N1—C7	−171.16 (10)	C4—C5—C6—C1	−0.02 (19)
O1W^i—Cu1—N1—S1	−175.36 (7)	C4—C5—C6—C7	179.06 (12)
O1W—Cu1—N1—S1	4.64 (7)	S1—N1—C7—O3	177.59 (10)
O2—S1—C1—C6	112.89 (9)	Cu1—N1—C7—O3	−6.24 (18)
O1—S1—C1—C6	−117.86 (9)	S1—N1—C7—C6	−3.34 (13)
N1—S1—C1—C6	−3.53 (10)	Cu1—N1—C7—C6	172.83 (8)
O2—S1—C1—C2	−65.64 (13)	C1—C6—C7—O3	179.78 (12)
O1—S1—C1—C2	63.60 (13)	C5—C6—C7—O3	0.6 (2)
N1—S1—C1—C2	177.93 (12)	C1—C6—C7—N1	0.69 (15)
C6—C1—C2—C3	−0.18 (18)	C5—C6—C7—N1	−178.46 (12)
S1—C1—C2—C3	178.15 (10)

Symmetry code: (i) −x−1, −y, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W1···O3^ii	0.84 (3)	2.57 (3)	3.0298 (14)	116 (3)
O1W—H1W1···O3^i	0.84 (3)	1.75 (3)	2.5392 (14)	156 (3)
O1W—H2W1···O1	0.78 (3)	2.18 (2)	2.7689 (14)	132 (2)
C4—H4A···O2^iii	0.93	2.53	3.4050 (17)	157
C5—H5A···O1^iv	0.93	2.48	3.3542 (16)	157

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