catena-Poly­[[aqua­(diformato-κO)copper(II)]-μ-1,4-di­aza­bi­cyclo­[2.2.2]­octane-κ²N:N′]

The title compound, [Cu(CHO₂)₂(C₆H₁₂N₂)(H₂O)]_n, forms a polymeric chain, [Cu(HCOO)₂(dabco)(H₂O)]_∞ (dabco is 1,4-di­aza­bi­cyclo­[2.2.2]­octane). Both formate ligands are O-monodentate anions and dabco acts as a bridging ligand, creating a linear polymeric arrangement interconnected by O_water—H...O_carboxy hydrogen bonds. The deformed square-pyramidal Cu^II coordination comprises two N and two O atoms as the base, and a water mol­ecule in the apical position. The point symmetry of the Cu^II polyhedron and the dabco ligand is mm, and the formate anions lie on the mirror planes ¼, y, z and ¾, y, z.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.023
• wR factor = 0.062
• Data-to-parameter ratio = 10.9

checkCIF/PLATON results

No syntax errors found



Alert level C
CRYSC01_ALERT_1_C The word below has not been recognised as a standard
            identifier.
            turquoise
CRYSC01_ALERT_1_C No recognised colour has been given for crystal colour.
PLAT164_ALERT_4_C Nr. of Refined C-H H-Atoms in Heavy-At Struct...          4

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

   2 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
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

So far, Cu^II–dabco coordination has not been intensively investigated. Only one mononuclear structure (Karan et al., 1999), two dinuclear structures (Durley et al., 1980; Maverick et al., 1986) and one polymeric structure (Rao et al., 1983) of Cu^II compounds containing the dabco ligand have been reported. The present paper reports the first example of the coordination of the dabco ligand in an equatorial position of a square-pyramidal Cu^II polyhedron. The structure of the title complex, (I), is polymeric with [Cu(HCOO)₂(dabco)(H₂O)]_∞ chains running along the a axis. Fig. 1 shows the independent fragment of the chain.

The chain consists of pentacoordinated Cu^II ions in a distorted square-pyramidal (SQP) geometry, with two Cu—N bonds of 2.093 (2) Å and two Cu—O bonds of 1.962 (2) Å of the formate groups in the basal plane. The apical position is occupied by the water molecule [Cu—OH₂ = 2.238 (2) Å]. The Cu atom is displaced from the basal plane by 0.124 (1) Å towards atom O1. The point symmetry of the Cu^II polyhedron and the dabco ligand is mm, and the formate anions lie on the mirror planes 1/4,y,z and 3/4,y,z.

The observed SQP coordination is distinctly deformed in the direction of trigonal-bipiramidal (TBP) coordination, with the trigonality parameter τ = 0.24 [τ is defined by Addison et al. (1984); for a regular SQP structure, the trigonality parameter is 0, and for TBP distortion it increases to 1].

The formate group acts as a monodentate ligand, the distance between the Cu^II ion and uncoordinated atom O3 is 3.287 (3) Å. Such behaviour may be caused by the participation of this atom in a strong hydrogen bond with the water molecule. These interchain interactions, running along the z axis, are shown in Fig. 2. This strong hydrogen bond does not cause a delocalization of the π bond in the carboxyl group. The C2—O2 and C2—O3 bonds are distinctly different [1.257 (3) and 1.214 (4) Å, respectively].

The intrachain Cu···Cu distance of 6.808 (1) Å is longer than the shortest interchain Cu···Cu distance of 6.422 (2) Å along the c axis. Another short interchain Cu···Cu distances of 7.246 (2) and 8.157 (2) Å are between the two Cu^II ions related by the screw axis 2₁ and with no spacer between them.

S2. Experimental

The title complex was prepared by dissolving cupric formate [2 mmol, Cu(HCOO)₂·2H₂O] in 50 ml of water with dabco (2 mmol, C₆H₁₂N₂). After heating to boiling, a few drops of formic acid were added to clear the solution. The solution was filtered and allowed to cool. After several days, turquoise crystals were obtained.

S3. Refinement

All H atoms were located from a difference synthesis and refined isotropically.

Computing details

Data collection: P3 (Siemens, 1993); cell refinement: P3; data reduction: XDISK in SHELXTL/PC (Sheldrick, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); molecular graphics: XP in SHELXTL/PC; software used to prepare material for publication: PLATON (Spek, 1990).

Figures

	Fig. 1. A fragment of the polymeric structure of the title compound. Displacement ellipsoids for non-H atoms are drawn at the 40% probability level.
	Fig. 2. Perspective view of the crystal packing in the unit cell, showing the linkage of the polymeric chains by hydrogen bonding.

catena-Poly[[aqua(diformato-κO)copper(II)]-µ-1,4-diazabicyclo[2.2.2]octane- κ²N:N']

Crystal data

[Cu(CHO2)2(C6H12N2)(H2O)]	F(000) = 294
Mr = 283.77	Dx = 1.786 Mg m^−3
Orthorhombic, Pmmn	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ab 2a	Cell parameters from 38 reflections
a = 6.8084 (13) Å	θ = 5–18°
b = 12.071 (2) Å	µ = 2.08 mm^−1
c = 6.4224 (15) Å	T = 293 K
V = 527.80 (19) Å^3	Prism, turquoise
Z = 2	0.30 × 0.20 × 0.20 mm

Data collection

Siemens P3 diffractometer	710 reflections with I > 2σ(I)
Radiation source: FK60-10 Siemens Mo tube	Rint = 0.000
Graphite monochromator	θmax = 28.0°, θmin = 3.2°
ω–2θ scans	h = 0→8
Absorption correction: psi scan (North et al., 1968)	k = 0→15
Tmin = 0.557, Tmax = 0.661	l = 0→8
719 measured reflections	3 standard reflections every 100 reflections
719 independent reflections	intensity decay: none

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)] = 0.023	Hydrogen site location: difference Fourier map
wR(F^2) = 0.062	All H-atom parameters refined
S = 1.23	w = 1/[σ^2(Fo^2) + (0.0345P)^2 + 0.21P] where P = (Fo^2 + 2Fc^2)/3
719 reflections	(Δ/σ)max < 0.001
66 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3
0 constraints

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All e.s.d.'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 F^{2 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 F}2, conventional R-factors R are based on F, with F set to zero for negative F^{2. The observed criterion of F}2 > σ(F^{2) is used only for calculating -R-factor-obs etc. and is not relevant to the choice of reflections for refinement. R-factors based on F}2 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
Cu	0.25	0.25	0.33505 (5)	0.0180 (1)
O1	0.25	0.25	0.6835 (4)	0.0341 (8)
O2	0.25	0.08926 (14)	0.2903 (3)	0.0290 (4)
O3	0.25	0.0745 (2)	−0.0562 (4)	0.0630 (8)
N1	0.5573 (3)	0.25	0.3413 (3)	0.0197 (4)
C2	0.25	0.03800 (19)	0.1200 (4)	0.0315 (7)
C3	0.6379 (3)	0.25	0.1269 (4)	0.0299 (7)
C4	0.6384 (2)	0.15119 (16)	0.4490 (3)	0.0360 (5)
H1	0.25	0.316 (3)	0.761 (8)	0.074 (13)*
H2	0.25	−0.041 (3)	0.139 (5)	0.039 (9)*
H3	0.588 (4)	0.313 (2)	0.068 (5)	0.054 (7)*
H4A	0.585 (5)	0.089 (3)	0.385 (5)	0.083 (11)*
H4B	0.580 (5)	0.154 (3)	0.591 (6)	0.079 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0165 (2)	0.0164 (2)	0.0212 (2)	0	0	0
O1	0.0450 (15)	0.0361 (14)	0.0211 (11)	0	0	0
O2	0.0275 (8)	0.0212 (7)	0.0382 (8)	0	0	−0.0071 (7)
O3	0.109 (2)	0.0426 (12)	0.0373 (10)	0	0	0.0064 (10)
N1	0.0180 (7)	0.0182 (8)	0.0229 (8)	0	−0.0003 (6)	0
C2	0.0381 (13)	0.0194 (10)	0.0370 (11)	0	0	−0.0021 (9)
C3	0.0217 (11)	0.0467 (14)	0.0212 (9)	0	−0.0009 (8)	0
C4	0.0206 (8)	0.0337 (9)	0.0537 (10)	−0.0016 (7)	−0.0027 (7)	0.0226 (8)

Geometric parameters (Å, º)

Cu—O1	2.238 (2)	N1—C4	1.485 (2)
Cu—O2	1.962 (2)	C3—C3^i	1.526 (4)
Cu—N1	2.093 (2)	C4—C4^ii	1.520 (3)
O2—C2	1.257 (3)	C2—H2	0.97 (3)
O3—C2	1.214 (4)	C3—H3	0.92 (3)
O1—H1	0.94 (4)	C4—H4A	0.93 (4)
N1—C3	1.482 (3)	C4—H4B	1.00 (4)
O1—Cu—O2	98.42 (6)	N1—C3—C3^i	111.7 (2)
O1—Cu—N1	88.90 (5)	N1—C4—C4^ii	111.82 (15)
O2—Cu—N1	90.16 (1)	O2—C2—H2	112.2 (19)
O2—Cu—O2^iii	163.16 (11)	O3—C2—H2	118.6 (19)
N1—Cu—N1^iii	177.81 (9)	N1—C3—H3	104 (2)
Cu—O2—C2	127.92 (16)	C3^i—C3—H3	111.8 (17)
H1—O1—H1^iii	116 (4)	H3—C3—H3^iv	112 (3)
Cu—O1—H1	122 (3)	N1—C4—H4A	107 (2)
Cu—N1—C3	110.63 (14)	N1—C4—H4B	105 (2)
Cu—N1—C4	112.37 (10)	H4A—C4—H4B	106 (3)
C4—N1—C4^iv	106.85 (16)	C4^ii—C4—H4A	113 (2)
C3—N1—C4	107.16 (12)	C4^ii—C4—H4B	114 (2)
O2—C2—O3	129.2 (2)
N1—Cu—O2—C2	−91.09 (5)	O2—Cu—N1—C4	−38.15 (13)
O1—Cu—N1—C4	60.28 (12)	Cu—N1—C4—C4^ii	178.97 (12)
O2—Cu—N1—C3	81.58 (6)	C3—N1—C4—C4^ii	57.25 (19)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3^v	0.94 (4)	1.77 (4)	2.699 (3)	170 (4)

Symmetry code: (v) −x+1/2, −y+1/2, z+1.