Di-μ-formato-1κ²O:2κ²O′-di-μ-pyridin-2-olato-1κO:2κN;1κN:2κO-bis­[(2-pyridone-κO)copper(II)] acetonitrile 1.02-solvate

In the title compound, [Cu₂(CHO₂)₂(C₅H₄NO)₂(C₅H₅NO)₂]·1.02CH₃CN, the dimeric unit is centrosymmetric, with two bidentate pyridin-2-olate and two bidentate formate syn–syn bridges, and two apical 2-pyridone ligands coordinated through the O atoms. The N atom from the apical 2-pyridone ligand is a donor of a hydrogen bond to the O atom of the bridging pyridinolate ligand of the same complex. The coordination polyhedron of the Cu atom is a distorted square pyramid.

S1. Comment

Copper(II) carboxylates are well known to form a variety of structures, even with ligands of the same homologous series. One of the objectives of our recent work involved the development of new synthetic methods for the preparation of copper(II) formate with additional N– and O-donor ligands. We present here a new structure of cooper(II) formate with 2-hydroxypyridine. It is interesting that among a large number of structures of dimeric copper(II) carboxylates, there are only two structures containing this ligand, viz. tetrakis(µ-acetato)bis(2-pyridone)dicopper (Blake et al., 1991; Sun et al., 1994), which has four bidentate acetate bridges and two apical 2-pyridone ligands, and tetrakis(µ-2α-pyridinato-N,O)bis(dimethylsulfoxide-O)dicooper (Yeh et al., 1987), which has four N,O-bidentate pyridinate bridges and two apical dimethysulfoxide ligands. In contrast to these two structures, the title compound, (I), whose structure consists of Cu₂(O₂CH)₂(C₅H₅NO)₂(C₅H₄NO)₂ dimers and acetonitrile solvent molecules (Fig. 1), contains 2-hydroxypyridine as a monodentate apical ligand and its anion as a bidentate bridging ligand. The dimeric unit is centrosymmetric, with two apical 2-pyridone ligands coordinated through atom O2, and two N,O-bidentate 2-pyridinolate and two bidentate formate syn--syn bridges. This compound is the first example among dimeric copper(II) formates with four bridging ligands where one or more formate bridges are replaced by some other kind of ligand, i.e. pyridinolate. Different kinds of bridges within dimers are also uncommon within the structures of other copper(II) carboxylates.

In (I), the coordination polyhedron of the Cu atom is a slightly distorted square pyramid; τ is 0.023 (Addison et al., 1984). The Cu atom is displaced by 0.188 (1) Å from the basal N2/O4/O11/O12 plane. The Cu···Cu separation within the dimer is 2.6468 (4) Å, which is comparable to those in other dimeric copper(II) formates (Uekusa et al., 1989; Yamanaka et al., 1991; Cejudo et al., 2002; Sapina et al., 1994). Atom N1 from the apical 2-pyridone ligand is a donor of a hydrogen bond to atom O4 from the bridging pyridinolate ligand of the same complex. The N1···O4 distance is 2.768 (3) Å. Fig. 2 presents the packing of the title compound looking along the c axis. The apical pyridone ligand forms stacking interactions with the two adjacent symmetry-related [(x, 1 - y, -1/2 + z) and (x, 1 - y, 1/2 + z)] 2-pyridone ligands. The dihedral angles between π-stacked rings are in both cases 0.48°, and the distances between the ring centroids are 3.622 (2) Å. The stacking interactions run along the c axis and can be seen in the projection along this direction shown in Fig. 2 as the overlapping of apical 2-pyridone rings. Fig. 2 also shows that the structure is layered, where the layers of dimeric complex molecules are separated by the layers of solvent acetonitrile molecules. All layers are parallel to the ac plane and stack along the [100] direction.

On exposure to air and in the absence of the solvent, the acetonitrile molecules can easily leave the structure, causing the destruction of the crystal. Despite the fact that the single-crystal was protected by silicon grease and was transferred very quickly from the mother liquor into the stream of cold nitrogen, some acetonitrile molecules succeeded in escaping from the crystal. As a consequence, the sites of the acetonitrile molecules are only partially [0.51 (3)] occupied, resulting in there being 1.02 (3) of solvate molecules per one dimeric complex molecule. The disorder in that part of the structure is also exhibited in the deviation of the C31—C32 bond length [1.326 (17) Å] from the expected Csp³—Csp¹ [1.470 (13) Å] (Allen et al., 1987). The distance 1.12 (2) Å of C31—N3 bond is close to 1.136 (10) Å, the reported distance of a Csp¹≡ N bond (Allen et al., 1987). It seems that at the decay of the crystal structure, the dimeric complex does not decompose. This is supported by the results of elemental analysis, IR spectroscopy and gravimetric measurement, which will be published elsewhere. Unfortunately, attempts to prepare suitable crystals of such complexes with no or with other kinds of solvent (acetone, water, ethanol and chloroform) were unsuccessful.

S2. Experimental

Single crystals of (I) were prepared by the reaction of Cu₂(O₂CH)₄(2-mpy)₂ (2-mpy is 2-methylpyridine) and 2-hydroxypyridine in acetonitrile. 2-Hydroxypyridine (0.38 g, 4 mmol) was dissolved in acetonitrile (27 ml). Cu₂(O₂CH)₄(2-mpy)₂ (0.31 g, 0.8 mmol) was added in the solution during mixing and heating. The undissolved solid residue was filtered off and the resulting solution was left to stand at 278 K for 24 h. Green crystals obtained from the solution were used for X-ray diffraction. The compound is very unstable in air.

S3. Refinement

All H atoms, with the exception of two bonded to the C atom in the acetonitrile solvent molecule, were located from difference Fourier maps; the remaining two positions were calculated. Owing to the disorder of the acetonitrile solvent molecules, their C and N atoms were refined isotropically, together with the occupancy parameter, which was constrained to be equal for all atoms of acetonitrile. The solvent H-atom parameters were not refined.

Computing details

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: Xtal3.6 (Hall et al., 1999); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: Xtal3.6 and PLATON (Spek, 2003).

Figures

	Fig. 1. A view of the structure of (I); atoms of the asymmetric unit are labeled. Displacement ellipsoids are drawn at the 50% probability level. Dashed lines show intramolecular hydrogen bonds.
	Fig. 2. The packing of (I), viewed along the c axis. π–π stacking interactions are present between overlapping apical 2-pyridone rings. H atoms haev been omitted.

Di-µ-formato-1κ²O:2κ²O'-di-µ-pyridin-2-olato-1κO:2κN;1κN:2κO- bis[(2-pyridone-κO)copper(II)] acetonitrile 1.02-solvate

Crystal data

[Cu2(CHO2)2(C5H4NO)2(C5H5NO)2]·1.02(3)CH3CN	F(000) = 1297.8
Mr = 637.39	Dx = 1.495 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -c 2yc	Cell parameters from 3136 reflections
a = 26.1571 (8) Å	θ = 2.6–27.5°
b = 15.3971 (5) Å	µ = 1.55 mm^−1
c = 7.1673 (2) Å	T = 150 K
β = 101.078 (2)°	Plate, green
V = 2832.80 (15) Å^3	0.20 × 0.10 × 0.03 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	2605 reflections with F^2 > 2σ(F^2)
Graphite monochromator	Rint = 0.026
ω scans with κ offsets	θmax = 27.5°, θmin = 3.9°
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor 1997)	h = −33→33
Tmin = 0.73, Tmax = 0.96	k = −19→19
13938 measured reflections	l = −9→9
3182 independent reflections

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	5 constraints
R[F^2 > 2σ(F^2)] = 0.050	Only H-atom displacement parameters refined
wR(F^2) = 0.044	A Regina weighting scheme (Wang & Robertson, 1985) using the normal equation of the second order was applied for individual reflections so that w = A(0,0) + A(1,0)V(F) + A(0,1)V(S) + A(2,0)V(F)^2 + A(0,2)V(S)^2 + A(1,1)V(F)V(S), where V(F) = Fobs/Fobs(max), Fobs(max) = 274.38 and V(S) = (sinθ/λ)/((sinθ/λ)(max)), (sinθ/λ)(max) = 0.6486. The parameters were: A(0,0) = 151.7662, A(1,0) = 0.0099395, A(0,1) = -587.9600, A(2,0) = -0.0003962, A(1,1) = 0.0243166 , A(0,2) = 570.2360.
S = 1.09	(Δ/σ)max = 0.001
2986 reflections	Δρmax = 1.39 e Å^−3
186 parameters	Δρmin = −1.16 e Å^−3

Special details

Geometry. #<< supplementary material

PLANE NUMBER 1 (O11 O4 O12 N2) =============== EQUATION OF PLANE AS AX+BY+CZ=D, XYZ IN FRACTIONAL AND ORTHOGONAL UNITS A B C D ESDA ESDB ESDC ESDD 21.8681 6.9070 1.0710 8.3264. 0122. 0122. 0060. 0021. 8812. 4486. 1494 8.3264. 0005. 0008. 0008. 0021

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cu	0.296520 (10)	0.28380 (2)	0.06522 (5)	0.0226 (2)
O2	0.37017 (9)	0.34656 (15)	0.1603 (3)	0.0300 (10)
O4	0.26485 (9)	0.38256 (14)	−0.0887 (3)	0.0295 (9)
O11	0.26384 (9)	0.32483 (15)	0.2805 (3)	0.0306 (9)
O12	0.31537 (9)	0.23085 (15)	−0.1654 (3)	0.0327 (10)
N1	0.34442 (10)	0.48710 (18)	0.0994 (3)	0.0259 (10)
N2	0.31591 (10)	0.17498 (17)	0.2102 (3)	0.0255 (10)
C1	0.21706 (13)	0.30906 (19)	0.2862 (4)	0.0283 (13)
C2	0.38007 (12)	0.4258 (2)	0.1797 (4)	0.0251 (12)
C3	0.42796 (12)	0.4602 (2)	0.2854 (4)	0.0296 (13)
C4	0.43547 (13)	0.5478 (2)	0.3026 (4)	0.0330 (14)
C5	0.39657 (15)	0.6071 (2)	0.2180 (5)	0.0346 (14)
C6	0.35132 (13)	0.5745 (2)	0.1168 (4)	0.0316 (13)
C7	0.21953 (12)	0.39037 (19)	−0.1965 (4)	0.0247 (12)
C8	0.20616 (13)	0.4681 (2)	−0.3034 (5)	0.0302 (13)
C9	0.15793 (15)	0.4773 (2)	−0.4118 (5)	0.0348 (14)
C10	0.12150 (15)	0.4097 (3)	−0.4239 (5)	0.0399 (16)
C11	0.36367 (14)	0.1658 (2)	0.3219 (5)	0.0370 (15)
H1	0.20428	0.32773	0.39374	0.026 (9)*
H3	0.45486	0.42142	0.34431	0.041 (11)*
H4	0.46517	0.56837	0.36297	0.050 (13)*
H5	0.40201	0.66857	0.23149	0.029 (9)*
H6	0.32124	0.60740	0.06261	0.038 (11)*
H8	0.23170	0.50652	−0.28377	0.040 (11)*
H9	0.14159	0.51762	−0.50460	0.025 (9)*
H10	0.08674	0.41603	−0.49991	0.037 (11)*
H11	0.38862	0.22037	0.33576	0.040 (11)*
H1'	0.31541	0.46660	0.02972	0.018 (8)*
C31	0.4803 (4)	0.2109 (7)	−0.0315 (13)	0.056 (3)*	.51 (3)
C32	0.4410 (5)	0.1555 (9)	−0.044 (2)	0.075 (4)*	.51 (3)
N3	0.5118 (7)	0.2603 (12)	−0.033 (2)	0.100 (5)*	.51 (3)
H321	0.45071	0.11310	0.06040	0.11800*	.51 (3)
H322	0.41020	0.19106	−0.02101	0.11800*	.51 (3)
H323	0.43234	0.12701	−0.16769	0.11800*	.51 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.0264 (2)	0.01875 (19)	0.0214 (2)	−0.00077 (13)	0.00171 (11)	−0.00045 (13)
O2	0.0312 (10)	0.0263 (11)	0.0308 (10)	−0.0022 (8)	0.0017 (8)	−0.0007 (8)
O4	0.0301 (10)	0.0253 (10)	0.0300 (10)	−0.0031 (8)	−0.0023 (8)	0.0041 (8)
O11	0.0341 (11)	0.0297 (10)	0.0268 (10)	−0.0011 (9)	0.0032 (8)	−0.0059 (8)
O12	0.0361 (11)	0.0346 (12)	0.0275 (10)	−0.0017 (9)	0.0062 (9)	−0.0031 (9)
N1	0.0242 (11)	0.0281 (12)	0.0240 (11)	−0.0017 (9)	0.0014 (9)	0.0006 (9)
N2	0.0287 (12)	0.0256 (11)	0.0207 (10)	0.0016 (10)	0.0008 (9)	0.0012 (9)
C1	0.0384 (16)	0.0237 (13)	0.0232 (13)	0.0035 (11)	0.0068 (11)	−0.0024 (10)
C2	0.0273 (13)	0.0281 (14)	0.0205 (11)	−0.0004 (11)	0.0061 (10)	0.0001 (10)
C3	0.0270 (14)	0.0345 (15)	0.0257 (13)	−0.0021 (12)	0.0010 (11)	0.0015 (11)
C4	0.0318 (15)	0.0407 (17)	0.0257 (13)	−0.0074 (13)	0.0032 (11)	−0.0044 (12)
C5	0.0415 (17)	0.0298 (14)	0.0326 (15)	−0.0067 (13)	0.0076 (13)	−0.0041 (12)
C6	0.0364 (16)	0.0297 (15)	0.0285 (13)	0.0017 (12)	0.0055 (12)	0.0004 (11)
C7	0.0318 (14)	0.0223 (12)	0.0210 (12)	−0.0001 (11)	0.0079 (10)	−0.0015 (10)
C8	0.0386 (16)	0.0230 (13)	0.0308 (14)	0.0020 (12)	0.0107 (12)	0.0016 (11)
C9	0.0413 (17)	0.0324 (15)	0.0310 (15)	0.0081 (13)	0.0077 (13)	0.0066 (12)
C10	0.0381 (17)	0.0391 (18)	0.0404 (17)	0.0059 (14)	0.0024 (13)	0.0101 (14)
C11	0.0356 (16)	0.0343 (17)	0.0390 (16)	−0.0005 (13)	0.0018 (13)	0.0049 (13)

Geometric parameters (Å, º)

Cu—O2	2.146 (2)	C5—C6	1.360 (5)
Cu—O4	1.966 (2)	C7—C8	1.428 (4)
Cu—O11	2.004 (2)	C8—C9	1.356 (5)
Cu—O12	1.988 (2)	C9—C10	1.403 (6)
Cu—N2	1.985 (3)	C10—C11^i	1.388 (5)
O2—C2	1.249 (4)	C1—H1	0.9421
O4—C7	1.290 (4)	C3—H3	0.9569
O11—C1	1.256 (4)	C4—H4	0.8729
O12—C1^i	1.251 (4)	C5—H5	0.9592
N1—C2	1.373 (4)	C6—H6	0.9535
N1—C6	1.360 (4)	C8—H8	0.8831
N2—C11	1.355 (4)	C9—H9	0.9493
N2—C7^i	1.359 (4)	C10—H10	0.9709
N1—H1'	0.8827	C11—H11	1.0568
N3—C31	1.12 (2)	C31—C32	1.326 (17)
C2—C3	1.435 (4)	C32—H321	0.9887
C3—C4	1.365 (4)	C32—H322	1.0134
C4—C5	1.414 (5)	C32—H323	0.9760
O2—Cu—O4	94.92 (9)	O4—C7—N2^i	120.7 (3)
O2—Cu—O11	95.93 (9)	C7—C8—C9	120.0 (3)
O2—Cu—O12	95.61 (9)	C8—C9—C10	120.3 (3)
O2—Cu—N2	95.18 (10)	C9—C10—C11^i	118.1 (3)
O4—Cu—O11	89.55 (9)	N2—C11—C10^i	122.1 (3)
O4—Cu—O12	89.76 (9)	O11—C1—H1	117.95
O4—Cu—N2	169.82 (10)	O12^i—C1—H1	114.59
O11—Cu—O12	168.46 (10)	C2—C3—H3	119.73
O11—Cu—N2	88.11 (10)	C4—C3—H3	119.72
O12—Cu—N2	90.56 (9)	C3—C4—H4	120.14
Cu—O2—C2	129.0 (2)	C5—C4—H4	118.48
Cu—O4—C7	130.4 (2)	C4—C5—H5	120.88
Cu—O11—C1	121.77 (19)	C6—C5—H5	121.00
Cu—O12—C1^i	122.2 (2)	N1—C6—H6	113.81
C2—N1—C6	125.0 (3)	C5—C6—H6	125.93
Cu—N2—C11	120.7 (2)	C7—C8—H8	112.10
Cu—N2—C7^i	119.0 (2)	C9—C8—H8	127.83
C7^i—N2—C11	120.3 (3)	C8—C9—H9	135.55
C2—N1—H1'	115.60	C10—C9—H9	103.47
C6—N1—H1'	119.35	C9—C10—H10	120.80
O11—C1—O12^i	127.4 (3)	C11^i—C10—H10	121.09
N1—C2—C3	114.9 (3)	N2—C11—H11	117.07
O2—C2—C3	124.1 (3)	C10^i—C11—H11	120.75
O2—C2—N1	121.0 (3)	N3—C31—C32	175.0 (13)
C2—C3—C4	120.6 (3)	C31—C32—H321	106.90
C3—C4—C5	121.3 (3)	C31—C32—H322	105.77
C4—C5—C6	118.1 (3)	C31—C32—H323	113.10
N1—C6—C5	120.0 (3)	H321—C32—H322	109.29
N2^i—C7—C8	119.3 (3)	H321—C32—H323	111.82
O4—C7—C8	120.1 (3)	H322—C32—H323	109.73

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