Copper(II)-induced methano­lysis of a stable enediol: isolation and crystallographic characterization of chloro­(methyl­picolinato-N,O)(picolinato-N,O)copper(II)

A square-pyramidal geometry is found about the copper(II) centre in the title complex, [CuCl(C₆H₄NO₂)(C₇H₇NO₂)] or [Cu(2-pic)(2-picMe)Cl], a product of Cu^II-induced methan­olysis of 1,2-di(2-pyridyl)-1,2-di­hydroxy­ethyl­ene. Each of the 2-pic and 2-picMe ligands chelates the copper centre via N and and one of their O-donor atoms. In the case of 2-picMe, the donor atoms span basal and axial positions via the N and O atoms, respectively. Weak secondary Cu...Cl interactions link mol­ecules of the complex in the crystal into centrosymmetric dimeric aggregates.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.028
• wR factor = 0.081
• Data-to-parameter ratio = 16.4

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



ABSTM_02  Alert C The ratio of Tmax/Tmin expected RT(exp) is > 1.10
          Absorption corrections should be applied.
          Tmin and Tmax expected:      0.621     0.734
          RT(exp) =      1.182


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

The coordination behaviour of 1,2-di(2-pyridyl)-1,2-dihydroxyethylene (H₂L) versus the first row transition metal ions has been documented (Brierley & Geary, 1967). However, rather complex nature of some of the products calls for detailed structural studies.

The present communication indicates that a metal ion-induced solvolysis of the coordinated ligand in methanol solution has occurred when CuCl₂·2H₂O has been used as the metal ion precursor. The solvolysis generates the picolinic acid anion (2-pic) and methyl picolinate (2-picMe), both of which remain coordinated to the copper(II) centre in the mononuclear product, [Cu(2-pic)(2-picMe)Cl], (I), as proven crystallographically.

The copper(II) centre in(I)I (Fig. 1 and Table 1) has a distorted square-pyramidal environment in which the basal plane is defined by the O1 and N1 atoms of the 2-pic anion, the N2 atom of the neutral 2-picMe ligand, and Cl1. The axial position is occupied by the carbonyl O3 atom of the 2-picMe ligand. Thus, both non-chloride ligands function as bidentate donors, forming five-membered rings in each case. There is some puckering in each of the chelate rings as manifested in the Cu—O1—C6—C1 and Cu—O3—C12—C7 torsion angles of 11.3 (2) and 16.5 (2)°, respectively. Within the basal plane of the square pyramid, the N atoms occupy mutually trans positions. The deviations of the Cl1, O1, N1 and N2 atoms from their least-squares plane are -0.1943 (6), -0.2609 (16), 0.2362 (19) and 0.2191 (19) Å, respectively, with the Cu atom lying essentially in the same plane [its displacement in the direction of the O3 atom is equal to 0.0367 (3) Å]. The Cu—N distances are similar to each other but the Cu—O1 distance of 1.9712 (17) Å is significantly shorter than the Cu—O3 distance of 2.3903 (17) Å reflecting, in part, the difference in donor strengths of the O1 and O3 atoms. The Jahn–Teller effect operating in this d⁹ system will also cause elongation of the Cu—O3 bond.

The most significant intermolecular contact in the lattice occurs between the Cu atom and a symmetry related Cl1 atom so that Cu···Cl1ⁱ is 3.0634 (14) Å [symmetry code: (i) -x, -y, 1 - z]. This association leads to the formation of centrosymmetric dimeric aggregates built around (Cu···Cl)₂ rectangles.

S2. Experimental

A solution of CuCl₂·2H₂O (0.17 g, 1.0 mmol) in 20 ml of methanol was added dropwise to a stirred solution of 1,2-di(2-pyridyl)-1,2-dihydroxyethylene (0.21 g, 1.0 mmol), also in methanol (20 ml), to form a deep-green solution. The solution was stirred at room temperature for ca 4 h and filtered. The filtrate was rotary evaporated to ca 10 ml volume and stored at 277 K overnight; a blue crystalline compound precipitated. The product was collected by filtration, washed with a chilled methanol–diethyl ether mixture (2:1 v/v, 4 × 10 ml) and finally dried in vacuo. It was then recrystallized from acetonitrile solution. Yield: 85 mg (50%). The crop also contained a few diffraction quality crystals which were characterized as the title complex. Found: C 43.8, H 3.0, N 7.6%; calculated for C₁₃H₁₁ClCuN₂O₄: C 43.57, H 3.07, N 7.82%.

S3. Refinement

The H atoms were placed in the geometrically calculated positions and included in the final refinement in the riding-model approximation with an overall displacement parameter.

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1996); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1997); program(s) used to solve structure: DIRDIF (Beurskens et al., 1992); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular structure and crystallographic numbering scheme for [Cu(2-pic)(2-picMe)Cl]. Displacement ellipsoids are shown at the 50% probability level (Johnson, 1976).

(I)

Crystal data

[CuCl(C6H4NO2)(C7H7NO2)]	F(000) = 724
Mr = 358.24	Dx = 1.748 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2yn	Cell parameters from 19 reflections
a = 10.415 (2) Å	θ = 7.2–10.5°
b = 9.466 (2) Å	µ = 1.82 mm^−1
c = 14.357 (6) Å	T = 173 K
β = 105.88 (2)°	Block, blue
V = 1361.4 (6) Å^3	0.27 × 0.27 × 0.17 mm
Z = 4

Data collection

Rigaku AFC-7R diffractometer	Rint = 0.027
Radiation source: Rotating anode	θmax = 27.5°, θmin = 3.1°
Graphite monochromator	h = 0→13
ω–2θ scans	k = 0→12
3497 measured reflections	l = −18→17
3130 independent reflections	3 standard reflections every 400 reflections
2414 reflections with I > 2σ(I)	intensity decay: 1.2%

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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.081	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0394P)^2 + 0.7048P] where P = (Fo^2 + 2Fc^2)/3
3130 reflections	(Δ/σ)max < 0.001
191 parameters	Δρmax = 0.44 e Å^−3
0 restraints	Δρmin = −0.42 e Å^−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
Cu	0.07757 (3)	0.07383 (3)	0.397225 (19)	0.02233 (9)
Cl1	−0.02125 (6)	0.19152 (6)	0.49830 (4)	0.02622 (13)
O1	0.14409 (16)	−0.07055 (17)	0.32304 (12)	0.0259 (3)
O2	0.06930 (19)	−0.22470 (18)	0.20241 (13)	0.0336 (4)
O3	0.14506 (16)	0.29462 (18)	0.34497 (12)	0.0285 (4)
O4	0.29089 (17)	0.46077 (17)	0.42006 (12)	0.0273 (4)
N1	−0.08537 (19)	0.0590 (2)	0.28732 (13)	0.0227 (4)
N2	0.26237 (18)	0.1045 (2)	0.48374 (14)	0.0227 (4)
C1	−0.0753 (2)	−0.0422 (2)	0.22439 (16)	0.0209 (4)
C2	−0.1773 (2)	−0.0683 (3)	0.14132 (17)	0.0274 (5)
H2	−0.1685	−0.1407	0.0976	0.040 (3)*
C3	−0.2919 (3)	0.0125 (3)	0.12300 (18)	0.0327 (6)
H3	−0.3637	−0.0042	0.0669	0.040 (3)*
C4	−0.3006 (2)	0.1178 (3)	0.18728 (18)	0.0339 (6)
H4	−0.3778	0.1759	0.1755	0.040 (3)*
C5	−0.1955 (2)	0.1377 (3)	0.26911 (18)	0.0306 (5)
H5	−0.2020	0.2096	0.3137	0.040 (3)*
C6	0.0559 (2)	−0.1211 (2)	0.25102 (17)	0.0236 (5)
C7	0.3226 (2)	0.2294 (2)	0.48179 (16)	0.0215 (4)
C8	0.4473 (2)	0.2604 (3)	0.54277 (17)	0.0264 (5)
H8	0.4879	0.3496	0.5396	0.040 (3)*
C9	0.5121 (2)	0.1585 (3)	0.60882 (18)	0.0309 (5)
H9	0.5970	0.1774	0.6524	0.040 (3)*
C10	0.4509 (3)	0.0298 (3)	0.60995 (18)	0.0313 (5)
H10	0.4938	−0.0422	0.6536	0.040 (3)*
C11	0.3259 (2)	0.0065 (3)	0.54657 (18)	0.0283 (5)
H11	0.2840	−0.0824	0.5478	0.040 (3)*
C12	0.2438 (2)	0.3303 (2)	0.40733 (16)	0.0228 (4)
C13	0.2138 (3)	0.5656 (3)	0.3533 (2)	0.0341 (6)
H13A	0.2559	0.6585	0.3683	0.040 (3)*
H13B	0.1227	0.5693	0.3601	0.040 (3)*
H13C	0.2109	0.5394	0.2867	0.040 (3)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.01902 (14)	0.02343 (15)	0.02114 (15)	0.00178 (11)	−0.00026 (10)	−0.00417 (11)
Cl1	0.0264 (3)	0.0265 (3)	0.0245 (3)	−0.0010 (2)	0.0048 (2)	−0.0060 (2)
O1	0.0231 (8)	0.0265 (8)	0.0274 (8)	0.0046 (7)	0.0056 (7)	−0.0007 (7)
O2	0.0423 (10)	0.0241 (8)	0.0353 (10)	0.0049 (8)	0.0121 (8)	−0.0070 (7)
O3	0.0238 (8)	0.0299 (9)	0.0265 (8)	−0.0026 (7)	−0.0021 (7)	0.0082 (7)
O4	0.0296 (9)	0.0190 (8)	0.0288 (9)	0.0021 (7)	0.0006 (7)	0.0028 (7)
N1	0.0227 (9)	0.0212 (9)	0.0211 (9)	0.0013 (7)	0.0008 (7)	−0.0018 (7)
N2	0.0196 (9)	0.0239 (9)	0.0218 (9)	0.0004 (8)	0.0008 (7)	0.0002 (8)
C1	0.0259 (11)	0.0173 (9)	0.0193 (10)	−0.0024 (8)	0.0060 (8)	0.0004 (8)
C2	0.0320 (12)	0.0259 (12)	0.0222 (11)	−0.0058 (10)	0.0037 (9)	−0.0023 (9)
C3	0.0307 (13)	0.0382 (14)	0.0234 (12)	−0.0063 (11)	−0.0025 (10)	0.0025 (10)
C4	0.0244 (12)	0.0421 (15)	0.0309 (13)	0.0098 (11)	−0.0001 (10)	0.0054 (11)
C5	0.0286 (12)	0.0324 (12)	0.0275 (12)	0.0077 (10)	0.0020 (10)	−0.0038 (10)
C6	0.0284 (12)	0.0188 (10)	0.0257 (11)	0.0002 (9)	0.0110 (9)	0.0030 (9)
C7	0.0224 (10)	0.0207 (10)	0.0198 (10)	0.0015 (8)	0.0033 (8)	0.0003 (8)
C8	0.0229 (11)	0.0256 (11)	0.0272 (12)	−0.0024 (9)	0.0012 (9)	0.0006 (9)
C9	0.0233 (12)	0.0341 (13)	0.0295 (12)	−0.0021 (10)	−0.0028 (10)	0.0039 (11)
C10	0.0284 (12)	0.0325 (13)	0.0278 (12)	0.0033 (10)	−0.0013 (10)	0.0106 (10)
C11	0.0260 (12)	0.0235 (11)	0.0316 (12)	−0.0015 (9)	0.0015 (10)	0.0053 (10)
C12	0.0224 (11)	0.0238 (11)	0.0220 (11)	0.0007 (9)	0.0056 (9)	0.0005 (9)
C13	0.0361 (14)	0.0244 (12)	0.0374 (14)	0.0062 (11)	0.0028 (11)	0.0075 (11)

Geometric parameters (Å, º)

Cu—Cl1	2.2855 (8)	N2—C7	1.342 (3)
Cu—O1	1.9712 (17)	N2—C11	1.337 (3)
Cu—O3	2.3903 (17)	C1—C2	1.385 (3)
Cu—N1	1.981 (2)	C1—C6	1.512 (3)
Cu—N2	2.0058 (19)	C2—C3	1.382 (4)
O1—C6	1.274 (3)	C3—C4	1.378 (4)
O2—C6	1.233 (3)	C4—C5	1.382 (3)
O3—C12	1.212 (3)	C7—C8	1.385 (3)
O4—C12	1.323 (3)	C7—C12	1.500 (3)
O4—C13	1.458 (3)	C8—C9	1.391 (3)
N1—C1	1.340 (3)	C9—C10	1.377 (4)
N1—C5	1.332 (3)	C10—C11	1.387 (3)
O1—Cu—N1	82.62 (7)	N1—C1—C6	114.48 (19)
O1—Cu—N2	90.89 (8)	C2—C1—C6	123.8 (2)
N1—Cu—N2	166.23 (8)	C3—C2—C1	119.0 (2)
O1—Cu—Cl1	165.21 (5)	C4—C3—C2	119.0 (2)
N1—Cu—Cl1	95.96 (6)	C3—C4—C5	119.1 (2)
N2—Cu—Cl1	93.36 (6)	N1—C5—C4	122.0 (2)
O1—Cu—O3	105.05 (7)	O2—C6—O1	126.2 (2)
N1—Cu—O3	94.21 (7)	O2—C6—C1	119.0 (2)
N2—Cu—O3	75.70 (7)	O1—C6—C1	114.9 (2)
Cl1—Cu—O3	89.73 (5)	N2—C7—C8	122.5 (2)
C6—O1—Cu	114.66 (14)	N2—C7—C12	114.06 (19)
C12—O3—Cu	105.94 (15)	C8—C7—C12	123.5 (2)
C12—O4—C13	115.32 (19)	C7—C8—C9	118.7 (2)
C5—N1—C1	119.3 (2)	C10—C9—C8	118.8 (2)
C5—N1—Cu	128.36 (16)	C9—C10—C11	119.2 (2)
C1—N1—Cu	112.32 (15)	N2—C11—C10	122.3 (2)
C11—N2—C7	118.5 (2)	O3—C12—O4	124.7 (2)
C11—N2—Cu	122.09 (16)	O3—C12—C7	122.5 (2)
C7—N2—Cu	119.31 (15)	O4—C12—C7	112.70 (19)
N1—C1—C2	121.7 (2)