Aqua­(5,6-di­methyl-1,10-phenanthroline-N,N′)­(glycolato-O,O′)­copper(II) nitrate

The title compound, [Cu(C₂H₃O₃)(C₁₄H₁₂N₂)(H₂O)]NO₃, is the first example of a mixed copper glycolate compound with a di­imine ligand. The copper(II) compound lies in a slightly distorted square-pyramidal coordination environment with one water mol­ecule coordinated in the apical position. The glycolate ligand binds to the Cu atom as a chelate through a carboxyl­ate and the α-OH O atom which, together with the N atoms of the substituted phenanthroline, constitute the base of the pyramid.

S1. Comment

Solution equilibrium studies performed on a wide variety of ternary copper chelates in which one ligand is a good π-acceptor like 2,2'-bipyridine or 1,10-phenanthroline and the other is an oxygen donor have always shown that, contrary to what is expected on a statistical basis, the stability constant for the reaction:

Cu(N—N)²⁺(aq) + O—O^n-(aq) ←→ Cu(N—N)(O—O)^(2-n)+(aq)

is always larger than the one for the reaction:

Cu²⁺(aq) + O—O^n-(aq) ←→ Cu(O—O)^(2-n)+(aq)

This behaviour has been explained by Sigel et al. (1973) based on the HSAB principle. Since a π-acceptor ligand will withdraw electron density from a bound copper ion, Cu(N—N)²⁺ will be a harder acid than simple aqueous Cu²⁺ and consequently hard bases such as oxygen donors will prefer the former over the latter.

To be able to evaluate the effect of the variations in π-accepting properties of differently substituted phenanthrolines, of which ternary complexes have low solubility, we have studied the variation in Cu—O stretching frequencies of a series of these complexes in the solid state (Gasque, Medina et al., 1999), finding a very good correlation between them and the pK_a values of the substituted phenanthrolines. It has been previously accepted (Drago & Joerg, 1996), that the π-acceptor ability of a ligand increases as its σ basicity, or pK_a, decreases.

Furthermore, for these spectroscopic studies to be valid, isostructurality of all the complexes must be proven. With this objective, we have crystallized and determined the structure of a series of Cu(x-phen)(O—O) complexes (Solans et al., 1987; Gasque, Moreno-Esparza, Mollins et al., 1999; Gasque, Moreno-Esparza, Ruiz-Ramirez & Medina-Dickinson, 1999a,b), where x-phen is a substituted phenanthroline and O—O is malonate or salicylaldehydate. In this paper, the O—O ligand is an α-hydroxyacid anion. Since we have also performed a systematic study of the IR spectra of metal glycolates (Medina et al., 2000a), comparison of the Cu—O frequencies for the title complex, (I), shows that they are indeed shifted to higher values, as expected. \sch

The glycolate anion is known to form both monomeric and polymeric complexes. The Mn and Zn complexes are six-coordinate pseudooctahedral discrete molecules having the formula cis-MG₂(H₂O)₂ (G = glycolato, M = Mn, Zn), (Fischinger & Webb, 1969; Lis, 1980) while the Cu and Co complexes constitute a bidimensional sheet-coordination polymer in which each metal atom is octahedrally coordinated to glycolato ligands in a trans configuration and carbonyl oxygen atoms from adjacent units complete the coordination octahedra (Prout et al., 1968; Medina et al., 2000b).

In (I), each Cu^II atom is in the center of a distorted octehedron, defined by the α-OH and the carboxy O atoms from the glycolato ligand, both N atoms from the phenanthroline ligand and two trans oxygen atoms, one from a water molecule and the other from the nitrate moiety. The plane defined by the four donor atoms from the two chelating ligands has a r.m.s. deviation of 0.0573 Å [distances: N1 0.0549 (9), N12 − 0.0588 (10), O17 0.0597 (10) and O21 − 0.0558 (9) Å]. Atom Cu1 is 0.1593 Å above the least-squares plane. Indicative of a typical Jahn-Teller distortion, distances from the copper atom to the two axial oxygen atoms are elongated and very different from each other. While O22(W) is 2.2681 (18) Å from the metal center, O26(NO₃) is 2.932 (3) Å fro Cu1, with a O—Cu—O angle of 170.12 (16)°.

The free rotation of the coordinated water molecule is hindered by a rather strong hydrogen bond to the free carbonyl group of a neighbouring cation, with a H22A···O19ⁱ separation of 1.997 Å and a O22—H22A···O19ⁱ angle of 172.24° (i = −x, −y, −z + 1). Additional hydrogen bonding stabilizes the overall packing, as shown in Figure 2, involving the three O atoms of the nitrate ions, the OH group of the glycolate, O21, and the water molecule O22. Separations range from 1.995 to 2.329 Å (Table 2).

S2. Experimental

5,6-Dimethyl-1,10-phenanthroline (0.5 mmol) was dissolved in methanol and added to a methanolic solution of Cu(NO₃)₂ (0.5 mmol). To this mixture an aqueous solution of glycolic acid (0.5 mmol) neutralized with NaHCO₃ (0.5 mmol) was added. The resulting deep blue solution was left standing until crystals formed, which were then filtered and vacuum dried.

S3. Refinement

H atoms on water molecule O22 were located in a difference Fourier map and were then constrained to ride on the O atom. The remaining H atoms were placed in idealized positions and refined with a riding model.

Computing details

Data collection: XSCANS (Fait, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Sheldrick, 1995); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. A view of the title compound with displacement ellipsoids shown at the 40% probability level.
	Fig. 2. A representative of the complete coordination around the Cu atom and the hydrogen bonding in the title compound.

Aqua(5,6-dimethyl-1,10-phenanthroline)(glycolato)copper(II) nitrate

Crystal data

[Cu(C2H3O3)(C14H12N2)(H2O)]NO3	Z = 2
Mr = 426.87	F(000) = 438
Triclinic, P1	Dx = 1.705 Mg m^−3
a = 7.0373 (7) Å	Mo Kα radiation, λ = 0.71073 Å
b = 10.0928 (11) Å	Cell parameters from 35 reflections
c = 13.1649 (13) Å	θ = 4.6–12.5°
α = 103.225 (8)°	µ = 1.36 mm^−1
β = 105.450 (12)°	T = 293 K
γ = 103.760 (9)°	Needle, blue
V = 831.68 (15) Å^3	0.7 × 0.3 × 0.2 mm

Data collection

Siemens P4 diffractometer	3406 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 28.0°, θmin = 2.2°
2θ/ω scans	h = −1→9
Absorption correction: ψ scan 24 psi scans with XSCANS (Fait, 1991)	k = −12→12
Tmin = 0.614, Tmax = 0.762	l = −17→17
4927 measured reflections	3 standard reflections every 97 reflections
3969 independent reflections	intensity decay: 7.2%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.034	H-atom parameters constrained
wR(F^2) = 0.092	w = 1/[σ^2(Fo^2) + (0.0419P)^2 + 0.3303P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
3969 reflections	Δρmax = 0.38 e Å^−3
245 parameters	Δρmin = −0.36 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0109 (14)

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.

Hydrogen from the water molecule O(22) were found on difference Fourier map and refined as riding to O(22).

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

	x	y	z	Uiso*/Ueq
Cu1	0.00049 (4)	0.18606 (2)	0.306460 (18)	0.03179 (10)
N1	−0.0404 (3)	0.36015 (18)	0.26942 (13)	0.0298 (4)
C2	0.0097 (4)	0.4922 (2)	0.33640 (18)	0.0376 (5)
H2A	0.0703	0.5108	0.4123	0.045*
C3	−0.0252 (4)	0.6040 (2)	0.2972 (2)	0.0415 (5)
H3A	0.0107	0.6955	0.3464	0.050*
C4	−0.1127 (4)	0.5786 (2)	0.18570 (19)	0.0385 (5)
H4A	−0.1353	0.6533	0.1591	0.046*
C5	−0.1689 (3)	0.4393 (2)	0.11067 (17)	0.0299 (4)
C6	−0.2596 (3)	0.4025 (2)	−0.00892 (17)	0.0314 (4)
C7	−0.3100 (3)	0.2640 (2)	−0.07512 (17)	0.0323 (4)
C8	−0.2707 (3)	0.1539 (2)	−0.02594 (15)	0.0281 (4)
C9	−0.3182 (3)	0.0088 (2)	−0.08691 (16)	0.0336 (4)
H9A	−0.3790	−0.0217	−0.1637	0.040*
C10	−0.2748 (4)	−0.0875 (2)	−0.03289 (17)	0.0349 (5)
H10A	−0.3073	−0.1835	−0.0728	0.042*
C11	−0.1814 (3)	−0.0402 (2)	0.08263 (16)	0.0321 (4)
H11A	−0.1518	−0.1058	0.1187	0.038*
N12	−0.1340 (3)	0.09543 (17)	0.14184 (13)	0.0278 (3)
C13	−0.1780 (3)	0.1902 (2)	0.08941 (15)	0.0258 (4)
C14	−0.1281 (3)	0.3345 (2)	0.15818 (15)	0.0263 (4)
C15	−0.2911 (4)	0.5220 (3)	−0.0550 (2)	0.0423 (5)
H15A	−0.3516	0.4846	−0.1344	0.063*
H15B	−0.1594	0.5945	−0.0346	0.063*
H15C	−0.3823	0.5631	−0.0255	0.063*
C16	−0.4092 (4)	0.2181 (3)	−0.19971 (18)	0.0485 (6)
H16A	−0.4276	0.2996	−0.2222	0.073*
H16B	−0.5421	0.1460	−0.2222	0.073*
H16C	−0.3211	0.1796	−0.2339	0.073*
O17	0.0560 (3)	0.01614 (16)	0.32853 (12)	0.0427 (4)
C18	0.1748 (4)	0.0287 (2)	0.42474 (17)	0.0359 (5)
O19	0.2113 (3)	−0.07235 (19)	0.45395 (14)	0.0538 (5)
C20	0.2771 (4)	0.1779 (2)	0.50724 (18)	0.0406 (5)
H20A	0.2529	0.1786	0.5765	0.049*
H20B	0.4260	0.2065	0.5221	0.049*
O21	0.1923 (3)	0.27627 (16)	0.46286 (12)	0.0438 (4)
H21	0.2678	0.3578	0.5119	0.066*
O22	−0.2927 (3)	0.13929 (19)	0.35139 (14)	0.0453 (4)
H22A	−0.2642	0.1166	0.4027	0.068*
H22B	−0.3535	0.2060	0.3584	0.068*
N23	0.4971 (3)	0.4160 (2)	0.34116 (14)	0.0381 (4)
O24	0.6400 (3)	0.4286 (2)	0.42635 (16)	0.0614 (5)
O25	0.4569 (4)	0.5245 (2)	0.32854 (18)	0.0662 (6)
O26	0.3957 (4)	0.2972 (2)	0.27269 (17)	0.0733 (7)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.04435 (17)	0.02269 (13)	0.02083 (13)	0.00956 (10)	0.00114 (10)	0.00574 (9)
N1	0.0354 (9)	0.0249 (8)	0.0247 (7)	0.0082 (7)	0.0058 (7)	0.0061 (6)
C2	0.0467 (13)	0.0284 (10)	0.0286 (10)	0.0099 (9)	0.0056 (9)	0.0025 (8)
C3	0.0507 (14)	0.0259 (10)	0.0421 (12)	0.0117 (10)	0.0130 (10)	0.0038 (9)
C4	0.0460 (13)	0.0271 (10)	0.0451 (12)	0.0136 (9)	0.0154 (10)	0.0144 (9)
C5	0.0297 (10)	0.0281 (9)	0.0344 (10)	0.0109 (8)	0.0106 (8)	0.0128 (8)
C6	0.0295 (10)	0.0353 (10)	0.0347 (10)	0.0129 (8)	0.0098 (8)	0.0194 (8)
C7	0.0300 (10)	0.0380 (11)	0.0286 (9)	0.0094 (8)	0.0059 (8)	0.0164 (8)
C8	0.0266 (10)	0.0307 (10)	0.0243 (8)	0.0071 (8)	0.0055 (7)	0.0094 (7)
C9	0.0348 (11)	0.0341 (10)	0.0221 (8)	0.0049 (9)	0.0037 (8)	0.0041 (8)
C10	0.0407 (12)	0.0256 (9)	0.0302 (10)	0.0068 (9)	0.0075 (9)	0.0025 (8)
C11	0.0378 (11)	0.0234 (9)	0.0292 (9)	0.0077 (8)	0.0058 (8)	0.0061 (7)
N12	0.0321 (9)	0.0243 (8)	0.0235 (7)	0.0078 (7)	0.0049 (6)	0.0078 (6)
C13	0.0261 (9)	0.0242 (9)	0.0243 (8)	0.0059 (7)	0.0058 (7)	0.0074 (7)
C14	0.0264 (9)	0.0250 (9)	0.0266 (9)	0.0077 (7)	0.0072 (7)	0.0092 (7)
C15	0.0460 (13)	0.0454 (13)	0.0477 (13)	0.0220 (11)	0.0160 (11)	0.0288 (11)
C16	0.0588 (16)	0.0474 (13)	0.0294 (11)	0.0083 (12)	0.0018 (10)	0.0182 (10)
O17	0.0604 (11)	0.0267 (7)	0.0279 (7)	0.0138 (7)	−0.0035 (7)	0.0061 (6)
C18	0.0447 (12)	0.0304 (10)	0.0269 (9)	0.0107 (9)	0.0041 (9)	0.0092 (8)
O19	0.0798 (14)	0.0339 (8)	0.0383 (9)	0.0209 (9)	−0.0008 (9)	0.0152 (7)
C20	0.0473 (13)	0.0321 (11)	0.0296 (10)	0.0096 (10)	−0.0020 (9)	0.0068 (8)
O21	0.0583 (11)	0.0237 (7)	0.0296 (7)	0.0074 (7)	−0.0068 (7)	0.0032 (6)
O22	0.0521 (10)	0.0479 (10)	0.0424 (9)	0.0199 (8)	0.0148 (8)	0.0235 (8)
N23	0.0455 (11)	0.0349 (9)	0.0276 (8)	0.0107 (8)	0.0083 (8)	0.0055 (7)
O24	0.0562 (12)	0.0710 (14)	0.0447 (10)	0.0197 (11)	−0.0032 (9)	0.0198 (9)
O25	0.0868 (16)	0.0429 (10)	0.0636 (13)	0.0250 (11)	0.0105 (11)	0.0201 (9)
O26	0.0939 (17)	0.0449 (11)	0.0488 (11)	0.0124 (11)	0.0064 (11)	−0.0144 (9)

Geometric parameters (Å, º)

Cu1—O17	1.9144 (15)	C7—C16	1.510 (3)
Cu1—N1	1.9913 (17)	C8—C13	1.403 (3)
Cu1—O21	1.9918 (15)	C8—C9	1.410 (3)
Cu1—N12	2.0044 (16)	C9—C10	1.373 (3)
Cu1—O22	2.2681 (18)	C10—C11	1.400 (3)
Cu1—O26	2.932 (3)	C11—N12	1.322 (2)
N1—C2	1.323 (3)	N12—C13	1.348 (2)
N1—C14	1.365 (2)	C13—C14	1.431 (3)
C2—C3	1.390 (3)	O17—C18	1.277 (2)
C3—C4	1.367 (3)	C18—O19	1.227 (3)
C4—C5	1.414 (3)	C18—C20	1.512 (3)
C5—C14	1.394 (3)	C20—O21	1.430 (3)
C5—C6	1.452 (3)	N23—O25	1.230 (3)
C6—C7	1.372 (3)	N23—O26	1.231 (3)
C6—C15	1.504 (3)	N23—O24	1.248 (2)
C7—C8	1.453 (3)
O17—Cu1—N1	172.93 (7)	C8—C7—C16	117.2 (2)
O17—Cu1—O21	83.09 (6)	C13—C8—C9	115.97 (18)
N1—Cu1—O21	99.98 (6)	C13—C8—C7	119.77 (18)
O17—Cu1—N12	93.32 (7)	C9—C8—C7	124.26 (18)
N1—Cu1—N12	82.30 (7)	C10—C9—C8	120.01 (18)
O21—Cu1—N12	167.20 (7)	C9—C10—C11	119.52 (19)
O17—Cu1—O22	93.45 (7)	N12—C11—C10	121.75 (19)
N1—Cu1—O22	92.64 (7)	C11—N12—C13	119.01 (17)
O21—Cu1—O22	94.83 (7)	C11—N12—Cu1	128.38 (14)
N12—Cu1—O22	97.65 (7)	C13—N12—Cu1	112.61 (13)
O22—Cu1—O26	170.12 (16)	N12—C13—C8	123.73 (18)
C2—N1—C14	118.26 (18)	N12—C13—C14	116.42 (16)
C2—N1—Cu1	129.10 (15)	C8—C13—C14	119.84 (17)
C14—N1—Cu1	112.62 (13)	N1—C14—C5	123.86 (18)
N1—C2—C3	122.2 (2)	N1—C14—C13	116.00 (17)
C4—C3—C2	119.6 (2)	C5—C14—C13	120.14 (17)
C3—C4—C5	120.3 (2)	C18—O17—Cu1	116.71 (14)
C14—C5—C4	115.71 (19)	O19—C18—O17	124.2 (2)
C14—C5—C6	119.96 (18)	O19—C18—C20	118.24 (19)
C4—C5—C6	124.31 (19)	O17—C18—C20	117.59 (19)
C7—C6—C5	120.14 (18)	O21—C20—C18	109.29 (17)
C7—C6—C15	122.63 (19)	C20—O21—Cu1	112.77 (12)
C5—C6—C15	117.2 (2)	O25—N23—O26	120.8 (2)
C6—C7—C8	120.12 (18)	O25—N23—O24	118.5 (2)
C6—C7—C16	122.71 (19)	O26—N23—O24	120.7 (2)
O17—Cu1—N1—C2	−127.8 (5)	N1—Cu1—N12—C13	1.74 (14)
O21—Cu1—N1—C2	−12.6 (2)	O21—Cu1—N12—C13	−99.5 (3)
N12—Cu1—N1—C2	−179.8 (2)	O22—Cu1—N12—C13	93.38 (14)
O22—Cu1—N1—C2	82.8 (2)	C11—N12—C13—C8	−0.6 (3)
O17—Cu1—N1—C14	50.5 (6)	Cu1—N12—C13—C8	179.42 (16)
O21—Cu1—N1—C14	165.70 (14)	C11—N12—C13—C14	178.38 (19)
N12—Cu1—N1—C14	−1.55 (14)	Cu1—N12—C13—C14	−1.6 (2)
O22—Cu1—N1—C14	−98.92 (15)	C9—C8—C13—N12	0.2 (3)
C14—N1—C2—C3	0.3 (4)	C7—C8—C13—N12	−179.31 (19)
Cu1—N1—C2—C3	178.52 (18)	C9—C8—C13—C14	−178.74 (19)
N1—C2—C3—C4	−0.5 (4)	C7—C8—C13—C14	1.8 (3)
C2—C3—C4—C5	0.5 (4)	C2—N1—C14—C5	−0.2 (3)
C3—C4—C5—C14	−0.3 (3)	Cu1—N1—C14—C5	−178.64 (16)
C3—C4—C5—C6	−179.1 (2)	C2—N1—C14—C13	179.60 (19)
C14—C5—C6—C7	1.6 (3)	Cu1—N1—C14—C13	1.1 (2)
C4—C5—C6—C7	−179.7 (2)	C4—C5—C14—N1	0.2 (3)
C14—C5—C6—C15	−177.4 (2)	C6—C5—C14—N1	178.97 (19)
C4—C5—C6—C15	1.3 (3)	C4—C5—C14—C13	−179.61 (19)
C5—C6—C7—C8	−0.7 (3)	C6—C5—C14—C13	−0.8 (3)
C15—C6—C7—C8	178.3 (2)	N12—C13—C14—N1	0.3 (3)
C5—C6—C7—C16	178.6 (2)	C8—C13—C14—N1	179.34 (18)
C15—C6—C7—C16	−2.5 (4)	N12—C13—C14—C5	−179.87 (18)
C6—C7—C8—C13	−1.0 (3)	C8—C13—C14—C5	−0.9 (3)
C16—C7—C8—C13	179.7 (2)	N1—Cu1—O17—C18	118.1 (5)
C6—C7—C8—C9	179.6 (2)	O21—Cu1—O17—C18	1.88 (18)
C16—C7—C8—C9	0.3 (3)	N12—Cu1—O17—C18	169.55 (18)
C13—C8—C9—C10	0.4 (3)	O22—Cu1—O17—C18	−92.58 (19)
C7—C8—C9—C10	179.9 (2)	Cu1—O17—C18—O19	174.0 (2)
C8—C9—C10—C11	−0.7 (3)	Cu1—O17—C18—C20	−6.3 (3)
C9—C10—C11—N12	0.3 (3)	O19—C18—C20—O21	−171.9 (2)
C10—C11—N12—C13	0.3 (3)	O17—C18—C20—O21	8.4 (3)
C10—C11—N12—Cu1	−179.65 (16)	C18—C20—O21—Cu1	−6.4 (3)
O17—Cu1—N12—C11	7.3 (2)	O17—Cu1—O21—C20	3.01 (17)
N1—Cu1—N12—C11	−178.3 (2)	N1—Cu1—O21—C20	−170.56 (16)
O21—Cu1—N12—C11	80.5 (3)	N12—Cu1—O21—C20	−71.3 (3)
O22—Cu1—N12—C11	−86.63 (19)	O22—Cu1—O21—C20	95.90 (17)
O17—Cu1—N12—C13	−172.69 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O21—H21···O24^i	0.86	2.00	2.795 (2)	154
O21—H21···O25^i	0.86	2.27	3.030 (2)	146
O21—H21···N23^i	0.86	2.48	3.344 (2)	176
O22—H22A···O19^ii	0.88	2.00	2.747 (3)	172
O22—H22B···O24^iii	0.88	2.24	3.052 (3)	154
O22—H22B···O26^iii	0.88	2.33	3.103 (3)	147
O22—H22B···N23^iii	0.88	2.61	3.469 (3)	166

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