Jahn–Teller distorted copper(II) in poly[bis­(μ-4,4′-bipyridine)tetra-μ-cyanido-copper(II)disilver(I)]

The title compound, [Ag₂Cu(CN)₄(C₁₀H₈N₂)₂]_n, contains a three-dimensional doubly penetrating framework structure composed of copper(II) bridged by 4,4′-bipyridine and dicyano­argentate groups. The Cu atom is located on an inversion center and is coordinated by six N atoms in a distorted tetra­gonal–bipyramidal geometry as a result of a significant Jahn–Teller distortion. The equatorial plane of Cu is coordinated by two bridging bipyridine ligands and two N-bound dicyano­argentate anions, while the axial positions are occupied by two N atoms from bridging dicyano­argentate anions. A three-coordinate Ag atom is present, due to two Ag—C bonds and one longer Ag—N inter­action.

Key indicators

• Single-crystal X-ray study
• T = 290 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.024
• wR factor = 0.065
• Data-to-parameter ratio = 14.1

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT063_ALERT_3_B Crystal Probably too Large for Beam Size .......       1.00 mm

Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Cu1         (1)       1.20

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

   0 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
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

---

S1. Comment

Numerous dicyanoargentates have been prepared in recent years due to their interesting structural and magnetic properties (Černák et al., 2002; Lefebvre & Leznoff, 2005). By incorporating various amine ligands along with Cu²⁺ cations and dicyanoargentate anions, structure types containing molecular units, Cu(pn)₂Ag₂(CN)₄ (pn = 1,2-diaminopropane) (Triščíková et al., 2004), one-dimensional chains, Cu(bpy)₂Ag₂(CN)₄.H₂O (bpy = 2,2'-bipyridine) (Černák et al., 1993), two-dimensional sheets, [Cu(en)₂][Ag₂(CN)₃][Ag(CN)₂] (en = ethylenediamine) (Shorrock et al., 2002), and three-dimensional networks, [Cu₂(C₄H₁₂N₂)₂{Ag(CN)₂}₄(NH₃)].2H₂O (Potočňák et al., 2003) have all been prepared. Numerous other metal organic compounds containing various transition metal cations, amine ligands, and dicyanoargentate anions have also been prepared. One such structure-type type containing 4,4'-bipyridine (bpy), M(bpy)₂[Ag(CN)₂]₂, where M is Mn (Dong et al., 2003), Fe (Niel et al., 2002), or Cd (Soma et al., 1994) has been prepared. This structure contains a distorted octahedral coordination polyhedron for the M(II) cations, bridging 4,4'-bipyridine ligands, and a three coordinate Ag atom. The title compound, bis(µ-4,4'-bipyridine)bis[µ-dicyanoargentate(I)]copper(II), was prepared in order to determine (1) if the same structure was possible with copper(II) and (2) to probe the effects on the structure.

There is one symmetrically unique copper atom in the structure of Cu(bpy)₂[Ag(CN)₂]₂ and it is located on an inversion center. The coordination geometry around the Cu atoms (Fig. 1) is composed of six nitrogen atoms in a tetragonal bipyramidal arrangement. Two bridging bipyridine ligands and two nitrogen-bound dicyanoargentate anions account for the nitrogen atoms located in the equatorial plane, while the apical positions are occupied by two nitrogen atoms from bridging dicyanoargentate anions. A significant Jahn-Teller distortion is evident in the lengthened Cu—N distance (2.563 (3) Å) of the apical nitrogen atoms as compared to the equatorial Cu—N distances (1.961 (3) and 2.056 (3) Å). In the previously reported Mn, Fe, and Cd structures, the coordination geometries of these metals can be described as distorted octahedral and the M—N bond distances showed much less variation. In Cd(bpy)₂[Ag(CN)₂]₂ the three unique Cd—N bond distances are 2.288, 2.369, and 2.377 Å, in Fe(bpy)₂[Ag(CN)₂]₂ the three Fe—N bond distances are 2.129, 2.188, and 2.248 Å, and in Mn(bpy)₂[Ag(CN)₂]₂ the three Mn—N bond distances are 2.193, 2.264, and 2.320 Å.

There are no unusual features in the bond distances found in the dicyanoargentate anions in Cu(bpy)₂[Ag(CN)₂]₂, although there is a significant bond angle decrease from linearity, C1—Ag1—C2 angle of 157.40 (13)°, as also observed in the previous Mn, Fe, and Cd structures, which have angles of 153.9°, 154.2°, and 153.6°, respectively. The three-dimensional double penetrating framework (Fig 2.) (Soma et al., 1994) built up by the bridging 4,4'-bipyridine and dicyanoargentate anions is preserved in the structure of Cu(bpy)₂[Ag(CN)₂]₂.

Related literature

For related literature, see: Dong et al. (2003); Lefebvre & Leznoff (2005); Niel et al. (2002); Potočňák et al. (2003); Shorrock et al. (2002); Soma et al. (1994); Triščíková et al. (2004); Černák et al. (1993, 2002).

S2. Experimental

A methanolic solution of 4,4'-bipyridine (0.25 ml, 1.0 M) and aqueous KAg(CN)₂ (2.5 ml, 0.2 M) were added to an aqueous solution of CuSO₄ (2.5 ml, 0.1 M). This resulted in the precipitation of a blue powder, which was then dissolved by the addition of 2.5 ml of a concentrated NH₃ (26%) solution. The solution was left for 5 days, resulting in dark blue crystals of the title compound suitable for single-crystal X-ray analysis.

S3. Refinement

H atoms were placed in calculated positions and allowed to ride during subsequent refinement, with U_iso(H) = 1.2U_eq(C) and C—H distances of 0.93 Å.

Computing details

Data collection: CAD-4-PC Software (Enraf–Nonius, 1993); cell refinement: CAD-4-PC Software; data reduction: XCAD4PC (Harms, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: publCIF (Westrip, 2007).

Figures

	Fig. 1. Part of the structure of Cu(bpy)2[Ag(CN)2]2, with atom labeling for the independent atoms. Displacement ellipsoids are shown at the 50% probability level. H atoms are shown as spheres of arbitrary size.
	Fig. 2. The packing diagram of the three-dimensional network in Cu(bpy)2[Ag(CN)2]2. The hydrogen atoms have been omitted for clarity.

poly[bis(µ-4,4'-bipyridine)tetra-µ-cyanido-copper(II)disilver(I)]

Crystal data

[Ag2Cu(CN)4(C10H8N2)2]	F(000) = 678
Mr = 695.73	Dx = 1.873 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 8.9056 (9) Å	θ = 8.7–12.0°
b = 11.4712 (10) Å	µ = 2.46 mm^−1
c = 12.5918 (11) Å	T = 290 K
β = 106.484 (8)°	Irregular prism, dark blue
V = 1233.5 (2) Å^3	1.00 × 0.51 × 0.42 mm
Z = 2

Data collection

Enraf–Nonius CAD-4 diffractometer	1969 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.022
Graphite monochromator	θmax = 25.4°, θmin = 2.5°
θ/2θ scans	h = 0→10
Absorption correction: ψ scan (North et al., 1968)	k = 0→13
Tmin = 0.255, Tmax = 0.353	l = −15→14
2418 measured reflections	3 standard reflections every 120 min
2267 independent reflections	intensity decay: none

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)] = 0.025	H-atom parameters constrained
wR(F^2) = 0.065	w = 1/[σ^2(Fo^2) + (0.0257P)^2 + 1.3204P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max = 0.001
2267 reflections	Δρmax = 0.45 e Å^−3
161 parameters	Δρmin = −0.38 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: 0.0043 (4)

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 > 2σ(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
Ag1	0.17340 (3)	0.82881 (2)	0.67239 (2)	0.04213 (12)
Cu1	0.0000	1.0000	1.0000	0.04178 (18)
N1	0.0760 (3)	0.9291 (3)	0.8833 (2)	0.0374 (6)
N2	0.1216 (4)	1.1913 (3)	0.9593 (3)	0.0479 (7)
N3	0.2061 (3)	0.9593 (3)	1.1172 (2)	0.0395 (6)
N4	0.9171 (3)	0.8550 (3)	1.5329 (2)	0.0475 (7)
C1	0.1135 (4)	0.8918 (3)	0.8110 (3)	0.0370 (7)
C2	0.1904 (4)	1.2467 (3)	0.9156 (3)	0.0408 (8)
C3	0.3430 (4)	0.9961 (4)	1.1058 (3)	0.0510 (10)
H3A	0.3437	1.0357	1.0415	0.061*
C4	0.4829 (4)	0.9777 (4)	1.1853 (3)	0.0492 (9)
H4A	0.5754	1.0053	1.1741	0.059*
C5	0.4869 (4)	0.9184 (3)	1.2819 (3)	0.0373 (7)
C6	0.3451 (4)	0.8779 (3)	1.2912 (3)	0.0427 (8)
H6A	0.3415	0.8355	1.3533	0.051*
C7	0.2092 (4)	0.9001 (3)	1.2089 (3)	0.0432 (8)
H7A	0.1152	0.8726	1.2176	0.052*
C8	0.6358 (4)	0.8986 (3)	1.3694 (3)	0.0349 (7)
C9	0.7772 (4)	0.8921 (3)	1.3440 (3)	0.0394 (8)
H9A	0.7809	0.9030	1.2716	0.047*
C10	0.9128 (4)	0.8692 (3)	1.4276 (3)	0.0459 (9)
H10A	1.0063	0.8634	1.4089	0.055*
C11	0.7813 (4)	0.8638 (4)	1.5570 (3)	0.0474 (9)
H11A	0.7821	0.8560	1.6307	0.057*
C12	0.6401 (4)	0.8835 (3)	1.4798 (3)	0.0423 (8)
H12A	0.5483	0.8867	1.5010	0.051*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.04338 (18)	0.04940 (19)	0.03717 (17)	0.00608 (12)	0.01719 (12)	−0.00403 (11)
Cu1	0.0309 (3)	0.0685 (4)	0.0239 (3)	0.0119 (3)	0.0044 (2)	−0.0064 (3)
N1	0.0332 (14)	0.0481 (17)	0.0309 (14)	0.0011 (12)	0.0091 (12)	−0.0005 (13)
N2	0.0454 (17)	0.0549 (19)	0.0482 (18)	−0.0031 (15)	0.0213 (15)	0.0052 (15)
N3	0.0309 (14)	0.0556 (18)	0.0306 (14)	0.0032 (13)	0.0064 (12)	−0.0008 (13)
N4	0.0367 (16)	0.063 (2)	0.0383 (16)	0.0033 (14)	0.0038 (13)	0.0012 (14)
C1	0.0333 (16)	0.0432 (19)	0.0343 (17)	0.0037 (14)	0.0094 (14)	0.0011 (14)
C2	0.0380 (17)	0.049 (2)	0.0346 (17)	−0.0039 (16)	0.0096 (15)	0.0002 (16)
C3	0.0386 (19)	0.073 (3)	0.0389 (19)	0.0012 (18)	0.0075 (15)	0.0181 (19)
C4	0.0309 (17)	0.067 (3)	0.046 (2)	−0.0084 (17)	0.0056 (15)	0.0126 (18)
C5	0.0349 (17)	0.0399 (18)	0.0344 (17)	−0.0007 (14)	0.0054 (14)	0.0018 (14)
C6	0.0362 (17)	0.056 (2)	0.0340 (17)	−0.0029 (16)	0.0070 (14)	0.0093 (16)
C7	0.0292 (16)	0.062 (2)	0.0390 (18)	−0.0035 (16)	0.0106 (14)	0.0030 (16)
C8	0.0321 (16)	0.0333 (17)	0.0358 (17)	−0.0029 (13)	0.0038 (14)	−0.0007 (13)
C9	0.0382 (17)	0.049 (2)	0.0296 (16)	−0.0027 (15)	0.0069 (14)	−0.0025 (14)
C10	0.0336 (18)	0.060 (2)	0.043 (2)	0.0023 (16)	0.0098 (15)	−0.0037 (17)
C11	0.0406 (19)	0.067 (2)	0.0318 (18)	0.0020 (17)	0.0055 (15)	0.0057 (17)
C12	0.0335 (17)	0.056 (2)	0.0363 (18)	0.0006 (15)	0.0078 (14)	0.0032 (16)

Geometric parameters (Å, º)

Ag1—C2^i	2.086 (4)	C3—H3A	0.9300
Ag1—C1	2.093 (3)	C4—C5	1.385 (5)
Ag1—N4^ii	2.472 (3)	C4—H4A	0.9300
Cu1—N1^iii	1.961 (3)	C5—C6	1.381 (5)
Cu1—N1	1.961 (3)	C5—C8	1.481 (4)
Cu1—N3^iii	2.056 (3)	C6—C7	1.376 (5)
Cu1—N3	2.056 (3)	C6—H6A	0.9300
Cu1—N2	2.563 (3)	C7—H7A	0.9300
N1—C1	1.138 (4)	C8—C9	1.386 (5)
N2—C2	1.128 (4)	C8—C12	1.391 (5)
N3—C7	1.333 (5)	C9—C10	1.384 (5)
N3—C3	1.336 (5)	C9—H9A	0.9300
N4—C10	1.325 (5)	C10—H10A	0.9300
N4—C11	1.332 (5)	C11—C12	1.372 (5)
N4—Ag1^iv	2.472 (3)	C11—H11A	0.9300
C2—Ag1^v	2.086 (4)	C12—H12A	0.9300
C3—C4	1.375 (5)
C2^i—Ag1—C1	157.40 (13)	C4—C3—H3A	118.7
C2^i—Ag1—N4^ii	103.67 (12)	C3—C4—C5	120.5 (3)
C1—Ag1—N4^ii	98.52 (12)	C3—C4—H4A	119.8
N1—Cu1—N1^iii	180	C5—C4—H4A	119.8
N1—Cu1—N3^iii	89.09 (11)	C6—C5—C4	116.3 (3)
N1^iii—Cu1—N3^iii	90.91 (11)	C6—C5—C8	122.2 (3)
N1—Cu1—N3	90.91 (11)	C4—C5—C8	121.5 (3)
N1^iii—Cu1—N3	89.09 (11)	C7—C6—C5	120.3 (3)
N3^iii—Cu1—N3	180	C7—C6—H6A	119.9
N1—Cu1—N2^iii	92.88 (11)	C5—C6—H6A	119.9
N1^iii—Cu1—N2^iii	87.12 (11)	N3—C7—C6	123.0 (3)
N3^iii—Cu1—N2^iii	89.78 (11)	N3—C7—H7A	118.5
N3—Cu1—N2^iii	90.22 (11)	C6—C7—H7A	118.5
N1—Cu1—N2	87.12 (11)	C9—C8—C12	117.1 (3)
N1^iii—Cu1—N2	92.88 (11)	C9—C8—C5	121.1 (3)
N3^iii—Cu1—N2	90.22 (11)	C12—C8—C5	121.8 (3)
N3—Cu1—N2	89.78 (11)	C10—C9—C8	119.3 (3)
N2^iii—Cu1—N2	180	C10—C9—H9A	120.4
C1—N1—Cu1	175.9 (3)	C8—C9—H9A	120.4
C7—N3—C3	117.3 (3)	N4—C10—C9	123.8 (3)
C7—N3—Cu1	122.2 (2)	N4—C10—H10A	118.1
C3—N3—Cu1	120.5 (2)	C9—C10—H10A	118.1
C10—N4—C11	116.6 (3)	N4—C11—C12	124.0 (3)
C10—N4—Ag1^iv	119.0 (2)	N4—C11—H11A	118.0
C11—N4—Ag1^iv	124.2 (2)	C12—C11—H11A	118.0
N1—C1—Ag1	176.9 (3)	C11—C12—C8	119.2 (3)
N2—C2—Ag1^v	172.6 (3)	C11—C12—H12A	120.4
N3—C3—C4	122.7 (3)	C8—C12—H12A	120.4
N3—C3—H3A	118.7

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