Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100004996/sk1357sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270100004996/sk1357Isup2.hkl |
CCDC reference: 147621
Single crystals of the title compound in the form of violet prisms suitable for X-ray studies were crystallized from a solution formed by the following procedure. Ni(NO3)2 solution (10 ml of 0.1 M) (1 mmol), 500 ml of water and 10 ml of 0.1M K2Ni(CN)4 solution (1 mmol) were mixed and yielded a nickel cyanide precipitate, which was immediately dissolved by addition of a concentrated solution of ammonia (25%). To the resultant solution, 0.3124 g of bipy (2 mmol) in 20 ml of methanol was added. Finally, the solution was filtered and left for crystallization in an Erlenmayer flask at room temperature (291 K). At first big needles of Ni(bipy)3][Ni(CN)4]. 6H2O.1/2bipy (Černák et al., 1996; Akyüz et al., 1996) appeared, and they dissolved after a short time. Small single crystals of the title compound suitable for X-ray work formed after one month.
The IR spectrum was measured on a Specord M40 spectrometer. ν(CH): 3112 (vw), 3080 (bvw); ν(CN): 2148 (versus), 2120 (versus); ρ(NH): 1600 (versus); \v(C═C): 1576 (m), 1568 (m); δ(Ni—CN): 428 (s), 418 (s).
The H atoms were placed in idealized positions and were refined riding on their parent atoms. A C—H distance of 0.95 Å was used for all Csp2 atoms. The H-atom displacement parameters were set at 1.2Ueq of the parent C atom. Full data collection details are reported elsewhere (Abboud et al., 1997). Four data sets using four different crystals were collected for this structure and each solution revealed the presence of disorder in the position of the two bipyridine ligands. The data reported here has the least disorder (less than 5%) and it was not possible to resolve.
Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruke, 1998); data reduction: SAINT and SHELXTL (Bruker, 1998); program(s) used to solve structure: SHELXTL (Bruker, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
[Ni2(CN)4(C10H8N2)2] | Dx = 1.572 Mg m−3 |
Mr = 533.87 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbcn | Cell parameters from 3962 reflections |
a = 14.067 (1) Å | θ = 2.5–27.5° |
b = 10.1759 (7) Å | µ = 1.70 mm−1 |
c = 15.755 (1) Å | T = 173 K |
V = 2255.2 (3) Å3 | Platelets, light violet |
Z = 4 | 0.19 × 0.19 × 0.06 mm |
F(000) = 1088 |
SMART platform/CCD diffractometer | 2591 independent reflections |
Radiation source: normal-focus sealed tube | 1498 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.056 |
ω scans | θmax = 27.5°, θmin = 2.5° |
Absorption correction: face-indexed (gaussian) ? | h = −17→18 |
Tmin = 0.684, Tmax = 0.911 | k = −13→6 |
13421 measured reflections | l = −20→20 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.046 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.142 | Riding |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0754P)2 + 1.2512P] where P = (Fo2 + 2Fc2)/3 |
2591 reflections | (Δ/σ)max < 0.001 |
156 parameters | Δρmax = 1.19 e Å−3 |
0 restraints | Δρmin = −0.39 e Å−3 |
[Ni2(CN)4(C10H8N2)2] | V = 2255.2 (3) Å3 |
Mr = 533.87 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 14.067 (1) Å | µ = 1.70 mm−1 |
b = 10.1759 (7) Å | T = 173 K |
c = 15.755 (1) Å | 0.19 × 0.19 × 0.06 mm |
SMART platform/CCD diffractometer | 2591 independent reflections |
Absorption correction: face-indexed (gaussian) ? | 1498 reflections with I > 2σ(I) |
Tmin = 0.684, Tmax = 0.911 | Rint = 0.056 |
13421 measured reflections |
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.142 | Riding |
S = 1.01 | Δρmax = 1.19 e Å−3 |
2591 reflections | Δρmin = −0.39 e Å−3 |
156 parameters |
Experimental. A hemisphere of frames, 0.3° in ω, was collected. The first 50 frames were remeasured at the end of data collection to monitor instrument and crystal stability. Full data collection details are reported elsewhere (Abboud et al., 1997). |
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. |
x | y | z | Uiso*/Ueq | ||
Ni1 | 0.0000 | 1.0000 | 0.0000 | 0.0358 (2) | |
C1 | −0.1310 (4) | 0.9967 (4) | 0.0161 (3) | 0.0487 (12) | |
N1 | −0.2120 (3) | 0.9886 (4) | 0.0280 (3) | 0.0705 (13) | |
C2 | 0.0104 (3) | 0.8965 (3) | 0.0977 (2) | 0.0374 (9) | |
N2 | 0.0122 (2) | 0.8285 (3) | 0.1555 (2) | 0.0379 (8) | |
Ni2 | 0.0000 | 0.68814 (6) | 0.2500 | 0.02755 (19) | |
N3 | 0.1456 (2) | 0.6696 (3) | 0.25754 (19) | 0.0373 (7) | |
N4 | 0.0246 (3) | 0.5378 (3) | 0.1602 (2) | 0.0392 (9) | |
C3 | 0.2020 (3) | 0.7405 (5) | 0.3074 (3) | 0.0560 (12) | |
H3A | 0.1748 | 0.8070 | 0.3420 | 0.067* | |
C4 | 0.3003 (4) | 0.7203 (7) | 0.3104 (4) | 0.0808 (18) | |
H4A | 0.3399 | 0.7714 | 0.3464 | 0.097* | |
C5 | 0.3382 (4) | 0.6218 (7) | 0.2584 (4) | 0.0789 (18) | |
H5A | 0.4046 | 0.6051 | 0.2591 | 0.095* | |
C6 | 0.2808 (4) | 0.5501 (6) | 0.2071 (4) | 0.0706 (15) | |
H6A | 0.3067 | 0.4844 | 0.1710 | 0.085* | |
C7 | 0.1838 (3) | 0.5742 (4) | 0.2079 (3) | 0.0475 (11) | |
C8 | 0.1153 (3) | 0.4985 (4) | 0.1559 (3) | 0.0477 (11) | |
C9 | 0.1415 (4) | 0.3923 (5) | 0.1049 (3) | 0.0660 (15) | |
H9A | 0.2056 | 0.3634 | 0.1021 | 0.079* | |
C10 | 0.0703 (5) | 0.3299 (5) | 0.0581 (3) | 0.0773 (19) | |
H10A | 0.0863 | 0.2574 | 0.0228 | 0.093* | |
C11 | −0.0191 (4) | 0.3704 (5) | 0.0620 (3) | 0.0686 (17) | |
H11A | −0.0672 | 0.3280 | 0.0297 | 0.082* | |
C12 | −0.0412 (4) | 0.4761 (5) | 0.1144 (3) | 0.0548 (13) | |
H12A | −0.1053 | 0.5052 | 0.1175 | 0.066* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Ni1 | 0.0625 (5) | 0.0245 (3) | 0.0203 (3) | −0.0033 (4) | −0.0065 (3) | 0.0036 (2) |
C1 | 0.070 (3) | 0.037 (2) | 0.038 (3) | 0.002 (2) | −0.009 (2) | 0.010 (2) |
N1 | 0.066 (3) | 0.084 (3) | 0.061 (3) | 0.010 (2) | −0.005 (2) | 0.019 (2) |
C2 | 0.062 (3) | 0.0259 (17) | 0.0243 (17) | −0.0039 (19) | −0.0022 (19) | −0.0006 (14) |
N2 | 0.060 (2) | 0.0297 (15) | 0.0235 (15) | −0.0055 (15) | −0.0073 (15) | 0.0013 (12) |
Ni2 | 0.0443 (4) | 0.0217 (3) | 0.0167 (3) | 0.000 | 0.0015 (3) | 0.000 |
N3 | 0.0479 (19) | 0.0328 (16) | 0.0313 (17) | −0.0019 (13) | −0.0005 (16) | 0.0049 (15) |
N4 | 0.067 (3) | 0.0285 (16) | 0.0223 (15) | −0.0076 (15) | 0.0136 (15) | −0.0003 (14) |
C3 | 0.057 (3) | 0.056 (3) | 0.055 (3) | −0.006 (2) | −0.011 (2) | 0.008 (2) |
C4 | 0.061 (4) | 0.097 (5) | 0.085 (4) | −0.020 (3) | −0.022 (3) | 0.025 (4) |
C5 | 0.047 (3) | 0.107 (5) | 0.082 (4) | 0.004 (3) | 0.008 (3) | 0.024 (4) |
C6 | 0.057 (3) | 0.075 (4) | 0.079 (4) | 0.007 (3) | 0.024 (3) | 0.013 (3) |
C7 | 0.052 (3) | 0.041 (2) | 0.049 (3) | 0.006 (2) | 0.019 (2) | 0.008 (2) |
C8 | 0.070 (3) | 0.034 (2) | 0.039 (2) | 0.000 (2) | 0.021 (2) | 0.0013 (18) |
C9 | 0.086 (4) | 0.057 (3) | 0.055 (3) | 0.004 (3) | 0.037 (3) | −0.001 (3) |
C10 | 0.133 (6) | 0.047 (3) | 0.052 (3) | −0.030 (3) | 0.031 (4) | −0.022 (3) |
C11 | 0.120 (6) | 0.050 (3) | 0.036 (2) | −0.021 (3) | 0.024 (3) | −0.019 (2) |
C12 | 0.089 (4) | 0.044 (3) | 0.031 (2) | −0.020 (2) | 0.012 (2) | −0.006 (2) |
Ni1—C1i | 1.860 (6) | C3—H3A | 0.9500 |
Ni1—C1 | 1.860 (6) | C4—C5 | 1.400 (9) |
Ni1—C2 | 1.871 (4) | C4—H4A | 0.9500 |
Ni1—C2i | 1.871 (4) | C5—C6 | 1.355 (8) |
C1—N1 | 1.159 (7) | C5—H5A | 0.9500 |
C2—N2 | 1.144 (5) | C6—C7 | 1.386 (7) |
Ni2—N2 | 2.070 (3) | C6—H6A | 0.9500 |
Ni2—N3 | 2.060 (4) | C7—C8 | 1.481 (6) |
Ni2—N3ii | 2.060 (4) | C8—C9 | 1.395 (6) |
Ni2—N2ii | 2.070 (3) | C9—C10 | 1.396 (8) |
Ni2—N4 | 2.112 (3) | C9—H9A | 0.9500 |
Ni2—N4ii | 2.112 (3) | C10—C11 | 1.326 (8) |
N3—C3 | 1.330 (5) | C10—H10A | 0.9500 |
N3—C7 | 1.358 (5) | C11—C12 | 1.390 (6) |
N4—C12 | 1.332 (6) | C11—H11A | 0.9500 |
N4—C8 | 1.340 (5) | C12—H12A | 0.9500 |
C3—C4 | 1.399 (7) | ||
C1i—Ni1—C1 | 180.0 | N3—C3—C4 | 122.0 (5) |
C1i—Ni1—C2 | 92.6 (2) | N3—C3—H3A | 119.0 |
C1—Ni1—C2 | 87.4 (2) | C4—C3—H3A | 119.0 |
C1i—Ni1—C2i | 87.4 (2) | C3—C4—C5 | 117.5 (6) |
C1—Ni1—C2i | 92.6 (2) | C3—C4—H4A | 121.3 |
C2—Ni1—C2i | 180.0 (2) | C5—C4—H4A | 121.3 |
N1—C1—Ni1 | 176.6 (4) | C6—C5—C4 | 120.5 (5) |
N2—C2—Ni1 | 175.7 (4) | C6—C5—H5A | 119.7 |
C2—N2—Ni2 | 171.1 (3) | C4—C5—H5A | 119.7 |
N3—Ni2—N3ii | 169.5 (2) | C5—C6—C7 | 119.1 (5) |
N3—Ni2—N2ii | 96.0 (1) | C5—C6—H6A | 120.5 |
N3ii—Ni2—N2ii | 91.3 (1) | C7—C6—H6A | 120.5 |
N3—Ni2—N2 | 91.3 (1) | N3—C7—C6 | 121.5 (5) |
N3ii—Ni2—N2 | 96.0 (1) | N3—C7—C8 | 115.6 (4) |
N2ii—Ni2—N2 | 92.7 (2) | C6—C7—C8 | 122.9 (5) |
N3—Ni2—N4 | 79.0 (1) | N4—C8—C9 | 120.8 (5) |
N3ii—Ni2—N4 | 93.3 (1) | N4—C8—C7 | 115.8 (4) |
N2ii—Ni2—N4 | 174.2 (1) | C9—C8—C7 | 123.4 (5) |
N2—Ni2—N4 | 90.3 (1) | C8—C9—C10 | 117.9 (5) |
N3—Ni2—N4ii | 93.3 (1) | C8—C9—H9A | 121.1 |
N3ii—Ni2—N4ii | 79.0 (1) | C10—C9—H9A | 121.1 |
N2ii—Ni2—N4ii | 90.3 (1) | C11—C10—C9 | 120.9 (5) |
N2—Ni2—N4ii | 174.2 (1) | C11—C10—H10A | 119.5 |
N4—Ni2—N4ii | 87.2 (2) | C9—C10—H10A | 119.5 |
C3—N3—C7 | 119.4 (4) | C10—C11—C12 | 118.7 (5) |
C3—N3—Ni2 | 125.3 (3) | C10—C11—H11A | 120.6 |
C7—N3—Ni2 | 115.2 (3) | C12—C11—H11A | 120.6 |
C12—N4—C8 | 119.6 (4) | N4—C12—C11 | 122.1 (5) |
C12—N4—Ni2 | 126.2 (3) | N4—C12—H12A | 119.0 |
C8—N4—Ni2 | 114.0 (3) | C11—C12—H12A | 119.0 |
C1i—Ni1—C1—N1 | 124 (8) | N2ii—Ni2—N4—C8 | −25.7 (14) |
C2—Ni1—C1—N1 | −29 (8) | N2—Ni2—N4—C8 | 95.6 (3) |
C2i—Ni1—C1—N1 | 151 (8) | N4ii—Ni2—N4—C8 | −89.6 (3) |
C1i—Ni1—C2—N2 | −135 (5) | C7—N3—C3—C4 | 0.1 (7) |
C1—Ni1—C2—N2 | 45 (5) | Ni2—N3—C3—C4 | 178.6 (4) |
C2i—Ni1—C2—N2 | −152 (100) | N3—C3—C4—C5 | 0.2 (8) |
Ni1—C2—N2—Ni2 | 7 (7) | C3—C4—C5—C6 | 0.3 (9) |
C2—N2—Ni2—N3 | 130 (2) | C4—C5—C6—C7 | −1.1 (9) |
C2—N2—Ni2—N3ii | −42 (2) | C3—N3—C7—C6 | −0.9 (6) |
C2—N2—Ni2—N2ii | −133 (2) | Ni2—N3—C7—C6 | −179.6 (4) |
C2—N2—Ni2—N4 | 51 (2) | C3—N3—C7—C8 | 178.8 (4) |
C2—N2—Ni2—N4ii | −12 (3) | Ni2—N3—C7—C8 | 0.2 (5) |
N3ii—Ni2—N3—C3 | −137.2 (3) | C5—C6—C7—N3 | 1.5 (8) |
N2ii—Ni2—N3—C3 | −3.7 (3) | C5—C6—C7—C8 | −178.3 (5) |
N2—Ni2—N3—C3 | 89.1 (3) | C12—N4—C8—C9 | −1.0 (6) |
N4—Ni2—N3—C3 | 179.2 (4) | Ni2—N4—C8—C9 | 174.5 (3) |
N4ii—Ni2—N3—C3 | −94.4 (3) | C12—N4—C8—C7 | 179.0 (4) |
N3ii—Ni2—N3—C7 | 41.4 (3) | Ni2—N4—C8—C7 | −5.5 (4) |
N2ii—Ni2—N3—C7 | 174.8 (3) | N3—C7—C8—N4 | 3.6 (6) |
N2—Ni2—N3—C7 | −92.3 (3) | C6—C7—C8—N4 | −176.6 (4) |
N4—Ni2—N3—C7 | −2.3 (3) | N3—C7—C8—C9 | −176.3 (4) |
N4ii—Ni2—N3—C7 | 84.2 (3) | C6—C7—C8—C9 | 3.4 (7) |
N3—Ni2—N4—C12 | 179.4 (3) | N4—C8—C9—C10 | 0.8 (7) |
N3ii—Ni2—N4—C12 | 6.7 (3) | C7—C8—C9—C10 | −179.3 (4) |
N2ii—Ni2—N4—C12 | 149.4 (12) | C8—C9—C10—C11 | 0.0 (8) |
N2—Ni2—N4—C12 | −89.3 (3) | C9—C10—C11—C12 | −0.5 (8) |
N4ii—Ni2—N4—C12 | 85.5 (3) | C8—N4—C12—C11 | 0.5 (6) |
N3—Ni2—N4—C8 | 4.3 (3) | Ni2—N4—C12—C11 | −174.4 (3) |
N3ii—Ni2—N4—C8 | −168.4 (3) | C10—C11—C12—N4 | 0.2 (7) |
Symmetry codes: (i) −x, −y+2, −z; (ii) −x, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | [Ni2(CN)4(C10H8N2)2] |
Mr | 533.87 |
Crystal system, space group | Orthorhombic, Pbcn |
Temperature (K) | 173 |
a, b, c (Å) | 14.067 (1), 10.1759 (7), 15.755 (1) |
V (Å3) | 2255.2 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.70 |
Crystal size (mm) | 0.19 × 0.19 × 0.06 |
Data collection | |
Diffractometer | SMART platform/CCD diffractometer |
Absorption correction | Face-indexed (Gaussian) |
Tmin, Tmax | 0.684, 0.911 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13421, 2591, 1498 |
Rint | 0.056 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.142, 1.01 |
No. of reflections | 2591 |
No. of parameters | 156 |
H-atom treatment | Riding |
Δρmax, Δρmin (e Å−3) | 1.19, −0.39 |
Computer programs: SMART (Bruker, 1998), SMART (Bruke, 1998), SAINT and SHELXTL (Bruker, 1998), SHELXTL (Bruker, 1998), SHELXTL.
Ni1—C1 | 1.860 (6) | Ni2—N3 | 2.060 (4) |
Ni1—C2 | 1.871 (4) | Ni2—N4 | 2.112 (3) |
Ni2—N2 | 2.070 (3) | ||
C1i—Ni1—C1 | 180.0 | N3ii—Ni2—N2ii | 91.3 (1) |
C1i—Ni1—C2 | 92.6 (2) | N2ii—Ni2—N2 | 92.7 (2) |
C1—Ni1—C2 | 87.4 (2) | N3—Ni2—N4 | 79.0 (1) |
C2—Ni1—C2i | 180.0 (2) | N3ii—Ni2—N4 | 93.3 (1) |
N3—Ni2—N3ii | 169.5 (2) | N2ii—Ni2—N4 | 174.2 (1) |
N3—Ni2—N2ii | 96.0 (1) | N2—Ni2—N4 | 90.3 (1) |
Symmetry codes: (i) −x, −y+2, −z; (ii) −x, y, −z+1/2. |
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One-dimensional (one-dimensional) magnetic materials are of current interest due to their interesting magnetic properties [Dagotto, 1996; Chen & Suslick, 1993; Orendáč et al., 1995; Delhaes & Drillon, 1987). The synthetic strategy of such materials can be based on the use of the so-called `brick and mortar' method (Willett et al., 1993), where paramagnetic entities (bricks) are linked by suitable bridging units (mortar). Square-planar tetracyano complexes are suitable bridging units due to the possibility of using cyano groups to link metal atoms. Stereochemical considerations and literature data (Iwamoto, 1996) indicate that various types of one-dimensional structures may be formed. As examples of different types of one-dimensional structures, we can mention Ni(en)2Ni(CN)4 exhibiting a TT-type chain structure [two bridging cyano groups occupy trans (T) positions in both the cation and anion; Černák, Chomič et al., 1988], diamagnetic Cd(en)2Ni(CN)4 (two polymorphs) forming CC-type chains (Yuge et al., 1995), Ni(en)2Ni(CN)4.nH2O with more complicated CCTC-type chains (periodicity doubled; Černák et al., 1990) and [Eu(dmf)4Ni(CN)4] exhibiting a ladder-like one-dimensional structure with three bridging cyano groups (Knoeppel & Shore, 1997). To date, no crystal structures with CT– or TC-type chains containing square-planar tetracyano complexes as bridging units have been reported.
The results of crystal structure analyses of the one-dimensional compounds [Ni(bipy)2N3]ClO4 and [Ni(bipy)2N3]PF6 (Urtiaga et al., 1994) have shown that the presence of two bulky 2,2'-bipyridine (bipy) ligands in the nickel octahedral coordination sphere leads to zigzag-type chains. CT-type chains were found in [Cu(bipy)2Ag2(CN)4]·H2O, a compound with linear dicyanoargentate anions (Černák et al., 1993). These results indicate that the Ni(bipy)2Ni(CN)4 compound, (I), initially described a long time ago (Feigl et al., 1945), may be a good candidate for a CT (or CC) type chain. The results of its crystal structure analysis are reported here and are discussed with respect to similar one-dimensional structures containing square-planar tetracyano complex anions.
The centrosymmetric structure of the title compound consists of zigzag-type chains. The chains are composed of paramagnetic [Ni(bipy)2]2+ cations (bricks), which are linked by diamagnetic [Ni(CN)4]2− anions (mortar). The bridging cyano groups occupy cis positions in the cation, thereby completing the chromophore to NiN4N2. On the other hand, they occupy trans positions in the anion giving rise to a CT-type chain not yet found among square tetracyano complexes. Only van der Waals forces operate between the chains, so the packing of the chains is directed mainly by geometric requirements. The shortest distance between two atoms of neighbouring chains is 2.42 (1) Å [H11A···H4A(x − 0.5, y − 0.5, 0.5 − z)], which is in line with the sum of the van der Waals radii of H atoms (2.40 Å; Taylor & Kennard, 1982). The shortest distance between two paramagnetic Ni atoms is 8.681 (1) Å [e.g. Ni2···Ni2(x − 0.5, y − 0.5, 0.5 − z)], but there is no effective bridging between these atoms. Two paramagnetic Ni atoms (Ni2) within the chain are separated by 10.116 (2) Å and the –N—C—Ni—C—N– five-atom bridge may serve as an exchange path for the observed superexchange-type interaction (Orendáč et al., 2000). The bridge is quite linear, where the highest deviation from linearity is represented by the Ni2—-N2—C2—(Ni1) angle [171.1 (3)°]. Similar, but positively charged chains, were found in the [Cu(bipy)2Ag2(CN)4]·H2O compound with linear dicyanoargentate anions, where the positive charge of the chains is counterbalanced by the negative charge of free dicyanoargentate anions (Černák et al., 1993). The same type of five-atom bridges were found in many other tetracyanonickellates or dicyanoargentates (Iwamoto, 1996).
The Ni atom in the anion (Ni1) lies on a symmetry center, so the NiC4 chromophore is exactly planar. The geometrical parameters (bond distances and angles) have typical values and are similar to those found in other tetracyanonickellates (Černák, Dunaj-Jurčo et al., 1988).
The central Ni atom in the cation exhibits a hexacoordination in the cis-NiN4N2 form and lies on a twofold symmetry. If we assign the coordination sites letters A to F, with A and D being axial sites, the bridging cyano groups occupy neighboring positions E and F. Geometrical considerations indicate two possible arrangements of the chelate bipy ligands: they can be bound in positions A–B and C–D, or in positions A–C and B–D, respectively. Both orientations in the form of disorder were found to a different extent in various crystals.
The shape of the nickel coordination sphere is significant in connection with the zero-field splitting of the 3A2 ground state as an important parameter in the interpretation of the magnetic properties. In the present compound, the nickel coordination sphere exhibits rather unusual deformation from the ideal octahedral one; four Ni—N coordination bonds [two Ni—N(C) and two among four Ni—N(bipy)] exhibit the same value within experimental error (3σ) with a mean value of 2.065 (6) Å, the remaining two Ni—N(bipy) bonds (Ni2—N4) in the trans positions with respect to the bridging cyano groups are somewhat longer with a distance of 2.112 (3) Å. Similar elongation of the trans positioned Ni—N(bipy) bonds (2.114 and 2.091 Å) versus cis-positioned Ni—N(bipy) bonds (2.083 and 2.066 Å) was observed in the [Ni(bipy)2(N3)2]·H2O compound (Urtiaga et al., 1995). On the other hand, in the Ni(en)2Ni(CN)4.nH2O compound with en as chelating ligands the Ni—N(en) bonds are almost the same within s.u. [2.11 (1) and 2.12 (1) Å] regardless to their positions to the bridging cyano groups (Černák et al., 1990). The normalized bite value (b = 1.272; Kepert, 1982), and the bond distances and angles in the bipy ligands have standard values (Wada et al., 1976).