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The single-crystal structure of potassium manganese tris­[di­cyano­argentate(I)], KMnAg3(CN)6, is described. This is the first Mn-containing example of the triply interpenetrating MAg3(CN)6 type. The K+ ion is found to be located in an ordered manner on one of two possible interstitial sites, leading to a chiral space group.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103001264/bc1004sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103001264/bc1004Isup2.hkl
Contains datablock I

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S0108270103001264/bc1004sup3.pdf
Supplementary material

Comment top

The construction of three-dimensional and interpenetrating lattices is a contemporary challenge for crystal engineering (for a review of interpenetrating networks, see Batten & Robson, 1998). Transition metals can be conveniently linked through the use of pseudohalides, leading to the formation of such polymeric networks. The magnitude of magnetic superexchange in pseudohalide-based coordination polymers has remained an area of active research interest. While the cyanide and dicyanamide anions have been extensively studied in this regard, much less is known about related structures incorporating the dicyanoargentate anion, the high aspect ratio of which makes it ideal for the formation of interpenetrating structures. We are interested in the crystallization of magnetic anionic networks and chose to study the dicyanoargentate anion, a nearly linear analog to the bent dicyanamide ligand, as a building block for cyano-bridged heterobimetallic complexes.

Pauling & Pauling (1968) suggested that very large open cubic frameworks of the type M[Ag(CN)2]3 can be prepared through the incorporation of large neutral molecules into the center of the cubes. Alternatively, doubly or triply interpenetrating lattices can be formed to fill the voids. While attempting to crystallize the three-dimensional anionic network Mn[Ag(CN)2]3, in which a tetrapropyl ammonium cation would fill the cubic void, the salt KMnAg3(CN)6 formed instead.

The structure of KMnAg3(CN)6 consists of three interpenetrating trigonally distorted cubic lattices of composition MnAg3(CN)6 and intercalated K+ ions. The six-coordinate Mn atoms occupy the corners of the cubes, whereas the two-coordinate Ag atoms are found in the middle of the cube edges. The cyanide groups bridge between the Mn and Ag atoms. Alternatively, the structure can be thought of as being composed of close-packed double layers of cyanide ions, with one-third of the octahedral holes filled by Mn, and another third by K atoms. The C atoms of the cyanide groups protrude out of the double layer in a tilted direction (along the a+c diagonal), and Ag+ ions then bridge the double layers via C—Ag—C bonds.

We have carefully established (see Experimental) that the cyanide groups bind to Mn through the N atoms and to Ag through the C atoms. This assignment is also consistent with the observed bond lengths of 2.060 (2) Å for Ag—C and 2.236 (1) Å for Mn—N. These short Ag—C and relatively long Mn—N bond lengths are consistent with other cyanide-bridged Mn—Ag systems, e.g. catena-(tetrakis{µ2-cyano-bis[2-(4-pyridyl)-4,4,5,5- tetramethylimidazoline-1-oxyl-3-oxide]disilvermanganese(II)} Please check brackets − a closing) is missing (Dasna et al., 2001), where the corresponding values are 2.060–2.072 and 2.252–2.253 Å, respectively. The site symmetry on the Mn center is 32, with a small trigonal distortion from octahedral symmetry corresponding to a rotation of the `top' versus the `bottom' (with respect to the ab plane) N3 triangle of 1.5 (1)° and a 5.0 (2)% elongation along the c axis. The distortion at the K site is much more severe, i.e. a rotation of 20.9 (1)° and a 19.8 (2)% trigonal flattening. Except for the K atom, the deviations from P31m symmetry are slight, e.g. the Ag(CN)2 group is essentially linear (Table 1), and the trans-N—Mn—N angles are 178.8 (1)°.

A similar triply interpenetrating MAg3(CN)6 network has been found in a number of compounds, e.g. CoAg3(CN)6 (Pauling & Pauling, 1968; Ludi & Güdel, 1968), K2NaAg3(CN)6 (Zabel et al., 1989), and RbCdAg3(CN)6 (Hoskins et al., 1994), but the title compound is the first example containing the Mn2+ ion at the six-coordinate site. In the first two examples, the symmetry is P31m, because the two extra octahedral sites are either both empty or both filled. In contrast, RbCdAg3(CN)6 is isomorphous with the title compound, as is gold-containing KCoAu3(CN)6, with a demonstrated piezoelectric effect as proof for the noncentrosymmetric crystal symmetry (Abrahams et al., 1980). In KAg(CN)2 (Hoard, 1933) and KAu(CN)2 (Rosenzweig & Cromer, 1959), all octahedral holes are filled, but the sequence of double layers contains additional shifts, therefore leading to a doubling and tripling, respectively, of the c axis. Interestingly, CoAg3(CN)6 is the only salt in the series where the Co ion was assumed, without discussion by either group of authors (Pauling & Pauling, 1968; Ludi & Güdel, 1968), to be bonded to the C atom of the cyanide group. It would be interesting to examine whether this assumption holds in a rigorous refinement of diffraction data obtained by the use of modern instrumentation.

Experimental top

Tetrapropylammonium bromide (Aldrich, 532 mg, 2 mmol) was dissolved in absolute ethanol (10 ml). Potassium dicyanoargentate(I) (Aldrich, 1194 mg, 6 mmol) was dissolved in water (15 ml). These two solutions were combined and layered on top of an aqueous solution (10 ml) of manganese(II) nitrate hydrate (Aldrich, 358 mg, 2 mmol). Colorless hexagonal plates of KMnAg3(CN)6 formed within 1 d.

Refinement top

The crystal structure was initially solved by direct methods in space group P3. After inspection with the routine MISSYM (Le Page, 1987, 1988) in the program PLATON (Spek, 1990), we added a vertical mirror plane and concomitant twofold axis to arrive at space group P31m. Refinement in this space group (with half-occupied disordered K atoms) converged at R1 = 0.053, wR2 = 0.218, with peaks on the difference map of +2 (near Ag) and −3 e Å−3 (near C). Subsequently, the inversion center was removed and only one of the now inequivalent K positions retained, leading to the final refinement in space group P312. We also explored the effect of exchanging the C and N atoms in space group P312. This led to convergence at R1 = 0.028, wR2 = 0.088, peaks of +1 (near C) and −1 e Å−3 (near N), and highly dissimilar atomic displacement parameters for the C and N atoms, so the assignment listed in the tables here was accepted as correct. The chirality of the crystal resulted in a Flack parameter (Flack, 1983) of 0.18 (4), which was interpreted and included in the refinement as racemic twinning of the same volume fraction. The 234 Friedel pairs were not merged in the final refinement.

Computing details top

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. The unit-cell packing of KMnAg3(CN)6, with 50% probability displacement ellipsoids. The coordination spheres of one Mn and one K atom are completed outside the unit cell for clarity. The three interpenetrating networks are represented by the solid bonded strands (a,b,0) to (0,0,c), (a,b,0) to (0,0,0) to (0,b,c), and (a,0,0) to (a,b,c) to (0,b,0), respectively.
[Figure 2] Fig. 2. A space-filling packing diagram of the three interpenetrating networks of KMnAg3(CN)6 (shown in three different shading styles), viewed approximately along the trigonal axis. A more artistic rendering of this view may be found in the supplementary material.
Potassium manganese(II) dicyanoargentate(I) top
Crystal data top
C6Ag3KMnN6Dx = 2.819 Mg m3
Mr = 573.77Mo Kα radiation, λ = 0.71073 Å
Trigonal, P312Cell parameters from 772 reflections
Hall symbol: P 3 2"θ = 3.4–28.2°
a = 6.9219 (10) ŵ = 5.48 mm1
c = 8.1465 (16) ÅT = 293 K
V = 338.03 (10) Å3Hexagonal plate, colorless
Z = 10.46 × 0.32 × 0.03 mm
F(000) = 263
Data collection top
Siemens SMART CCD area-detector
diffractometer
558 independent reflections
Radiation source: fine-focus sealed tube551 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.025
area–detector ω scansθmax = 28.2°, θmin = 2.5°
Absorption correction: integration
(XPREP in SHELXTL; Sheldrick, 2001)
h = 89
Tmin = 0.155, Tmax = 0.829k = 89
3417 measured reflectionsl = 1010
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.0183P)2 + 0.008P]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.012(Δ/σ)max < 0.001
wR(F2) = 0.032Δρmax = 0.25 e Å3
S = 1.11Δρmin = 0.35 e Å3
558 reflectionsExtinction correction: SHELXTL (Sheldrick, 2001), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
30 parametersExtinction coefficient: 0.058 (2)
0 restraintsAbsolute structure: Flack (1983)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.18 (4)
Crystal data top
C6Ag3KMnN6Z = 1
Mr = 573.77Mo Kα radiation
Trigonal, P312µ = 5.48 mm1
a = 6.9219 (10) ÅT = 293 K
c = 8.1465 (16) Å0.46 × 0.32 × 0.03 mm
V = 338.03 (10) Å3
Data collection top
Siemens SMART CCD area-detector
diffractometer
558 independent reflections
Absorption correction: integration
(XPREP in SHELXTL; Sheldrick, 2001)
551 reflections with I > 2σ(I)
Tmin = 0.155, Tmax = 0.829Rint = 0.025
3417 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0120 restraints
wR(F2) = 0.032Δρmax = 0.25 e Å3
S = 1.11Δρmin = 0.35 e Å3
558 reflectionsAbsolute structure: Flack (1983)
30 parametersAbsolute structure parameter: 0.18 (4)
Special details top

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 (Å2) top
xyzUiso*/Ueq
Ag0.49498 (2)0.01004 (4)0.50000.05041 (11)
Mn0.00000.00000.00000.02307 (12)
K0.66670.33330.00000.0394 (2)
C0.3426 (3)0.0042 (4)0.2843 (2)0.0391 (3)
N0.2590 (3)0.0040 (3)0.16637 (16)0.0376 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ag0.05723 (13)0.05722 (15)0.03678 (13)0.02861 (8)0.02267 (6)0.000
Mn0.02715 (16)0.02715 (16)0.0149 (2)0.01357 (8)0.0000.000
K0.0383 (3)0.0383 (3)0.0418 (5)0.01913 (15)0.0000.000
C0.0378 (10)0.0437 (8)0.0346 (7)0.0195 (9)0.0068 (7)0.0036 (9)
N0.0364 (7)0.0450 (7)0.0308 (6)0.0199 (7)0.0060 (6)0.0052 (8)
Geometric parameters (Å, º) top
Ag—C2.0599 (16)K—N2.9266 (18)
Mn—N2.2365 (13)C—N1.138 (2)
Ag···Agi3.3568 (7)K···C3.258 (2)
Mn···K3.9964 (6)
Cii—Ag—C178.05 (15)N—K—Nviii66.75 (5)
Niii—Mn—N93.76 (9)N—K—Nix100.27 (4)
Niii—Mn—Niv178.78 (10)N—C—Ag178.3 (2)
N—Mn—Niv87.08 (5)C—N—Mn159.36 (14)
Niv—Mn—Nv92.08 (9)C—N—K96.52 (14)
Nvi—K—N95.15 (7)Mn—N—K100.58 (5)
Nvii—K—N161.53 (6)
Symmetry codes: (i) y, xy1, z; (ii) x+y+1, y, z+1; (iii) y, x, z; (iv) y, xy, z; (v) x+y, y, z; (vi) x+y+1, y, z; (vii) y+1, x+1, z; (viii) x, xy, z; (ix) x+y+1, x+1, z.

Experimental details

Crystal data
Chemical formulaC6Ag3KMnN6
Mr573.77
Crystal system, space groupTrigonal, P312
Temperature (K)293
a, c (Å)6.9219 (10), 8.1465 (16)
V3)338.03 (10)
Z1
Radiation typeMo Kα
µ (mm1)5.48
Crystal size (mm)0.46 × 0.32 × 0.03
Data collection
DiffractometerSiemens SMART CCD area-detector
diffractometer
Absorption correctionIntegration
(XPREP in SHELXTL; Sheldrick, 2001)
Tmin, Tmax0.155, 0.829
No. of measured, independent and
observed [I > 2σ(I)] reflections
3417, 558, 551
Rint0.025
(sin θ/λ)max1)0.665
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.012, 0.032, 1.11
No. of reflections558
No. of parameters30
Δρmax, Δρmin (e Å3)0.25, 0.35
Absolute structureFlack (1983)
Absolute structure parameter0.18 (4)

Computer programs: SMART (Siemens, 1995), SAINT (Bruker, 2001), SAINT, SHELXTL (Sheldrick, 2001), SHELXTL.

Selected geometric parameters (Å, º) top
Ag—C2.0599 (16)K—N2.9266 (18)
Mn—N2.2365 (13)C—N1.138 (2)
Ci—Ag—C178.05 (15)N—K—Nvii66.75 (5)
Nii—Mn—N93.76 (9)N—K—Nviii100.27 (4)
Nii—Mn—Niii178.78 (10)N—C—Ag178.3 (2)
N—Mn—Niii87.08 (5)C—N—Mn159.36 (14)
Niii—Mn—Niv92.08 (9)C—N—K96.52 (14)
Nv—K—N95.15 (7)Mn—N—K100.58 (5)
Nvi—K—N161.53 (6)
Symmetry codes: (i) x+y+1, y, z+1; (ii) y, x, z; (iii) y, xy, z; (iv) x+y, y, z; (v) x+y+1, y, z; (vi) y+1, x+1, z; (vii) x, xy, z; (viii) x+y+1, x+1, z.
 

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