catena-Poly[[bis­(acetonitrile-κN)manganese(II)]-bis­(μ-trifluoro­methane­sulfonato-κ²O:O′)]

The title compound, [Mn(CF₃SO₃)₂(CH₃CN)₂]_n, has an Mn^II cation on an inversion centre in an octa­hedral environment. The trifluoro­methane­sulfonate anions act as bridging ligands and form a one-dimensional coordination polymer in the direction of the a axis. The F atoms of the trifluoro­methane­sulfonate anions form layers parallel to the ab plane, but despite short inter­molecular distances, no stabilizing F...F inter­actions are detected. The Mn—N and C—C bonds of the acetonitrile ligand are analyzed according to the Hirshfeld rigid-bond test. Renninger effects in the reflection data are considered, explored and discussed.

S1. Comment

The title compound, (I), was prepared as a starting material for complexation reactions with biomimetic ligands. In the literature the stoichiometry of the compound is given as [Mn(SO₃CF₃)_2].CH₃CN (Bryan & Dabrowiak, 1975), but also contains indications for a variable composition. The present crystal structure determination proves the presence of two coordinated acetonitrile molecules and thus the composition [Mn(SO₃CF₃)₂.2CH₃CN]_n, with the manganese in oxidation state +2 (Fig. 1).

The Mn^II ion in (I) is located on an inversion centre and surrounded by six donor atoms in a slightly distorted octahedral geometry. The equatorial plane is formed by four O atoms of the trifluoromethanesulfonate anions, with Mn—O distances in the expected range for Mn^II. The axial positions are occupied by acetonitrile ligands, with similar Mn—N distances as observed in the [Mn(CH₃CN)₆]²⁺ ion (Weller et al., 1996). Due to the inversion symmetry, the equatorial plane is exactly planar and the axial donor atoms are exactly trans. Consequently, the angular variance (Robinson et al., 1971) is very small (0.75°²). The slight octahedral distortion can be seen in the small difference between Mn—O and Mn—N distances.

The trifluoromethanesulfonate anions, which are located on general positions, act a bridging ligands between the Mn^II cations. Bridging trifluoromethanesulfonate anions occur mainly in copper and silver complexes. In fact, there is only one Mn complex known with a bridging trifluoromethanesulfonate anion (Berben & Peters, 2008), but there the bridging is supported by an additional bridging isopropoxide linker, resulting in a discrete binuclear complex. In (I), the Mn^II cations are connected only by trifluoromethanesulfonate anions. In this way a one-dimensional chain is formed in the direction of the crystallographic a axis. The distance between the Mn^II ions in the chain therefore corresponds to the length of the a axis [5.13763 (8) Å]. The S—O distances of the coordinated O atoms are about 0.03 Å longer than that of the non-coordinated O atom. The CF₃ group adopts a staggered conformation with respect to the SO₃ group.

While in most transition metal complexes of acetonitile the coordination is approximately linear, (I) deviates significantly from linearity by 26.73 (9)° at the N atom. Previous cases of such a bent coordination mode have been ascribed to crystal packing effects or steric hindrance with neighbouring groups (Murthy et al., 2001). Indeed, the crystal structure of (I) has a packing index of 69.0% (Kitajgorodskij, 1973), indicating an efficient arrangement of the molecules (Dunitz, 1995). The C2···O3(2 - x, -y, 1 - z) distance is 3.1612 (15) Å, which is approximately the sum of the van der Waals radii (3.22 Å; Reference?), and this prevents linearization of the acetonitrile coordination (Fig. 2). Other close contacts of C2···O3(x - 1, y, z) = 3.3374 (15) Å and C2···F1(1 - x, 1 - y, 1 - z) = 3.2299 (15) Å.

The Mn—N and C—C bonds of the acetonitrile fail the rigid-bond test (Hirshfeld, 1976), with Δm.s.d.a/σ of 8.11 and 5.24, respectively (m.s.d. is mean square displacement ?). The reason is obviously the non-spherical electron distribution of the triple bond, which cannot be adequately modelled with spherical scattering factors. A similar situation is well known from metal carbonyl complexes (Braga & Koetzle, 1988). It should be noted that the absolute magnitudes for the Δm.s.d.a values of the Mn—N and C—C bonds in (I) of 0.0041 (5) and 0.0042 (8) Ų, respectively, are still small and well below 0.01 Ų. A comparison with acetonitrile structures from the literature shows that the Δm.s.d.a values of (I) are within the expected range (Table 2).

Besides the coordination chains in the a direction, the crystal structure of (I) contains layers of F atoms in the ab plane (Fig. 3). The shortest F···F distance is F1···F1ⁱⁱⁱ = 2.7796 (15) Å [symmetry code: (iii) 1 - x, 1 - y, 2 - z], which is shorter than the sum of the van der Waals radii (2.94 Å). According to Ramasubbu et al. (1986) and Reichenbächer et al. (2005), F···F interactions with two equal C—F···F angles are caused by close packing (Type I), and stabilizing F···F interactions are characterized by C—F···F angles of 180° on one side and 90° on the other (Type II). The above-mentioned short F···F interaction in (I) is located on an inversion centre and consequently has two equal angles [137.69 (9)°]. The interaction is thus not stabilizing. Nevertheless, it is interesting to note that the crystals have the shape of plates with (001) as the smallest dimension, which is parallel to the fluorine layers.

Integration of the raw diffractometer images was performed using the EVAL15 program (Xian et al., 2006), with an accurate description of the diffraction experiment for the prediction of the reflection profiles. A relatively large isotropic mosaicity of 1.3° was used as part of this description, indicating severe defects in the crystal. Nevertheless, some equivalents of weak reflections had significant intensities, which we could interpret as Renninger effects (Original reference?) (Table 3). It has been known for a long time that Renninger effects can also be present in imperfect crystals (Zachariasen, 1965) and examples of organic salts can also be found in the literature (Speakman, 1965; Grochowski et al. 2000). In the examples of Table 3, the intensity of one of the (411) equivalents (reflA) is caused by the strong (201) reflection (reflB), with F²_calc = 3565.42, and for the (reflB - reflA) reflection (210) F²_calc = 1400.59. In the case of (512), the interfering reflection is again (201). Here, for the (reflB - reflA) reflection (313), F²_calc = 2387.81.

Based on these observations, we calculated Renninger scores for all reflections. In the first instance the geometric condition is checked, whether two reflections are simultaneously active or, in other words, whether the corresponding lattice points are both on the Ewald sphere. This condition is fulfilled if the lengths of both reflected beam vectors are equal to the radius of the Ewald sphere with a chosen tolerance of 0.12%. A second condition is the intensity condition, meaning that (reflB) and (reflB - reflA) must both be strong. We consider a reflection as strong if the intensity is larger than 0.02F(000)²_calc. If both conditions are fulfilled, the Renninger score is calculated as intensity(reflB) × intensity(reflB - reflA)/(F(000)²_calc × sinth), where sinth = sin(θ)/λ. We did not try to correct the affected intensities for multiple diffraction (Hauback et al., 1990), but omitted all reflections with a Renninger score larger than 500 from the final dataset. This omission corresponds to 3.8% of all reflections. Due to the redundant measurement this still resulted in a complete dataset of unique reflections.

S2. Experimental

Compound (I) was synthesized according to the literature procedure of Bryan & Dabrowiak (1975). Single crystals suitable for X-ray diffraction were obtained by vapour diffusion of diethyl ether into an acetonitrile solution of (I).

Spectroscopic analysis: IR (Medium?, ν, cm^-1): 3458.5, 2950.7, 2309.5 (CH₃CN), 2280.1 (CH₃CN), 1666.5, 1632.7, 1365.7, 1302.7 (SO₃, as), 1228.8 (SO₃, as), 1210.5 (CF₃, s), 1184.2 (CF₃, as), 1031.4 (SO₃, s), 938.6, 799.4, 769.1.

S3. Refinement

H atoms were located in difference Fourier maps and refined freely with isotropic displacement parameters [C—H = 0.90 (3)–0.94 (3) Å].

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: PEAKREF (Schreurs, 2005); data reduction: EVAL15 (Xian et al., 2006) and SADABS (Sheldrick, 2008a); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008b); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008b); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008b).

Figures

	Fig. 1. The coordination environment of Mn1 in (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. [Symmetry codes: (i) x - 1, y, z; (ii) x + 1, y, z; (iii) 1 - x, 1 - y, 1 - z; (iv) 2 - x, 1 - y, 1 - z.]
	Fig. 2. Space-filling plot of (I), showing the close intermolecular contacts between atoms O3 and C2^i, which prevent a linear coordination of the acetonitrile. [Symmetry code: (i) 2 - x, -y, 1 - z.]
	Fig. 3. The packing of (I) in the crystal structure, viewed along the b axis, showing the one-dimensional coordination chains in the a direction and the fluorine layers in the ab plane. Short F···F interactions are shown as dashed lines. [Symmetry codes: (i) x - 1, y, z; (ii) x + 1, y, z; (iii) 1 - x, 1 - y, 2 - z.]

catena-Poly[[bis(acetonitrile-κN)manganese(II)]-bis(µ- trifluoromethanesulfonato-κ²O:O')]

Crystal data

[Mn(CF3O3S)2(C2H3N)2]	Z = 1
Mr = 435.19	F(000) = 215
Triclinic, P1	Dx = 1.941 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.13763 (8) Å	Cell parameters from 11977 reflections
b = 8.11880 (12) Å	θ = 2.2–27.5°
c = 9.75293 (10) Å	µ = 1.26 mm^−1
α = 73.126 (1)°	T = 110 K
β = 76.885 (1)°	Plate, colourless
γ = 76.025 (1)°	0.36 × 0.33 × 0.09 mm
V = 372.35 (1) Å^3

Data collection

Nonius KappaCCD area-detector diffractometer	1710 independent reflections
Radiation source: rotating anode	1661 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.017
ϕ and ω scans	θmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2008a)	h = −6→6
Tmin = 0.626, Tmax = 0.746	k = −10→10
12368 measured reflections	l = −12→12

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)] = 0.018	Hydrogen site location: difference Fourier map
wR(F^2) = 0.048	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0242P)^2 + 0.1878P] where P = (Fo^2 + 2Fc^2)/3
1710 reflections	(Δ/σ)max = 0.004
118 parameters	Δρmax = 0.46 e Å^−3
0 restraints	Δρmin = −0.34 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
Mn1	0.5000	0.5000	0.5000	0.01132 (7)
S1	0.99675 (5)	0.28591 (3)	0.70541 (3)	0.01273 (8)
F1	0.7338 (2)	0.43972 (14)	0.91057 (11)	0.0505 (3)
F2	1.1028 (2)	0.25999 (16)	0.95941 (10)	0.0501 (3)
F3	0.7474 (2)	0.16068 (15)	0.96541 (10)	0.0479 (3)
O1	0.74153 (17)	0.31364 (11)	0.65396 (10)	0.02000 (19)
O2	1.13165 (16)	0.43632 (11)	0.64751 (9)	0.01617 (17)
O3	1.16580 (18)	0.11805 (11)	0.70540 (11)	0.0233 (2)
N1	0.5020 (2)	0.29525 (13)	0.39165 (12)	0.0186 (2)
C1	0.8878 (3)	0.2871 (2)	0.89665 (15)	0.0292 (3)
C2	0.3989 (2)	0.21583 (14)	0.34860 (12)	0.0153 (2)
C3	0.2578 (3)	0.11708 (18)	0.29665 (17)	0.0243 (3)
H3A	0.082 (5)	0.171 (3)	0.298 (3)	0.063 (7)*
H3B	0.327 (6)	0.120 (4)	0.203 (3)	0.084 (9)*
H3C	0.271 (5)	0.002 (3)	0.357 (3)	0.073 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Mn1	0.00789 (12)	0.00954 (12)	0.01834 (13)	−0.00257 (8)	−0.00395 (9)	−0.00416 (9)
S1	0.00860 (13)	0.01226 (14)	0.01705 (14)	−0.00256 (10)	−0.00345 (10)	−0.00178 (10)
F1	0.0606 (7)	0.0473 (6)	0.0306 (5)	0.0066 (5)	0.0100 (5)	−0.0173 (4)
F2	0.0570 (7)	0.0708 (7)	0.0280 (5)	−0.0140 (6)	−0.0239 (5)	−0.0062 (5)
F3	0.0450 (6)	0.0527 (6)	0.0297 (5)	−0.0181 (5)	0.0060 (4)	0.0122 (4)
O1	0.0145 (4)	0.0165 (4)	0.0294 (5)	−0.0065 (3)	−0.0114 (3)	0.0024 (3)
O2	0.0117 (4)	0.0155 (4)	0.0226 (4)	−0.0057 (3)	−0.0016 (3)	−0.0052 (3)
O3	0.0158 (4)	0.0142 (4)	0.0381 (5)	0.0003 (3)	−0.0056 (4)	−0.0055 (4)
N1	0.0176 (5)	0.0161 (5)	0.0245 (5)	−0.0034 (4)	−0.0041 (4)	−0.0081 (4)
C1	0.0302 (7)	0.0343 (7)	0.0182 (6)	−0.0051 (6)	−0.0021 (5)	−0.0013 (5)
C2	0.0137 (5)	0.0127 (5)	0.0188 (5)	−0.0007 (4)	−0.0025 (4)	−0.0043 (4)
C3	0.0207 (6)	0.0222 (6)	0.0372 (8)	−0.0037 (5)	−0.0114 (5)	−0.0136 (6)

Geometric parameters (Å, º)

Mn1—O1	2.1688 (8)	F1—C1	1.3250 (18)
Mn1—O1^i	2.1688 (8)	F2—C1	1.3246 (17)
Mn1—O2^ii	2.1734 (8)	F3—C1	1.3275 (18)
Mn1—O2^iii	2.1734 (8)	O2—Mn1^iv	2.1734 (8)
Mn1—N1^i	2.2106 (10)	N1—C2	1.1384 (16)
Mn1—N1	2.2106 (10)	C2—C3	1.4518 (16)
S1—O3	1.4283 (9)	C3—H3A	0.90 (3)
S1—O1	1.4534 (8)	C3—H3B	0.90 (3)
S1—O2	1.4564 (8)	C3—H3C	0.94 (3)
S1—C1	1.8237 (14)
O1—Mn1—O1^i	180.0	O1—S1—C1	103.18 (6)
O1—Mn1—O2^ii	89.59 (3)	O2—S1—C1	102.36 (6)
O1^i—Mn1—O2^ii	90.41 (3)	S1—O1—Mn1	140.84 (5)
O1—Mn1—O2^iii	90.41 (3)	S1—O2—Mn1^iv	137.58 (5)
O1^i—Mn1—O2^iii	89.59 (3)	C2—N1—Mn1	153.27 (9)
O2^ii—Mn1—O2^iii	180.0	F2—C1—F1	108.45 (13)
O1—Mn1—N1^i	88.62 (4)	F2—C1—F3	108.36 (12)
O1^i—Mn1—N1^i	91.38 (4)	F1—C1—F3	108.95 (12)
O2^ii—Mn1—N1^i	90.00 (3)	F2—C1—S1	110.00 (10)
O2^iii—Mn1—N1^i	90.00 (3)	F1—C1—S1	110.79 (10)
O1—Mn1—N1	91.38 (4)	F3—C1—S1	110.24 (11)
O1^i—Mn1—N1	88.62 (4)	N1—C2—C3	177.89 (13)
O2^ii—Mn1—N1	90.00 (3)	C2—C3—H3A	108.9 (15)
O2^iii—Mn1—N1	90.00 (3)	C2—C3—H3B	109.4 (18)
N1^i—Mn1—N1	180.0	H3A—C3—H3B	105 (2)
O3—S1—O1	114.69 (5)	C2—C3—H3C	109.2 (15)
O3—S1—O2	116.31 (5)	H3A—C3—H3C	111 (2)
O1—S1—O2	112.95 (5)	H3B—C3—H3C	113 (2)
O3—S1—C1	105.20 (6)
O3—S1—O1—Mn1	−128.75 (9)	O2^ii—Mn1—N1—C2	36.5 (2)
O2—S1—O1—Mn1	7.67 (11)	O2^iii—Mn1—N1—C2	−143.5 (2)
C1—S1—O1—Mn1	117.41 (10)	O3—S1—C1—F2	58.46 (12)
O2^ii—Mn1—O1—S1	−147.30 (9)	O1—S1—C1—F2	179.00 (10)
O2^iii—Mn1—O1—S1	32.70 (9)	O2—S1—C1—F2	−63.53 (11)
N1^i—Mn1—O1—S1	−57.29 (10)	O3—S1—C1—F1	178.35 (10)
N1—Mn1—O1—S1	122.71 (10)	O1—S1—C1—F1	−61.11 (12)
O3—S1—O2—Mn1^iv	23.16 (10)	O2—S1—C1—F1	56.36 (12)
O1—S1—O2—Mn1^iv	−112.52 (8)	O3—S1—C1—F3	−60.98 (11)
C1—S1—O2—Mn1^iv	137.22 (8)	O1—S1—C1—F3	59.57 (11)
O1—Mn1—N1—C2	126.1 (2)	O2—S1—C1—F3	177.03 (10)
O1^i—Mn1—N1—C2	−53.9 (2)

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