β-Phase of 1-(4-bromo­benz­yl)pyridinium bis­(1,2-dicyano­ethene-1,2-dithiol­ato-κ²S,S′)platinate(III)

The title compound, (C₁₂H₁₁BrN)[Pt(C₄N₂S₂)₂], is a new polymorphic modification, viz. the β-phase; the α-phase has been published recently [Ren et al. (2004). Inorg. Chem. 43, 2569–2576]. In the β-phase, the anions and cations form segregated columnar stacks along the a axis, which is similar to the α-phase. Compared with the α-phase, the significant structural differences in the β-phase relate to the mol­ecular conformation of the cation and the stacking architecture of both anions and cations.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.021 Å
• R factor = 0.059
• wR factor = 0.138
• Data-to-parameter ratio = 17.3

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT241_ALERT_2_B Check High      Ueq as Compared to Neighbors for        C14
PLAT242_ALERT_2_B Check Low       Ueq as Compared to Neighbors for        C18
PLAT342_ALERT_3_B Low Bond Precision on C-C bonds (x 1000) Ang ...         21

Alert level C
PLAT199_ALERT_1_C Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_C Check the Reported _diffrn_ambient_temperature .        293 K
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for        C10
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         N5
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C15
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C8
PLAT371_ALERT_2_C Long   C(sp2)-C(sp1) Bond  C3     -   C4     ...       1.42 Ang.
PLAT371_ALERT_2_C Long   C(sp2)-C(sp1) Bond  C7     -   C8     ...       1.42 Ang.

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

   2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   8 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

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S1. Comment

Organic charge-transfer salts with segregated stacks are the subject of intensive study, due to their unusual properties in magnetism and conductivity (Coomber et al., 1996; Kawamura et al., 1997; Xie, Ren, Song, Zou & Meng, 2002; Xie, Ren, Song, Zhang et al., 2002; Xie et al., 2003). Recently, we reported the crystal structure of an ion-pair compound, 1-(4'-bromobenzyl)pyridinium bis(maleonitriledithiolato)platinate(III), which possesses segregated and regular stacks of cations and anions. Such an anionic stack behaves as a one-dimensional magnet with S = 1/2 and undergoes a magnetostructural transition at ca 260 K, which results from the instability of the one-dimensional electron gas (Ren et al., 2004). Here, we present the crystal structure of a new polymorph of the title compound, (I) (Fig. 1), which we have called the β-phase. The α-phase corresponds to the crystal form reported earlier (Ren et al., 2004).

The β-phase crystallizes in a monoclinic space group, with one cation and one anion in the asymmetric unit. The anionic moiety, [Pt(mnt)₂]⁻, shows a square-planar geometry (mnt is maleonitriledithiolate). The Pt—S bond lengths (Table 1) range from 2.249 (3) to 2.267 (3) Å. The S—Pt—S angles in the two chelate rings [89.79 (11) and 89.75 (11)°] are in a good agreement with the values observed in the α-phase. In the cation, the plane formed by atoms N5/C14/C15 makes dihedral angles with the benzene and pyridine rings of 72.6 (15) and 104.6 (10)°, respectively, while in the α-phase, the corresponding dihedral angles are 98.5 (6) and 93.1 (5)°, respectively. The dihedral angles between the benzene and pyridine rings in the β- and α-phases are 75.9 (4) and 114.1 (2)°, respectively. In the crystal structure of (I), the anions and cations stack into segregated columns along the a axis (Fig. 2).

There are remarkable differences in the crystal structures of the two polymorphs. The anionic stacks in the α- and β-phases are regular (Fig. 3a) and irregular (Fig. 3b), respectively. In the β-phase, two stacking patterns exist between adjacent anions, namely face-to-face overlap, and longitudinal and transverse offset. The face-to-face overlap involves an anionic pair containing atoms Pt1 and Pt1ⁱ [symmetry code: (i) 1 − x, 2 − y, 1 − z], in which the distance between the Pt^III ions [3.4838 (8) Å] is comparable with that between the corresponding mean planes defined by the four coordinating S atoms [3.489 (3) Å]. The longitudinal and transverse offset involves an anionic pair containing atoms Pt1 and Pt1ⁱⁱ [symmetry code: (ii) 2 − x, 2 − y, 1 − z], in which the distances between the Pt^III ions and between the corresponding mean planes are 4.3038 (9) and 3.6235 (4) Å, respectively. Within a cationic stack, neighbouring cations in the α- and β-phases are stacked in chair-conformation-like (Fig. 4a) and boat-conformation-like (Fig. 4b) fashions, respectively. In the β-phase, the anionic molecular planes in neighbouring stacks are inclined to each other with a dihedral angle of 27.73 (5)° [1.32 (5)° in the α-phase]. The dihedral angle between benzene rings in neighbouring cationic stacks is 21.94 (25)° [3.58 (18)° in the α-phase].

With respect to the [M(mnt)₂]⁻-based compounds (M = Ni, Pd or Pt), their physical properties, such as conductivity and magnetism, are sensitive to the anionic stacking pattern. Therefore, the two polymorphs of (I) probably possess distinct conducting and magnetic behaviours, and such measurements are in progress.

S2. Experimental

Disodium maleonitriledithiolate (Na₂mnt) was prepared following the known procedure of Davison & Holm (1967). 1-(4-Bromobenzyl)pyridinium chloride was prepared by reacting 4-bromobenzylchlorine with 1.5 equivalents of pyridine in refluxing acetone for 4 h. The obtained product, containing white microcrystals, was filtered and washed with acetone and diethyl ether in turn, and then dried in vacuo, with a yield ca 80%. K₂PtCl₄, Na₂mnt and 1-(4'-bromobenzyl)pyridinium chloride (equivalent molar ratio 1:2:2) were mixed in water. The red product which precipitated was separated, washed with water and then dissolved in a MeCN. Iodine (1.5 molar equivalents) was added to the boiling solution with stirring. Five times the resulting volume of MeOH was then added and the mixture allowed to stand for 24 h. The microcrystals which formed were separated, washed with MeOH and dried in vacuo, with a yield ca 55%. The saturated MeCN solution of (I) at room temperature was placed in a refrigerator at 277 K for one week, and single crystals of (I) suitable for X-ray crystal structure analysis were obtained.

S3. Refinement

All H atoms were placed in geometrically calculated positions and refined as riding, with C—H = 0.93–0.97 Å and U_iso(H) = 1.2U_eq(C). The residual electron density of 1.86 e Å⁻³ and the deepest hole of −1.58 e Å⁻³ are situated at 1.04 and 1.74 Å from Pt1, respectively.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997a); molecular graphics: SHELXTL (Sheldrick, 1997b); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A view of (I), showing 30% probability displacement ellipsoids and the atom-numbering scheme. H atoms have been omitted for clarity.
	Fig. 2. The crystal packing of (I), viewed approximately along the a axis.
	Fig. 3. The anionic packing in (a) the α-phase and (b) the β-phase.
	Fig. 4. The cationic packing in (a) the α-phase and (b) the β-phase.

1-(4-bromobenzyl)pyridinium bis(1,2-dicyanoethene-1,2-dithiolato-κ²S,S')platinate(III)

Crystal data

(C12H11BrN)[Pt(C4N2S2)2]	F(000) = 1372
Mr = 724.58	Dx = 2.046 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 851 reflections
a = 7.3814 (8) Å	θ = 2.9–23.8°
b = 26.180 (3) Å	µ = 8.04 mm^−1
c = 12.6488 (14) Å	T = 293 K
β = 105.739 (2)°	Needle, black
V = 2352.7 (5) Å^3	0.20 × 0.15 × 0.10 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	4851 independent reflections
Radiation source: fine-focus sealed tube	2886 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.097
ϕ and ω scans	θmax = 26.5°, θmin = 1.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.24, Tmax = 0.45	k = −32→28
13418 measured reflections	l = −13→15

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)] = 0.059	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.138	H-atom parameters constrained
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0566P)^2] where P = (Fo^2 + 2Fc^2)/3
4851 reflections	(Δ/σ)max = 0.001
280 parameters	Δρmax = 1.86 e Å^−3
0 restraints	Δρmin = −1.58 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
Pt1	0.71258 (6)	0.977887 (18)	0.48253 (3)	0.04922 (17)
Br1	0.8054 (3)	1.07958 (7)	0.0098 (3)	0.1851 (14)
S1	0.8524 (4)	1.02629 (12)	0.6303 (2)	0.0566 (7)
S2	0.7040 (4)	1.04611 (12)	0.3725 (2)	0.0606 (8)
S3	0.7259 (4)	0.90745 (11)	0.5886 (2)	0.0577 (7)
S4	0.5705 (4)	0.93170 (13)	0.3331 (2)	0.0622 (8)
N1	1.0213 (17)	1.1546 (4)	0.7077 (9)	0.085 (3)
N2	0.829 (2)	1.1787 (5)	0.3721 (11)	0.116 (5)
N3	0.6142 (19)	0.7689 (5)	0.5580 (11)	0.103 (4)
N4	0.424 (2)	0.8005 (6)	0.2463 (12)	0.131 (5)
N5	0.7887 (17)	0.8212 (4)	−0.0571 (11)	0.075 (3)
C1	0.9528 (18)	1.1241 (5)	0.6459 (10)	0.065 (3)
C2	0.8713 (14)	1.0842 (4)	0.5749 (9)	0.051 (3)
C3	0.8034 (16)	1.0935 (5)	0.4631 (10)	0.060 (3)
C4	0.818 (2)	1.1418 (5)	0.4154 (12)	0.079 (4)
C5	0.6219 (18)	0.8114 (6)	0.5307 (10)	0.074 (4)
C6	0.6339 (15)	0.8620 (5)	0.4944 (8)	0.056 (3)
C7	0.5614 (15)	0.8723 (5)	0.3828 (9)	0.059 (3)
C8	0.4851 (19)	0.8322 (5)	0.3087 (11)	0.073 (4)
C9	0.776 (2)	0.8045 (6)	−0.1567 (13)	0.104 (5)
H9A	0.6660	0.8108	−0.2119	0.125*
C10	0.917 (3)	0.7786 (6)	−0.1818 (13)	0.118 (6)
H10A	0.9023	0.7658	−0.2522	0.142*
C11	1.080 (2)	0.7714 (6)	−0.1025 (16)	0.100 (5)
H11A	1.1815	0.7557	−0.1198	0.120*
C12	1.097 (2)	0.7869 (5)	0.0013 (14)	0.093 (5)
H12A	1.2052	0.7802	0.0571	0.111*
C13	0.947 (3)	0.8132 (5)	0.0226 (12)	0.086 (4)
H13A	0.9575	0.8253	0.0931	0.103*
C14	0.637 (2)	0.8527 (6)	−0.0313 (15)	0.120 (6)
H14A	0.5214	0.8479	−0.0891	0.144*
H14B	0.6157	0.8404	0.0367	0.144*
C15	0.6801 (17)	0.9062 (5)	−0.0204 (11)	0.065 (3)
C16	0.6734 (19)	0.9332 (6)	−0.1101 (11)	0.082 (4)
H16A	0.6432	0.9167	−0.1778	0.098*
C17	0.709 (2)	0.9838 (7)	−0.1060 (12)	0.094 (6)
H17A	0.7029	1.0019	−0.1701	0.113*
C18	0.7574 (17)	1.0093 (6)	−0.0018 (16)	0.086 (5)
C19	0.759 (2)	0.9788 (7)	0.0909 (13)	0.094 (5)
H19A	0.7856	0.9934	0.1605	0.113*
C20	0.723 (2)	0.9293 (6)	0.0777 (11)	0.082 (4)
H20A	0.7272	0.9096	0.1395	0.098*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1	0.0389 (2)	0.0672 (3)	0.0432 (2)	0.0059 (2)	0.01388 (17)	−0.0015 (2)
Br1	0.0758 (12)	0.0711 (12)	0.427 (5)	0.0013 (9)	0.100 (2)	0.0005 (17)
S1	0.0483 (16)	0.074 (2)	0.0460 (16)	−0.0005 (15)	0.0103 (13)	−0.0040 (15)
S2	0.0565 (18)	0.078 (2)	0.0474 (17)	0.0068 (16)	0.0147 (14)	0.0069 (15)
S3	0.0550 (18)	0.0653 (19)	0.0495 (17)	0.0065 (15)	0.0089 (14)	−0.0002 (14)
S4	0.064 (2)	0.082 (2)	0.0414 (16)	0.0014 (17)	0.0160 (14)	−0.0048 (15)
N1	0.103 (9)	0.078 (8)	0.072 (8)	0.001 (7)	0.020 (7)	0.000 (6)
N2	0.170 (14)	0.083 (10)	0.113 (11)	0.032 (10)	0.068 (10)	0.025 (8)
N3	0.109 (10)	0.085 (10)	0.113 (10)	0.014 (8)	0.030 (8)	0.004 (8)
N4	0.119 (12)	0.150 (14)	0.116 (12)	−0.017 (10)	0.022 (9)	−0.060 (10)
N5	0.073 (8)	0.072 (8)	0.088 (9)	−0.015 (6)	0.033 (7)	−0.025 (7)
C1	0.073 (9)	0.065 (9)	0.057 (8)	0.002 (7)	0.019 (7)	−0.010 (7)
C2	0.044 (6)	0.064 (8)	0.052 (7)	0.014 (6)	0.025 (6)	0.005 (6)
C3	0.056 (7)	0.070 (9)	0.061 (8)	0.007 (6)	0.026 (6)	0.002 (6)
C4	0.102 (11)	0.062 (10)	0.089 (10)	0.020 (8)	0.052 (9)	0.006 (8)
C5	0.065 (9)	0.092 (12)	0.062 (9)	0.010 (9)	0.012 (7)	−0.010 (8)
C6	0.054 (7)	0.071 (9)	0.044 (7)	0.017 (6)	0.014 (5)	−0.001 (6)
C7	0.051 (7)	0.078 (9)	0.052 (7)	−0.001 (6)	0.020 (6)	−0.019 (6)
C8	0.075 (9)	0.081 (10)	0.063 (9)	0.007 (8)	0.020 (7)	−0.010 (7)
C9	0.105 (13)	0.111 (14)	0.084 (12)	0.026 (10)	0.005 (10)	−0.014 (10)
C10	0.19 (2)	0.099 (13)	0.067 (11)	0.034 (13)	0.039 (13)	−0.003 (9)
C11	0.099 (13)	0.082 (11)	0.117 (14)	0.021 (10)	0.025 (11)	−0.001 (11)
C12	0.098 (13)	0.059 (10)	0.103 (13)	−0.008 (9)	−0.003 (10)	0.002 (9)
C13	0.113 (13)	0.081 (11)	0.067 (10)	−0.022 (10)	0.029 (10)	−0.012 (8)
C14	0.084 (11)	0.110 (15)	0.189 (19)	−0.015 (10)	0.076 (12)	−0.026 (12)
C15	0.066 (9)	0.071 (9)	0.065 (8)	−0.008 (7)	0.031 (7)	0.000 (7)
C16	0.088 (11)	0.089 (11)	0.065 (9)	0.022 (9)	0.015 (8)	0.014 (8)
C17	0.075 (10)	0.154 (17)	0.063 (9)	0.052 (11)	0.037 (8)	0.059 (11)
C18	0.040 (8)	0.087 (12)	0.139 (16)	0.015 (7)	0.037 (9)	0.018 (10)
C19	0.070 (10)	0.127 (15)	0.078 (11)	0.042 (11)	0.008 (8)	−0.013 (11)
C20	0.098 (11)	0.092 (12)	0.070 (10)	0.019 (9)	0.049 (9)	0.010 (8)

Geometric parameters (Å, º)

Pt1—S4	2.249 (3)	C9—C10	1.35 (2)
Pt1—S2	2.255 (3)	C9—H9A	0.9300
Pt1—S1	2.262 (3)	C10—C11	1.36 (2)
Pt1—S3	2.267 (3)	C10—H10A	0.9300
Br1—C18	1.871 (16)	C11—C12	1.348 (19)
S1—C2	1.691 (11)	C11—H11A	0.9300
S2—C3	1.713 (12)	C12—C13	1.385 (19)
S3—C6	1.691 (12)	C12—H12A	0.9300
S4—C7	1.687 (12)	C13—H13A	0.9300
N1—C1	1.137 (14)	C14—C15	1.436 (18)
N2—C4	1.124 (15)	C14—H14A	0.9700
N3—C5	1.169 (16)	C14—H14B	0.9700
N4—C8	1.149 (16)	C15—C16	1.325 (16)
N5—C9	1.312 (17)	C15—C20	1.339 (17)
N5—C13	1.339 (18)	C16—C17	1.349 (19)
N5—C14	1.496 (17)	C16—H16A	0.9300
C1—C2	1.403 (16)	C17—C18	1.43 (2)
C2—C3	1.387 (15)	C17—H17A	0.9300
C3—C4	1.417 (17)	C18—C19	1.42 (2)
C5—C6	1.413 (18)	C19—C20	1.325 (18)
C6—C7	1.393 (14)	C19—H19A	0.9300
C7—C8	1.418 (16)	C20—H20A	0.9300
S4—Pt1—S2	88.78 (11)	C11—C10—H10A	120.6
S4—Pt1—S1	178.45 (11)	C12—C11—C10	120.4 (16)
S2—Pt1—S1	89.79 (11)	C12—C11—H11A	119.8
S4—Pt1—S3	89.75 (11)	C10—C11—H11A	119.8
S2—Pt1—S3	177.76 (10)	C11—C12—C13	118.3 (15)
S1—Pt1—S3	91.70 (11)	C11—C12—H12A	120.9
C2—S1—Pt1	103.3 (4)	C13—C12—H12A	120.9
C3—S2—Pt1	103.1 (4)	N5—C13—C12	120.7 (13)
C6—S3—Pt1	102.2 (4)	N5—C13—H13A	119.7
C7—S4—Pt1	103.8 (4)	C12—C13—H13A	119.7
C9—N5—C13	119.5 (13)	C15—C14—N5	113.6 (11)
C9—N5—C14	122.0 (15)	C15—C14—H14A	108.9
C13—N5—C14	118.4 (13)	N5—C14—H14A	108.9
N1—C1—C2	176.5 (14)	C15—C14—H14B	108.9
C3—C2—C1	119.6 (11)	N5—C14—H14B	108.9
C3—C2—S1	122.2 (9)	H14A—C14—H14B	107.7
C1—C2—S1	118.1 (9)	C16—C15—C20	119.9 (14)
C2—C3—C4	122.9 (12)	C16—C15—C14	118.9 (14)
C2—C3—S2	121.6 (9)	C20—C15—C14	121.3 (14)
C4—C3—S2	115.4 (10)	C15—C16—C17	121.9 (14)
N2—C4—C3	175.9 (15)	C15—C16—H16A	119.0
N3—C5—C6	177.8 (15)	C17—C16—H16A	119.0
C7—C6—C5	118.0 (11)	C16—C17—C18	119.4 (13)
C7—C6—S3	123.2 (10)	C16—C17—H17A	120.3
C5—C6—S3	118.7 (9)	C18—C17—H17A	120.3
C6—C7—C8	120.1 (12)	C19—C18—C17	116.2 (15)
C6—C7—S4	120.9 (9)	C19—C18—Br1	122.0 (15)
C8—C7—S4	119.0 (9)	C17—C18—Br1	121.7 (14)
N4—C8—C7	178.1 (16)	C20—C19—C18	119.4 (14)
N5—C9—C10	122.2 (16)	C20—C19—H19A	120.3
N5—C9—H9A	118.9	C18—C19—H19A	120.3
C10—C9—H9A	118.9	C19—C20—C15	123.2 (14)
C9—C10—C11	118.9 (15)	C19—C20—H20A	118.4
C9—C10—H10A	120.6	C15—C20—H20A	118.4