3-Methylamido-3′,4′-ethyl­enedithiotetra­thia­fulvalene­(+) potassium tetra­isothio­cyanato­mercury(II)

In the title compound, (C₁₀H₉NOS₆)K[Hg(SCN)₄] or (EDT–TTF–CONHMe)K[Hg(SCN)₄)], fully oxidized organic (EDT–TTF–CONHMe)^+· radical cations form quasi-one-dimensional stacks running along the monoclinic 2₁ axis and alternating along the crystallographic [101] direction with inorganic anion stacks made from mixed K⁺–[Hg(SCN)₄]²⁻ ribbons. For each anion, three essentially collinear SCN ligands inter­act with the K⁺ ions via short N...K contacts, while the terminal N atom of the fourth SCN group is engaged in a number of hydrogen-bond contacts with the –CH, –NH and –CH₂ hydrogen-bond donors of the amide function. Radical cations are dimerized along the stacks and the crystal conductivity is activated.

S1. Comment

3',4'-Ethylenedithio-3-methylamido-tetrathiafulvalene (EDT–TTF–CONHMe; Heuzé et al., 1999) is one of a series of π-donor molecules whose hydrogen-bond donor/acceptor group acts in the solid state as a structure-directing functionality, eventually enhanced upon redox activation (Fourmigué & Batail, 2004), as illustrated by several recent examples (Heuzé et al., 2000, 2003; Baudron et al., 2003). The anion, [Hg(SCN)₄]^2-, was selected to be used in the title compound because of its versatile conformation in addition to a noted ability to form metallic and superconducting radical cation salts with a variety of organic donors.

As exemplified in Fig. 1, radical cation stacks and chains of anionic motifs are segregated and run along the monoclinic 2₁ axis. The labeled molecules with displacement ellipsoids are shown in Figs. 2 (organic donor) and 3(b) (anion), respectively. There is one independent radical cation located in a general position. The central C1═C2 bond length [1.391 (5) Å] of the TTF fragment is the most sensitive to the degree of charge transfer, or net π-donor oxidation state, and is characteristic of a fully oxidized (1+) donor molecule. A zigzag mode of intermolecular overlap with two different patterns of overlap is observed, indicating that the stack is dimerized (Fig. 2). The intradimer overlap A qualifies a strong intradimer interaction with short S···S, S···C and C···C van der Waals contacts, presented in Table 1 and Fig. 3(a), while only one S3···S3 contact for interdimer interaction B is observed. The intra- and inter-dimer interplanar separations within the stack, calculated using the central six atoms of the TTF fragment, are 3.355 (8) and 3.460 (8) Å, respectively.

The complex anion, K⁺[Hg(SCN)₄]^2-, is located in a general position near the twofold screw axis 2₁. The Hg atom adopts a tetrahedral coordination by S atoms, yet each of the SCN ligand adjusts to the crystal environment by rotating around the Hg—S bonds. Note that the conformation of the anion revealed in (I) has not been reported previously. Analysis of structures collected in the Cambridge Structural Database (Bruno et al., 2002; Allen, 2002) indicates that, in the previously reported structures, at most two SCN vectors of the [Hg(SCN)₄]^2- anion appear to be near collinear instead of three in the present compound. These three ligands interact with the K⁺ ion via short N···K contacts of 2.780 (4)–3.108 (4) Å, stabilizing the anion ribbon as shown in Fig. 3(b). The fourth SCN ligand protrudes out towards the donor molecules, its terminal N2A atom being involved in a number of hydrogen contacts with the amide groups (Fig. 3a and Table 2). The recurrent tweezer-like hydrogen-bonded seven-membered ring motif (Heuzé et al., 2000; Fourmigué & Batail, 2004) acting upon the combined effect of activated –NH and –Csp²H hydrogen-bond donors, is again identified here. In addition, the radical cation stacks are connected to adjacent anion ribbons by short O···K [2.606 (3) Å] and S···S contacts along [101]. The coordination polyhedron around the K⁺ cation is a distorted octahedron composed of one O and five N atoms; this differs from the eight- (4 N + 4S) and seven-coordination (4 N + 3S) of K in α- and δ-(BEDT-TTF)₂K[Hg(SCN)₄], respectively (Oshima et al., 1989; Kazheva et al., 2002). The crystals of (I) are semiconducting, as expected for a dimerized stack.

Related literature

For related literature, see: Allen (2002); Baudron et al. (2003); Bruno et al. (2002); Fourmigué & Batail (2004); Heuzé et al. (1999, 2000, 2003); Kazheva et al. (2002); Oshima et al. (1989); Sheldrick (1997).

S2. Experimental

Single crystals of (I) were obtained by electrooxidation, at constant current (I = 2 µA) and 293 K, of the above donor in 1,1,2-trichloroethane solution containing 10%(v/v) of dried ethanol. Plate-like crystals grew on the anode after three weeks.

S3. Refinement

The final refinement was carried out in space group P2₁/n, chosen on the basis of the systematic absences and successful refinement of the structure. The positions of the methyl and ethylene H atoms were calculated as riding, in accordance with HFIX 137 and HFIX 23 instructions of SHELXL97 (Sheldrick, 1997), with U_iso(H) values of 1.5 and 1.2 times U_eq(C), respectively. The H atoms of –Csp²H and –NH groups were located in difference electron density syntheses and constrained by AFIX 43 [U_iso(H) = 1.2U_eq(C,N)]. The terminal ethylene group of the radical cation is disordered over two positions in a \sim3:1 ratio and C—C distances were restrained to be equal.

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: APEX2 and WinGX (Farrugia, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The crystal structure of (I).
	Fig. 2. Intra- (A) and inter-dimer (B) patterns of overlap between the radical cations along the stack. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 3. (a) Donor–donor (dashed lines) and donor–anion (dotted lines) interactions. (b) The anion ribbon stabilized by N···K contacts. [Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) -x + 2, -y + 1, -z + 1; (ii) -x + 2, -y + 2, -z + 1; (iv) x + 1, y + 1, z; (v) -x + 3/2, y + 1/2, -z + 1/2; (vi) x, y + 1, z.]

potassium 3',4'-ethylenedithio-3-methylamidotetrathiafulvalene(+) tetraisothiocyanatomercury(II)

Crystal data

K(C10H9NOS6)[Hg(SCN)4]	F(000) = 1580
Mr = 823.55	Dx = 2.065 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 7058 reflections
a = 13.7129 (17) Å	θ = 3.0–25.1°
b = 7.9403 (9) Å	µ = 6.78 mm^−1
c = 24.862 (3) Å	T = 294 K
β = 101.879 (5)°	Small, black
V = 2649.2 (6) Å^3	0.15 × 0.06 × 0.02 mm
Z = 4

Data collection

Bruker X8Apex CCD detector diffractometer	6827 independent reflections
Radiation source: fine-focus sealed tube	4594 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
ω and ϕ scans	θmax = 29.5°, θmin = 3.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −15→18
Tmin = 0.430, Tmax = 0.876	k = −10→10
25746 measured reflections	l = −34→34

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)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.069	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0176P)^2 + 0.5772P] where P = (Fo^2 + 2Fc^2)/3
6827 reflections	(Δ/σ)max = 0.002
309 parameters	Δρmax = 0.88 e Å^−3
1 restraint	Δρmin = −0.61 e Å^−3

Special details

Experimental. The DC resistance measurements were performed on single crystals by the two-probe method with the current flow applied along a stack direction in the 300 – 4.2 K temperature interval. Four annealed platinum wires (10 µm in diameter) were attached to a crystal surface by a graphite paste. The applied current was 10–20 µA.

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	Occ. (<1)
K1	0.75749 (6)	0.75738 (11)	0.24987 (3)	0.0543 (2)
Hg1	0.545783 (10)	0.17603 (2)	0.405668 (6)	0.05455 (7)
S1A	0.57404 (9)	0.49464 (14)	0.40134 (4)	0.0665 (3)
S2A	0.42967 (9)	0.18028 (17)	0.47338 (5)	0.0775 (4)
S3A	0.70128 (7)	−0.00148 (14)	0.43133 (4)	0.0630 (3)
S4A	0.44076 (8)	0.06819 (16)	0.31431 (4)	0.0679 (3)
C1A	0.6468 (3)	0.5093 (5)	0.35541 (15)	0.0552 (10)
C2A	0.3259 (3)	0.1450 (4)	0.42753 (18)	0.0544 (10)
C3A	0.7625 (3)	0.0745 (5)	0.38504 (16)	0.0597 (10)
C4A	0.5364 (3)	0.0068 (5)	0.28683 (15)	0.0554 (10)
N1A	0.6971 (3)	0.5234 (4)	0.32416 (15)	0.0749 (11)
N2A	0.2527 (3)	0.1223 (5)	0.39675 (18)	0.0778 (11)
N3A	0.8090 (3)	0.1246 (6)	0.35470 (16)	0.0953 (14)
N4A	0.6007 (3)	−0.0348 (5)	0.26654 (15)	0.0793 (11)
S1	0.95388 (7)	0.63311 (12)	0.59003 (3)	0.0468 (2)
S2	0.79938 (7)	0.54608 (11)	0.49483 (3)	0.0465 (2)
S3	1.07862 (7)	0.81842 (10)	0.50766 (4)	0.0445 (2)
S4	0.91880 (6)	0.72987 (12)	0.41446 (4)	0.0453 (2)
S5	0.85699 (9)	0.47352 (14)	0.67181 (4)	0.0673 (3)
S6	0.67353 (9)	0.35747 (15)	0.55617 (5)	0.0702 (3)
C1	0.9125 (3)	0.6423 (4)	0.51974 (14)	0.0421 (8)
C2	0.9645 (3)	0.7223 (4)	0.48453 (14)	0.0420 (8)
C3	0.8539 (3)	0.5168 (4)	0.60246 (14)	0.0447 (8)
C4	0.7817 (3)	0.4746 (4)	0.55869 (13)	0.0434 (8)
C5	1.0896 (3)	0.8895 (4)	0.44392 (14)	0.0448 (8)
H5	1.1449	0.9516	0.4393	0.054*
C6	1.0157 (3)	0.8524 (4)	0.40067 (14)	0.0435 (8)
C7	0.7252 (6)	0.4346 (11)	0.6668 (3)	0.078 (3)	0.772 (13)
H7A	0.7143	0.4022	0.7027	0.094*	0.772 (13)
H7B	0.6890	0.5385	0.6563	0.094*	0.772 (13)
C8	0.6836 (10)	0.3000 (11)	0.6260 (4)	0.076 (3)	0.772 (13)
H8A	0.6180	0.2689	0.6316	0.091*	0.772 (13)
H8B	0.7258	0.2011	0.6335	0.091*	0.772 (13)
C7A	0.7563 (13)	0.315 (3)	0.6708 (7)	0.052 (6)	0.228 (13)
H7C	0.7772	0.2055	0.6600	0.063*	0.228 (13)
H7D	0.7408	0.3047	0.7071	0.063*	0.228 (13)
C8A	0.667 (2)	0.375 (5)	0.6301 (12)	0.062 (9)	0.228 (13)
H8C	0.6553	0.4927	0.6379	0.075*	0.228 (13)
H8D	0.6090	0.3124	0.6358	0.075*	0.228 (13)
C9	1.0028 (3)	0.8939 (5)	0.34079 (15)	0.0497 (9)
C10	1.0619 (4)	1.0440 (6)	0.26857 (16)	0.0840 (14)
H10A	1.0696	0.9449	0.2477	0.126*
H10B	1.1137	1.1230	0.2660	0.126*
H10C	0.9981	1.0942	0.2542	0.126*
N1	1.0682 (2)	0.9981 (4)	0.32603 (12)	0.0569 (8)
H1	1.1153	1.0395	0.3508	0.068*
O1	0.9321 (2)	0.8306 (3)	0.30909 (11)	0.0678 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
K1	0.0548 (5)	0.0585 (5)	0.0513 (5)	−0.0006 (4)	0.0147 (4)	0.0047 (4)
Hg1	0.03656 (10)	0.08054 (13)	0.04928 (10)	−0.00362 (7)	0.01514 (7)	−0.00187 (7)
S1A	0.0664 (7)	0.0698 (7)	0.0700 (7)	−0.0063 (6)	0.0291 (6)	−0.0114 (5)
S2A	0.0497 (7)	0.1372 (11)	0.0519 (6)	0.0130 (6)	0.0251 (5)	0.0146 (6)
S3A	0.0426 (6)	0.0915 (8)	0.0578 (6)	0.0094 (5)	0.0168 (5)	0.0222 (5)
S4A	0.0462 (6)	0.1066 (9)	0.0504 (6)	−0.0049 (6)	0.0085 (5)	−0.0158 (6)
C1A	0.059 (3)	0.052 (2)	0.052 (2)	−0.005 (2)	0.007 (2)	−0.0028 (18)
C2A	0.051 (3)	0.046 (2)	0.075 (3)	0.0051 (18)	0.034 (2)	0.0074 (18)
C3A	0.042 (2)	0.086 (3)	0.050 (2)	0.019 (2)	0.0059 (19)	0.016 (2)
C4A	0.055 (3)	0.066 (3)	0.046 (2)	−0.006 (2)	0.0105 (19)	−0.0053 (18)
N1A	0.097 (3)	0.066 (2)	0.072 (2)	−0.010 (2)	0.042 (2)	0.0002 (18)
N2A	0.043 (2)	0.077 (2)	0.116 (3)	−0.0107 (19)	0.023 (2)	−0.008 (2)
N3A	0.070 (3)	0.146 (4)	0.079 (3)	0.034 (3)	0.036 (2)	0.053 (3)
N4A	0.075 (3)	0.090 (3)	0.077 (2)	0.009 (2)	0.027 (2)	−0.008 (2)
S1	0.0436 (6)	0.0534 (5)	0.0430 (5)	−0.0010 (4)	0.0075 (4)	−0.0065 (4)
S2	0.0362 (5)	0.0568 (5)	0.0457 (5)	−0.0021 (4)	0.0062 (4)	0.0056 (4)
S3	0.0367 (5)	0.0480 (5)	0.0486 (5)	−0.0027 (4)	0.0082 (4)	−0.0053 (4)
S4	0.0367 (5)	0.0522 (5)	0.0464 (5)	−0.0045 (4)	0.0070 (4)	0.0014 (4)
S5	0.0777 (8)	0.0828 (7)	0.0443 (5)	0.0019 (6)	0.0196 (5)	0.0041 (5)
S6	0.0541 (7)	0.0852 (8)	0.0730 (7)	−0.0195 (6)	0.0167 (6)	0.0107 (6)
C1	0.039 (2)	0.0409 (19)	0.0463 (19)	0.0025 (15)	0.0086 (16)	−0.0041 (15)
C2	0.038 (2)	0.0411 (19)	0.047 (2)	0.0042 (15)	0.0085 (16)	−0.0027 (15)
C3	0.046 (2)	0.0435 (19)	0.047 (2)	0.0057 (16)	0.0151 (17)	0.0003 (15)
C4	0.040 (2)	0.0449 (19)	0.047 (2)	0.0073 (16)	0.0128 (16)	0.0056 (15)
C5	0.039 (2)	0.0446 (19)	0.054 (2)	−0.0037 (16)	0.0171 (17)	−0.0070 (16)
C6	0.0367 (19)	0.042 (2)	0.053 (2)	−0.0011 (15)	0.0124 (17)	−0.0045 (15)
C7	0.073 (5)	0.106 (6)	0.066 (4)	0.019 (5)	0.040 (4)	0.018 (4)
C8	0.074 (7)	0.070 (6)	0.094 (6)	0.004 (4)	0.040 (5)	0.025 (5)
C7A	0.052 (12)	0.059 (14)	0.051 (11)	0.018 (9)	0.023 (9)	0.024 (9)
C8A	0.031 (12)	0.10 (3)	0.059 (16)	0.002 (16)	0.010 (11)	0.017 (18)
C9	0.047 (2)	0.056 (2)	0.049 (2)	−0.0033 (19)	0.0165 (19)	−0.0046 (18)
C10	0.096 (4)	0.104 (4)	0.058 (3)	−0.027 (3)	0.033 (3)	0.004 (2)
N1	0.056 (2)	0.068 (2)	0.0496 (17)	−0.0116 (17)	0.0191 (15)	−0.0051 (15)
O1	0.064 (2)	0.087 (2)	0.0508 (16)	−0.0227 (15)	0.0079 (15)	−0.0072 (14)

Geometric parameters (Å, º)

Hg1—S3A	2.5259 (10)	S6—C8	1.773 (11)
Hg1—S2A	2.5444 (11)	S6—C8A	1.86 (3)
Hg1—S1A	2.5650 (12)	C1—C2	1.391 (5)
Hg1—S4A	2.5729 (10)	C3—C4	1.354 (5)
S1A—C1A	1.668 (4)	C5—C6	1.349 (5)
S2A—C2A	1.654 (5)	C5—H5	0.9300
S3A—C3A	1.671 (4)	C6—C9	1.499 (5)
S4A—C4A	1.672 (4)	C7—C8	1.502 (9)
C1A—N1A	1.146 (5)	C7—H7A	0.9700
C2A—N2A	1.144 (5)	C7—H7B	0.9700
C3A—N3A	1.154 (5)	C8—H8A	0.9700
C4A—N4A	1.150 (5)	C8—H8B	0.9700
S1—C1	1.724 (3)	C7A—C8A	1.504 (11)
S1—C3	1.733 (4)	C7A—H7C	0.9700
S2—C1	1.726 (4)	C7A—H7D	0.9700
S2—C4	1.749 (3)	C8A—H8C	0.9700
S3—C5	1.718 (4)	C8A—H8D	0.9700
S3—C2	1.730 (4)	C9—O1	1.224 (4)
S4—C2	1.727 (3)	C9—N1	1.327 (4)
S4—C6	1.737 (4)	C10—N1	1.459 (5)
S5—C3	1.750 (3)	C10—H10A	0.9600
S5—C7	1.812 (7)	C10—H10B	0.9600
S5—C7A	1.87 (2)	C10—H10C	0.9600
S6—C4	1.741 (4)	N1—H1	0.8600
S1···S4^i	3.384 (1)	C1···C1^i	3.577 (7)
S2···S3^i	3.350 (1)	C4···C5^i	3.394 (5)
S3···S3^ii	3.574 (2)	C1···C2^i	3.363 (5)
S3···C4^i	3.620 (3)	C3···C6^i	3.442 (5)
S5···C9^i	3.543 (4)	C3···C5^i	3.564 (5)
S3A—Hg1—S2A	116.81 (3)	C9—C6—S4	112.3 (3)
S3A—Hg1—S1A	115.72 (4)	C8—C7—S5	113.7 (7)
S2A—Hg1—S1A	97.77 (4)	C8—C7—H7A	108.8
S3A—Hg1—S4A	109.11 (4)	S5—C7—H7A	108.8
S2A—Hg1—S4A	106.00 (4)	C8—C7—H7B	108.8
S1A—Hg1—S4A	110.68 (4)	S5—C7—H7B	108.8
C1A—S1A—Hg1	102.38 (14)	H7A—C7—H7B	107.7
C2A—S2A—Hg1	96.24 (14)	C7—C8—S6	114.8 (7)
C3A—S3A—Hg1	98.17 (13)	C7—C8—H8A	108.6
C4A—S4A—Hg1	96.54 (13)	S6—C8—H8A	108.6
N1A—C1A—S1A	178.4 (4)	C7—C8—H8B	108.6
N2A—C2A—S2A	178.2 (4)	S6—C8—H8B	108.6
N3A—C3A—S3A	176.7 (4)	H8A—C8—H8B	107.5
N4A—C4A—S4A	178.2 (4)	C8A—C7A—S5	107 (2)
C1—S1—C3	95.52 (17)	C8A—C7A—H7C	110.3
C1—S2—C4	95.75 (16)	S5—C7A—H7C	110.3
C5—S3—C2	94.79 (17)	C8A—C7A—H7D	110.3
C2—S4—C6	94.89 (17)	S5—C7A—H7D	110.3
C3—S5—C7	98.3 (3)	H7C—C7A—H7D	108.6
C3—S5—C7A	104.6 (5)	C7A—C8A—S6	116 (2)
C4—S6—C8	102.0 (4)	C7A—C8A—H8C	108.3
C4—S6—C8A	98.0 (11)	S6—C8A—H8C	108.3
C2—C1—S1	123.6 (3)	C7A—C8A—H8D	108.3
C2—C1—S2	121.0 (3)	S6—C8A—H8D	108.3
S1—C1—S2	115.4 (2)	H8C—C8A—H8D	107.4
C1—C2—S4	121.6 (3)	O1—C9—N1	124.7 (4)
C1—C2—S3	122.5 (3)	O1—C9—C6	117.7 (3)
S4—C2—S3	115.8 (2)	N1—C9—C6	117.6 (3)
C4—C3—S1	117.6 (3)	N1—C10—H10A	109.5
C4—C3—S5	127.5 (3)	N1—C10—H10B	109.5
S1—C3—S5	114.9 (2)	H10A—C10—H10B	109.5
C3—C4—S6	129.6 (3)	N1—C10—H10C	109.5
C3—C4—S2	115.8 (3)	H10A—C10—H10C	109.5
S6—C4—S2	114.64 (19)	H10B—C10—H10C	109.5
C6—C5—S3	118.0 (3)	C9—N1—C10	121.3 (3)
C6—C5—H5	121.0	C9—N1—H1	119.4
S3—C5—H5	121.0	C10—N1—H1	119.4
C5—C6—C9	131.2 (3)	C9—O1—K1	165.8 (3)
C5—C6—S4	116.4 (3)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C7A—H7C···N1^i	0.97	2.63	3.45 (2)	142
C8—H8B···N2A^iii	0.97	2.71	3.539 (9)	144
N1—H1···N2A^iv	0.86	2.10	2.938 (5)	165
C5—H5···N2A^iv	0.93	2.41	3.298 (5)	160

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