Pyridine–pyridine π–π stacking interactions in penta­carbonyl­[pyridine-4(1H)-thione]­tungsten(0)

In the title compound, [W(C₅H₅NS)(CO)₅], the pyridine-4-thiol ligand coordinates through the sulfur in the thione mode. The coordination sphere around the W atom is distorted from octahedral geometry by intermolecular hydrogen bonding and steric interactions between the pyridine ring and two CO ligands. An intermolecular pyridine–pyridine ring distance of 3.47 (1) Å indicates π–π stacking interactions between these ligand units.

S1. Comment

Pyridine-4-thiol has been widely used as a ligand in transition metal complexes where it can act as a monodentate ligand to one metal or a bridging ligand to two metals (Bajaj et al., 1998; Coe et al., 1998; Maekawa et al., 1998; Paw et al., 1998). It exists mainly as the pyridine-4-thione tautomer in solution (Etter et al., 1992). Recently, pyridine-4-thiol attracted considerable attention because of its relevance as an electron promoter in the redox chemistry of cytochrome c (Hinner & Niki, 1989) and also because of its self-assembly as monolayers on gold electrodes (Zhong et al., 1999). Although X-ray structural studies of pyridine-4-thione in the [RuCl(pdma)₂(pyridine-4-thione)](PF₆) [pdma = o-phenylenebis(dimethylarsine)] (Coe et al., 1998) and [Pd₂(µ-dppm)₂(pyridine-4-thione)](ClO₄)₂, (dppm = diphenylphoshinomethane) (Maekawa et al., 1998) complexes have been previously reported, neither compound exhibits hydrogen bonding or π-π pyridine interactions as occurs in (CO)₅W(pyridine-4-thione), (I), as described herein. \sch

The molecular structure (Fig. 1) of (I) shows that the S atom of a pyridine-4-thione ligand is coordinated to the tungsten. The W—S bond length 2.557 (2) Å is similar to the W—S distances observed in the W(CO)₅(2-thiouracilate) anion [2.533 (3) Å] (Darensbourg et al., 1999) and in W(CO)₅(pyridine-2-thione) [2.568 (2) Å] (Broomhead et al., 1986). The geometry about W is distorted octahedral with a S—W—C11 angle of 171.5 (1)°. This distortion appears to be due to steric repulsion between the pyridine ring and two CO ligands, as well as hydrogen bonding between the pyridium N—H and the O11 atom of an adjacent molecule. Figure 2 depicts a ball-and-stick representation of the hydrogen-bonding motif. It is interesting that the hydrogen bonding exhibited by W(CO)₅(pyridine-2-thione) is of a different type (N—H···S bonds forming a cyclic dimer) than that seen in W(CO)₅(pyridine-4-thione); however, the two crystals do have the same space group and similar cell constants.

The intermolecular hydrogen-bonding distance of N—H···O11 [symmetry code: −1 + x, 3/2 − y, −1/2 + z] is 2.15 (1) Å, the N—H—O11 angle is 158°, and the N···O1 distance is 2.983 (5) Å. This hydrogen bonding increases the C11—W—C13 [92.8 (2)°] angle and decreases the C11—W—C14 [86.7 (1)°] angle. In the pyridine-4-thione ligand, the C—S bond distance [1.719 (4) Å] suggests considerable double-bond character. Mean C—S bond lengths in thiol and thione crystal structures from the Cambridge Structural Database are 1.81 (2) and 1.66 (4) Å, respectively (Etter et al., 1992). It is also noteworthy that the C4—S distance [1.719 (4) Å] is longer than that of free pyridine-4-thione ligand [1.703 (2) Å] which indicates a decrease in C—S π bonding upon complexation.

The pyridine ring, which approximately bisects two CO ligands, is nearly planar with an average standard deviation from planarity of the ring atoms of 0.01 Å. The S atom is in the pyridine ring plane. The C4—S—W angle is 117.9 (2)°, which suggests sp² hybridization of the S atom. The angle between the W—S vector and the pyridine ring plane is 8(1)°. The C2—N—C6 angle of 121.5 (4)° is larger than that of the corresponding bond angles in di-2-pyridyl disulfide which range from 116 to 119° (Raghavan & Seff, 1977). This widening of the C2—N—C6 angle is attributed to the presence of the proton on the N atom. The corresponding angle in pyridine hydrochloride is 128° (Rérat, 1962). Singh proposed the empirical rule that the angle at a protonated N atom in a six-membered ring will fall within the range 125 (3)°, while the angle at an unprotonated nitrogen is 116 (3)° (Singh, 1965). The C3—C4 [1.397 (6) Å] and C4—C5 [1.417 (6) Å] carbon-carbon lengths of the ring are slightly longer than those of C2—C3 [1.378 (6) Å] and C5—C6 [1.351 (6) Å]; this difference in C—C bond lengths is not as pronounced as in free pyridine-4-thione (Etter et al., 1992): 1.419 (3), 1.419 (3) versus 1.375 (3), 1.368 (3) Å. The C—N bond lengths [1.334 (6) and 1.352 (6) Å] are similar to those [1.346 (3) Å] in free pyridine-4-thione (Etter et al., 1992). These distances in (I) are consistent with some localized single and double bonding, but there is considerable delocalization in the pyridine ring, more than is found in free pyridine-4-thione. The overall structure of the pyridine-4-thione moiety in (I) is similar to that found in the free ligand and in its other complexes (Coe et al., 1997; Maekawa et al., 1998).

In the W(CO)₅ moiety, the W—C11 bond [1.945 (5) Å] is shorter than the W—CO bonds to the four equatorial CO groups which have an average W—C bond length of 2.044 (5) Å. The short W—C11 bond is due to increased π-back bonding from the W to the CO trans to the S atom.

An examination of the packing diagram in Fig. 2 shows an intermolecular pyridine-pyridine ring distance of 3.47 (1) Å indicative of π-π stacking interactions. The π-π stacking interactions are stronger than those of W(CO)₅(pyridine-2-thione), in which the intermolecular pyridine-pyridine ring distance is 3.64 (1) Å (Broomhead et al., 1986). Also important to the crystal packing are the N—H···O hydrogen bonds which give rise to hydrogen-bonded chains of c glide related molecules. The chains are related to one another by inversion centers. Thus, N—H···O hydrogen bonding and pyridine-pyridine π-π interactions dominate the crystal packing in the structure.

S2. Experimental

The title compound was synthesized by substitution of the weakly coordinated THF (THF = tetrahydrofuran) ligand with pyridine-4-thiol. A yellow solution of W(CO)₅(THF) was prepared (Choi & Angelici, 1991) by photolysis (450 W A ce-Hanovia lamp) of W(CO)₆ (500 mg, 1.42 mmol) in THF (40 ml). Addition of pyridine-4-thiol (150 mg, 1.35 mmol) to the W(CO)₅(THF) solution causes the color to change from yellow to orange. The resulting orange solution was stirred for 2 h at room temperature and then evaporated under vacuum. The residue was dissolved in CH₂Cl₂ and chromatographed on a neutral alumina column (1 x 15 cm). The yellow-orange fraction was collected and concentrated under vacuum to give orange microcrystals of (I) (382 mg, 65% yield). Crystals were obtained by layering hexanes onto a solution of (I) in CH₂Cl₂ at 253 K. Analysis calculated for C₁₀H₅O₅NSW: C 27.61, H 1.16, N 3.13%. Found: C 27.86, H 1.18, N 3.17%. ¹H NMR (CDCl₃): 7.47 (br.t, 2,6H), 7.71 (d, 3,5H), 9.4 (br.s, NH) p.p.m.

S3. Refinement

H atoms were added at calculated positions and refined using a riding model. Anisotropic displacement parameters were used for all non-H atoms. Except for some residual density in the region of W (deepest hole −1.36 e Å⁻³ at 0.79 Å from W), the final difference map showed no significant features.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SMART; data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL.

Figures

	Fig. 1. The structure of (I) showing 50% probability displacement ellipsoids and the atomic numbering scheme.
	Fig. 2. The molecular packing diagram of (I).

Pentacarbonyl(pyridine-4-thione)tungsten (0)

Crystal data

[W(C5H5NS)(CO)5]	F(000) = 808
Mr = 435.06	Dx = 2.317 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.2267 (6) Å	Cell parameters from 2167 reflections
b = 13.2561 (11) Å	θ = 2–26°
c = 13.1906 (11) Å	µ = 9.44 mm^−1
β = 99.189 (1)°	T = 173 K
V = 1247.41 (18) Å^3	Block, orange
Z = 4	0.28 × 0.16 × 0.16 mm

Data collection

Siemens SMART CCD diffractometer	2537 independent reflections
Radiation source: fine-focus sealed tube	2167 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ϕ scans and ω scans	θmax = 26.4°, θmin = 2.2°
Absorption correction: empirical (using intensity measurements) (SADABS; Siemens, 1995)	h = −9→9
Tmin = 0.12, Tmax = 0.22	k = −16→16
9890 measured reflections	l = −16→16

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)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.054	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0283P)^2] where P = (Fo^2 + 2Fc^2)/3
2537 reflections	(Δ/σ)max = 0.001
163 parameters	Δρmax = 0.45 e Å^−3
0 restraints	Δρmin = −1.36 e Å^−3

Special details

Experimental. Data were collected over a hemisphere of reciprocal space, by a combination of three sets of exposures; each set had a different phi angle for the crystal and each exposure of 10 s covered 0.4 in ω. The crystal to detector distance was 5 cm. In each case a total of 450 frames was collected. The crystal showed no significant decay. Only reflections with 2θ less than 53° were used for the structure refinement. The structure was solved by direct methods and refined by full matrix least-squares.

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
W1	0.42778 (2)	0.688411 (13)	0.588425 (13)	0.02055 (7)
S1	0.42336 (16)	0.85552 (9)	0.49131 (10)	0.0291 (3)
O11	0.5072 (4)	0.4847 (2)	0.7058 (2)	0.0291 (8)
C14	0.6618 (7)	0.6563 (4)	0.5250 (4)	0.0260 (10)
C4	0.2103 (6)	0.9008 (3)	0.4323 (3)	0.0216 (9)
C5	0.2124 (6)	0.9863 (3)	0.3681 (3)	0.0229 (10)
H5	0.3286	1.0160	0.3596	0.027*
C6	0.0503 (7)	1.0259 (4)	0.3189 (4)	0.0300 (11)
H6	0.0532	1.0823	0.2748	0.036*
C11	0.4711 (6)	0.5608 (4)	0.6612 (3)	0.0220 (9)
N1	−0.1159 (5)	0.9855 (3)	0.3321 (3)	0.0301 (9)
H1	−0.2203	1.0119	0.2992	0.036*
O14	0.7953 (5)	0.6357 (3)	0.4938 (3)	0.0423 (9)
C12	0.2037 (7)	0.7137 (4)	0.6605 (4)	0.0322 (12)
C2	−0.1255 (6)	0.9066 (4)	0.3938 (4)	0.0302 (11)
H2	−0.2444	0.8810	0.4030	0.036*
C3	0.0354 (6)	0.8619 (4)	0.4442 (3)	0.0243 (10)
H3	0.0274	0.8049	0.4870	0.029*
O12	0.0808 (5)	0.7251 (3)	0.7046 (3)	0.0511 (11)
O13	0.1651 (5)	0.5860 (3)	0.3997 (3)	0.0491 (11)
C13	0.2561 (7)	0.6229 (4)	0.4661 (4)	0.0289 (11)
C15	0.5977 (7)	0.7562 (3)	0.7066 (4)	0.0282 (11)
O15	0.6954 (5)	0.7902 (3)	0.7760 (3)	0.0420 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
W1	0.02056 (11)	0.02194 (11)	0.01846 (11)	0.00169 (8)	0.00106 (7)	0.00101 (8)
S1	0.0199 (6)	0.0290 (6)	0.0371 (7)	−0.0003 (5)	0.0006 (5)	0.0120 (6)
O11	0.0246 (17)	0.0263 (18)	0.035 (2)	−0.0001 (14)	0.0010 (15)	0.0050 (16)
C14	0.027 (3)	0.026 (2)	0.024 (3)	0.000 (2)	0.001 (2)	0.007 (2)
C4	0.022 (2)	0.027 (2)	0.014 (2)	−0.0009 (19)	−0.0010 (18)	−0.0050 (18)
C5	0.022 (2)	0.024 (2)	0.021 (2)	−0.0020 (18)	−0.0009 (18)	0.0012 (19)
C6	0.033 (3)	0.029 (3)	0.026 (3)	0.000 (2)	−0.001 (2)	0.001 (2)
C11	0.016 (2)	0.030 (3)	0.020 (2)	−0.0013 (19)	0.0026 (17)	−0.005 (2)
N1	0.021 (2)	0.035 (2)	0.030 (2)	0.0045 (17)	−0.0102 (17)	−0.0015 (19)
O14	0.031 (2)	0.053 (2)	0.047 (2)	0.0085 (18)	0.0152 (18)	0.007 (2)
C12	0.035 (3)	0.033 (3)	0.029 (3)	0.009 (2)	0.005 (2)	0.006 (2)
C2	0.022 (2)	0.033 (3)	0.034 (3)	−0.005 (2)	0.000 (2)	−0.003 (2)
C3	0.025 (2)	0.027 (3)	0.020 (2)	−0.005 (2)	0.0045 (19)	0.001 (2)
O12	0.049 (2)	0.067 (3)	0.042 (2)	0.027 (2)	0.024 (2)	0.016 (2)
O13	0.039 (2)	0.066 (3)	0.038 (2)	0.003 (2)	−0.0087 (18)	−0.024 (2)
C13	0.028 (3)	0.030 (3)	0.029 (3)	0.006 (2)	0.005 (2)	0.000 (2)
C15	0.029 (3)	0.023 (3)	0.032 (3)	0.004 (2)	0.000 (2)	0.005 (2)
O15	0.049 (2)	0.039 (2)	0.034 (2)	0.0004 (18)	−0.0048 (18)	−0.0056 (17)

Geometric parameters (Å, º)

W1—S1	2.5566 (12)	C2—C3	1.378 (6)
W1—C11	1.945 (5)	C3—C4	1.397 (6)
W1—C12	2.033 (5)	C4—C5	1.417 (6)
W1—C13	2.063 (5)	C5—C6	1.351 (6)
W1—C14	2.048 (5)	N1—C2	1.334 (6)
W1—C15	2.033 (5)	N1—C6	1.352 (6)
S1—C4	1.719 (4)	C5—H5	0.9500
C11—O11	1.176 (5)	C6—H6	0.9500
C12—O12	1.146 (6)	N1—H1	0.8800
C13—O13	1.121 (6)	C2—H2	0.9500
C14—O14	1.140 (5)	C3—H3	0.9500
C15—O15	1.154 (6)
S1—W1—C11	171.40 (12)	C5—C4—S1	117.1 (3)
S1—W1—C12	98.29 (14)	C6—C5—C4	120.4 (4)
S1—W1—C13	90.86 (14)	C6—C5—H5	119.8
S1—W1—C14	85.45 (13)	C4—C5—H5	119.8
S1—W1—C15	87.66 (13)	C5—C6—N1	120.3 (4)
C4—S1—W1	117.91 (16)	C5—C6—H6	119.8
C11—W1—C12	89.44 (18)	N1—C6—H6	119.8
C11—W1—C13	92.84 (18)	O11—C11—W1	176.5 (3)
C11—W1—C14	86.69 (17)	C2—N1—H1	119.2
C11—W1—C15	88.60 (18)	C6—N1—H1	119.2
C2—N1—C6	121.5 (4)	O12—C12—W1	176.9 (4)
C12—W1—C15	89.8 (2)	N1—C2—C3	120.6 (4)
C12—W1—C14	175.68 (18)	N1—C2—H2	119.7
C15—W1—C14	88.17 (19)	C3—C2—H2	119.7
C12—W1—C13	90.6 (2)	C2—C3—C4	119.7 (4)
C15—W1—C13	178.50 (18)	C2—C3—H3	120.1
C14—W1—C13	91.48 (19)	C4—C3—H3	120.1
O14—C14—W1	176.7 (4)	O13—C13—W1	178.7 (4)
C3—C4—C5	117.3 (4)	O15—C15—W1	176.7 (4)
C3—C4—S1	125.6 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O11^i	0.88	2.15	2.983 (5)	158

Symmetry code: (i) x−1, −y+3/2, z−1/2.