trans-(2-Acetylpyridine-κ²N,O)dichlorobis(dimethyl sulfoxide-κS)ruthenium(II)

In the title complex, [RuCl₂(C₇H₇NO)(C₂H₆OS)₂], the metal ion is at the centre of a distorted octahedral NOCl₂S₂ coordination sphere. The neutral 2-acetyl­pyridine ligand binds to the metal ion through the pyridine N and carbonyl O atoms, forming a five-membered chelate ring. The monodentate S-coordinating di­methyl sulfoxide mol­ecules are mutually cis, and the two remaining positions in the coordination sphere are occupied by two mutually trans Cl⁻ ions.

S1. Comment

Dimethyl sulfoxide (dmso) is an ambidentate ligand, in that it can bind a metal ion via the O or the S atom. Interest in complexes with this ligand is primarily directed towards gaining an understanding of the nature of the bond between the metal and the coordinating atom (Calligaris & Carugo, 1996; Sano & Taube, 1994). In general, coordination via O is preferred by harder high-valent metal ions, while S-coordination is favoured by softer low-valent ones. Although dmso-containing ruthenium complexes have been known for some time (Evans et al., 1973), the recent discovery of anticancer activity (Smith et al., 1996) displayed by haloruthenium(sulfoxide) species has revived interest in such complexes (Rack & Gray, 1999; Cingi et al., 2000) and prompted further scrutiny of the bonding of dmso to Ru. Here, we report the synthesis, characterization data and molecular structure of a relevant new complex, [RuCl₂(apy)(dmso)₂], (I), containing 2-acetylpyridine (apy) as the ancillary ligand. \sch

The molecular structure of (I) is depicted in Fig. 1. The bond parameters associated with the Ru^II centre indicate a distorted octahedral NOCl₂S₂ coordination sphere around the metal ion. The two S-coordinated dmso molecules and the two Cl^- ions in the coordination sphere are found to be cis and trans pairs, respectively. The two remaining cis sites are occupied by the chelating N,O-donor 2-acetylpyridine, with a chelate bite angle of 76.59 (13)°.

The Ru—O [2.084 (3) Å] and Ru—N [2.122 (3) Å] bond lengths in (I) are similar to those of known Ru^II to keto-O (Basuli et al., 2000) and pyridine-N bonds (Bellachioma et al., 1998; Sengupta et al., 2001). The Ru—Cl distances of 2.3753 (16) and 2.3977 (16) Å are unexceptional (Cingi et al., 2000; Alessio et al., 2000).

The Cl1—Ru—Cl2 bond angle of 173.35 (4)° deviates noticeably from the ideal value of 180°. The deviation of the S1—Ru—S2 bond angle [94.98 (6)°] from 90° is most probably due to the steric repulsion between the dmso molecules, with the larger angle being accommodated by the small chelate angle of apy.

The Ru—S bond lengths are significantly different: Ru—S1 2.2520 (15) and Ru—S2 2.225 (2) Å. The longer value is possibly the consequence of the better trans-directing ability of the pyridine N atom compared with that of the keto O atom. However, in the coordinated dmso molecules of (I), the corresponding S—O bond lengths [1.472 (3) and 1.461 (4) Å] are comparable. In general, the Ru—S and S—O bond lengths in (I) are well within the range reported for other Ru^II complexes containing S-coordinated dmso (Alessio et al., 1988, 2000; Cingi et al., 2000).

S2. Experimental

A mixture of trans-[Ru(dmso)₄Cl₂] (200 mg, 0.41 mmol) and 2-acetylpyridine (0.14 ml, 1.25 mmol) in methanol (30 ml) was refluxed for 8 h. The clear purple reaction mixture was evaporated to dryness. The dark solid obtained was dissolved in a minimum volume of dichloromethane, followed by the addition of excess hexane. The complex which precipitated was collected by filtration. Purification was performed on a neutral alumina Query column. The first purple band was eluted with a dichloromethane-methanol (50:1) mixture. This eluent Query was collected and evaporated to dryness. The yield of the title complex, (I), thus obtained was 60 mg (32%). Single crystals of (I) were grown by slow evaporation of a dichloromethane-hexane (1:1) solution. Analysis: calculated for C₁₁H₁₉NO₃Cl₂S₂Ru: C 29.40, H 4.26, N 3.12%; found: C 29.17, H 4.39, N 2.91%; selected IR bands (cm^-1): 3017 (m), 1591 (w), 1561 (w), 1410 (m), 1371 (m), 1329 (m), 1310 (m), 1254 (m), 1175 (w), 1092 (s), 1045 (w), 1011 (s), 974 (m), 918 (w), 789 (s), 719 (m), 681 (s), 637 (w), 600 (w), 426 (s); electronic spectroscopic data in CH₂Cl₂ (nm, dm³ mol^-1 cm^-1): 537 (2140), 341 (1410), 282 (6970); ¹H NMR (200 MHz, CDCl₃, δ, p.p.m.): 3.06 [s, 3H, C(CH₃)], 3.53 [s, 6H, S(CH₃)₂], 3.55 [s, 6H, S(CH₃)₂], 7.83 (t, 1H), 8.07 (t, 1H), 8.26 (d, 1H), 10.56 (d, 1H); cyclic voltammetric data (versus Fc⁺/Fc) at a Pt electrode in CH₂Cl₂ (E_1/2/V, ΔE_p/mV): 0.69 (260), -1.53 (140).

S3. Refinement

The H atoms of the methyl groups were located from difference Fourier syntheses and refined as part of rigid rotating groups, with C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C). The remaining aromatic H atoms were placed geometrically and refined using a riding model, with C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: WinGX (Farrugia, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEX6a (McArdle, 1995); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular structure of (I) with the atom-numbering scheme. Displacement ellipsoids are drawn at the 40% probability level and H atoms are shown as small spheres of arbitrary radii.

trans-(2-Acetylpyridine-κ²N,O)dichlorobis(dimethyl sulfoxide-κS)ruthenium(II)

Crystal data

[Ru(C7H7NO)(C2H6OS)2Cl2]	Z = 2
Mr = 449.36	F(000) = 452
Triclinic, P1	Dx = 1.738 Mg m^−3
a = 8.177 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.214 (3) Å	Cell parameters from 25 reflections
c = 14.456 (6) Å	θ = 9.6–10.7°
α = 84.69 (3)°	µ = 1.47 mm^−1
β = 81.13 (4)°	T = 298 K
γ = 63.53 (5)°	Rectangular block, dark brown
V = 858.6 (7) Å^3	0.48 × 0.44 × 0.28 mm

Data collection

Enraf-Nonius MACH-3 four-circle diffractometer	3300 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.003
Graphite monochromator	θmax = 27.5°, θmin = 1.4°
ω scans	h = 0→10
Absorption correction: ψ scan (WinGX; Farrugia, 1999)	k = −9→10
Tmin = 0.386, Tmax = 0.662	l = −18→18
4006 measured reflections	3 standard reflections every 90 min
3934 independent reflections	intensity decay: none

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.118	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.071P)^2 + 1.433P] where P = (Fo^2 + 2Fc^2)/3
3934 reflections	(Δ/σ)max = 0.001
186 parameters	Δρmax = 1.22 e Å^−3
0 restraints	Δρmin = −0.91 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
Ru	0.31554 (4)	0.33029 (4)	0.25515 (2)	0.02843 (12)
Cl1	0.50587 (19)	0.47984 (17)	0.20563 (10)	0.0535 (3)
Cl2	0.12909 (17)	0.18202 (17)	0.32330 (8)	0.0465 (3)
S1	0.17551 (16)	0.41105 (15)	0.12458 (7)	0.0378 (2)
S2	0.53627 (15)	0.06717 (14)	0.20067 (7)	0.0370 (2)
O1	0.1159 (4)	0.5782 (4)	0.3084 (2)	0.0390 (7)
N1	0.3801 (5)	0.3254 (4)	0.3923 (2)	0.0324 (7)
O3	0.6682 (5)	−0.0469 (5)	0.2643 (3)	0.0580 (10)
O2	0.2271 (6)	0.2893 (5)	0.0457 (2)	0.0583 (10)
C1	0.5106 (6)	0.1945 (6)	0.4364 (3)	0.0407 (10)
H1	0.5940	0.0917	0.4034	0.049*
C2	0.5280 (7)	0.2040 (6)	0.5288 (3)	0.0451 (11)
H2	0.6216	0.1089	0.5569	0.054*
C3	0.4089 (7)	0.3515 (7)	0.5786 (3)	0.0464 (11)
H3	0.4178	0.3585	0.6414	0.056*
C4	0.2733 (7)	0.4921 (6)	0.5340 (3)	0.0409 (10)
H4	0.1906	0.5963	0.5661	0.049*
C5	0.2629 (6)	0.4749 (5)	0.4411 (3)	0.0331 (8)
C6	0.1235 (6)	0.6139 (6)	0.3878 (3)	0.0348 (8)
C7	−0.0035 (7)	0.7959 (6)	0.4244 (3)	0.0474 (11)
H7A	0.0660	0.8595	0.4345	0.071*
H7B	−0.0718	0.7829	0.4825	0.071*
H7C	−0.0873	0.8635	0.3799	0.071*
C8	0.1775 (12)	0.6157 (8)	0.0752 (5)	0.081 (2)
H8A	0.3019	0.5948	0.0530	0.122*
H8B	0.1261	0.7071	0.1220	0.122*
H8C	0.1055	0.6563	0.0239	0.122*
C9	−0.0629 (7)	0.4888 (11)	0.1579 (4)	0.0729 (19)
H9A	−0.1264	0.5379	0.1039	0.109*
H9B	−0.1050	0.5817	0.2034	0.109*
H9C	−0.0874	0.3893	0.1846	0.109*
C10	0.6662 (8)	0.0939 (8)	0.0948 (4)	0.0610 (15)
H10A	0.7376	0.1540	0.1072	0.092*
H10B	0.5841	0.1657	0.0503	0.092*
H10C	0.7472	−0.0234	0.0696	0.092*
C11	0.4511 (8)	−0.0738 (6)	0.1603 (4)	0.0538 (13)
H11A	0.5516	−0.1768	0.1299	0.081*
H11B	0.3655	−0.0060	0.1166	0.081*
H11C	0.3898	−0.1151	0.2124	0.081*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ru	0.03304 (18)	0.02725 (17)	0.02383 (17)	−0.01049 (13)	−0.00832 (12)	−0.00178 (11)
Cl1	0.0623 (8)	0.0494 (6)	0.0621 (8)	−0.0359 (6)	−0.0107 (6)	0.0003 (6)
Cl2	0.0461 (6)	0.0539 (7)	0.0416 (6)	−0.0253 (5)	−0.0023 (5)	0.0003 (5)
S1	0.0436 (6)	0.0367 (5)	0.0284 (5)	−0.0110 (5)	−0.0127 (4)	−0.0002 (4)
S2	0.0399 (6)	0.0304 (5)	0.0336 (5)	−0.0081 (4)	−0.0056 (4)	−0.0050 (4)
O1	0.0384 (16)	0.0295 (14)	0.0373 (16)	−0.0008 (12)	−0.0140 (13)	−0.0044 (12)
N1	0.0348 (17)	0.0314 (16)	0.0292 (16)	−0.0106 (14)	−0.0106 (14)	−0.0023 (13)
O3	0.056 (2)	0.0433 (19)	0.053 (2)	0.0021 (17)	−0.0166 (17)	−0.0099 (16)
O2	0.073 (2)	0.0497 (19)	0.0339 (17)	−0.0038 (18)	−0.0203 (17)	−0.0117 (14)
C1	0.046 (2)	0.034 (2)	0.038 (2)	−0.0097 (19)	−0.0175 (19)	−0.0053 (17)
C2	0.055 (3)	0.043 (2)	0.039 (2)	−0.018 (2)	−0.024 (2)	0.0058 (19)
C3	0.064 (3)	0.058 (3)	0.028 (2)	−0.034 (3)	−0.019 (2)	0.0035 (19)
C4	0.050 (3)	0.043 (2)	0.032 (2)	−0.021 (2)	−0.0054 (18)	−0.0082 (17)
C5	0.033 (2)	0.0311 (19)	0.034 (2)	−0.0118 (17)	−0.0079 (16)	−0.0019 (15)
C6	0.034 (2)	0.033 (2)	0.035 (2)	−0.0122 (17)	−0.0061 (17)	−0.0037 (16)
C7	0.050 (3)	0.036 (2)	0.044 (3)	−0.006 (2)	−0.009 (2)	−0.0082 (19)
C8	0.127 (6)	0.057 (3)	0.076 (4)	−0.047 (4)	−0.056 (4)	0.036 (3)
C9	0.038 (3)	0.112 (5)	0.051 (3)	−0.012 (3)	−0.019 (2)	−0.006 (3)
C10	0.058 (3)	0.055 (3)	0.054 (3)	−0.016 (3)	0.016 (3)	−0.010 (2)
C11	0.071 (4)	0.034 (2)	0.056 (3)	−0.019 (2)	−0.014 (3)	−0.010 (2)

Geometric parameters (Å, º)

Ru—O1	2.084 (3)	C3—H3	0.9300
Ru—N1	2.122 (3)	C4—C5	1.384 (6)
Ru—S1	2.2520 (15)	C4—H4	0.9300
Ru—S2	2.225 (2)	C5—C6	1.464 (6)
Ru—Cl1	2.3753 (16)	C6—C7	1.478 (6)
Ru—Cl2	2.3977 (16)	C7—H7A	0.9600
S2—O3	1.461 (4)	C7—H7B	0.9600
S2—C11	1.771 (5)	C7—H7C	0.9600
S2—C10	1.779 (5)	C8—H8A	0.9600
S1—O2	1.472 (3)	C8—H8B	0.9600
S1—C9	1.760 (6)	C8—H8C	0.9600
S1—C8	1.771 (6)	C9—H9A	0.9600
O1—C6	1.228 (5)	C9—H9B	0.9600
N1—C1	1.327 (5)	C9—H9C	0.9600
N1—C5	1.351 (5)	C10—H10A	0.9600
C1—C2	1.378 (6)	C10—H10B	0.9600
C1—H1	0.9300	C10—H10C	0.9600
C2—C3	1.353 (7)	C11—H11A	0.9600
C2—H2	0.9300	C11—H11B	0.9600
C3—C4	1.386 (7)	C11—H11C	0.9600
O1—Ru—N1	76.59 (13)	C5—C4—C3	118.9 (4)
O1—Ru—S1	86.62 (10)	C5—C4—H4	120.5
O1—Ru—S2	177.91 (9)	C3—C4—H4	120.5
O1—Ru—Cl1	87.16 (11)	N1—C5—C4	122.3 (4)
O1—Ru—Cl2	90.69 (11)	N1—C5—C6	114.4 (4)
N1—Ru—S1	163.12 (10)	C4—C5—C6	123.4 (4)
N1—Ru—S2	101.85 (11)	O1—C6—C5	118.1 (4)
N1—Ru—Cl1	87.05 (10)	O1—C6—C7	119.1 (4)
N1—Ru—Cl2	86.33 (10)	C5—C6—C7	122.9 (4)
S1—Ru—S2	94.98 (6)	C6—C7—H7A	109.5
S1—Ru—Cl1	93.94 (6)	C6—C7—H7B	109.5
S1—Ru—Cl2	92.21 (6)	H7A—C7—H7B	109.5
S2—Ru—Cl1	91.38 (6)	C6—C7—H7C	109.5
S2—Ru—Cl2	90.60 (6)	H7A—C7—H7C	109.5
Cl1—Ru—Cl2	173.35 (4)	H7B—C7—H7C	109.5
O3—S2—C11	106.0 (2)	S1—C8—H8A	109.5
O3—S2—C10	107.0 (3)	S1—C8—H8B	109.5
C11—S2—C10	99.1 (3)	H8A—C8—H8B	109.5
O3—S2—Ru	116.79 (15)	S1—C8—H8C	109.5
C11—S2—Ru	113.4 (2)	H8A—C8—H8C	109.5
C10—S2—Ru	112.85 (19)	H8B—C8—H8C	109.5
O2—S1—C9	107.0 (3)	S1—C9—H9A	109.5
O2—S1—C8	105.9 (3)	S1—C9—H9B	109.5
C9—S1—C8	99.4 (4)	H9A—C9—H9B	109.5
O2—S1—Ru	123.42 (16)	S1—C9—H9C	109.5
C9—S1—Ru	108.3 (2)	H9A—C9—H9C	109.5
C8—S1—Ru	110.2 (2)	H9B—C9—H9C	109.5
C6—O1—Ru	117.4 (3)	S2—C10—H10A	109.5
C1—N1—C5	117.5 (4)	S2—C10—H10B	109.5
C1—N1—Ru	129.1 (3)	H10A—C10—H10B	109.5
C5—N1—Ru	113.3 (3)	S2—C10—H10C	109.5
N1—C1—C2	122.9 (4)	H10A—C10—H10C	109.5
N1—C1—H1	118.6	H10B—C10—H10C	109.5
C2—C1—H1	118.6	S2—C11—H11A	109.5
C3—C2—C1	120.0 (4)	S2—C11—H11B	109.5
C3—C2—H2	120.0	H11A—C11—H11B	109.5
C1—C2—H2	120.0	S2—C11—H11C	109.5
C2—C3—C4	118.5 (4)	H11A—C11—H11C	109.5
C2—C3—H3	120.8	H11B—C11—H11C	109.5
C4—C3—H3	120.8