(OC-6-35)-(2,2′-Bipyridine-κ2 N,N′)dimeth­yl(3-sulfido­propionato-κ2 S,O)platinum(IV)

Matthew S McCready; Richard J Puddephatt

doi:10.1107/S1600536811013626

. 2011 Apr 16;67(Pt 5):m604–m605. doi: 10.1107/S1600536811013626

(OC-6-35)-(2,2′-Bipyridine-κ² N,N′)dimethyl(3-sulfidopropionato-κ² S,O)platinum(IV)

Matthew S McCready ^a, Richard J Puddephatt ^a,^*

PMCID: PMC3089277 PMID: 21754323

Abstract

The title complex, [Pt(CH₃)₂(SCH₂CH₂CO₂)(C₁₀H₈N₂)], is formed by the unusual oxidative addition of the disulfide, R ₂S₂ (R = CH₂CH₂CO₂H), to (2,2′-bipyridine)dimethylplatinum(II) with elimination of RSH. The product contains an unusual six-membered thiolate–carboxylate chelate ring. This slightly distorted octahedral complex exhibits cis angles ranging from 77.55 (11) to 97.30 (8)° due to the presence of the thiolate–carboxylate chelate ring and the constrained bipyridine group. The crystal packing appears to be controlled by a combination of π-stacking [centroid–centroid distance = 3.611 (2) Å] and C—H⋯O interactions.

Related literature

For general background to metal complexes with thiolate–carboxylate chelates, see: Henderson et al. (2000 ▶); McCready & Puddephatt (2011 ▶); Phillips & Burford (2008 ▶). For the utility and application of disulfides and their reactivity towards transition metals, see: Aye et al. (1993 ▶); Bonnington et al. (2008 ▶); Wei et al. (2005 ▶). For normal ranges of bond angles at platinum(IV) between cis ligands, see: Achar et al. (1993 ▶); Aye et al. (1988 ▶). For interplanar spacing between bipyridine rings in platinum(IV) complexes of 2,2′-bipyridine, see: Au et al. (2009 ▶). For the preparation of dimethyl(2,2′-bipyridine)platinum(II), see: Monaghan & Puddephatt (1984 ▶).

Experimental

Crystal data

[Pt(CH₃)₂(C₃H₄O₂S)(C₁₀H₈N₂)]
M _r = 485.46
Monoclinic,
a = 14.0759 (6) Å
b = 7.7487 (3) Å
c = 14.2306 (5) Å
β = 98.978 (2)°
V = 1533.11 (10) Å³
Z = 4
Mo Kα radiation
μ = 9.29 mm⁻¹
T = 150 K
0.04 × 0.04 × 0.02 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2006 ▶) T _min = 0.708, T _max = 0.858
52534 measured reflections
4672 independent reflections
3735 reflections with I > 2σ(I)
R _int = 0.074

Refinement

R[F ² > 2σ(F ²)] = 0.026
wR(F ²) = 0.049
S = 1.04
4672 reflections
192 parameters
H-atom parameters constrained
Δρ_max = 0.92 e Å⁻³
Δρ_min = −1.42 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811013626/tk2735sup1.cif

e-67-0m604-sup1.cif^{(19.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811013626/tk2735Isup2.hkl

e-67-0m604-Isup2.hkl^{(228.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected geometric parameters (Å, °).

Pt1—C15	2.046 (4)
Pt1—C14	2.048 (4)
Pt1—N1	2.107 (3)
Pt1—O2	2.143 (3)
Pt1—N2	2.149 (3)
Pt1—S1	2.2916 (9)

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C15—Pt1—C14	87.88 (17)
C15—Pt1—N1	96.54 (14)
C14—Pt1—N1	90.17 (13)
C15—Pt1—O2	92.60 (15)
N1—Pt1—O2	86.39 (11)
C14—Pt1—N2	92.92 (14)
N1—Pt1—N2	77.55 (11)
O2—Pt1—N2	86.26 (11)
C15—Pt1—S1	88.64 (12)
C14—Pt1—S1	87.34 (11)
N1—Pt1—S1	174.16 (9)
O2—Pt1—S1	96.09 (7)
N2—Pt1—S1	97.30 (8)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C10—H10⋯O2ⁱ	0.95	2.33	3.175 (5)	148

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Symmetry code: (i) Inline graphic .

Acknowledgments

We would like to thank the NSERC (Canada) for financial support.

supplementary crystallographic information

Comment

Activation of the S—S bond of a disulfide, R₂S₂, has shown significant promise in the areas of medicinal chemistry and catalysis when cleaved by a transition metal complex (Wei et al., 2005). One route of interest for the activation of an S—S bond is the oxidative addition to a transition metal complex, of which there have been many studies involving platinum(II) complexes (Aye et al., 1993; Bonnington et al., 2008). Unexpectedly, the oxidative addition of 3,3'-dithiodipropionic acid led to the formation of a thiolate-carboxylate chelate ring. This type of chelate ring is not without precedent (Henderson et al., 2000; Phillips & Burford, 2008) but the title complex, (I), is the first example of a thiolate-carboxylate chelate with platinum(IV) (McCready & Puddephatt, 2011). In this context, the crystal structure of (I) is presented.

The stereochemistry at the platinum(IV) center is octahedral with two mutually cis methyl groups and chelating 2,2'-bipyridine and 3-thiolatopropionato groups (Fig. 1 and Table 1). The distance Pt—N2 = 2.149 (3) Å is significantly longer than Pt—N1 = 2.107 (3) Å, because the methyl group has a higher trans influence than the thiolato group. The angles at platinum(IV) between cis ligands range from 77.55 (11) to 97.30 (8) °, Table 1, as a result of constraints of the chelate ligands and lie in the expected ranges (Aye et al., 1988; Achar et al., 1993).

The chief intermolecular interactions arise through π-stacking between the bipyridine rings of centrosymmetrically related molecules of (I) (Fig. 2). The mean interplanar spacing between the bipyridine rings comprising the dimer unit is 3.36 Å, which is consistent with observed values of about 3.3 Å for platinum(IV) complexes of 2,2'-bipyridine (Au et al., 2009). The ring centroid(N3-pyridyl)···ring centroid(N4-pyridyl)^A distance = 3.611 (2) Å for A = -x, -y, 1-z. The dimer formation through π-stacking is further stabilized by the presence of a weak C10—H···O2 interaction (Table 2).

Experimental

Dimethyl(2,2'-bipyridine)platinum(II) was prepared according to a previously published procedure by Monaghan and Puddephatt (1984). Spectroscopic Analysis, IR (ν, cm^-1, KBr disk): ν(Aromatic CH) = 3107, ν(aliphatic CH) = 2847 and 2781; ν(CC) = 1601, 1465 and 1443. ¹H NMR in acetone-d⁶: δ = 0.97 [s, 6H, ²J(PtH) = 86 Hz, MePt); 7.70 [dd, 2H, ³J(H₅H₆) = 6 Hz, ³J(H₅H₄) = 7 Hz, H₅]; 8.33 [dd, 2H, ³J(H₄H₅) = 7 Hz, ³J(H₄H₃) = 8 Hz, H₄]; 8.43 [d, 2H, ³J(H₃H₄) = 8 Hz, H₃]; 9.23 [d, 2H, ³J(H₆H₅) = 6 Hz, H₅]. A solution of PtMe₂(bipy) (0.010 g, 0.026 mmol) in minimum acetone was added to a solution of dithiopropionic acid (0.0056 g, 0.026 mmol) in minimum acetone. Mixing of the two solutions led to the formation of a red-brown colour which persists while precipitation of the product is observed. After 30 h the red-orange precipitate can be isolated by decantation of the solvent and was washed with diethyl ether. PtMe₂(bipy) (0.0010 g) was then dissolved in minimal chlorobenzene and added to an NMR analysis tube. To this solution, a buffer layer of chlorobenzene followed by acetone was added in order to slow the rate of diffusion of the subsequently added acetone solution of (0.0006 g) of dithiopropionic acid. The sample was placed in a cool dark place and allowed to crystallize over the course of two weeks producing crystals of (I). Yields of 68–73% were achieved. Spectroscopic Analysis, IR (ν, cm^-1, Bruker Tenser 27 FTIR spectrophotometer as KBr disk): ν(Aromatic CH) = 3107; ν(aliphatic CH) = 2847 and 2781; ν(CC) = 1601, 1465 and 1443; ν(CO) = 1710. ¹H NMR ( acetone-d⁶, p.p.m., Mercury 400 MHz NMR spectrometer): δ = 0.50 [s, 3H, ²J(PtH)=74 Hz, MePt trans to O]; 1.63 [s, 3H, ²J(PtH) = 69 Hz, MePt trans to N]; 2.73 [t, 2H, ³J(HH) = 7 Hz, CH₂]; 2.96 [t, 2H, ³J(HH)=7 Hz, CH₂]; 7.42 – 9.78 [8H, aromatic protons (bipy)]. MALDI-MS (CHCA): m/z = 499 (PtMe₃(NN)(S(CH₂)₂COO)]⁺, m/z = 486 (Complex 1 + H⁺); m/z = 381([PtMe₂(bipy)]⁺). The