(4-Methoxy­benzene­thiol­ato-κS)oxido[2,2′-(propyl­imino)bis­(ethanethiol­ato)-κ³S,N,S′]rhenium(V)

The central Re atom of the mononuclear title complex, [Re(C₈H₁₈NS₂)(C₆H₄OS)O], is five-coordinate (ReNOS₃) with a square-pyramidal geometry comprising a tridentate 2,2′-(propyl­imino)diethanethiol­ate ligand, a 4-methoxy­benzene­thiol­ate ligand and a doubly-bonded O atom.

Key indicators

• Single-crystal X-ray study
• T = 295 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.035
• wR factor = 0.078
• Data-to-parameter ratio = 21.1

checkCIF/PLATON results

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Alert level C
PLAT220_ALERT_2_C Large Non-Solvent    C     Ueq(max)/Ueq(min) ...       2.53 Ratio
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C13
PLAT342_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ...          9

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 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
   0 ALERT type 5 Informative message, check

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S1. Comment

Recently a new method has been described that allows to use metal complexes as prosthetic groups in fluorine-18 labelling of biologically relevant molecules (Noll et al., 2002). The principle is based on labelling a tridentate dithiole ligand with ¹⁸F and combining it with a monodentate thiole ligand to form mixed-ligand rhenium complexes. To better understand the reaction route a non-radioactive fluorine model compound was prepared and all by-products obtained were characterized by X-ray structure analysis, among them the title compound. Similar complexes are currently under study as model compounds with regard to the development of novel technetium-based radiopharmaceuticals for the noninvasive diagnosis of myocardial metabolism (Chelminiak et al., 2005, Femia et al., 2000, Friebe et al., 2000, Heimbold et al., 2002, Jung et al., 2002, Maresca et al., 2002, Marsh, 2005).

The molecular structure of the title complex reveals a neutral square pyramidal mononuclear complex, depicted in Fig. 1. The Re atom is coordinated by two sulfur atoms and a nitrogen atom from the tridentate ligand; another sulfur atom from the 4-methoxybenzenethiol ligand and an additional oxygen atom complete the square pyramidal coordination sphere with an axial Re—O distance of 1.679 (4) Å, a Re—N distance of 2.189 (5) Å and with Re—S bond lengths ranging from 2.2762 (16) to 2.3030 (16) Å. The Re—S3—C5 angle between the methoxyphenyl moiety and the central Re atom amounts to 110.64 (18)°, the torsion angle S2—Re—S3—C5 to -35.52 (1)°. The values mentioned above are in good agreement with those reported in the CCSD (Version 5.27; Allen, 2002); (d_Re—O = 1.663–1.720 Å, av: 1.693 Å; d_Re—N = 2.149–2.245 Å, av: 2.213 Å; d_Re—S = 2.221–2.320 Å, av. 2.287 Å). The averages are based on 45 structures. A weak intramolecular hydrogen bond can be found in the crystal structure, namely C12—H12B ··· O1 with H ··· A=2.59, D ··· A=2.971 (6) Å and an inclined angle of 103°. It should be noticed, that this hydrogen bond is more likely a result of the compound geometry than of any attractive interaction. The analysis of the crystal packing reveals that no classic hydrogen bonds and π-π interactions are present. The head to tail arrangement of the molecules within the layers leads to a zigzag formation of the Re atoms along the c axis, with a Re—Re distance of 6.7410 (2) Å (Fig. 2.).

Related literature

Similar complexes are currently under study as model compounds with regard to the development of novel technetium-based radiopharmaceuticals for the non-invasive diagnosis of myocardial metabolism, see: Chelminiak et al. (2005); Femia et al. (2000); Friebe et al. (2000); Heimbold et al. (2002); Jung et al. (2002); Maresca et al. (2002); Marsh (2005). For related literature, see: Allen (2002); Corbin et al. (1984); Noll et al. (2002).

S2. Experimental

The first intermediate bis(2-benzylthioethyl)amine was prepared by the reaction of benzyl mercaptane and bis(2-chloroethyl)amine hydrochloride (Fluka) as described in (Corbin et al., 1984). Then the hydroxypropyl group was introduced by reaction of bromopropanol with the bis(2-benzylthioethyl)amine. For fluorination of this compound it was necessary to insert a tosyl group at the hydroxypropyl group as leaving group. In the next step the flourine was introduced by nucleophilic substitution using the KF crown ether kryptofix 2.2.2 complex in acetonitrile at 140°C. Subsequent both benzyl protecting groups were split off by reductive cleavage in liquid ammonia and metallic sodium to get the fluorine substituted tridentate NS2 ligand. This reaction is accompanied by a competitive reaction forming the N,N-bis(mercaptoethyl)-N-(propyl)amine by cleavage the flourine. Without further purification the reaction mixture was combined with the monodentate p-methoxy benzene thiol ligand as model compound and Re at the oxidation state +5 to give "3 + 1" complexes. The two Re complexes were separated by column chromatography on silica gel and methylene chloride as eluent. The fractions were collected and evaporated to dryness. The crystals of the metal complex were grown from ethanol. Here we describe the metal complex of the by-product as shown in Fig. 3.

S3. Refinement

All H atoms were included using a riding model, with C–H: 0.93–0.97 Å, U(H)_iso=1.2–1.5× U(host)_equiv. The H atoms of the methyl group were treated as being static.

Computing details

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

Figures

	Fig. 1. : Molecular structure of the title compound, shown with 30% probability displacement ellipsoids. The intramolecular hydrogen bond is indicated via a dotted line.
	Fig. 2. : The crystal packing of the title compound, showing the Re—Re distance of 6.7410 (2) Å (dotted line).
	Fig. 3. : Synthesis of the tridentate ligand and the by-products occurring after reductive cleavage of the protecting groups

(4-Methoxybenzenethiolato-κS)oxido[2,2'-(propylimino)bis(ethanethiolato)- κ³S,N,S']rhenium(V)

Crystal data

C14H22NO2ReS3	F(000) = 1008
Mr = 518.71	Dx = 1.918 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1013 reflections
a = 12.160 (3) Å	θ = 2.7–27.9°
b = 16.809 (4) Å	µ = 7.12 mm^−1
c = 9.441 (2) Å	T = 295 K
β = 111.459 (4)°	Needle, red
V = 1796.0 (7) Å^3	0.45 × 0.4 × 0.2 mm
Z = 4

Data collection

Bruker SMART CCD diffractometer	4013 independent reflections
Radiation source: fine-focus sealed tube	2835 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.060
ω–scan	θmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −12→15
Tmin = 0.058, Tmax = 0.247	k = −18→21
10348 measured reflections	l = −12→11

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.078	H-atom parameters constrained
S = 0.89	w = 1/[σ^2(Fo^2) + (0.0372P)^2] where P = (Fo^2 + 2Fc^2)/3
4013 reflections	(Δ/σ)max = 0.001
190 parameters	Δρmax = 1.68 e Å^−3
0 restraints	Δρmin = −1.24 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
Re	0.700310 (19)	0.893135 (12)	0.01570 (2)	0.04417 (9)
S2	0.72046 (17)	1.02603 (9)	0.06904 (18)	0.0645 (5)
S1	0.52443 (14)	0.82875 (9)	−0.04378 (17)	0.0609 (4)
S3	0.63447 (14)	0.92485 (10)	−0.23912 (16)	0.0575 (4)
N	0.7014 (4)	0.8856 (2)	0.2477 (5)	0.0473 (11)
O1	0.8211 (3)	0.8372 (2)	0.0448 (4)	0.0608 (11)
O2	0.8870 (4)	1.2026 (3)	−0.3639 (5)	0.0802 (14)
C1	0.5151 (6)	0.8080 (4)	0.1407 (6)	0.0689 (18)
H1B	0.4615	0.8455	0.1597	0.083*
H1C	0.4837	0.7549	0.1402	0.083*
C2	0.6344 (6)	0.8141 (4)	0.2648 (7)	0.0703 (19)
H2A	0.6249	0.8166	0.3623	0.084*
H2B	0.6797	0.7667	0.2641	0.084*
C3	0.7113 (6)	1.0310 (3)	0.2570 (6)	0.0638 (17)
H3A	0.7902	1.0329	0.3343	0.077*
H3B	0.6696	1.0789	0.2655	0.077*
C4	0.6471 (5)	0.9593 (3)	0.2808 (6)	0.0544 (15)
H4A	0.6508	0.9581	0.3852	0.065*
H4B	0.5647	0.9621	0.2143	0.065*
C5	0.7100 (5)	1.0101 (3)	−0.2697 (6)	0.0483 (14)
C6	0.8320 (5)	1.0194 (4)	−0.2006 (6)	0.0553 (15)
H6A	0.8766	0.9817	−0.1313	0.066*
C7	0.8863 (6)	1.0841 (4)	−0.2349 (7)	0.0605 (16)
H7A	0.9677	1.0898	−0.1882	0.073*
C8	0.8217 (6)	1.1413 (4)	−0.3381 (7)	0.0573 (15)
C9	0.7015 (6)	1.1325 (4)	−0.4051 (7)	0.0582 (16)
H9A	0.6569	1.1704	−0.4739	0.070*
C10	0.6463 (5)	1.0677 (4)	−0.3710 (6)	0.0570 (15)
H10A	0.5647	1.0627	−0.4169	0.068*
C11	0.8255 (7)	1.2612 (4)	−0.4715 (9)	0.101 (3)
H11A	0.8803	1.3004	−0.4794	0.151*
H11B	0.7677	1.2862	−0.4391	0.151*
H11C	0.7867	1.2366	−0.5689	0.151*
C12	0.8277 (5)	0.8757 (3)	0.3550 (6)	0.0576 (16)
H12A	0.8746	0.9178	0.3351	0.069*
H12B	0.8572	0.8256	0.3320	0.069*
C13	0.8477 (7)	0.8768 (4)	0.5254 (7)	0.074 (2)
H13A	0.8189	0.9267	0.5500	0.088*
H13B	0.8027	0.8341	0.5473	0.088*
C14	0.9746 (8)	0.8674 (6)	0.6222 (8)	0.124 (3)
H14A	0.9835	0.8685	0.7275	0.186*
H14B	1.0192	0.9100	0.6019	0.186*
H14C	1.0029	0.8175	0.5996	0.186*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Re	0.04516 (15)	0.04144 (14)	0.04578 (15)	0.00048 (10)	0.01648 (10)	−0.00574 (10)
S2	0.1001 (14)	0.0421 (8)	0.0571 (9)	−0.0062 (8)	0.0356 (9)	−0.0031 (7)
S1	0.0518 (9)	0.0694 (10)	0.0571 (9)	−0.0097 (8)	0.0146 (7)	−0.0114 (8)
S3	0.0595 (10)	0.0647 (9)	0.0461 (8)	−0.0043 (8)	0.0166 (7)	−0.0062 (7)
N	0.045 (3)	0.040 (3)	0.053 (3)	0.000 (2)	0.014 (2)	−0.003 (2)
O1	0.062 (3)	0.056 (3)	0.064 (2)	0.004 (2)	0.023 (2)	−0.008 (2)
O2	0.087 (4)	0.069 (3)	0.079 (3)	−0.009 (3)	0.024 (3)	0.015 (2)
C1	0.070 (5)	0.076 (4)	0.062 (4)	−0.028 (4)	0.028 (3)	−0.008 (3)
C2	0.079 (5)	0.065 (4)	0.062 (4)	−0.021 (4)	0.019 (3)	0.002 (3)
C3	0.088 (5)	0.051 (4)	0.054 (4)	0.010 (3)	0.027 (3)	−0.007 (3)
C4	0.056 (4)	0.059 (4)	0.049 (3)	0.005 (3)	0.021 (3)	−0.005 (3)
C5	0.052 (4)	0.061 (4)	0.033 (3)	0.005 (3)	0.016 (2)	−0.004 (3)
C6	0.055 (4)	0.064 (4)	0.045 (3)	0.008 (3)	0.017 (3)	0.007 (3)
C7	0.045 (4)	0.077 (4)	0.054 (4)	0.006 (3)	0.012 (3)	0.005 (3)
C8	0.065 (4)	0.058 (4)	0.053 (4)	0.004 (3)	0.026 (3)	0.002 (3)
C9	0.059 (4)	0.060 (4)	0.051 (4)	0.011 (3)	0.014 (3)	0.008 (3)
C10	0.049 (4)	0.070 (4)	0.049 (3)	0.006 (3)	0.013 (3)	−0.003 (3)
C11	0.124 (7)	0.067 (5)	0.104 (6)	−0.001 (4)	0.034 (5)	0.028 (4)
C12	0.056 (4)	0.058 (4)	0.055 (4)	−0.001 (3)	0.016 (3)	0.001 (3)
C13	0.079 (5)	0.089 (5)	0.048 (4)	0.002 (4)	0.018 (3)	0.001 (3)
C14	0.088 (6)	0.193 (9)	0.062 (5)	0.030 (7)	−0.007 (4)	−0.010 (6)

Geometric parameters (Å, º)

Re—O1	1.679 (4)	C5—C10	1.382 (7)
Re—N	2.189 (5)	C5—C6	1.393 (7)
Re—S1	2.2762 (16)	C6—C7	1.370 (8)
Re—S2	2.2833 (16)	C6—H6A	0.9300
Re—S3	2.3030 (16)	C7—C8	1.390 (8)
S2—C3	1.820 (6)	C7—H7A	0.9300
S1—C1	1.820 (6)	C8—C9	1.372 (8)
S3—C5	1.782 (6)	C9—C10	1.377 (8)
N—C4	1.489 (6)	C9—H9A	0.9300
N—C2	1.493 (7)	C10—H10A	0.9300
N—C12	1.509 (7)	C11—H11A	0.9600
O2—C8	1.376 (7)	C11—H11B	0.9600
O2—C11	1.416 (7)	C11—H11C	0.9600
C1—C2	1.498 (8)	C12—C13	1.536 (8)
C1—H1B	0.9700	C12—H12A	0.9700
C1—H1C	0.9700	C12—H12B	0.9700
C2—H2A	0.9700	C13—C14	1.486 (10)
C2—H2B	0.9700	C13—H13A	0.9700
C3—C4	1.497 (8)	C13—H13B	0.9700
C3—H3A	0.9700	C14—H14A	0.9600
C3—H3B	0.9700	C14—H14B	0.9600
C4—H4A	0.9700	C14—H14C	0.9600
C4—H4B	0.9700
O1—Re—N	96.85 (18)	H4A—C4—H4B	108.2
O1—Re—S1	117.42 (14)	C10—C5—C6	118.4 (5)
N—Re—S1	83.14 (12)	C10—C5—S3	118.9 (5)
O1—Re—S2	119.65 (14)	C6—C5—S3	122.6 (4)
N—Re—S2	82.81 (11)	C7—C6—C5	120.0 (5)
S1—Re—S2	122.34 (6)	C7—C6—H6A	120.0
O1—Re—S3	104.45 (14)	C5—C6—H6A	120.0
N—Re—S3	158.59 (13)	C6—C7—C8	121.2 (6)
S1—Re—S3	85.19 (6)	C6—C7—H7A	119.4
S2—Re—S3	88.41 (6)	C8—C7—H7A	119.4
C3—S2—Re	102.7 (2)	C9—C8—O2	125.9 (6)
C1—S1—Re	103.7 (2)	C9—C8—C7	118.8 (6)
C5—S3—Re	110.64 (18)	O2—C8—C7	115.3 (6)
C4—N—C2	110.2 (5)	C8—C9—C10	120.4 (6)
C4—N—C12	111.8 (4)	C8—C9—H9A	119.8
C2—N—C12	107.4 (4)	C10—C9—H9A	119.8
C4—N—Re	108.7 (3)	C9—C10—C5	121.2 (6)
C2—N—Re	110.5 (3)	C9—C10—H10A	119.4
C12—N—Re	108.1 (4)	C5—C10—H10A	119.4
C8—O2—C11	117.4 (6)	O2—C11—H11A	109.5
C2—C1—S1	110.7 (5)	O2—C11—H11B	109.5
C2—C1—H1B	109.5	H11A—C11—H11B	109.5
S1—C1—H1B	109.5	O2—C11—H11C	109.5
C2—C1—H1C	109.5	H11A—C11—H11C	109.5
S1—C1—H1C	109.5	H11B—C11—H11C	109.5
H1B—C1—H1C	108.1	N—C12—C13	115.7 (5)
N—C2—C1	112.4 (5)	N—C12—H12A	108.4
N—C2—H2A	109.1	C13—C12—H12A	108.4
C1—C2—H2A	109.1	N—C12—H12B	108.4
N—C2—H2B	109.1	C13—C12—H12B	108.4
C1—C2—H2B	109.1	H12A—C12—H12B	107.4
H2A—C2—H2B	107.9	C14—C13—C12	111.9 (6)
C4—C3—S2	109.3 (4)	C14—C13—H13A	109.2
C4—C3—H3A	109.8	C12—C13—H13A	109.2
S2—C3—H3A	109.8	C14—C13—H13B	109.2
C4—C3—H3B	109.8	C12—C13—H13B	109.2
S2—C3—H3B	109.8	H13A—C13—H13B	107.9
H3A—C3—H3B	108.3	C13—C14—H14A	109.5
N—C4—C3	110.0 (5)	C13—C14—H14B	109.5
N—C4—H4A	109.7	H14A—C14—H14B	109.5
C3—C4—H4A	109.7	C13—C14—H14C	109.5
N—C4—H4B	109.7	H14A—C14—H14C	109.5
C3—C4—H4B	109.7	H14B—C14—H14C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12B···O1	0.97	2.59	2.971 (7)	104