Reactions of [Ru3(CO)12] with thiosaccharin: Synthesis and structure of di-, tri-, tetra- and penta-ruthenium complexes containing a thiosaccharinate ligand(s)

Journal Pre-proof Reactions of [Ru3(CO)12] with thiosaccharin: Synthesis and structure of di-, tri-, tetraand penta-ruthenium complexes containing a thiosaccharinate ligand(s) Md Jadu Mia, Md Selim Reza, Nikhil C. Bhoumik, Shishir Ghosh, Vladimir N. Nesterov, Michael G. Richmond, Shariff E. Kabir PII:

S0022-328X(19)30491-7

DOI:

https://doi.org/10.1016/j.jorganchem.2019.121048

Reference:

JOM 121048

To appear in:

Journal of Organometallic Chemistry

Received Date: 16 August 2019 Revised Date:

19 November 2019

Accepted Date: 25 November 2019

Please cite this article as: M.J. Mia, M.S. Reza, N.C. Bhoumik, S. Ghosh, V.N. Nesterov, M.G. Richmond, S.E. Kabir, Reactions of [Ru3(CO)12] with thiosaccharin: Synthesis and structure of di-, tri-, tetra- and penta-ruthenium complexes containing a thiosaccharinate ligand(s), Journal of Organometallic Chemistry (2019), doi: https://doi.org/10.1016/j.jorganchem.2019.121048. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier B.V.

Reactions of [Ru3(CO)12] with thiosaccharin: Synthesis and structure of di-, tri-, tetra- and penta-ruthenium complexes containing a thiosaccharinate ligand(s) Md. Jadu Mia a, Md. Selim Reza a, Nikhil C. Bhoumik a, Shishir Ghosh Nesterov b, Michael G. Richmond b, Shariff E. Kabir

a,*

, Vladimir N.

a,*

a

Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh

b

Department of Chemistry, University of North Texas, 1155 Union Circle, Box 305070, Denton,

TX 76203, USA

*Corresponding authors. E-mail addresses: [email protected] (S. Ghosh); [email protected] (S.E. Kabir)

Abstract

Reactions of [Ru3(CO)12] with thiosaccharin (tsacH) at different temperatures have been investigated. At 40 ºC, the diruthenium complex [Ru2(CO)6(µ-N,S-tsac)2] (1) is produced and whose ruthenium atoms are bridged by two tsac ligands that are oriented in a head-tail fashion. When this reaction is carried out at 66 ºC, the tri-, tetra- and penta-ruthenium complexes [H2Ru3(CO)7(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)] (2), [Ru4(CO)12(µ-N,S-tsac)2(µ4-S)] (3) and [H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)(µ4-S)] (4), respectively, were also isolated in addition to 1. The triruthenium complex 2 exhibits an arachno SRu3 polyhedron containing edge-bridging tsac and C6H4CNSO2 ligands. The tetraruthenium complex 3 consists of two [Ru2(CO)6(µ-N,S-tsac)] fragments linked via a µ4-S ligand, while the pentaruthenium complex 4 is composed of individual Ru3 and Ru2 units linked via a µ4-S ligand. At 81 ºC, the same reaction furnishes the pentaruthenium complex [HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5) containing tsac and µ5-S bridging ligands. The molecular structures of the new complexes have been determined by single-crystal X-ray diffraction analyses, and the bonding in each product has been examined by DFT.

Keywords: Ruthenium clusters; Metal carbonyls; Thiosaccharin (tsacH); DFT; X-ray structures. 1

1. Introduction The use of saccharin (sacH) and its water-soluble saccharinate anion (sac-1) as a ligand auxiliary in a variety of metal compounds remains under active investigation due to the unique coordination properties these ligands provide for bonding with transition metal centers [1-8]. The current body of published work reveals that sac-based ligands display versatile and flexible coordination properties by providing up to four potential donor atoms for bonding with transition metal centers. Our group and others have also investigated the reactivity of sacH with low-valent polynuclear clusters. For instance, Buck and Mass reported the formation of the di- and tetraruthenium complexes, [Ru2(CO)6(µ-N,O-sac)2] and [Ru2(CO)5(µ-N,O-sac)2]2 respectively, from the reaction of [Ru3(CO)12] and excess sacH at elevated temperatures [3] (Scheme 1), while we reported the synthesis of the sac-substituted triosmium cluster [HOs3(CO)10(µ-N,O-1,2-sac)] from the reaction of [Os3(CO)10-n(NCMe)n] (n = 1, 2) with sacH [8].

Scheme 1. Reactions of sacH with [Ru3(CO)12]. Thiosaccharin (tsacH), the sulfur analog of sacH, has received less attention as a ligand compared to saccharin despite the fact that the presence of a thiocarbonyl moiety can function as a soft donor ligand for the coordination of soft metal acids [9-17]. TsacH can exist in two principal tautomeric forms in solution (Scheme 2) that parallel the well-known lactam ⇌ lactim equilibria established for dione-containing heterocycles. In the case of tsacH, this equilibrium involves the heterocyclic thione (thioamide) and the thiol (thioimine) forms of the molecule [18,19], with the thiol contributor favored computationally [20] and confirmed experimentally by NMR measurements [21]. 2

Scheme 2. Major tautomers of thiosaccharin (tsacH).

Recently, we investigated the reactivity of tsacH with [Os3(CO)10(NCMe)2] and were able to confirm the conversion between the isomeric tsac-substituted clusters [HOs3(CO)10(µ-tsac)] depicted in Scheme 3. The kinetic product of substitution involves a tsac ligand that bridges an Os-Os bond using the thiocarbonyl moiety (µ-S) while the thermodynamic product contains a bridging ligand that uses the sulfur and nitrogen groups (µ-S,N). The latter isomer is unstable at elevated temperature and transforms into the hexanuclear cluster [H2Os6(CO)17(µ-C,N-1,2C6H4CNSO2)2(µ3-S)(µ4-S)] via carbon-sulfur bond scission and subsequent capture of the extruded sulfur by the cluster core [9]. In continuation of our work on the reactivity of tsacH towards low-valent metal clusters, we wished to examine the reactivity of [Ru3(CO)12] with tsac in order to establish the reactivity pattern for the related ruthenium cluster. Herein we report synthesis and structure of the di-, tri-, tetra- and pentaruthenium complexes [Ru2(CO)6(µ-N,Stsac)2]

(1),

tsac)2(µ4-S)]

[H2Ru3(CO)7(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)] (3),

(2),

[Ru4(CO)12(µ-N,S-

[H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)(µ4-S)]

(4)

and

[HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5) obtained from the reactions of [Ru3(CO)12] with tsacH as a function of reaction temperature.

3

Scheme 3. Isomerization of the tsac ligand in [HOs3(CO)10(µ-tsac)]. 2. Experimental section

2.1. General

All reactions were carried out under a dry nitrogen atmosphere using standard Schlenk techniques unless otherwise noted. Reagent grade solvents were dried using appropriate drying agents and distilled prior to use by standard methods. Infrared spectra were recorded on a Shimadzu FTIR Prestige 21 spectrophotometer, and the NMR spectra were recorded on a Bruker Avance III HD 400 MHz instrument. All chemical shifts are reported in δ units and are referenced to the residual protons of the deuterated NMR solvent (1H). Elemental analyses were performed by the Microanalytical Laboratory of Wazed Miah Science Research Center at Jahangirnagar University. [Ru3(CO)12] was purchased from Strem Chemical Inc. and used without further purification. Thiosaccharin (tsacH) was prepared from saccharin (sacH) according to published methods [17]. Saccharin (sacH) was purchased from Acros Chemicals Inc. and used as received. All products reported herein were separated in the air by TLC plates coated with 0.25mm of silica gel (HF254-type 60, E. Merck, Germany). 2.2. Reaction of [Ru3(CO)12] with tsacH at 40 ºC A CH2Cl2 solution (20 mL) of [Ru3(CO)12] (0.10 g, 0.16 mmol) and tsacH (63 mg, 0.32 mmol) was heated to reflux for 8 h during which time the color of the solution changed from yellow to deep red. The reaction mixture was then allowed to cool at room temperature, and the solvent 4

was removed under reduced pressure. The residue was separated by TLC on silica gel using a binary eluent composed of n-hexane/CH2Cl2 (v/v, 1:1), yielding a single yellow band corresponding to [Ru2(CO)6(µ-N,S-tsac)2] (1). The product was recrystallized from nhexane/CH2Cl2 at 4 ºC and furnished orange crystals of analytically pure 1 in 12% yield (14 mg). Data for 1: Anal. Calc. for C20H8N2O10Ru2S4: C, 31.33; H, 1.05; N, 3.65. Found: C, 31.64; H, 1.12; N, 3.69%. IR (νCO, CH2Cl2): 2102s, 2075vs, 2032sh, 2027s, 1961w cm-1. 1H NMR (CDCl3): δ 8.01 (d, J 7.2 Hz, 2H), 7.88 (d, J 7.2 Hz, 2H), 7.78 (t, J 7.2 Hz, 2H), 7.73 (t, J 7.2 Hz, 2H).

2.3. Reaction of [Ru3(CO)12] with tsacH at 66 ºC To a thf solution (20 mL) of [Ru3(CO)12] (0.10 g, 0.16 mmol) was added tsacH (63 mg, 0.32 mmol). The reaction mixture was heated to reflux for 4 h, after which time the reaction mixture was then allowed to cool at room temperature. The solvent was removed under reduced pressure and the residue chromatographed by TLC on silica gel. Elution with n-hexane/CH2Cl2 (v/v, 1:1) developed four bands. The first band was unreacted [Ru3(CO)12] (14 mg). The second band afforded [H2Ru3(CO)7(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)] (2) as orange crystals (24 mg, 17%) after recrystallization from n-hexane/CH2Cl2 at 4 ºC. The third band afforded two types of crystals (yellow and orange) after recrystallization from n-hexane/CH2Cl2 at 4 °C which were physically separated by hand. The orange crystals were characterized as [Ru2(CO)6(µ-N,S-tsac)2] (1) (7 mg, 4%), while the yellow crystals were characterized as [Ru4(CO)12(µ-N,S-tsac)2(µ4-S)] (3) (10 mg, 7%). The fourth band afforded [H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3S)(µ4-S)] (4) (14 mg, 11%) as orange crystals after recrystallization from hexane/CH2Cl2 at 4 °C. Data for 2: Anal. Calc. for C21H10N2O11Ru3S4: C, 28.10; H, 1.12; N, 3.12. Found: C, 28.32; H, 1.15, N, 3.14%. IR (νCO, CH2Cl2): 2124vs, 2067vs, 2060sh, 2012s cm-1. 1H NMR (CDCl3): δ 8.29 (d, J 8.0 Hz, 1H), 8.02 (m, 1H), 7.91 (t, J 7.2 Hz, 1H), 7.85 (m, 1H), 7.82 (m, 1H), 7.78 (d, J 7.2 Hz, 1H), 7.73 (m, 2H), ‒14.31 (d, J 0.8 Hz, 1H), ‒16.14 (d, J 0.8 Hz, 1H). Data for 3: Anal. Calc. for C26H8N2O16Ru4S5: C, 26.72; H, 0.69; N, 2.40. Found: C, 27.08; H, 0.74; N, 2.48%. IR (νCO, CH2Cl2): 2124w, 2102s, 2087vs, 2066vs, 2021vs cm-1. 1H NMR (CD2Cl2): δ 8.06 (m, 1H), 7.99 (d, J 7.2 Hz, 1H), 7.90-7.76 (m, 6H).

5

Data for 4: Anal. Calc. for C27H10N2O17Ru5S5: C, 24.95; H, 0.78; N, 2.15. Found: C, 25.28; H, 0.85; N, 2.24%. IR (νCO, CH2Cl2): 2124s, 2093s, 2066vs, 2041s, 2016s, 1958w cm-1. 1H NMR (CD2Cl2): aromatic region, major isomer, δ 8.13 (d, J 7.2 Hz, 1H), 7.93-7.74 (m, 7H); hydride region, major isomer, δ −13.67 (d, J 2.0 Hz, 1H), −15.55 (d, J 2.0 Hz, 1H), minor isomer,

δ

−13.78 (d, J 2.0 Hz, 1H), −16.07 (d, J 2.0 Hz, 1H). Major/minor = 21:1.

2.4. Reaction of [Ru3(CO)12] with tsacH at 81 ºC TsacH (63 mg, 0.32 mmol) was added to a cyclohexane solution (20 mL) of [Ru3(CO)12] (0.10 g, 0.16 mmol) and the reaction mixture was heated to reflux for 30 min. The reaction mixture was then allowed to cool at room temperature. The solvent was removed under reduced pressure and the residue separated by TLC on silica gel. Elution with n-hexane/CH2Cl2 (v/v, 1:1) developed a yellow-orange band corresponding to [HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5). The product was recrystallized from n-hexane/CH2Cl2 at 4 ºC to afford 5 as red crystals (18 mg, 17%). Data for 5: Anal. Calc. for C22H5NO17Ru5S3: C, 22.84; H, 0.44; N, 1.21. Found: C, 23.14; H, 0.48; N, 1.23%. IR (νCO, CH2Cl2): 2106w, 2083s, 2071vs, 2034s, 2014s, 1967w cm-1. 1H NMR (CDCl3): δ 7.88 (d, J 7.6 Hz, 1H), 7.81 (t, J 7.6 Hz, 1H), 7.72 (d, J 7.6 Hz, 1H), 7.66 (t, 7.6 Hz, 1H), -17.87 (s, 1H). 2.5. Crystal structure determinations

Single crystals of 1-5 suitable for X-ray diffraction analysis were grown by slow diffusion of nhexane into a CH2Cl2 solution containing each product. Suitable crystals were mounted on a Bruker Nonius Kappa CCD using a Nylon loop and Paratone oil, and the diffraction data were collected at 193.0(2) K using Mo-Kα radiation (λ = 0.71073). Unit cell determination, data reduction, and absorption corrections were carried out using CrysAlisPro [22]. The structures were solved with the ShelXS [23] structure solution program by direct methods and refined by full-matrix least-squares on the basis of F2 using ShelXL [23,24] within the OLEX2 [25] graphical user interface. All non-hydrogen atoms were anisotropically refined while the hydrogen atoms (except those directly bonded to metals which were located in the Fourier maps

6

and refined isotropically) were included using a riding model. Pertinent crystallographic parameters are given in Table 1.

2.6. Computational methodology

All calculations were performed with the hybrid meta exchange-correlation functional M06 [26], as implemented by the Gaussian 09 program package [27]. The ruthenium atoms were described by Stuttgart-Dresden effective core potentials (ecp) and an SDD basis set [28], while a 6-31G(d’) basis set was employed for the remaining atoms [29]. The reported geometries represent fully optimized ground states (positive eigenvalues) based on the analytical Hessian, and the natural charges and Wiberg indices were computed using Weinhold’s natural bond orbital (NBO) program (version 3.1) [30,31]. The geometry-optimized structures presented here have been drawn with the JIMP2 molecular visualization and manipulation program [32].

3. Results and discussion 3.1. Reaction of [Ru3(CO)12] with tsacH at 40 ºC: isolation of a diruthenium complex Heating a CH2Cl2 solution of [Ru3(CO)12] with two molar equivalents of tsacH at 40 ºC led to the isolation of the diruthenium complex [Ru2(CO)6(µ-N,S-tsac)2] (1) in low yield (12%) after chromatographic separation and recrystallization (Scheme 4). We note that the TLC plates exhibited much streaking, and an extensive amount of a reddish brown colored material remained at the origin of the plates whose nature was not established. The use of excess tsacH (five molar equivalents) in this reaction marginally increased the yield of 1.

7

Scheme 4. Reaction of [Ru3(CO)12] with tsacH at 40 ºC. Fig. 1 shows the solid-state molecular structure of 1 determined by single-crystal X-ray diffraction analysis with selected bond distances and angles listed in the caption. The structure consists of a diruthenium core that is ligated by two tsac ligands. The gross structural features of 1 are very similar to those of its sac analog [Ru2(CO)6(µ-N,O-tsac)2] [3]. Both tsac groups function as edge-bridging ligands and bind the metal centers using the thiocarbonyl sulfur and nitrogen moieties. The idealized C2 symmetry observed in 1 is consistent with the head-to-tail coordination of the tsac ligands and the overall eclipsed ‘sawhorse’ arrangement of the ancillary tsac and CO ligands about the Ru(1)-Ru(2) vector. The Ru(1)-Ru(2) bond distance of 2.8487(9) Å closely mirrors the computed distance of 2.8185 Å found in the DFT-optimized structure depicted alongside the experimental structure in Fig. 1. The Ru(1)-Ru(2) bond distance is consistent with its single-bond designation. The ruthenium-nitrogen bond distances [av. 2.148(3) Å] are identical with those distances reported in [Ru2(CO)6(µ-N,O-tsac)2] [av. 2.145(3) Å] [3], while the ruthenium-sulfur bond distances [av. 2.4093(12) Å] in 1 are within the range reported in the literature for related complexes [33-36]. The three carbonyl groups exhibit facial orientation at each metal, with an 18-electron configuration is achieved at each ruthenium atom, assuming the tsac ligands serve as 3-electron donor ligands. The 1H NMR spectrum of 1 is consistent with the solid-state structure, displaying two doublets and two virtual triplets in the aromatic region in 1:1:1:1 intensity ratio. Place Figure 1 Here The bonding and charge distribution for the ruthenium, sulfur, and nitrogen atoms in the optimized structure of A were investigated by electronic structure calculations. These data are 8

summarized in Table 2. The natural charge (Q) computed for the symmetry equivalent ruthenium and nitrogen atoms is -1.14 and -0.72, respectively. The two different sulfur centers are positive with the S(1) center more electrophilic than the S(2) thiocarbonyl moiety; the Q value for these groups is 2.36 and 0.17, respectively. The Wiberg bond index (WBI) of 0.47 for the Ru-Ru vector is consistent with the bond index reported for polynuclear ruthenium compounds with RuRu single bonds [37]. The pairwise equivalent Ru-S and Ru-N bond indices are 0.66 and 0.45.

3.2. Reaction of [Ru3(CO)12] with tsacH at 66 ºC: formation of tri- and tetra-ruthenium complexes

When the same reaction was carried out at 66 ºC, three additional complexes were isolated namely [H2Ru3(CO)7(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)] (2), [Ru4(CO)12(µ-N,S-tsac)2(µ4S)] (3) and [H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)(µ4-S)] (4) in 17, 7 and 11% yield, respectively, besides [Ru2(CO)6(µ-N,S-tsac)2] (1) which was isolated as a minor product (4%) (Scheme 5). We did not observe any discernible change in the product distribution when excess tsacH was used for this reaction. CO

OC

CO

S

CO

Ru O

Ru

S

O S NH

1

+

S

S O

N

Ru

N

thf 66 oC

CO O

H

H

[Ru3(CO)12]

S

O

OC CO O 2

O

O O O

OC

OC OC

S

CO

OC

N

Ru

S

CO Ru OC

S

+

Ru OC

CO

Ru N

O CO

CO

O

CO 3

4

9

CO Ru

O Ru

S

CO

S

OC O

CO

CO Ru

H

Ru

CO

S

OC

S Ru

H

OC

N

S

OC

OC CO

N S

S

CO CO

Scheme 5. Reaction of [Ru3(CO)12] with tsacH at 66 ºC. The solid-state molecular structure of 2 is depicted in Fig. 2, whose caption contains selected bond distances and angles. The metallic core consists of an open triangle of ruthenium atoms with two formal ruthenium-ruthenium bonds [Ru(1)–Ru(2) 2.9326(12) and Ru(2)–Ru(3) 2.8981(12) Å]. The nonbonding distance between the Ru(1) and Ru(3) atoms is 3.724(12) Å, which precludes any significant bonding interaction between these two metals. This expanded vertex is the direct result of the 50-electron count in 2. The Ru3 core in 2 is ligated by seven terminal carbonyls, along with bridging tsac, C6H4CNSO2, µ3-sulfido, and two hydride ligands. The µ3-sulfido ligand caps one face of the metal triangle, while the intact tsac ligand bridges the Ru(1)–Ru(2) vector via the thiocarbonyl sulfur and nitrogen atoms in a manner analogous to that found in 1. The C6H4CNSO2 ligand, which is derived from a tsac ligand after the loss of the thiocarbonyl sulfur atom, bridges the nonbonding Ru(1)···Ru(3) edge through the C(15) and N(2) atoms of the heterocycle. The Ru(3)-N(2) distance is ca. 0.1 Å smaller compared to the Ru(1)-N(1) distance involving the intact tsac ligand that bridges the Ru(1)-Ru(2) vector. The Ru(1)-C(15) bond distance of 2.021(2) Å associated with the metalated heterocycle falls within the range reported in the literature for related complexes [36,38]. Both hydride ligands were located during data refinement and were confirmed to span the two Ru-Ru single bonds in 2. The existence of two hydride ligands in 2 was also supported by 1H NMR spectroscopy. The two highfield doublets recorded at δ -14.31 and -16.14 (J 0.8 Hz) are consistent with the formulated structure. The observed hydride splitting of 0.8 Hz is attributed to the geminal coupling between the inequivalent hydrides. Place Figure 2 Here The M06-optimized structure of B is shown alongside the solid-state structure of 2 in Fig. 2. The computed structure of B closely mirrors its solid-state counterpart. The three ruthenium atoms are all electron-rich and the Q value ranges from -1.01 [Ru(1)] to -1.26 [Ru(2)]. The charge on the S(1) and S(2) centers is similar in magnitude to the related groups computed in A while the charge on the face-capping S(3) atom is 0.21. The loss of the sulfur from the bridging 1,2-N,C-C7H4NO2S ligand does not affect the charge on the N(2) atom relative to the N(1) atom on the intact tsac ligand as both nitrogen atoms reveal comparable Q values (-0.68 vs. -0.71). The bridging hydrides are both electropositive and display a mean Q of 0.14. The mean WBI for the 10

two Ru-Ru bonds is 0.23, and while slightly shorter than that value found in A, the magnitude is consistent with the Ru-Ru single-bond designation ascribed to the Ru(1)-Ru(2) and Ru(2)-Ru(3) vectors. Finally, the mean Ru-H bond index of 0.37 is not unlike that computed by us for other polynuclear ruthenium clusters [37].

Attempts to grow suitable crystals of 3 for structural analysis were unsuccessful, affording only very thin needles. However, we did collect diffraction data on one of these thin needle shaped crystals determined and were able to verify the atom composition for this cluster (see Fig. S1 in the ESI). The refinement of this structure gave poor R-values but was instrumental in establishing the number of ruthenium atoms and the fate of the tsac ligands. Cluster 3 contains two [Ru2(CO)6(µ-N,S-tsac)] units linked by a µ4-S ligand. The DFT-optimized structure of C is depicted in Fig. 3 and with it the important structural features involving the activation of one of the tsac ligands and formation of the µ4-sulfido ligand. The computed natural charges and WBIs in C are consistent with the other cluster compounds reported here. The two ruthenium atoms in each unit are held together by a Ru-Ru bond and a bridging tsac ligand, in addition to six carbonyls that are equally distributed between them. The IR spectrum of 3 exhibits five absorptions between 2124 - 2021 cm-1, while the 1H NMR spectrum displays a series of multiplets in the aromatic region for the protons of the carbocyclic ring of the tsac ligand. The spectroscopic data are consistent with the proposed formulation based on diffraction data and the DFT-computed structure.

There are two independent molecules in the asymmetric unit of 4 together with three disordered CH2Cl2 molecules (used for crystallization); the presence of the latter leads to poor overall refinement of this structure. Since only minor differences being noted between the crystallographically independent molecules, we will discuss only one of those which is shown in Fig. 4. The molecule consists of individual Ru3 and Ru2 units linked by a µ4-S. The Ru3 unit, defined by Ru(1)-Ru(2)-Ru(3) atoms, is capped by a µ3-S ligand and possesses two formal RuRu bonds with the open edge bridged by the C6H4CNSO2 ligand. The Ru-C [2.009(17) Å] and Ru-N [2.119(14) Å] bond distances involving this ligand are similar to those observed in 2. The Ru2 unit, defined by Ru(4)-Ru(5) atoms, displays one formal Ru-Ru bond, which is bridged by the ancillary tsac ligand. The linking µ4-S ligand also serves as an edge-bridging ligand to both 11

ruthenium units. The hydride ligands, whose presence is supported by 1H NMR spectroscopy, were not located during refinement, and they were assumed to span the Ru-Ru edges of the Ru3 unit [Ru(1)-Ru(2) and Ru(2)-Ru(3)] in 4. The locus of the two edge-bridging hydrides at the metallic face opposite the face-capping sulfide ligand was subsequently established by DFT calculations. The optimized structure of D (Fig. 4) confirms the presence of a hydride at each of the two Ru-Ru vectors in the Ru3 portion of the cluster. The hydride region of the 1H NMR spectrum of 4 exhibits two sets of doublets indicating that 4 exists as a pair of isomers in solution. The doublets at δ −13.67 and −15.55 (J 2.0 Hz) correspond to the major isomer, while those at δ −13.78 and −16.07 (J 2.0 Hz) are attributed to the minor isomer. The magnitude of the 2

JH-H coupling between the two hydrides is consistent with their bridging the Ru-Ru bonding

edges at the Ru3 unit. The Ru(2)–Ru(3) bond distance of 2.910(3) Å is significantly longer than the other two Ru-Ru bonds present in the molecule [Ru(1)–Ru(2) 2.762(3) and Ru(4)–Ru(5) 2.772(3) Å], presumably due to ligand crowding at the Ru(2)-Ru(3) vector as a result of the three edge-bridging ligands.

3.2. Reaction of [Ru3(CO)12] with tsacH at 66 ºC: formation of tri- and tetra-ruthenium complexes Heating [Ru3(CO)12] and tsacH in refluxing cyclohexane (81 °C) affords the pentaruthenium cluster [HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5) in 20% yield (Scheme 6). We have also treated 5 with excess tsacH in boiling thf to check the possibility of 5 acting as the source of the other clusters on reaction with free tsac. No evidence for the formation of clusters 1-4 was found in those reactions that were monitored by IR and TLC. Non-specific decomposition was observed by TLC, as evidenced by the material that remained at the origin of the TLC plate. The molecular structure of 5 was established by single-crystal X-ray diffraction analysis, the results of which are summarized in Fig. 5 and its caption. Two independent molecules were found in the unit cell of 5, whose main difference concerns the orientation of the tsac ligand about the Ru(4)Ru(5) vector. Since the bond distances and angles of the two molecules were statistically insignificant, only one of the molecules will be discussed in detail here. The product consists of five ruthenium atoms where the µ5-S ligand caps the triangular face defined by the Ru(1)-Ru(2)-

12

Ru(3) atoms in addition to serving as an edge-bridging ligand for the Ru(4)-Ru(5) atoms, which are also bridged by the ancillary tsac ligand.

Scheme 6. Reaction of [Ru3(CO)12] with tsacH at 81 ºC. Fifteen terminal carbonyls are equally distributed about the five ruthenium atoms, and there is an edge-bridging hydride that spans the Ru(1)-Ru(2) vector. The triangular array defined by the Ru(1)-Ru(2)-Ru(3) atoms exhibits an isosceles geometry with the shorter Ru-Ru bond distances corresponding to the Ru(2)–Ru(3) [2.777(2) Å] and Ru(1)–Ru(3) [2.758(2) Å] vectors. The Ru(1)–Ru(2) vector [2.876(2) Å] is 0.1085 Å longer than the mean distance of the shorter two Ru-Ru bonds. The Ru(4)-Ru(5) bond [2.811(2) Å] is edge-bridged by both the tsac and capping sulfido moieties and is tethered to the Ru3 polyhedron through a long Ru(3)-Ru(4) bond [3.171(2) Å]. The Ru(5)-N(1) [2.13(2) Å] and the Ru(4)-S(1) [2.424(5) Å] bond distances are similar to those distances found in 1. The ruthenium-sulfur bond distances between the µ5-S ligand and Ru(1), Ru(2) and Ru(5) atoms are significantly shorter [Ru(1)–S(3) 2.348(6), Ru(2)– S(3) 2.336(5) and Ru(5)–S(3) 2.344(6) Å] than those with Ru(3) and Ru(4) atoms [Ru(3)–S(3) 2.478(6) and Ru(4)–S(3) 2.515(5) Å], but all these distances fall are within the range of related Ru-S bond distances reported for di- and polynuclear systems in the literature [33-36, 38]. The hydride ligand, whose presence is supported by the upfield resonance at δ -17.87 in the 1H NMR spectrum, was located crystallographically and is found to span the Ru(1)-Ru(2) edge. The locus of the hydride is underscored by electronic structure calculations, as depicted in the optimized structure of E in Fig. 5. Species E exhibits all of the important features displayed by the solid-

13

state structure and the computed charges and the Wiberg bond indices parallel the date reported for species A and B. Place Figure 5 Here 4. Conclusions In summary, we have explored the reaction of the complex heterocycle tsacH with [Ru3(CO)12] at different experimental conditions. The new polynuclear ruthenium complexes [Ru2(CO)6(µN,S-tsac)2] (1), [H2Ru3(CO)7(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)] (2), [Ru4(CO)12(µ-N,Stsac)2(µ4-S)]

(3),

[H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)(µ4-S)]

(4)

and

[HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5) have been isolated and the molecular structure of each product determined by X-ray crystallography. The nature of the isolated products is highly dependent on the reaction temperature and less so on the Ru3(CO)12:tsac stoichiometry. The formation of a capping sulfido moiety results from the extrusion of sulfur from the thiocarbonyl moiety in tsac when the reaction is conducted in refluxing THF and cyclohexane, thus preventing formation of the tsac analogue of [Ru2(CO)5(µ-N,O-sac)2]2 isolated by Buck and Mass (Scheme 1). The use of tsac as a selective sulfur delivery agent for the synthesis of new sulfido-bridged polynuclear clusters is under active investigation by our groups, and the new cluster compounds produced by this methodology will be reported in due course.

Acknowledgments Financial support from the Ministry of Science and Technology, the Government of the People’s Republic of Bangladesh (SG) and the Robert A. Welch Foundation (Grant B-1093-MGR) is acknowledged. The DFT calculations were performed at UNT through CASCaM, which is an NSF-supported facility (CHE-1531468). We also thank the Wazed Miah Science Research Center, Jahangirnagar University, Bangladesh, for providing us some technical facilities required for this work.

Appendix A. Supplementary data

14

CCDC 1886824 (for 1), 1886826 (for 2), 1961705 (for 4) and 1886827 (for 5) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Electronic Supplementary Information (ESI) contains an ORTEP diagram, crystal data and structure refinement details for compounds 3. Atomic coordinates and energies for all DFToptimized structures are available upon request (MGR).

15

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Allg. Chem. 635 (2009) 1604; (d) S.H. Tarulli, O.V. Quinzani, E.J. Baran, O.E. Piro, E.E. Castellano, J. Mol. Struct. 656 (2003) 161. [15] (a) S.A. Al-Jibori, M.H.S. Al-Jibori, G. Hogarth, Inorg. Chim. Acta 398 (2013) 117; (b) S.A. Al-Jibori, Q.K.A. Al-Jibori, H. Schmidt, K. Merzweiler, C. Wagner, G. Hogarth, Inorg. Chim. Acta 402 (2013) 69; (c) S.A. Al-Jibori, A.T. Habeeb, G.H.H. Al-Jibori, N.A. Dayaaf, K. Merzweiler, C. Wagner, H. Schmidt, G. Hogarth, Polyhedron 67 (2014) 338; (d) S.A. Al-Jibori, W.J. Hameed, A.S. Al-Jibori, S. Basak-Modi, C. Wagner, G. Hogarth, Inorg. Chim. Acta 479 (2018) 197. [16] S.A. Al-Jibori, G.H. Al-Jibori, L.J. Al-Hayaly, C. Wagner, H. Schmidt, S. Timur, F.B. Barlas, E. Subasi, S. Ghosh, G. Hogarth, J. Inorg. Biochem. 141 (2014) 55. [17] O. Grupče, M. Penavić, G. Jovanovski, J. Chem. Crystallogr. 24 (1994) 581. [18] S. Stoyanov, T. Stoyanova, I. Antonov, P. Karagiannidis, P. Akrivos, Monatsch. Chem. 127 (1996) 495. [19] S. Stoyanov, T. Stoyanova, P.D. Akrivos, Trends Appl. Spectrosc. 2 (1998) 89. [20] M.M. Branda, N.J. Castellani, S.H. Tarulli, O.V. Quinzani, E.J. Baran, R.H. Contreras, Int. J. Quant. Chem. 89 (2002) 525. [21] M. Vieites, D. Gambino, M. Gonz´alez, H. Cerecetto, S.H. Tarulli, O.V. Quinzani, E.J. Baran, J. Coord. Chem. 59 (2006) 101. [22] CrysAlisPro; Oxford Diffraction: Yarnton, England, 2015. [23] G.M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr. 64 (2008) 112. [24] G.M. Sheldrick, Acta Cryst. C71 (2015) 3. [25] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, J. Appl. Crystallogr. 42 (2009) 339. [26] Y. Zhao, D.G. Truhlar, Theor. Chem. Acc. 120 (2008) 215. [27] M.J. Frisch et al., Gaussian 09, Revision E.01, Gaussian, Inc., Wallingford, CT, USA, 2009. [28] D. Andrae, U. Haeussermann, M. Dolg, H. Stoll, H. Preuss, Theor. Chim. Acta 77 (1990) 123. [29] (a) G. A. Petersson, A. Bennett, T. G. Tensfeldt, M. A. Al-Laham, W. A. Shirley, J. Mantzaris, J. Chem. Phys. 89 (1988) 2193. (b) G. A. Petersson, M. A. Al-Laham, J. Chem. Phys. 94 (1991) 6081. [30] A.E. Reed, L.A. Curtiss, F. Weinhold, Chem. Rev. 88 (1988) 899. [31] K.B. Wiberg, Tetrahedron 24 (1968) 1083. 17

[32] (a) JIMP2, version 0.091, a free program for the visualization and manipulation of molecules: M.B. Hall, R.F. Fenske, Inorg. Chem. 11 (1972) 768; (b) J. Manson, C.E. Webster, M.B. Hall, Texas A&M University, College Station, TX, 2006, http://www.chem.tamu.edu/jimp2/index.html. [33] (a) M.R. Moni, M.J. Mia, S. Ghosh, D.A. Tocher, S.M. Mobin, T.A. Siddiquee, S.E. Kabir, Polyhedron 146 (2018) 154; (b) M.F. Ahmad, J.C. Sarker, K.A. Azam, S.E. Kabir, S. Ghosh, G. Hogarth, T.A. Siddiquee, M.G. Richmond, J. Organomet. Chem. 728 (2013) 30; (c) M.I. Hossain, M.D.H. Sikder, S. Ghosh, S.E. Kabir, G. Hogarth, L. Salassa, Organometallics 31 (2012) 2546. [34] (a) M.D.H. Sikder, S. Ghosh, S.E. Kabir, G. Hogarth, D.A. Tocher, Inorg. Chim. Acta 376 (2011) 170; (b) A.K. Raha, S. Ghosh, M.I. Hossain, S.E. Kabir, B.K. Nicholson, G. Hogarth, L. Salassa, J. Organomet. Chem. 696 (2011) 2153. [35] (a) S. Ghosh, K.N. Khanam, G.M.G. Hossain, D.T. Haworth, S.V. Lindeman, G. Hogarth, S.E. Kabir, New J. Chem. 34 (2010) 1875; (b) S. Ghosh, K.N. Khanam, M.K. Hossain, G.M.G. Hossain, D.T. Haworth, S.V. Lindeman, G. Hogarth, S.E. Kabir, J. Organomet. Chem. 695 (2010) 1146; (c) S. Ghosh, S.E. Kabir, S. Pervin, A.K. Raha, G.M.G. Hossain, D.T. Haworth, S.V. Lindeman, D.W. Bennett, T.A. Siddiquee, L. Salassa, H.W. Roesky, Dalton Trans. (2009) 3510. [36] S. Ghosh, F.K. Camellia, K. Fatema, M.I. Hossain, M.R. Al-Mamun, G.M.G. Hossain, G. Hogarth, S.E. Kabir, J. Organomet. Chem. 696 (2011) 2935. [37] (a) M.M. Uddin, N. Begum, S. Ghosh, J.C. Sarker, D.A. Tocher, G. Hogarth, M.G. Richmond, E. Nordlander, S.E. Kabir, J. Organomet. Chem. 812 (2016) 197; (b) M.M.M. Khan, S. Ghosh, G. Hogarth, D.A. Tocher, M.G. Richmond, S.E. Kabir, H.W. Roesky, J. Organomet. Chem. 840 (2017) 47. [38] (a) S. Ghosh, G. Hogarth, S.E. Kabir, E. Nordlander, L. Salassa, D.A. Tocher, J. Organomet. Chem. 696 (2011) 1982; (b) S. Rajbangshi, S. Ghosh, G. Hogarth, S.E. Kabir, J. Clust. Sci. 26 (2015) 169; (c) M.M. Uddin, N. Begum, S. Ghosh, J.C. Sarker, D.A. Tocher, G. Hogarth, M.G. Richmond, E. Nordlander, S.E. Kabir, 812 (2016) 197.

18

Table 1. Crystal data and structure refinement details for compounds 1, 2, 4 and 5 Compound

1

2

4

5

CCDC Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) α (°) β (°) γ (°) Volume (Å3) Z Density (calculated) (Mg/m3) Absorption coefficient (mm-1) F(000) Crystal size (mm3) Ɵ range for data collection (°) Index ranges

1886824 C20H8N2O10Ru2S4 766.66 193.0(2) 0.71073 monoclinic P21/c

1886826 C21H10O11 Ru3N2S4 897.76 193.0(2) 0.71073 triclinic P-1

1886827 2 C27H8N2O17Ru5S5·3 CH2Cl2 2850.78 223(2) 0.71073 triclinic P-1

1886827 C22H5NO17Ru5S3·CH2Cl2 1241.73 193.0(2) 0.71073 tetragonal P41

7.821(2) 15.803(3) 20.321(4) 90 95.85(3) 90 2498.5(9) 4 2.038 1.602 1496 0.296 × 0.288 × 0.147 2.77 to 23.35 ‒8 ≤ h ≤ 8, ‒17 ≤ k ≤ 17, ‒22 ≤ l ≤ 22 29361 3614 [Rint = 0.0208] 3614 / 0 / 344 1.143 R1 = 0.0222, wR2 = 0.0543 R1 = 0.0237, wR2 = 0.0552 0.37 and ‒0.38

10.358(6) 10.826(5) 13.554(7) 111.569(18) 93.812(15) 94.814(18) 1400.7(13) 2 2.129 1.955 868 0.195 × 0.106 × 0.041 2.429 to 25.453 ‒12 ≤ h ≤ 12, ‒13 ≤ k ≤ 13, ‒16 ≤ l ≤ 16 36349 5140 [Rint = 0.0225] 5140 / 0 / 379 1.061 R1 = 0.0154, wR2 = 0.0373 R1 = 0.0181, wR2 = 0.0383 0.41 and ‒0.37

16.078(13) 17.555(16) 18.276(14) 68.09(3) 65.71(2) 80.67(3) 4362(6) 2 2.170 2.184 2732 0.298 × 0.108 × 0.044 2.224 to 27.231 ‒20 ≤ h ≤ 20, ‒22 ≤ k ≤ 22, ‒23 ≤ l ≤ 23 113608 19299 [Rint = 0.0807] 19299 / 21 / 1044 1.071 R1 = 0.1071, wR2 = 0.2860 R1 = 0.1488, wR2 = 0.3101 4.36 and ‒2.55

9.560(4) 9.560(4) 78.21(4) 90 90 90 7149(7) 8 2.307 2.461 4720 0.221 × 0.161 × 0.079 2.193 to 26.370 ‒11 ≤ h ≤ 10, ‒11 ≤ k ≤ 11, ‒93 ≤ l ≤ 92 36327 13113 [Rint = 0.0513] 13113 / 6 / 545 1.174 R1 = 0.0660, wR2 = 0.1302 R1 = 0.0723, wR2 = 0.1322 2.24 and ‒1.75

Reflections collected Independent reflections [Rint] Data / restraints / parameters Goodness of fit on F2 Final R indices [I > 2σ(I)] R indices (all data) Largest diff. peak and hole (e. Å-3)

19

Table 2. Natural charges (Q) and Wiberg indices for compounds A-Ea

Atom

A

Charge (Q) B

C

D -1.16

-1.32

Ru(1)-Ru(2)

WBI Bond

E

A

B

C

D

E

0.22

0.43

0.27

0.23

Ru(1)

-1.14

-1.01

-1.37

Ru(2)

-1.14

-1.26

-1.15

-1.28

-1.31

Ru(2)-Ru(3)

0.23

0.23

0.42

-1.17

-1.37

-1.20

-1.23

Ru(1)-Ru(3)

0.03

0.04

0.43

-1.14

-1.38

-1.23

Ru(3)-Ru(4)

-1.16

-1.10

Ru(4)-Ru(5)

Ru(3) Ru(4) Ru(5)

0.47

0.43 0.43

S(1)

2.36

0.23

0.32

S(2)

0.17

2.36

0.24

2.38

2.36

Ru(1)-S(2)

S(3)

2.36

0.21

2.42

0.33

0.39

Ru(1)-S(4)

0.66

S(4)

0.17

2.35

0.21

0.23

Ru(2)-S(2)

0.66

2.43

2.41

Ru(2)-S(1)

0.73

Ru(1)-S(3)

0.70

S(5)

0.24

0.20

Ru(1)-S(1)

0.65 0.71

N(1)

-0.72

-0.71

-0.74

-0.67

N(2)

-0.72

-0.68

-0.74

-0.72

H(1) H(2)

0.12

0.18

0.16

0.15

-0.71

0.66

Ru(2)-S(3)

0.76

Ru(3)-S(3)

0.74

0.76

Ru(4)-S(1)

0.65

0.70

Ru(4)-S(3)

0.65

Ru(4)-S(4)

0.70

Ru(5)-S(3)

0.66

Ru(2)-N(1) 20

0.65 0.47

0.70

0.45

0.66

0.75 0.65

Ru(3)-S(4)

Ru(1)-N(1)

0.38

0.69

0.55 0.66

Ru(3)-S(1) 0.14

0.19

0.42 0.45

0.40 0.61

Ru(2)-N(2)

0.45 0.50

Ru(3)-N(1) Ru(3)-N(2)

0.50 0.46

Ru(4)-N(2) Ru(5)-N(2)

0.47

Ru(1)-C(14)

0.80

0.47

Ru(1)-C(15)

0.83

Ru(1)-H(1)

0.38

0.34

0.37

Ru(2)-H(1)

0.37

0.35

0.37

Ru(2)-H(2)

0.38

0.37

Ru(3)-H(2)

0.36

0.37

a

Atom numbering for the non-hydrogen atoms follows that employed in the solid-state structure of compounds 1, 2, 4, and 5. The numbering system for compound 3 is shown below. O O

S3 O N1

N2

S2 S1

Ru2

S4 Ru1

Ru3

21

O S5

Ru4

Fig. 1. ORTEP drawing of the molecular structure of [Ru2(CO)6(µ-N,S-tsac)2] (1) showing 50% probability thermal ellipsoids (left) and DFT-optimized structure of A (right). Hydrogen atoms are omitted for clarity in the experimental structure. Selected bond distances (Å) and angles (o) for the solid-state structure: Ru(1)–Ru(2) 2.8487(9), Ru(1)–N(1) 2.150(3), Ru(1)–S(4) 2.4058(11), Ru(2)–N(2) 2.145(3), Ru(2)–S(2) 2.4128(12), N(1)–Ru(1)–S(4) 90.07(8), N(1)– Ru(1)–Ru(2) 86.52(7), C(14)–S(4)–Ru(1) 109.76(12), C(7)–N(1)–Ru(1) 129.3(2), C(14)–N(2)– Ru(2) 128.9(2), S(4)–Ru(1)–Ru(2) 88.08(3), N(1)–C(7)–S(2) 125.6(2), N(2)–Ru(2)–S(2) 89.18(8), N(2)–Ru(2)–Ru(1) 86.73(7), S(2)–Ru(2)–Ru(1) 88.40(3), N(2)–C(14)–S(4) 125.8(3), C(7)–S(2)–Ru(2) 109.49(11).

22

Fig. 2. ORTEP drawing of the molecular structure of [H2Ru3(CO)7(µ-N,S-tsac)(µ-C,NC6H4CNSO2)(µ3-S)] (2) showing 50% probability thermal ellipsoids (left) and DFT-optimized structure of B (right). The ring hydrogen atoms on the heterocyclic ligand are omitted for clarity in the experimental structure. Selected bond distances (Å) and angles (o) for the solid-state structure: Ru(1)–Ru(2) 2.9326(12), Ru(2)–Ru(3) 2.8981(12), Ru(1)–N(1) 2.2018(19), Ru(3)– N(2) 2.1187(19), Ru(1)–S(3) 2.3827(9), Ru(2)–S(1) 2.3742(10), Ru(2)–S(3) 2.3733(12), Ru(3)– S(3) 2.3913(11), Ru(1)–C(15) 2.021(2), Ru(3)–Ru(2)–Ru(1) 79.38(3), C(15)–Ru(1)–N(1) 176.94(7),

Ru(1)–S(3)–Ru(3) 102.52(4),

Ru(2)–S(3)–Ru(1) 76.14(4), Ru(2)–S(3)–Ru(3)

74.93(3), S(3)–Ru(2)–S(1) 99.60(4).

23

Fig. 3. DFT-optimized structure of [Ru4(CO)12(µ-N,S-tsac)2(µ4-S)] (3) (C).

24

Fig. 4. ORTEP drawing of the molecular structure of [H2Ru5(CO)13(µ-N,S-tsac)(µ-C,N-C6H4CNSO2)(µ3-S)(µ4-S)] (4) showing 50% probability thermal ellipsoids (left) and DFT-optimized structure of D (right). Ring hydrogen atoms on the tsac ligand in the experimental structure are omitted for clarity. Selected bond distances (Å) and angles (o) for the solid-state structure: Ru(1)–Ru(2) 2.762(3), Ru(2)– Ru(3) 2.910(3), Ru(4)–Ru(5) 2.772(3), Ru(1)–C(14) 2.009(17), Ru(3)–N(1) 2.119(14), Ru(5)–N(2) 2.148(15), Ru(1)–S(1) 2.411(5), Ru(1)–S(3) 2.437(5), Ru(2)–S(1) 2.376(5), Ru(2)–S(3) 2.386(5), Ru(3)–S(1) 2.384(5), Ru(4)–S(3) 2.374(5), Ru(4)–S(4) 2.427(5), Ru(5)– S(3) 2.364(5), C(14)–Ru(1)–Ru(2) 101.0(5), C(14)–Ru(1)–S(3) 154.8(5), C(14)–Ru(1)–S(1) 89.0(5), N(1)–Ru(3)–Ru(2) 91.2(4), N(1)– Ru(3)–S(1) 85.9(4), N(2)–Ru(5)–Ru(4) 87.1(4), S(4)–Ru(4)–Ru(5) 89.01(12), S(3)–Ru(4)–Ru(5) 54.03(11), S(3)–Ru(1)–Ru(2) 54.21(12), S(1)–Ru(1)–Ru(2) 54.17(12), Ru(1)–S(1)–Ru(2) 70.48(14), Ru(1)–S(3)–Ru(2) 69.88(13), Ru(1)–S(3)–Ru(4) 129.7(2), Ru(4)–S(3)–Ru(5) 71.62(14). 25

26

Fig. 5. ORTEP drawing of the molecular structure of [HRu5(CO)15(µ-N,S-tsac)(µ5-S)] (5) showing 50% probability thermal ellipsoids (left) and DFT-optimized structure of E (right). Ring hydrogen atoms on the tsac ligand in the experimental structure are omitted for clarity. Selected bond distances (Å) and angles (o) for the solid-state structure: Ru(1)–Ru(2) 2.876(2), Ru(2)–Ru(3) 2.777(2), Ru(1)–Ru(3) 2.758(2), Ru(3)–Ru(4) 3.171(2), Ru(4)–Ru(5) 2.811(2), Ru(5)–N(1) 2.13(2), Ru(1)–S(3) 2.348(6), Ru(2)–S(3) 2.336(5), Ru(3)–S(3) 2.478(6), Ru(4)–S(3) 2.515(5), Ru(5)–S(3) 2.344(6), Ru(4)–S(1) 2.424(5), S(3)–Ru(4)–Ru(5) 51.84(13), S(1)–Ru(4)–Ru(5) 89.46(14), S(1)–Ru(4)–S(3) 88.45(18), N(1)–Ru(5)–Ru(4) 87.1(5), N(1)–Ru(5)–S(3) 87.7(5).

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Graphical Abstract

Reactions of [Ru3(CO)12] with thiosaccharin: Synthesis and structure of di-, tri-, tetra- and penta-ruthenium complexes containing a thiosaccharinate ligand(s) Md. Jadu Mia, Md. Selim Reza, Nikhil C. Bhoumik, Shishir Ghosh*, Vladimir N. Nesterov, Michael G. Richmond, Shariff E. Kabir*

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Research Highlights

•

Reactions of [Ru3(CO)12] with thiosaccharin (tsacH) at different experimental conditions

•

Synthesis and structure of diruthenium complex [Ru2(CO)6(µ-N,S-tsac)2]

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Synthesis and structure of tri-, tetra- and penta-ruthenium clusters

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Carbon-sulfur bond scission and subsequent capture of the extruded sulfur by the cluster core

Declaration of interests

E fne authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. DThe authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

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