Bimetallic Perthiocarbonate Complexes of Cobalt: Synthesis, Structure and Bonding

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{µ-TePh}{µ-TeBH3-ĸ2Te,H}{Cp*Co}] (Cp* = ɳ5-C5Me5) (1) in the presence of CS2 afforded the bimetallic perthiocarbonate complex [(Cp*Co)2(μ-CS4-κ1S:κ2S′)(μ-S2-κ2S″:κ1S‴)] (2) and the dithiolene complex [(Cp*Co)(μ-C3S5-κ1S,S′] (3). Complex 2 contains a four-membered metallaheterocycle (Co2S2) comprising a perthiocarbonate [CS4]2− unit and a disulfide [S2]2− unit, attached opposite to each other. Complex 2 was characterized by employing different multinuclear NMR, infrared spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies. Preliminary studies show that [Cp*VCl2]3 (4) with an intermediate generated from CS2 and [LiBH4·THF] yielded thiolate species, albeit different from the cobalt system. Furthermore, a computational analysis was performed to provide insight into the bonding of this bimetallic perthiocarbonate complex.


Introduction
The efficiency of metal sulfides as heterogeneous catalysts and the activity of metalloproteins in enzyme-mediated catalysis are generally significantly impacted by the nature of the metal-sulfur entities.An intriguing and unusual structural chemistry became apparent via a systematic search for metal-sulfur types of compounds given the variety of coordination possibilities that sulfur ligands can provide [1,2].Indeed, CS 2 ligands have been shown to be versatile synthetic reagents ever since the first transition metal-CS 2 complexes were synthesized in 1967 [3] due to their electron donating and electron accepting properties, yielding an array of binding modes with one or more transition metal atoms [4][5][6].

Reactivity of 1 with CS 2
Transition metal-chalcogen complexes are well documented in the literature.Recently, we have shown that the reaction of [Cp*Ru(µ-Cl)Cl] 2 with Na[BH 3 (SCHS)] led to the formation of several bimetallic dithioformato ruthenium complexes, where the dithioformate ligand (CH 2 S 2 ) shows diverse binding modes with the metal center(s) [20].In addition, the reaction of [1,2-(Cp*Ru) 2 (µ-H) 2 B 3 H 7 ] with CS 2 yielded the arachno-ruthenaborane [(Cp*Ru) 2 (B 3 H 8 )(CS 2 H)], with a dithioformato ligand attached to it by the metal-assisted hydroboration [22].Thus, investigation of the CS 2 ligand with transition metal boron species became of interest.With this background, we reacted 1 with CS 2 under thermolytic condition.Thus the reaction of 1 with CS 2 under thermolytic conditions.The reaction of 1 with CS 2 in toluene at 70 • C for 6 h led to the formation of an air-stable complex, the brown solid 2 (18% yield, R f = 0.46), and the known green dithiolene complex [(Cp*Co)(µ-C 3 S 5 -κ 1 S:κ 1 S ′ ] 3 [25] (12% yield, R f = 0.58) (Scheme 1).The identification of complex 2 was confirmed by combined 1 H, 13 C{ 1 H} NMR, IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies.The detailed characterization of complex 2 is discussed below.
content was not achieved, interesting cobalt and vanadium thiolate complexes were isolated.

Reactivity of 1 with CS2
Transition metal-chalcogen complexes are well documented in the literature.Recently, we have shown that the reaction of [Cp*Ru(µ-Cl)Cl]2 with Na[BH3(SCHS)] led to the formation of several bimetallic dithioformato ruthenium complexes, where the dithioformate ligand (CH2S2) shows diverse binding modes with the metal center(s) [20].In addition, the reaction of [1,2-(Cp*Ru)2(µ-H)2B3H7] with CS2 yielded the arachno-ruthenaborane [(Cp*Ru)2(B3H8)(CS2H)], with a dithioformato ligand attached to it by the metal-assisted hydroboration [22].Thus, investigation of the CS2 ligand with transition metal boron species became of interest.With this background, we recently performed the photolytic reaction of 1 [19] with CS2, which led to the formation of the air-stable violet bimetallic thiotellurite complex [(Cp*Co)2{µ-S3TeS3-κ 2 S:κ 2 Te:κ 2 S′}].So, relying on these results, as well as with interest in exploring the chemistry under different conditions, we reacted 1 with CS2 under thermolytic conditions.The reaction of 1 with CS2 in toluene at 70 °C for 6 h led to the formation of an air-stable complex, the brown solid 2 (18% yield, Rf = 0.46), and the known green dithiolene complex [(Cp*Co)(µ-C3S5-κ 1 S:κ 1 S′] 3 [25] (12% yield, Rf = 0.58) (Scheme 1).The identification of complex 2 was confirmed by combined 1 H, 13 C{ 1 H} NMR, IR spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies.The detailed characterization of complex 2 is discussed below.The 11 B NMR of complex 2 shows no chemical shifts, and the 1 H NMR spectrum shows no upfield region peaks, which rules out the possibility of the formation of a boroncontaining complex.Indeed, complex 2 is formed by the release of BH3 from complex 1.We confirmed the release of the [BH3·PPh3] adduct by trapping it with PPh3.The 11 B{ 1 H} and 31 P{ 1 H} NMR spectra (Figures S7 and S8) of the reaction mixture show resonances at δ = −39.3and 20.8 ppm, respectively.The 1 H NMR spectrum displays two resonances at δ = 1.38 and 1.63 ppm at a 1:1 ratio, corresponding to Cp* ligands.The presence of two different Cp* ligands is also supported by the 13 C{ 1 H} NMR spectrum.In addition to Cp* peaks, the 13 C{ 1 H} NMR shows resonance at δ = 252.7 ppm, which indicates the presence of a C=S moiety.The infrared spectrum shows a peak at 1020 cm −1 that confirms the presence of this C=S double bond.Further, the mass spectrometric analysis of 2 shows an isotopic pattern (ESI + mode) at m/z = 592.9376,which corresponds to the molecular formula C21H31Co2S6.Although all the spectroscopic and mass spectrometric data point toward the formation of a thiolate complex, the solid-state framework of 2 was confirmed by singlecrystal X-ray diffraction studies.The crystals were grown by slow evaporation of an nhexane/CH2Cl2 (30:70) solution at 5 °C.
The 11 B NMR of complex 2 shows no chemical shifts, and the 1 H NMR spectrum shows no upfield region peaks, which rules out the possibility of the formation of a boroncontaining complex.Indeed, complex 2 is formed by the release of BH 3 from complex 1.We confirmed the release of the [BH 3 •PPh 3 ] adduct by trapping it with PPh 3 .The 11 B{ 1 H} and 31 P{ 1 H} NMR spectra (Figures S7 and S8) of the reaction mixture show resonances at δ = −39.3and 20.8 ppm, respectively.The 1 H NMR spectrum displays two resonances at δ = 1.38 and 1.63 ppm at a 1:1 ratio, corresponding to Cp* ligands.The presence of two different Cp* ligands is also supported by the 13 C{ 1 H} NMR spectrum.In addition to Cp* peaks, the 13 C{ 1 H} NMR shows resonance at δ = 252.7 ppm, which indicates the presence of a C=S moiety.The infrared spectrum shows a peak at 1020 cm −1 that confirms the presence of this C=S double bond.Further, the mass spectrometric analysis of 2 shows an isotopic pattern (ESI + mode) at m/z = 592.9376,which corresponds to the molecular formula C 21 H 31 Co 2 S 6 .Although all the spectroscopic and mass spectrometric data point toward the formation of a thiolate complex, the solid-state framework of 2 was confirmed by single-crystal X-ray diffraction studies.The crystals were grown by slow evaporation of an n-hexane/CH 2 Cl 2 (30:70) solution at 5 • C.
The solid-state X-ray structure of complex 2 shows the bimetallic perthiocarbonate complex [(Cp*Co) 2 (µ-CS 4 -κ 1 S:κ 2 S ′ )(µ-S 2 -κ 2 S ′′ :κ 1 S ′′′ )] (Figure 1).Note that there are two molecules in the asymmetric unit.To the best of our knowledge, complex 2 is the first structurally characterized perthiocarbonate complex of cobalt.It consists of a four-membered metallaheterocycle (Co  The average Co-S bond length of 2.242 Å is comparable to that in coba complexes [28,29], and the average bridged Co-S distance of 2.233 Å is sligh than the unbridged Co-S bonds (2.261 Å).Further, the Co•••Co distance of 3.332 suggests the absence of any metal-metal (Co-Co) bond, making it a coordinat rated 18-electron species.Transition metal-perthiocarbonate complexes are w mented in the literature, in which the [CE4] 2-ion (E = S, Se) acts as a 1,1′-dithiol Some examples of such complexes are listed in Table 1 [30][31][32][33], which describe ent bonding modes, structural parameters, and spectroscopic data of comp [CE4] 2-units.
Generally, the perthiocarbonate anion, [CS4] 2-, is obtained by the reaction o disulfide or polysulfide dianions.Perthiocarbonate complexes can be synthes trithiolate complexes [M(CS3)2] 2-by I2 oxidation or the addition of sulfur [34].co-workers reported the first example of [CE4] 2-incorporated into transition bonyl complexes, [(CE4)2Mn2(CO)6] 2-(E = S, Se) (Table 1) [32], where two [CE4] 2- were connected to two {Mn(CO)3} units symmetrically.In the case of complex 2  The average Co-S bond length of 2.242 Å is comparable to that in cobalt-thiolate complexes [28,29]   DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS4] unit (Figure 2b).Overall, the contour line diagram reveals the CS3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS4] unit (Figure 2b).Overall, the contour line diagram reveals the CS3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS4] unit (Figure 2b).Overall, the contour line diagram reveals the CS3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS4] unit (Figure 2b).Overall, the contour line diagram reveals the CS3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS4] unit (Figure 2b).Overall, the contour line diagram reveals the CS3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).DFT theoretical calculations were carried out for insight into the electronic structure and bonding situation in 2 (see Section 3.3 for the computational details).The molecular orbital (MO) analysis of 2 shows a large HOMO-LUMO energy gap of 3.19 eV.Among the important MOs, the HOMO-12 of 2 shows a large d (M)-p (S) interaction of atom Co2 with the sulfur atoms of the disulfur unit (Co2-S5 and Co2-S6) (Figure 2a).Moreover, the HOMO-26 of 2 depicts the S-S end-to-end σ-bonding interaction of the disulfur unit, which is also confirmed by the contour line diagram (Figure 2c,d).The HOMO-26 also shows a side-to-side overlap of the p orbitals of C41-S1 (π-interaction).This double-bond character is also reflected by a higher Wiberg bond index (WBI) computed for C41-S1 (1.585 Å) and a shorter calculated bond distance of 1.652 Å.On the other hand, the HOMO-17 of 2 shows the σ-bonding interaction of the [CS 4 ] unit (Figure 2b).Overall, the contour line diagram reveals the CS 3 bonding interaction in the S1-C41-S2-S3 plane, which also indicates the sp 2 character of the atom C41 (Figure 2e).In the recent past, we isolated and structurally characterized paramagnetic thioc bonate complexes from the reaction of Na5[B(CH2S2)4] and [Cp*VCl2]3 (4) [38].Thus, w the objective of isolating similar types of thiolate complexes to that of complex 2, we plored the reactivity of [Cp*VCl2]3 (4) with an intermediate generated from CS2 a [LiBH4·THF] under different reaction conditions, which yielded the inseparable yell solids 5 and 6 (Scheme S1).Although we do not have detailed characterizations of th inseparable complexes, preliminary studies (X-ray diffraction analysis) show that 5 an are binuclear vanadium trithiocarbonate [(Cp * V)2(µ-CS3-κ 2 S,S′)2] and (disulfaneyl)m thanethiolate [(Cp*V)2(µ-SCH2S2-κ 2 S,S′)2] complexes, respectively (Figures S1 and S2).

UV-vis Study of 2
The absorption patterns of the colored complex 2 may be of interest due to the pr ence of different chalcogen fragments.Therefore, the UV-vis absorption spectrum o was measured in the range of 280-800 nm in CH2Cl2 solution at 298 K (Figure 3).In f the most intense peaks in the higher-energy regions (280-320 nm) are due to the sp allowed π-π* transition of the Cp* ligands present in these complexes [39].Comparativ low-intensity peaks at a lower energy around 320-550 nm may be due to the charge tra fer bands.In order to obtain more detail, time-dependent DFT calculations were carr out on 2. In complex 2, the high-intensity absorption band near 326 nm is due to HOMO-6→LUMO electronic transition.The HOMO-6 is mostly from metal-based d bitals, while the LUMO has both metal (d orbital) and disulfide [S] 2-(p orbital on S atom orbital characters (Figure S10).Therefore, these absorption bands can be assigned metal-to-ligand charge transfer (MLCT) transitions.In the low-energy wavelength regi 2 shows a low-intensity absorption band at 570 nm, which could be due to the intram lecular LMCT transitions.In the recent past, we isolated and structurally characterized paramagnetic thiocarbonate complexes from the reaction of Na 5 [B(CH 2 S 2 ) 4 ] and [Cp*VCl 2 ] 3 (4) [38].Thus, with the objective of isolating similar types of thiolate complexes to that of complex 2, we explored the reactivity of [Cp*VCl 2 ] 3 (4) with an intermediate generated from CS 2 and [LiBH 4 •THF] under different reaction conditions, which yielded the inseparable yellow solids 5 and 6 (Scheme S1).Although we do not have detailed characterizations of these inseparable complexes, preliminary studies (X-ray diffraction analysis) show that 5 and 6 are binuclear vanadium trithiocarbonate [(Cp * V) 2 (µ-CS 3 -κ 2 S,S ′ ) 2 ] and (disulfaneyl)methanethiolate [(Cp*V) 2 (µ-SCH 2 S 2 -κ 2 S,S ′ ) 2 ] complexes, respectively (Figures S1 and S2).

UV-vis Study of 2
The absorption patterns of the colored complex 2 may be of interest due to the presence of different chalcogen fragments.Therefore, the UV-vis absorption spectrum of 2 was measured in the range of 280-800 nm in CH 2 Cl 2 solution at 298 K (Figure 3).In fact, the most intense peaks in the higher-energy regions (280-320 nm) are due to the spin-allowed π-π* transition of the Cp* ligands present in these complexes [39].Comparatively low-intensity peaks at a lower energy around 320-550 nm may be due to the charge transfer bands.In order to obtain more detail, time-dependent DFT calculations were carried out on 2. In complex 2, the high-intensity absorption band near 326 nm is due to the HOMO-6→LUMO electronic transition.The HOMO-6 is mostly from metal-based d orbitals, while the LUMO has both metal (d orbital) and disulfide [S] 2− (p orbital on S atoms) orbital characters (Figure S10).Therefore, these absorption bands can be assigned as metal-to-ligand charge transfer (MLCT) transitions.In the low-energy wavelength region, 2 shows a low-intensity absorption band at 570 nm, which could be due to the intramolecular LMCT transitions.

Electrochemical Study of 2
The redox properties of complex 2 dissolved in DMF were examined using cyclic voltammetry (Figure 4).The DMF solution displays two irreversible responses at Epc = −1.47V and −0.86 V vs. Fc/Fc + .They may originate from the reduction of the disulfide or metal-centered reduction based on the reported literature.The two irreversible anodic responses at Epa = 0.11 V and 0.27 V vs. Fc/Fc + are most likely due to the oxidation of the thiolate ligand [40][41][42][43][44].

Electrochemical Study of 2
The redox properties of complex 2 dissolved in DMF were examined using cyclic voltammetry (Figure 4).The DMF solution displays two irreversible responses at E pc = −1.47V and −0.86 V vs. Fc/Fc + .They may originate from the reduction of the disulfide or metalcentered reduction based on the reported literature.The two irreversible anodic responses at E pa = 0.11 V and 0.27 V vs. Fc/Fc + are most likely due to the oxidation of the thiolate ligand [40][41][42][43][44].

Electrochemical Study of 2
The redox properties of complex 2 dissolved in DMF were examined using cyclic voltammetry (Figure 4).The DMF solution displays two irreversible responses at Epc = −1.47V and −0.86 V vs. Fc/Fc + .They may originate from the reduction of the disulfide or metal-centered reduction based on the reported literature.The two irreversible anodic responses at Epa = 0.11 V and 0.27 V vs. Fc/Fc + are most likely due to the oxidation of the thiolate ligand [40][41][42][43][44].

General Procedures and Instrumentation
All the experimental procedures were performed in an argon atmosphere by using standard Schlenk line techniques and a glove box.All the solvents, n-hexane, DCM (dichloromethane), toluene, and THF (tetrahydrofuran), were distilled under an argon atmosphere prior to use.All the chemicals, such as Ph 2 Te 2 (diphenyl ditelluride) (Sigma Aldrich, Bangalore, India) and CS 2 (Loba Chemie Pvt. Ltd., Mumbai, India), were purchased and used as received.The complexes [{Cp*CoPh}{µ-TePh}{µ-TeBH 3 -κ 2 Te,H}{Cp*Co}] (1) [19] and [Cp*VCl 2 ] 3 (4) [45] were prepared according to the methods from the literature.Dialuminum-supported TLC plates (MERCK TLC plates, Bangalore, India) were used for the separation of the reaction mixtures.All the NMR spectra for the synthesized complexes were obtained on 500 MHz Bruker FT-NMR spectrometers, Billerica, MA, USA.The residual solvent protons (CDCl 3 , δ = 7.26 ppm) and carbons (CDCl 3 , δ = 77.1 ppm) were employed as references for the 1 H and 13 C{ 1 H} NMR spectra, respectively.The mass data of all the synthesized complexes were recorded on Q-Tof Micro YA263 HRMS, Milford, MA, USA and 6545 Q-Tof LC/MS instruments, Santa Clara, CA, USA.The IR spectrum of 2 was recorded in dichloromethane solvent with a JASCO FT/ IR-1400 spectrometer, Easton, MD, USA.The UV-vis spectrum was recorded on a JASCO V-650 spectrometer, Tokyo, Japan.The cyclic voltammetry measurement was performed on an OrigaLys potentiostat, Rillieux-la-Pape, France in a standard three-electrode system (glassy carbon working electrode, platinum wire counter electrode, and Ag/Ag + as pseudo reference electrode).For deoxygenation, argon was bubbled into the electrolyte medium for 10 min.The cyclic voltammograms were recorded at a scan rate of 50 mVs −1 .
Synthesis of 2. In a pre-dried Schlenk tube, 1 (0.10 g, 0.123 mmol) was suspended in 10 mL of toluene.Under the atmosphere of argon, CS (4 mL) was added slowly using a syringe at room temperature to the green solution of complex 1.Then, the reaction mixture was kept at 70 • C (temperature of oil bath) for 6 h with continuous stirring under an atmosphere of argon.The solvent was removed by vacuum, and the remaining residue was separated and purified using the TLC method on silica gel TLC plates.Elution with n-hexane/CH 2 Cl 2 (30:70 v/v) yielded the brown complex 2 (0.014 g, 18%) and the known green complex [(Cp*Co)(µ-C 3 S 5 -κ 1 S:κ 1 S ′ ] 3 (0.012 g, 12%) [25].

Single Crystal X-ray Diffraction Analysis
Suitable X-ray-quality crystals of 2 and 5/6 were grown by slow diffusion of an nhexane/CH 2 Cl 2 solution at 5 • C. The crystal data were collected and integrated using a Bruker D8 VENTURE diffractometer (Billerica, MA, USA) with a PHOTON 100 CMOS detector (Tokyo, Japan) for 2 and a Bruker AXS Kappa APEX2 CCD diffractometer (Billerica, MA, USA) for 5 and 6 with graphite monochromated Mo-Kα (λ = 0.71073 Å) radiation at 293(2) K.The structures of these complexes were solved by heavy atom methods using SHELXS-97 [46] and SHELXT-2014 and refined using SHELXL-2014, SHELXL-2017, and SHELXL-2018 [47].All the molecular structures were drawn using Olex2 [48].Note that complexes 5 and 6 co-crystallize in the same crystallographic unit with disorder mainly over the sulfur and carbon atoms, with 0.56 and 0.44 occupancies, respectively.The crystal structure of 6 is further disordered over two components with a site occupancy ratio of 0.31:0.13.The crystallographic data were deposited with the Cambridge Crystallographic Data Centre as supplementary publication, nos.CCDC-2111767 (2) and 2349360 (5 and 6).These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif access on 18 April 2024.

Computational Details
Density functional theory (DFT) optimization of complex 2 was carried out using the Gaussian 16 program [49] with the B3LYP functional [50] and the def2-TZVP [51,52] basis set from the EMSL (Environmental Molecular Sciences Laboratory) Basis Set Exchange

a
Average distance.b In ppm.na = Not available.