Chalcogenido‐Dimethylgallates and ‐Indates DMPyr2[Me2M(μ2−E)]2 (M=Ga, In; E=S, Se): Building Blocks for Higher and Lower Order Chalcogenidoindates

Abstract Metalation of the anions in the ionic liquids DMPyr[SH] and DMPyr[SeH] (DMPyr=1,1‐dimethylpyrrolidinium) by trimethylgallium and trimethylindium is investigated. The reaction proceeds via pre‐coordination of [EH]−, methane elimination and formation of an unprecedented series of chalcogenido metalates DMPyr2[Me2M(μ2−E)]2 (M=Ga, In; E=S, Se). These show the presences of dinuclear dianions with four‐membered ring structures displaying highly nucleophilic bridging chalcogenide ligands in their crystallographically determined molecular structures. Some representative reactions of these building blocks with amphoteric electrophiles were studied: Addition of two equivalents of E(SiMe3)2 (E=S, Se) to the indates DMPyr2[Me2In(μ 2−S)]2 and DMPyr2[Me2In(μ2−Se)]2 leads to a cleavage of the ring, E silylation and formation of mononuclear, monoanionic indates DMPyr[Me2In(SSiMe3)2], DMPyr[Me2In(SeSiMe3)2], and even a mixed sulfido‐selenido dimethylindate DMPyr[Me2In(SSiMe3)(SeSiMe3)]. Reaction of DMPyr2[Me2In(μ2−S)]2 with two equivalents of Lewis acid Me3In leads to charge delocalization, ring expansion and formation of six‐membered ring DMPyr3[Me2In(μ 2−S−InMe3)]3. The latter is a key intermediate in the formation of dianionic sulfidoindate DMPyr2[(Me2In)6(μ 3−S)4] displaying an unusual inverse heteroadamantane cage structure with four capping sulfido ligands.


General considerations
All preparative operations were conducted by using standard Schlenk techniques and freshly dried solvents.All solvents were dried according to common procedures 1 and passed through columns of aluminium oxide, R3-11G-catalyst (BASF) or stored over molecular sieves (3 Å or 4 Å).Other reagents were used as received unless stated otherwise.Literature known procedures were used as reported or slightly modified to synthesize DMPyr [SSiMe3], 2 Me2InCl 3 and E(SiMe3)2 (E = S, Se). 4   Elemental analyses (C, H, N, S) were carried out by the service department for routine analysis with a vario MICRO cube (Elementar).Samples for the elemental analysis were weighted into tin capsules inside a nitrogen filled glovebox. 1H and proton decoupled 13 C-NMR spectra were recorded in automation with a Bruker Avance II 300 spectrometer, 29 Si-and 77 Se-NMR spectra were recorded by the service department for NMR analyses with a Bruker Avance II HD 300, DRX 400 or Avance III 500 spectrometer.All spectra were recorded at ambient temperature. 1H-and 13 C-NMR spectra were calibrated using residual proton signals of the solvent (dmso-d6: H 2.50 ppm, C 39.52 ppm, thf-d8: H 3.58 & 1.72 ppm, C 67.21 & 25.31 ppm). 29Si-NMR spectra were referenced externally (SiMe4: Si 0.00 ppm) just as 77 Se-NMR spectra (Me2Se Se 0.00 ppm).
After flushing the solution with a constant flow of argon for 5 minutes all volatiles were removed in fine vacuum.The residue was recrystallized from a acetonitrile/diethyl ether mixture at -30 °C.After filtration and washing the residue for two times with 10 mL diethyl ether the crystals were dried in fine vacuum.DMPyr [SH] (1, 3.68 g, 27.6 mmol, 69%) was obtained as colorless solid.The yield can be enhanced by further saturation of the mother liquor and subsequent crystalisation cycles.1;H,11.4;N,10.5;S,24.1. Found: C,53.9;H,11.4;N,10.6;S,25.2.

Synthesis of N,N-Dimethylpyrrolidinium hydroselenide DMPyr[SeH] (2)
Se(SiMe3)2 (6.88 g, 30.5 mmol, 1.1 eq.) was added to a solution of N,N-dimethylpyrrolidinium methylcarbonat (4.86 g, 27.8 mmol, 1.0 eq) in 30 mL methanol at 0 °C.The reaction mixture was stirred for 30 min at 0 °C and for 1 hour at room temperature.All volatiles were removed in fine vacuum and the residue was diluted in acetonitrile until a saturated solution is obtained.Storing this saturated solution at -30 °C yields greenish crystals that are collected by filtration and washed two times with 10 mL diethyl ether.DMPyr [SeH] (2, 3.90 g, 21.6 mmol, 78%) was obtained as slightly greenish crystals.The yield can be enhanced by further saturation of the mother liquor and subsequent recrysalisation cycles.
To a suspension of DMPyr[EH] in 10 mL thf a solution of Me3M in 10 mL thf was slowly added at -20 °C.The reaction mixture is allowed to obtain room temperature within 18 h under continuous stirring.The mixture becomes clear after approximately 15 min, and after approximately 2 hours a colorless solid precipitates.After the 18 h a colorless cloudy suspension is obtained.All volatiles were removed in fine vacuum and the residue was washed twice with 10 mL of pentane.The target compound DMPyr2[Me2M(µ2-E)]2 is obtained as colorless powder.
Deviations might be traced back on the slight excess of Me3Ga used.

Synthesis of the N,N-Dimethylpyrrolidinium bis(trimethylsilylchalcogenolato)dimethylchalcogenidoindates DMPyr[Me2In(ESiMe3)2] (7-9)
As complexes with ESiMe3-moiety show a pronounced instability towards some common solvents, the usage was restricted on inert ethers and aliphats.As chlorinated solvents and dmso-d6 decompose the target anions, the usage of THF-d8 was indicated for NMR-analysis.Our first method to prepare DMPyr [Me2In(SSiMe3)2] ( 7) was the addition/substitution reaction between one equivalent of

Preparation of DMPyr[Me2In(SSiMe3)2] (7) by addition/substitution of DMPyr[SSiMe3] to Me2InCl
To a suspension of DMPyr [SSiMe3] (0.36 g, 1.76 mmol, 2.0 eq.) in 5 mL thf a solution of Me2InCl (0.16 g, 0.88 mmol, 1.0 eq.) is added dropwise at -78 °C.The reaction mixture is slowly warmed to room temperature within 18 h.the suspension is filtered.All volatiles were removed from the filtrate in fine vacuum, and the colorless oily residue was washed with 5 mL pentane, and the residue dried in fine vacuum.The target compound is obtained as colorless wax.The identity of the product was proven via 1 H-NMR and 29 Si-NMR that were identical to those of 7 prepared by the other method.*The signal for the indium attached methyl groups could hardly be identified, due to the low concentration of the saturated solution of 9 in THF-d8.Therefore also no 29 Si-and no 77 Se-NMR spectra could be obtained.

Preparation of DMPyr3[Me2In(µ2-S-InMe3)]3 (10)
To a suspension of DMPyr2[Me2In(µ2-S)]2 (5) (0.100 g, 0.180 mmol, 1.5 eq.) in 3 mL thf a solution of 0.058 g Me3In (0.058 g, 0.361 mmol, 3.0 eq.) in 5 mL thf was added dropwise at -78 °C.The reaction mixture was allowed to obtain room temperature within 18 h.A clear solution is obtained, that is separated from all volatiles in fine vacuum.The colorless residue is washed with 5 mL pentane and dried in fine vacuum.DMPyr3[Me2In(µ2-S-InMe3]3 (10) was obtained as colorless solid with a yield of 0.145 g (0.111 mmol, 92%).Structural XRD consideration for ]3 ( 10) Data was collected with a Bruker D8 QUEST area detector diffractometer equipped with with MoK radiation, a graded multilayer mirror monochromator ( = 0.71073 Å) and a PHOTON-100 CMOS detector using an oil-coated shock-cooled crystal at 100(2) K. Absorption effects were corrected semiempirical using multiscanned reflexions (SAINT V8.37A (Bruker AXS Inc., 2015)).Cell constants were refined using 9785 of observed reflections of the data collection.The structure was solved by direct methods by using the program XT V2014/1 (Bruker AXS Inc., 2014) and refined by full matrix least squares procedures on F 2 using SHELXL-2017/1 (Sheldrick, 2017).The non-hydrogen atoms have been refined anisotropically, carbon bonded hydrogen atoms were included at calculated positions and refined using the 'riding model' with isotropic temperature factors at 1.2 times (for CH3 groups 1.5 times) that of the preceding carbon atom.Data were of low quality.Only data up to Theta    S5: XRD crystal and refinement data for DMPyr3[Me2In(µ2-S-InMe3)]3 (10).

Identification code JG085_0m
Habitus, colour colorless needle Crystal size 0.180 x 0.170 x 0.120 mm

A: Attempt to prepare 11 starting from 7 by elimination of SiMe4
To a solution of DMPyr[Me2In(SSiMe3)2] (7) (0.076 g, 0.16 mmol, 2.0 eq.) in 5 mL thf a solution of Me3In (0.053 g, 0.32 mmol, 4.0 eq.) in 5 mL thf was added dropwise at -100 °C.The reaction mixture was allowed to obtain room temperature during a time period of 18 h.All volatiles of the To a suspension of Ph4P[Cl] (0.067 g, 0.17 mmol, 2.0 eq.) in 5 mL thf a solution of ClInMe2 (0.032 g, 0.17 mmol, 2.0 eq.) in 5 mL thf was stirred for 18 h at room temperature to obtain a clear solution of   of the thermolysis experiment can be found in the attempts to synthesise the anion (-0.63 ppm, the minor deviation could be a concentration effect).We think this is a good reason to assume this signal to be assignable to the [(H3C)2In)6(µ3-S)4] 2-anion.Though we want to point out, that we were not able to perform a complete and selective synthesis of 11.
Me2InCl and two equivalents ofDMPyr [SSiMe3].After separation of one equivalent of the byproduct DMPyr[Cl]  the target molecule is obtained.By silylation of the indate dianion DMPyr2[Me2In(µ2-S)]2(5) with S(SiMe3)2 no byproducts emerge, and the pure target compound is obtained quantitatively by simple removing all volatiles in fine vacuum.For both methods the target compounds could be obtained in purely and quantitatively, but the latter one is way more convenient, (SSiMe3)(SeSiMe3)] (7).

23. 3
was used during refinement.Split positions were refined for the In and S positions.Large anisotrop displacement factors for the cations indicate non-resolved disorder.High difference electron density indicates that the refinement is not complete.10 crystallizes in the space group P-1 with eight formula units per unit cell.Despite the low quality of the crystallographic data, the shape and the conformation and the connectivity of the anion can be qualitatively identified.A discussion of bond lengths and angles is only possible on a coarse level.The anion has a trimer-like six-membered ring structure in the twist-boat conformation that allows the terminal trimethylindate moieties to obtain an equatorial orientation.As methyl groups attached to the cyclic bond indium atoms obtain an axial and an equatorial orientation, we assume these methyl groups' signals in the 1 H-and 13 C-NMR-spectra are split into two.In figure S1 a qualitatively representative anion from the eight different formula units set of XRD data is shown without disordered atoms.
Ph4P[Me2InCl2].S(SiMe3)2 (0.064 g, 0.36 mmol, 4.0 eq.) was added dropwise to a solution of Me2InCl (0.065 g, 0.36 mmol, 4.0 eq.) in 5 mL at -20 °C.The solution was allowed to obtain room temperature within a time period of 18 h to obtain a solution of [Me2In(µ2-SSiMe3)]2.To the Ph4P[Me2InCl2] solution the solution of [Me2In(µ2-SSiMe3)]2 was slowly added at -78 °C.The reaction mixture was allowed to warm to room temperature within a time period of 18 h.All volatiles of the solution were removed in fine vacuum.The colorless residue was dried in fine vacuum and investigated by 1 H-NMR spectroscopy.