Homoleptic Group 13 Trimethylsilylchalcogenolato Metalates [M(ESiMe₃)₄]⁻ (M = Ga, In; E = S, Se): Metastable Precursors for Low-Temperature Syntheses of Chalcogenide-Based Materials

Abstract

We communicate the synthesis and full characterization of so far unknown tetrakis­(trimethylsilylsulfido) and -(trimethylsilylselenido) gallates and indates in form of their organic salts Cat+[M­(ESiMe3)4]− (M = Ga, In; E = S, Se; Cat = dimethylpyrrolidinium (DMPyr+), Ph4P+, (dppe)2Cu+, (dmpe)2Cu+). These thermally metastable silylchalcogenolatometalates can act as modular precursors for an ionic-liquid- or organic-solution-based low-temperature synthesis of multinary metal chalcogenide materials such as the CIGS species Cu­(In x Ga1–x )­(S y Se1–y )2.

Heavy Chalcogenide‐Based Ionic Liquids in Syntheses of Metal Chalcogenide Materials near Room Temperature

“…We developed a low‐temperature approach of using a solution (or ink in a proposed ink jet printed electronics process) of binary soluble precursors Cat + [M(ESiMe 3 ) 4 ] − as source for the elements In/Ga and S/Se and a solution (or film of ink) of Cu + ions in form of their tetramethylthiourea (tmtu) complexes [Cu(tmtu) 3 ]PF 6 . After removing by‐products Cat[PF 6 ] and tmtu, thermal annealing of the microcrystalline precipitate is leading to phase pure microcrystalline CIGS detected via PXRD [26] . This method has a higher potential to be further developed into a larger scale printed CIGS process for PV modules than the single‐source precursor approach demonstrated as well: As Cu(+1) tends to show a higher affinity towards sulfur and selenium anions than Ga(3+) and In(3+), copper has to be masked by diphosphine ligands dppe or dmpe in order to isolate single source precursors with cations such as [(dppe) 2 Cu] + or [(dmpe) 2 Cu] + [M(ESiMe 3 ) 4 ] − (M=Ga, In; E=S, Se).…”

“…After removing by-products Cat[PF 6 ] and tmtu, thermal annealing of the microcrystalline precipitate is leading to phase pure microcrystalline CIGS detected via PXRD. [26] This method has a higher potential to be further developed into a larger scale printed CIGS process for PV modules than the single-source precursor approach demonstrated as well: As Cu(+ 1) tends to show a higher affinity towards sulfur and selenium anions than Ga(3 +) and In(3 +), copper has to be masked by diphosphine ligands dppe or dmpe in order to isolate single source precursors with cations such as [(dppe) 2 Cu] + or [(dmpe) 2 Cu] + [M(ESiMe 3 ) 4 ] À (M = Ga, In; E = S, Se). Due to their high molecular mass, and higher load of waste components and ligand costs, this single-source CIGS precursor approach is probably only of academic interest.…”

“…By targeting this class of copper-indium-gallium-sulfides and selenides CIGS, our focus was the synthesis and full characterization of so far unknown tetrakis(trimethylsilylsulfido) and -(trimethylsilylselenido) gallates and indates in form of their organic cation salts Cat + [M(ESiMe 3 ) 4 ] À (M = Ga, In; E = S, Se; Cat + = DMPyr + , Ph 4 P + , (dppe) 2 Cu + , and (dmpe) 2 Cu + , dppe = diphenylphosphinoethane, dmpe = dimethylphosphinoethane). [26] There is a small corridor with respect to the reaction conditions allowing the isolation and full characterization of these thermally metastable molecular precursors in the presence of trimethylsilyl-chalcogenide ILs and MCl 3 . Only small deviations from the published protocol lead to premature precipitation of binary chalcogenides M 2 E 3 and ME at room temperature instead of the isolation of soluble molecular metalate title complexes.…”

Pseudohalogen Chemistry in Ionic Liquids with Non‐innocent Cations and Anions

“…Besides application in classic solid state chemistry, ILs can be used as reaction media to prepare (oligomeric) metal complexes, metal organic frameworks, coordination polymers [25–35] or cluster compounds incorporating main group elements [36–41] . Within SPP 1708, the synthesis of intermetallic cluster and nanoparticles, [3,42–56] the controlled synthesis of polyanions and cations, [57–61] solvent‐free chalcogenidometal‐containing materials, [62–75] deposition of nanocrystalline materials, [76–80] ionic liquids as precursors for inorganic materials, [81–83] ionic‐liquid‐modified hybrid materials, [84–87] as well as the low‐temperature synthesis of thermoelectric materials [88–92] were investigated. Moreover, theoretical [93–106] and solubility [107–114] aspects during the synthesis process were studied.…”