Organo‐Gallium/Indium Chalcogenide Complexes of Copper(I): Molecular Structures and Thermal Decomposition to Ternary Semiconductors

Several organo‐gallium/indium chalcogenide complexes of copper(I), stabilized by trialkylphosphines, were isolated, structurally characterized by using single‐crystal X‐ray diffraction, and investigated in thermolysis experiments. The syntheses with [E(Me 3 Si) 2 ] (E=S, Se) as a starting material and a chalcogen source involve the elimination of volatile silyl acetate, silyl ethers, and methane from copper(I) acetate, and Group 13 metal trimethyl compounds, respectively. Chalcogenide complexes, according to the general formulas [(R 3 PCu) 4 (MeM) 4 E 6 ] ( 1–6 ) and [(R 3 PCu) 6 (MeM) 4 M 4 S 13 ] ( 7–9 ; with R=alkyl and M=Ga, In), and mixed chalcogenide–phenylchalcogenolate complexes [( i Pr 3 PCuEPh) 3 (MeGaE) 4 ] ( 10, 11 ) were isolated. The heavy atom cores of 1–6 consist of an octahedron of chalcogen atoms, interpenetrated by a cube of metal atoms. Depending on the steric demand of the phosphine ligands, two constitutions are observed; the metal atoms of the same element either forming tetrahedra, or parallelograms, respectively. This constitutional isomerism is further investigated by quantum chemical calculations. Complexes 7–9 contain a central sulfur atom, surrounded by two interpenetrating tetrahedra of Group 13 metal atoms, an octahedron of copper atoms, and an icosahedron of twelve outer sulfur atoms; the heavy atom framework of 10 and 11 is a “cut‐out” of this structure. Thermolysis experiments include thermogravimetry measurements and subsequent Rietveld phase analysis of the residues by using powder X‐ray diffraction. The homologous compounds 1 , 3 , 4 , and 6 yield the respective crystalline ternary semiconductor material CuME 2 at temperatures below 300 °C. Partial release of Me 3 M during the thermolysis process results in excess copper in the residue and therefore in small amounts of additional binary copper chalcogenide phases or metallic CuM alloys. Compound 8 produces nanocrystalline CuGaS 2 at about 300 °C.