Trialkylphosphine-Stabilized Copper(I) Gallium(III)Phenylchalcogenolate Complexes: Crystal Structures and Generation of Ternary Semiconductors by Thermolysis

摘要

A series of organometallic trialkylphosphine-stabilized copper galliumnphenylchalcogenolate complexes [(R3P)mCunMe2−xGa(EPh)n+x+1] (R = Me, Et, iPr,ntBu; E = S, Se, Te; x = 0, 1) has been prepared and structurally characterized by X-rayndiffraction. From their molecular structures three groups of compounds can bendistinguished: ionic compounds, ring systems, and cage structures. All these complexesncontain one gallium atom bound to one or two methyl groups, whereas the number ofncopper atoms, and therefore the nuclearity of the complexes, is variable and dependsnmainly on size and amount of phosphine ligand used in synthesis. The Ga−E bondsnare relatively rigid, in contrast to flexible Cu−E bonds. The lengths of the latter arencontrolled by the coordination number and steric influences. The Ga−E bond lengthsndepend systematically on the number of methyl groups bound to the gallium atom,nwith somewhat shorter bonds in monomethyl compounds compared to dimethylncompounds. Quantum chemical computations reproduce this trend and shownfurthermore that the rotation of one phenyl group around the Ga−E bond is a low energy process with two distinct minima,ncorresponding to two different conformations found experimentally. Mixtures of different types of chalcogen atoms on molecularnscale are possible, and then ligand exchange reactions in solution lead to mixed site occupation. In thermogravimetric studies thencomplexes were converted into the ternary semiconductors CuGaE2. The thermolysis reaction is completed at temperaturesnbetween 250 and 400 °C, typically with lower temperatures for the heavier chalcogens. Because of significant release of Me3Ganduring the thermolysis process, and especially in case of copper excess in the precursor complexes, binary copper chalcogenidesnare obtained as additional thermolysis products. Quaternary semiconductors can be obtained from mixed chalcogen precursors.