Bistrimethylsilylamide Transition-Metal Complexes as Starting Reagents in the Synthesis of Ternary Cd−Mn−Se Cluster Complexes

The use of bis-trimethylsilylamide transition-metal complexes soluble in organic solvents offers new perspectives for the synthesis of metal chalcogenide cluster molecules, especially for multicomponent clusters. This is illustrated by the synthesis of the mixed cadmium−manganese chalcogenide clusters [Cd₄Mn₆Se₄(SePh)₁₂(PⁿPr₃)₄] and [Cd₄Mn₄S(SePh)₁₄(PⁿPr₃)₂] as reported here. These cluster molecules display interesting properties, such as a photoluminescence in the red to near-infrared spectral region, which is particularly bright at temperatures below ∼100 K, and an antiferromagnetic coupling between the manganese(II) ions. Electrospray Fourier transform ion cyclotron resonance mass spectra from the chemically charged clusters in solution show several ionic cluster species which indicate a fast Cd/Mn exchange in solution. Furthermore, single crystal X-ray analysis and magnetic measurements supported by density functional theory calculations suggest a cocrystallization of structural isomers of the ideal cluster composition [Cd₄Mn₄S(SePh)₁₄(PⁿPr₃)₂] as well as of species with the general formula [Cd_4+xMn_4−xS(SePh)₁₄(PⁿPr₃)₂] (x < 0 Mn enrichment; x > 0 Cd enrichment) without a significant decrease in the stability. Thermal cleavage of [Cd₄Mn₆Se₄(SePh)₁₂(PⁿPr₃)₄] results, in agreement with the CdSe/MnSe phase diagram, in the formation of a mixture of a hexagonal phase Cd_1−xMn_xSe (x ≈ 0.5) and a cubic phase Mn_1−xCd_xSe (x < 0.05).