Thiolate-Protected Trimetallic Au∼20Ag∼4Pd and Au∼20Ag∼4Pt Alloy Clusters with Controlled Chemical Composition and Metal Positions.

The mixing of heteroelements in metal clusters is a powerful approach to generate new physical/chemical properties and functions. However, as the kinds of elements increase, control of the chemical composition and geometric structure becomes difficult. We succeeded in the compositionally selective synthesis of phenylethanethiolate-protected trimetallic Au∼20Ag∼4Pd and Au∼20Ag∼4Pt clusters, Au∼20Ag∼4Pd(SC2H4Ph)18 and Au∼20Ag∼4Pt(SC2H4Ph)18. Single-crystal X-ray structural analysis revealed the precise position of each metal element in these metal clusters. Reacting with thiol at an elevated temperature was found to be important to direct the metal elements to the most stable positions. The electronic structures of these trimetallic clusters become more discretized than those of the related bimetallic clusters due to orbital splitting.