Embryonic brass: pseudo two electron Cu/Zn clusters

Abstract

The isoelectronic M₇ clusters [Cu₃Zn₄](Cp*)₅ (<b>1</b>) and {[Cu₂Zn₅](Cp*)₅}⁺ (<b>2</b>) are described. While <b>1</b> can be isolated only as a minor side product from the reaction of Cu(CH₃CO₂) with equimolar amounts of [Zn₂Cp*₂] with the trigonal cluster [CuZn₂](Cp*)₃ as the major product, <b>2</b> is available in acceptable yields from the reaction of [CuZn₂](Cp*)₃ with the Cp*Zn₂-transfer-reagent [Cp*Zn₂(Et₂O)₃][BAr₄ ^F]. The trigonal bipyramidal Cu/Zn-clusters exhibit exceptional bonding situations: with formally only one skeleton electron pair they can be regarded as highly electron deficient. However, a detailed DFT analysis reveals that the cluster bonding is supported by 3d orbital contributions of the trigonal metal base unit. The data contribute to the development of an advanced tool-box for synthesis of Hume-Rothery intermetallic (<i>e.g.</i> brass) inspired clusters.