Rational Synthesis and Electronic Structure of Functionalized Trinuclear Pd Metal Sheet Sandwich Complexes

Abstract

In this article we present the rational synthesis and full characterization of molecular Pd3 clusters sandwiched by imidazolium- and pyridinium-functionalized cycloheptatrienide ligands, of general formula [Pd3Br3(C7H6R)2]+. From functionalized η3-cycloheptatrienide Pd complexes as starting materials, PdBr2(η3-C7H6R), a number of synthetic routes were tested and a generally applicable strategy was developed on the basis of the formation of dimeric “preclusters”, [{PdBr(η3-C7H6R)}2(μ-Br)]+, which exhibit a Pd–Pd interaction. Spectroscopic and electrochemical results indicate a noninteger, common oxidation state of Pd in the trinuclear clusters, and crystallographic analysis reveals distinct differences in the binding properties of the Pd atoms in the solid state, suggesting that in certain environments there are even two discernible oxidation states, which is supported by computational analysis of the charge distribution.