“Bottled” spiro-doubly aromatic trinuclear [Pd2Ru]+ complexes

Following an ongoing interest in the study of transition metal complexes with exotic bonding networks, we report herein the synthesis of a family of heterobimetallic triangular clusters involving Ru and Pd atoms. These are the first examples of trinuclear complexes combining these nuclei. Structural and bonding analyses revealed both analogies and unexpected differences for these [Pd2Ru]+ complexes compared to their parent [Pd3]+ peers. Noticeably, participation of Ru atom in π-aromaticity of coordinated benzene ring makes synthesized compound the second reported example of ‘bottled’ double aromaticity. This can also be referred to as spiroaromaticity due to the participation of Ru in two aromatic systems at a time. Moreover, [Pd2Ru]+ kernel exhibits unprecedented orbital overlap of Ru 2 AO and two Pd or d2 ― 2 AOs. Present findings reveal the possibility to synthesize stable clusters with delocalized metal-metal bonding from the combination of non-adjacent elements of the periodic table which has not been reported previously