A Pd Halide Cluster from 1964: Pd6Cl8 Capped by Ring-Opened C3Ph3 Ligands from Oxidative Addition of Cyclopropenium Ions

On the basis of a protocol from 1964 on the reaction of K2PdCl4, triphenylcyclopropenium chloride, and ethylene, the product was now identified as a Pd6Cl8 cluster capped by μ3-η1:η1:η3-C3Ph3 ligands, [C3Ph3]2[Pd6Cl8(C3Ph3)2]. The ligand is formed in a two-step reaction involving first the partial reduction of Pd(II) to Pd(0) by ethylene and second the ring-opening oxidative addition of the cyclopropenium ion, leading to a rare binding mode with one allyl and two alkyl bonds. Although the structure was not recognized at that time, this compound represents the first isolated organometallic Pd cluster compound.