From Recovered Palladium to Molecular and Nanoscale Catalysts

[PdI2(Me2dazdt)] is obtained from palladium powder via a 100% atom-economical Pd(0) leaching reaction using Me2dazdt (N,N′-dimethyl-perhydrodiazepine-2,3-dithione) and iodine. This complex is a versatile starting point for ligand exchange reactions with (di)phosphines, yielding trans-[PdI2(PPh3)2] and [PdI2(dppe)] (dppe = 1,2-bis-(diphenylphosphino)ethane). Further reaction with dithiocarbamates provides compounds of the form [Pd(DTC)(L)n]+ (DTC = dithiocarbamate; L = PPh3, n = 2; L = dppe, n = 1), which are highly active catalysts for regio- and chemoselective C−H bond activation reactions. Using DTC ligands with trimethoxysilyl-terminated tethers, the palladium(II) units can be attached to the surface of core−shell, silica-coated Fe3O4 nanoparticles. Once tethered, these units form the catalytically active component of a recyclable, quasi-heterogeneous, Pd(II)-based catalytic system based on recovered palladium, illustrating the proposed circular model strategy. These investigations contribute to key steps in this process, such as efficient, atomeconomical recovery, chemoselectivity of ligand substitution reactions, demonstration of catalytic activity, and the potential for immobilization of catalytic surface units derived from recovered metal.