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, atom-economical recovery, chemoselectivity of ligand substitution reactions, demonstration of catalytic activity, and the potential for immobilization of catalytic surface units derived from recovered metal.