From recovered palladium to molecular and nanoscale catalysts

[PdI2(Me(2)dazdt)] is obtained from palladium powder via a 100% atom -economical Pd(0) leaching reaction using Me(2)dazdt (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 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