Difunctional poly(phosphorhydrazone) PPH dendritic catalysts. Influence of different parameters on the catalytic efficiency

Dendrimers are a special type of hyperbranched polymers constituted of branched monomers arranged radially around a central core, and synthesized step-by-step. Phosphorus-containing dendrimers of type poly(phosphorhydrazone, PPH, possess phosphorus atoms at each branching point, and P(S)Cl2 terminal functions every two steps. Such terminal functions enable the sequential grafting of one function, then of a second one, to get precisely difunctionalized dendrimers. Such process is used here for grafting both a fluoroalkyl chain and a ligand for complexing a metal (Pd or Cu). The dendritic Pd complexes have been used in Stille, Suzuki and Heck C-C cross-couplings, whereas the Cu complexes have been used in C-N couplings. The influence of the length of the fluoroalkyl chain, the generation of the dendrimers, the base, the solvent, and the possible recovery and re-use of the catalyst on the outcome of the catalytic reactions are described.