Controlling the Depolymerization of Paraformaldehyde with Pd-Phosphine Complexes.

Paraformaldehyde is an easy-to-handle chemical for the in situ generation of formaldehyde and is, therefore, often used in chemistry, structural biology, or medicine. We have investigated the depolymerization process of paraformaldehyde at different temperatures for the application as C1 surrogate in "CO-free" carbonylation reactions using in situ Raman spectroscopy. Rather surprisingly, it was found that small amounts of commonly applied carbonylation catalysts slow down the depolymerization process significantly. By applying H-1, O-17, and P-31 NMR spectroscopy coupled with DFT calculations the inhibition process could be assigned to an electron-withdrawing coordination behavior of the Pd complex at the chain end of the paraformaldehyde chain. This inhibition process can be controlled by the utilized phosphine ligand.