Aminomethylation transition metal complexes

Pincer ligands, that is, tridentate Hgands that enforce meridional geometry upon complexation to transition metals, result in pincer complexes which possess a unique balance of stability versus reactivity [3]. Transition-metal complexes of bulky, electron-rich pincer ligands have found important appHcations in synthesis, bond activation, and catalysis [4, 5]. Among these, pincer complexes of Pr-PNP (2,6-bis-(di-iso-propylphosphinomethyl)pyridine), Bu-PNP (2,6-bis-(di-terPbutyl-phosphinomethyl)pyridine), and PNN ((2-(di-tert-butylphosphinomethyl)-6-diethyl-aminomethyl)pyridine), PNN-BPy (6-di-tert-butylphosphinomethyl-2,2 -bipyridine) ligands exhibit diverse reactivity [6-8]. These bulky, electron-rich pincer ligands can stabilize coordinatively unsaturated complexes and participate in unusual bond activation and catalytic processes. 

The regular structure of the polymer not only causes the formation of intramolecular salts IV, but also favours the formation of chelate complexes with transition metal ions. As recently reported, divalent metal ions dissolved in an aqueous solution are readily taken up by the neutral polymer suspended in the same solution The structure of the polymer-metal complexes could not be determined yet. However, from infrared spectra an ionization of the carboxylic acid units is evident Since the aminomethyl groups are in positions adjacent to the carboxylate units, they likely act as ligands and contribute to the formation of chelate complexes with the metal ions, as schematically represented in Fig. 29. 

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