Hydrogen Peroxide:  A Poor Ligand to Gallium Tetraphenylporphyrin

Abstract

As models for possible heme-iron-H 2 O 2 enzymatic intermediates, tetraphenylporphyrin (TPP)-gallium chemistry has been explored in CD 2 Cl 2 . (TPP)GaOTf ( 1 ) and (TPP)Ga(ClO 4 ) ( 2 ) have been prepared from (TPP)GaCl and AgOTf or AgClO 4 . Trace water reacts with 2 to give [(TPP)Ga(OH 2 )](ClO 4 ) ( 5 ) and with (TPP)GaOO t Bu to give (TPP)GaOH ( 3 ). These complexes were fully characterized including X-ray structures for 1, 3, the bis(aquo) analogue of 5, and the methyl derivative (TPP)GaMe ( 4 ). A convenient procedure for preparing anhydrous dilute solutions of H 2 O 2 in methylene chloride is described. All of these gallium complexes, however, are unreactive with this anhydrous H 2 O 2 in CD 2 Cl 2 . H 2 O 2 does not displace even the weakly coordinating perchlorate or triflate anions, or coordinated water, indicating that H 2 O 2 is a very weak ligand.