Hydrogen Peroxide: A Poor Ligand to Gallium Tetraphenylporphyrin

As models for possible heme-iron-H2O2 enzymatic intermediates, tetraphenylporphyrin (TPP)-gallium chemistry has been explored in CD2Cl2. (TPP)GaOTf (1) and (TPP)Ga(ClO4) (2) have been prepared from (TPP)GaCl and AgOTf or AgClO4. Trace water reacts with 2 to give [(TPP)Ga(OH2)](ClO4) (5) and with (TPP)GaOOtBu 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 H2O2 in methylene chloride is described. All of these gallium complexes, however, are unreactive with this anhydrous H2O2 in CD2Cl2. H2O2 does not displace even the weakly coordinating perchlorate or triflate anions, or coordinated water, indicating that H2O2 is a very weak ligand.

在探讨可能作为血红素铁-过氧化氢酶催化中间体的模型方面，四苯基卟啉（TPP）-镓化学在CD2Cl2中的研究得到了深入。由（TPP）GaCl与AgOTf或AgClO4反应制备得到的（TPP）GaOTf（1）和（TPP）Ga(ClO4)（2），经过一系列反应转化生成了[(TPP)Ga(OH2)](ClO4)（5）以及（TPP）GaOH（3）。这些络合物均经过全面表征，包括1、3的结构，5的双水合类似物，以及甲基衍生物（TPP）GaMe（4）的X射线晶体结构。同时，描述了一种便捷的制备无水稀过氧化氢二氯化甲烷溶液的方法。然而，所有这些镓络合物均与CD2Cl2中的无水过氧化氢不发生反应。过氧化氢甚至不能取代弱配位的过氯酸根或三氟甲酸根阴离子，或配位水，这表明过氧化氢是一个非常弱的配体。