Carboxamido nitrogen: A versatile new donor group which imparts unique properties to iron(III) and copper(II) complexes

The coordination chemistry of carboxamido nitrogen bound to Fe III has opened the door to a new area of iron chemistry. Following the discovery of this type of coordination in nature, several molecules containing FeIII-N_amido bonds have been synthesized. The unique properties of this new class of compounds are now emerging. In chapters 2 and 3, several complexes that contain FeIII-N_amido bonds along with FeIII-O_phen coordination (O _phen = phenolato oxygen) have been reported and their properties systematically evaluated. The complexes have been characterized by spectroscopic techniques as well as X-ray crystallography. Our results show that the FeIII-N _amido bonds stabilize the FeIII center in several ways. These FeIII complexes are predominantly low-spin, stable toward hydrolysis and stabilized over FeII in proportion to the number of FeIII-N_amido bonds in the molecule. We have also examined several complexes that contain both FeIII-N_amido and FeIII-O_phen bonds in order to identify their influence on the spin-state of the FeIII center.; In chapters 4 we have explored a structure-spectroscopy relationship within a set of closely related CuII, complexes with pyridine-2,6-dicarboxamide ligands. Chapter 5 covers one aspect of the unique reactivity observed with these complexes, namely, the heterolytic cleavage of the C-C bond of acetonitrile. This type of reactivity had not been catalyzed by CuII prior to this work. We believe that such reactivity, usually only seen for low-valent metal centers, is a result of highly basic nature of the carboxamido ligands bonded to CuII ion which possibly gives this center a more “low-valent” character.; Appendix 1 covers some chemistry concerning carbon dioxide fixation by a simple N-methylimidazole complex of FeIII. In addition, we have assembled a unique and biologically relevant (μ-oxo)diiron(III) core in this system. Assembly of supramolecular structures of CuII complexes coordinated to ligands with a pyridine-2,6-dicarboxamide backbone is the subject matter of Appendix 2. In this section, we also report the self-assembly of a short double-stranded helicate and also a coordination polymer of Cu II. Appendix 3 deals with large hydrogen bonded structures based on intra- and inter-molecular hydrogen bonds between organic compounds that contain carboxamide moieties.