ABSTRACT
A series of transition metal chloro complexes with the tetradentate tripodal tris(2-amino-oxazoline)amine ligand (TAO) have been synthesized and characterized. X-Ray structural analyses of these compounds demonstrate the formation of the mononuclear complexes [M(II)(TAO)(Cl)](+), where M(II) = Cr, Mn, Fe, Co, Ni, Cu and Zn. These complexes exhibit distorted trigonal-bipyramidal geometry, coordinating the metal through an apical tertiary amine, three equatorial imino nitrogen atoms, and an axial chloride anion. All the complexes possess an intramolecular hydrogen-bonding (H-bonding) network within the cavity occupied by the metal-bound chloride ion. The metal-chloride bond distances are atypically long, which is attributed to the effects of the H-bonding network. Nuclear magnetic resonance (NMR) spectroscopy of the Zn complex suggests that the solid-state structures are representative of that observed in solution, and that the H-bonding interactions persist as well. Additionally, density functional theory (DFT) calculations were carried out to probe the electronic structures of the complexes.
Subject(s)
Amines/chemistry , Chlorine/chemistry , Coordination Complexes/chemistry , Oxazoles/chemistry , Transition Elements/chemistry , Amines/chemical synthesis , Coordination Complexes/chemical synthesis , Hydrogen Bonding , Magnetic Resonance Spectroscopy , Models, Molecular , Oxazoles/chemical synthesis , Transition Elements/chemical synthesisABSTRACT
The synthesis of M(II)(2) complexes (M(II)=Co, Mn) with terminal hydroxo ligands has been achieved utilizing a dinucleating ligand containing a bridging pyrazolate unit and appended (neopentyl)aminopyridyl groups. Structural studies on the complexes revealed that the M(II)-OH units are positioned in a syn-configuration, placing the hydroxo ligands in close proximity (ca. 3 Å apart), which may be a prerequisite for water oxidation.
Subject(s)
Cobalt/chemistry , Hydroxides/chemistry , Manganese/chemistry , Organometallic Compounds/chemistry , Hydrogen Bonding , Models, Molecular , Molecular Conformation , Organometallic Compounds/chemical synthesisABSTRACT
The synthesis of a (carboxyamido)pyridinepyrazolate (H(5)bppap) dinucleating ligand is described. Bimetallic iron and cobalt complexes of H(5)bppap ([M(II)(2)H(2)bppap](+)) showed structural differences in both their primary and secondary coordination spheres. The binding of small molecules into the preorganized ligand cavity is verified by the hydration of [Fe(II)(2)H(2)bppap](+) and [Co(II)(2)H(2)bppap](+), leading to the formation of complexes [{Co(II)(OH)}Co(II)H(3)bppap](+) and [{Fe(II)(OH)}Fe(II)H(3)bppap](+), in which one of the metal centers has a terminal hydroxo ligand.
