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Studies of low valent main group and transition metal complexes supported by nitrogen-based ligands
Lugo, Audra Faye
Lugo, Audra Faye
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[Fort Worth, Tex.] : Texas Christian University,
Date
2009
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Abstract
Beta-Diketiminate ligands of the general formula [R3C{C(R2)N(R1)}2]- are now among the most ubiquitous chelating systems in all of coordination chemistry. Nacnac (R1 = aryl, R2 = CH3, R3 = H) has been used to stabilize of a variety of elements in unusually low oxidation states and in the discovery of a variety of novel bonding modes. We were principally interested in investigating the reactivity of nacnac ligands with selenium and tellurium tetrahalides, due to the absence of group 16 centers in the library of nacnac complexes.^To this end we synthesized and characterized the first examples of Se- and Te-nacnac complexes, which avoided the usual N,N'-chelation and instead favored reaction at one of the backbone methyl groups via nucleophilic attack by the carbon-carbon double bond of the enamine form of the ligand.^Additionally, we have utilized two members of the related ketiminate ligand class, of general formula [R1NC(R2)C(R3)C(R2)O]- to synthesize a variety of metal complexes spanning the periodic table. By comparing and contrasting the coordination preferences of a bulkier, bidentate (R1 = aryl) ketiminate ligand to that of a more flexible, tridentate (R1 = (CH2)2NEt2) ketiminate ligand, we observed a greater ability of the tridentate ligand to stabilize mono-ligated complexes, as opposed to the bis-ketiminato complexes frequently formed using the bidentate ligand.^Furthermore, this investigation has led to a wide range of complex types, including monomers, dimers, tetramers, adducts, and hetero-elemental cages. We have synthesized a series of main group complexes of the commercially available 2,2'-dipyridylamine, an N,N'-chelating ligand not unlike the ?-diketiminates.^Complexes of this ligand have proven useful in a multitude of applications, in no small part due to the coordinative versatility of this ligand, which can bind in monodentate, bidentate, and tridentate fashions. Finally, we have generated a series of compounds derived from phosphorus ligands based on the bulky trityl (triphenylmethyl = Ph3C) group. We have found that the considerable steric bulk of trityl diphenylphosphine inhibits coordination to a variety of metal centers, but novel complexes have been formed by employing the HBF4 salt of Ph3CPPh2 as the phosphorus-based ligand.
Contents
Subject
Subject(s)
Transition metal complexes.
Ligands.
Chelates.
Organometallic chemistry.
Ligands.
Chelates.
Organometallic chemistry.
Research Projects
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Dissertation
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Department
Chemistry and Biochemistry