Chemistry & Biochemistry Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2752
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Item SYNTHESIS OF MAIN GROUP ELEMENT CLUSTERS OF GROUPS 13 AND 15 FROM DISPROPORTIONATION PATHWAYS AND ZINTL POLYANIONS(2019) Stevens, Lauren Marie; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis details the synthesis and characterization of main group element clusters of Groups 13 (aluminum) and 15 (phosphorus, arsenic). Aluminum clusters were synthesized from metastable Al(I)X (X = Cl, Br) solutions, which have proven adept at fostering the growth of metalloid clusters of the form AlnRm (where n > m). Group 15 – transition metal coordination complexes and ligand-free binary anions are synthesized through the use of Zintl ion precursors, originating from phases K3Pn7 (Pn = P, As, Sb). The novel cluster [(Bu2O)3Li][Li4Al5Ph12] has been synthesized and characterized, reported here in seven different crystallographic modifications. In addition to being the first low-valent phenyl aluminum cluster, this anion exhibits an unusual metastability in both the solid-state and solution, as indicated through ESI-MS, LDI-MS, and solid-state NMR analyses. The Zintl-derived coordination complexes [(η4-As7)Co(η3-As3)]3-, [(η4-As7)Rh(COD)]2-, and [(η4-As7)Ir(COD)]2- are reported as the first As / Group 9 clusters, and are isoelectronic to known coordination species of Zintl anions and transition metal carbonyl fragments. Additionally, the product [(η4-As7)Co(η3-As3)]3-is the first known carbon-free binary anion of As / Co. These complexes have been characterized via LDI-MS, NMR, single crystal XRD, and quantum chemical calculations. The doubly substituted coordination complex [(en)(CO)3Mo(η4-P7)Mo(CO)3]3- completes a series of previously reported Group 6 polyphosphide complexes, and is compared to its W congener, [(en)(CO)3W(η4-P7)W(CO)3]3-. Unlike coordination complexes, which retain the nuclearity of the seven-atom precursors [Pn7]3-, binary intermetalloids [Mo2P16]4- and [Rh3As16]3- show extensive reorganization of the original polypnictide cages. These anions feature cyclo-[P10]2- and cyclo-[As5]1- subunits, which are the first to be isolated and described in products of Zintl anions. Additionally, these are the first binary systems to be reported for Mo/P and Rh/As, and could potentially be used for the formation of binary phases (i.e. RhAs2) upon oxidationItem Synthesis and Characterization of Products Produced from Aluminum Monohalide Precursors(2015) DeCarlo, Samantha; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis, the synthesis, characterization and applications of aluminum compounds and cluster from aluminum monohalide solutions, AlX (where X = Cl or Br) are described. Chemistry of AlX solutions is not well understood, but AlX has proven adept at producing aluminum metalloid clusters (AlnLm where n>m). A brief overview of the renaissance of low-valent aluminum chemistry and select low-valent Al products is presented as background. The neutral mononuclear aluminum tris-bpy complexes [Al(Mebpy)3] and [Al(tBubpy)3] have been synthesized, isolated, and structurally characterized via X-ray single crystal diffraction. These complexes are the first structurally characterized homoleptic tris-bpy complexes and were studied via ESI-MS, d.c. magnetic susceptibility, electrochemical analyses. Electrochemistry demonstrates that six oxidation states are accessible from both neutral complexes: [Al(Rbpy)]n (n = -3 to 3, R = Me or tBu). The [Al(Mebpy)3] complex demonstrates unexpected magnetic ordering at 19 K which is not observed in [Al(tBubpy)3] nor in transition metal centered tris-bpy congeners. Synthesis, isolation, and characterization of the low-valent aluminum cluster [LiOEt2]2[HAl3(PPh2)6] via NMR and ESI-MS studies are also described. These experiments proved the presence of an H atom, and developed a complete and comprehensive picture of the structure, magnetism, and spectroscopy of this compound. Solution studies of reactions of AlBr with tBu-thiolate via ESI-MS show the formation and identification of [Al17Br(StBu)10S3]1-, [Al10(StBu)4S5]1-, [Al13(StBu)4BrS]1-, and [Al5(StBu)7Br]1-¬ in solution. The preparation and characterization of the aluminum (III) thiolate complex, Na[Al(SPh)4], is also described. These studies demonstrate the importance of reaction conditions in the formation of aluminum clusters in solution, and the viability of thiolate ligands to isolate low-valent aluminum products. Al nanoparticles (NP) can be produced from AlX solutions and have been successfully supported on both graphene and graphene oxide. The reduction of AlX solutions are quick, facile, and performed at low temperatures (-78°C). In the presence of graphene, faceted and well-dispersed graphene supported Al-NPs can be obtained. The [AlBrNEt3]4 cluster is isolated from AlBr⋅NEt3 solution and is soluble in toluene and diethyl ether. The burning rate of the hydrocarbon fuel doped with the tetramer is studied. There is an increase in burning rate attributed to the presence of [AlBrNEt3]4.