SYNTHESIS OF MAIN GROUP ELEMENT CLUSTERS OF GROUPS 13 AND 15 FROM DISPROPORTIONATION PATHWAYS AND ZINTL POLYANIONS

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2019

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Abstract

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 oxidation

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