Insight into the catalytic potential of water-soluble iridium phosphine complexes
Kubeika, Jaime Lynn
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The first part of this thesis involved the syntheses of a variety of iridium compounds containing the water-soluble ligands TPPTS and TPPMS. The aqueous solution behavior of select compounds was studied. Ir(CO)(CH 3 )(Cl)(I)(TPPTS) 2 underwent halide dissociation, forming Ir(CO)(CH 3 )(Cl)(H 2 O)(TPPTS) 2 + and Ir(CO)(CH 3 )(H 2 O)(I)(TPPTS) 2 + upon dissolution in water. These compounds are further converted to Ir(CO)(CH 3 )(OH)(I)(TPPTS) 2 and Ir(CO)(CH 3 )(OH) 2 (TPPTS) 2 under basic conditions. Above pH 10 the compounds decomposed, producing methane and trans -Ir(CO)(OH)(TPPTS) 2 . The pH dependent interconversion between Ir(H)(CO)(TPPTS) 3 and Ir(H) 2 (CO)(TPPTS) 3 + was studied. The stability of Ir(CO)(Cl)(TPPTS) 2 and its equilibria with Ir(CO)(H 2 O)(TPPTS) 2 + Cl - and Ir(CO)(OH)(TPPTS) 2 was also investigated. The second part of this thesis involved the reactivity of trans -Ir(CO)(Cl)(TPPTS) 2 with alkynols, alkenols and alkenes under homogeneous aqueous conditions. Reaction with 4-pentyn-1-ol and 3-pentyn-1-ol in water resulted in the formation of 5-hydroxy-2 pentanone. This indicates an intramolecular mechanism of hydration of the iridiumbound alkynol. 5-Hexyn-1-ol and 3-hexyn-1-ol also undergo catalytic hydration when reacted with trans -Ir(CO)(Cl)(TPPTS) 2 in water, forming 6-hydroxy-2-hexanone and 6-hydroxy-3-hexanone, respectively. In addition to the hydration reactivity, alkyne-containing iridium complexes were observed by NMR.Reaction of 2-pentyn-1-ol with trans -Ir(CO)(Cl)(TPPTS) 2 in water resulted in the formation of two ? 1 -allenyl iridium compounds, Ir(CO)(H 2 O)(C(CH 2 CH 3 )=C=CH 2 )(TPPTS) 2 + and Ir(CO)(OH)(C(CH 2 CH 3 )=C= CH 2 )(TPPTS) 2 which were characterized by NMR spectroscopy. Reaction with allyl alcohol resulted in the formation of propionaldehyde, acrolein, propene and carbon dioxide. Reactions with 1,3-substituted alkenols, 2-buten-1-ol, 3-buten-2-ol, 3-penten-2-ol and 1-penten-3-ol, resulted in the reshuffling of functionalities through a proposed 1,3-hydroxyl shift mechanism as well as isomerization to the ketone or aldehyde products. Reaction with dimethyl maleate formed two stable iridium-bound alkene complexes, Ir(CO)(H 2 O)(dimethyl maleate)(TPPTS) 2 + and Ir(CO)(Cl)(dimethyl maleate)(TPPTS) 2 . Reactions of ethylene and propene with trans -Ir(CO)(Cl)(TPPTS) 2 resulted in no significant reactivity. Lastly, biphasic reactions of the iridium(I) dimer, Ir 2 (Cl) 2 (COE) 4 , with TPPTS resulted in the formation of four novel orthometallated compounds. In the presence of ethylene the production of the orthometallated compounds was accelerated and went to completion.The formation of these orthometallated compounds was unusual in that similar reactivity is not seen with PPh 3 or TPPMS.