Small molecule activation by iridium complexes supported by a monoanionic NNN-pincer ligand

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Drescher, Sam L.
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Chemistry and Biochemistry
The synthesis of iridium 1,5-cyclooctadiene and cyclooctene complexes supported by a monoanionic NNN-pincer ligand is described. The 1,5-cyclooctadiene complexes, ArLIr(COD) (L = 2,5-(iPr2P=NAr)2C4H2N, Ar = Pipp, Dipp, Mes, COD = 1,5-cyclooctadiene) did not react with dihydrogen or silanes, precluding further work into catalytic processes, such as alkane dehydrogenation and hydrosilylation. As such, a more reactive species was sought. PippLIr(COE) (COE = cyclooctene) reacted with dihydrogen and silanes, allowing the synthesis of PippLIr(H)2 and PippLIr(H)(SiR3) (R3 = Et3, HPh2, H2Ph). These complexes were characterized by multinuclear (1H, 13C{1H}, 29Si, 31P{1H}) and 2-dimensional NMR spectroscopy, X-ray crystallography, and elemental analysis. Alternatives to PippLIr(COE), including PippLIr(CO), PippLIr(PPh3), and others were investigated. This was undertaken to avoid competing reactivity with free COE in solution. The efficacy of PippLIr(H)2 and PippLIr(H)(SiR3) (R3 = Et3, HPh2, H2Ph) as catalysts for alkene hydrogenation and alkane dehydrogenation, and hydrosilylation, respectively, was explored.
iridium , NNN-pincer ligand , organometallic chemistry