Rapid Synthesis, Characterization, and Catalytic Function of Rhodium(III) and Iridium(III) Chloro-bridged Dimers
| dc.contributor.author | Brown, Loren | en |
| dc.contributor.committeechair | Merola, Joseph S. | en |
| dc.contributor.committeechair | Deck, Paul A. | en |
| dc.contributor.committeemember | Lin, Feng | en |
| dc.contributor.committeemember | Yee, Gordon T. | en |
| dc.contributor.department | Chemistry | en |
| dc.date.accessioned | 2019-06-04T08:00:16Z | en |
| dc.date.available | 2019-06-04T08:00:16Z | en |
| dc.date.issued | 2019-06-03 | en |
| dc.description.abstract | Rh(III) and Ir(III) dimeric complexes with tunable cyclopentadienyl (Cp) rings have proven versatile for both catalysis and as synthetic precursors. An efficient microwave method to synthesize Rh(III) and Ir(III) dimeric complexes [(η5-ring)MCl]2(μ2-Cl)2, (where (η5-ring)MCl = (η5-Me4C5R)Rh(III)Cl or (η5-Me4C5R)Ir(III)Cl) was developed. A modular design for the substituted cyclopentadienes HC5Me4R was based on Grignard reactions of 2,3,4,5-tetramethylcyclopent-2-en-1-one (R = alkyl, 12 examples; R = aryl, 3 examples) or by SNAr reactions of potassium tetramethylcyclopentadienide with perfluoroarenes (R = perfluoroaryl, 3 examples). Reaction of the Me4CpHR ligands with [M(COD)](μ2-Cl)2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) produced the dimeric complexes [Cp*RMCl]2(μ2-Cl)2 in moderate to excellent yield. The resulting dimers were characterized by nuclear magnetic resonance (NMR) spectroscopy, single-crystal X-ray diffraction (XRD), high-resolution mass spectrometry (HRMS), elemental analysis, and examined as catalysts for oxidative lactonization of 1,4- and 1,5-diols. Oxidative lactonization of 1,4-butanediol to afford γ-butyrolactone proceeded selectively and efficiently using [(η5-Me4C5R)IrCl]2(μ2-Cl)2 as the catalyst. Several R substituents were tested to assess electronic substituent effects. The most active complex contained an electron donating group, R = CHMe2 and successfully catalyzed the formation of diols to lactones across a range of 1,4- and 1,5-diols, generally in high yield. Computational analysis of the rate-determining b-hydrogen elimination reactions provided an atomistic account of observed trends in reaction yield and selectivity as a function of substrate structure, while accounting neatly for the observed selective formation of lactones (vs. succinaldehyde) in the transfer dehydrogenation of 1,4-butyrolactone. | en |
| dc.description.abstractgeneral | Rhodium(III) and iridium(III) complexes are useful synthetic precursors, catalysts, and biologically active compounds. This dissertation explores a rapid synthesis of these metal complexes and their subsequent catalytic applications with 1,4- and 1,5-diols. The oxidative lactonization of diols with rhodium and iridium complexes is an attractive one-pot synthesis, opening a variety of lactones to be produced. Structural studies involving novel fluorinated rhodium and iridium chloro-bridged dimers are discussed in detail. | en |
| dc.description.degree | Doctor of Philosophy | en |
| dc.format.medium | ETD | en |
| dc.identifier.other | vt_gsexam:21089 | en |
| dc.identifier.uri | http://hdl.handle.net/10919/89732 | en |
| dc.publisher | Virginia Tech | en |
| dc.rights | In Copyright | en |
| dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
| dc.subject | iridium | en |
| dc.subject | rhodium | en |
| dc.subject | lactone | en |
| dc.subject | oxidative lactonization | en |
| dc.subject | transfer dehydrogenation | en |
| dc.subject | microwave synthesis | en |
| dc.subject | ligand effects | en |
| dc.title | Rapid Synthesis, Characterization, and Catalytic Function of Rhodium(III) and Iridium(III) Chloro-bridged Dimers | en |
| dc.type | Dissertation | en |
| thesis.degree.discipline | Chemistry | en |
| thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
| thesis.degree.level | doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |