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Denmark, Scott E. Denmark, Scott E. Hartwig, John F. Hergenrother, Paul J. Girolami, Gregory S. Smith, Russell C. 2010-08-20T17:59:12Z 2010-08-20T17:59:12Z 2010-08-20T17:59:12Z 2010-08 The development of alkali-metal arylsilanolates as notable organometallic reagents for the preparation of biaryls has been realized through in depth mechanistic and preparative studies. The alkali-metal salts (potassium and sodium) of a large number of arylsilanols undergo smooth cross-coupling with a wide range of aromatic bromides and chlorides. The critical feature for the success of these coupling reactions and their considerable scope is the use of bis(tri-tert-butylphosphine)palladium. Additionally, these studies have identified the use of phosphine oxides (e.g. triphenylphosphine oxide) as useful ligands for palladium-catalyzed cross-coupling reactions. This serendipitous discovery was founded on kinetic experiments which revealed a significant rate enhancement employing these species as ligands for palladium. Later, these ligands were implemented in the reaction of arylsilanolates for the preparation of biaryl products. The mechanism of palladium-catalyzed cross-coupling reactions of alkali-metal organosilanolates has also been investigated. Under catalysis by (t-Bu3P)2Pd, the coupling with aryl bromides displays the following rate equation: rate = kobs[R3SiOK]0[ArylBr]0, with kobs = k[(t-Bu3P)2Pd]0.98. An independent study of the individual steps of the catalytic cycle has revealed a dual mechanistic pathway. The transmetalation can occur by a thermal process via an 8-Si-4 intermediate without the need for anionic activation. Additionally, arylsilanolates can serve as activators for transmetalation via a hypervalent 10-Si-5 siliconate intermediate. The independent isolation of the putative arylpalladium(II) arylsilanolate intermediate has confirmed the generation of the Pd-O-Si linkage prior to transmetalation. The unique opportunity to isolate a pretransmetalation intermediate has allowed the transmetalation step to be further refined through a detailed Hammett analysis which has demonstrated that increased electron-density about the arylsilanolate nucleophile increases the rate of coupling. Furthermore, a number of alkenyl- and arylsilanolate pretransmetalation species have been isolated with various ligands in attempts to identify the critical features of the cross-coupling of this class of organonucleophiles. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2010-07-06T14:24:52Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 3 Smith_Russell.pdf: 27286513 bytes, checksum: a87e02f08ab4bed099025ca7ba658c3a (MD5) Smith_Russell_thesis_front matter.doc: 88576 bytes, checksum: 9777b1ac2b5d89b542d1069842aa57e4 (MD5) Smith_Russell_thesis.doc: 26628608 bytes, checksum: 59f153f1816202b756bcb8d3c9e58647 (MD5) Made available in DSpace on 2010-08-20T17:59:12Z (GMT). No. of bitstreams: 6 Smith_Russell.pdf: 27259965 bytes, checksum: 5c07a1856a8ecdbb8b2a4248fa9ffba3 (MD5) 1_Smith_Russell.pdf: 27286513 bytes, checksum: a87e02f08ab4bed099025ca7ba658c3a (MD5) 2_Smith_Russell.pdf: 27217647 bytes, checksum: 4e5f070628088487566c549b355b2064 (MD5) Smith_Russell_thesis_front matter.doc: 88576 bytes, checksum: 9777b1ac2b5d89b542d1069842aa57e4 (MD5) Smith_Russell_thesis.doc: 26628608 bytes, checksum: 59f153f1816202b756bcb8d3c9e58647 (MD5) license.txt: 4063 bytes, checksum: 2125c6ec4f4073a0a88bd646c91fedd7 (MD5) http://hdl.handle.net/2142/16830 en Copyright 2010 Russell C. Smith arylsilanolates biaryls mechanism palladium Preparative and mechanistic aspects of palladium-catalyzed cross-coupling reactions of alkali-metal arylsilanolates Chemistry 1413 Chemistry 0335 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Chemistry -UIUC 10KS0335PHD