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Utilization of the Silicon-Silicon Bond in the Generation of Species Unsaturated at Silicon William Dean Wulff Iowa State University

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Utilization of the Silicon-Silicon Bond in the Generation of Species Unsaturated at Silicon William Dean Wulff Iowa State University Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1979 Utilization of the silicon-silicon bond in the generation of species unsaturated at silicon William Dean Wulff Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Wulff, William Dean, "Utilization of the silicon-silicon bond in the generation of species unsaturated at silicon " (1979). Retrospective Theses and Dissertations. 6677. https://lib.dr.iastate.edu/rtd/6677 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This was produced from a copy of a document sent to us for microfîlming. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help you understand markings or notations which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting through an image and duplicating adjacent pages to assure you of complete continuity. 2. When an image on the film is obliterated with a round black mark it is an indication that the film inspector noticed either blurred copy because of movement during exposure, or duplicate copy. Unless we meant to delete copyrighted materials that should not have been Aimed, you will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., is part of the material being photo­ graphed the photographer has followed a defînite method in "sectioning" the material. It is customary to begin Hlming at the upper left hand comer of a large sheet and to continue from left to right in equal sections with small overlaps. If necessary, sectioning is continued again—beginning below the first row and continuing on until complete. 4. For any illustrations that cannot be reproduced satisfactorily by xerography, photographic prints can be purchased at additional cost and tipped into your xerographic copy. Requests can be made to our Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases we have filmed the best available copy. Unlversi^ Micrmlrns International 300 N. ZEEB ROAD, ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WCIR 4EJ, ENGLAND 7924275 WULFF, WILLIAM DEAN UTILIZATION OF THE SILICON-SILICON BONO IN THE GENERATION OF SPECIES UNSATURATED AT SILICON, IOWA STATE UNIVERSITY, PH.D., 1979 UniversiW Micrcxilms International soon, zeeb road, ann arbor, mi 48io6 utilization of the silicon-silicon bond in the generation of species unsaturated at silicon by William Dean Wulff A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY, Department ; Chemistry Major: Organic Chemistry Approved: Signature was redacted for privacy. In Charge o^XMaj or Work Signature was redacted for privacy. For the Major Department Signature was redacted for privacy. For the Graduate College Iowa State University Ames, Iowa 1979 11 TABLE OP CONTENTS Page DEDICATION Iv INTRODUCTION 1 NOMENCLATURE 3 HISTORICAL 6 Sllylenes 6 Sllenes 51 Dlsllenes 71 Sllanones 86 Thermal Migrations of Silicon 98 RESULTS AND DISCUSSION 107 Attempted Generation of Sllenes via Alpha Elimination of Silicon from Carbon 109 Synthesis of 1-Trlmethylsllyl-l-methyl- 2,5-dlphenylsllole gl^ and Some Reactions of Trlmethylsllylllthlum 116 The Generation and Gas Phase Reactions of Trlmethylsllylmethylsllene 2^ 130 Sllene Generation from a Sllyl 1,3-Mlgratlon l48 The Structure of the Adduct of 1-Methyl-l- trlmethylsllyl-2,5-dlphenylsllole 21.8 and Dlphenylacetylene and Some Thermal 1,5-Mlgrations of Silicon 159 Serendipitous Synthesis of a Slla-a- Pyran — Convenient, Penultimate Precursor to Dimethylsllanone l84 Ill CONCLUSION 195 EXPERIMENTAL 197 Instrumentation 197 Procedures and Results 198 BIBLIOGRAPHY 274 ACKNOWLEDGEMENTS 290 Iv DEDICATION To Mary 1 INTRODUCTION The established chemistry of (p-p) IT bonded silicon compounds begins in 1966 with the report of a silicon-carbon double bond by Nametkin and coworkers (1) and shortly there­ after by Gusel'nikov and Flowers (.2), The chemistry of the silicon-silicon and silicon-oxygen double bonds begins shortly after this but is far less developed. There are no known molecules containing a (p-p) ir bonded silicon that are isolable and this appears to be a conse­ quence of reactivity rather than of thermodynamic instability. Chemical information about (p-p) TT bonded silicon compounds has been garnered utilizing methods traditional in the study of reactive intermediates. The chemistry of divalent silicon (silylenes) predates that of (p-p) TT bonded silicon, yet it was also in 1966 that Atwell and Weyenberg (.3) reported a convenient method for the generation of organosilylenes. This report has brought about a dramatic increase in the study of organosilylenes, and has caused silylenes to be viewed not only as systems with the unstable oxidation state of silicon, but as valuable reagents for the synthetic organosllicon chemist. This thesis will describe new thermal methods for generation of silicon-carbon double bonds via 1,3- and 1,5- mlgrations of silicon. For the mildest such generator, a silicon-carbon double bond was found to exist in an 2 equilibrium concentration. A serendipitous discovery of a room temperature generator of silicon-oxygen double bonds has permitted an investigation into the chemistry of this scantily characterized species. Some new intramolecular reactions of silylenes are Investigated, In addition, the mechanism proposed by Roark and Peddle (4) to account for an intramolecular rearrangement of a silicon-silicon double bond is called into question and evidence presented to support an alternative mechanism. 3 NOMENCLATURE The nomenclature used in this thesis will, with the exceptions described below, follow the conventions set down by lUPAC. Divalent silicon species will be named as derivatives of the parent silylene (iSiHg). Simple organo- silicon compounds will be named as derivatives of silane (SiH^), while more complicated linear and cyclic systems will be named as sila-analogs of the corresponding carbon systems. Examples: MegSiClH dimethylchlorosilane CI MegSiSi-SiMe 2-chloroheptamethyltrlsilane ^ I Me Me Me-Si-Si-CH„-SiMe„ 2,2,3,5-tetramethyl- 3 I 2 I 2 2,3,5-trisilahexane H H Me Me \ / Si 1,1,4,4-tetramethyl-l,4- disilacyclohexa-2,5-diene Si / \ Me Me 4 The saturated and unsaturated three-membered rings containing one silicon atom and two carbon atoms will be named as derivatives of silarane and silarene, respectively. Me Me Me Me \A / \a / 1,l-dimethylsilarane 1,1-dimethylsilarene All compounds containing (p-p) w bonded silicon will be named as derivatives of silene (H2Si=CH2), disilene (HgSizSiHg), and silanone (HgSizQ). Conjugated silenes, disilenes, and silanones will be named as analogs of the corresponding carbon systems. Examples: H \ Si=CH2 1-methylsilene Me Me \ ^Si=0 dimethylsiIanone Me Me .Me \ / Si=Si tetramethyldisilene Me'^ ^ Me 5 ^CH Si 2-methyl-2-sllabutadiene I HC ^ ^CH 2 O 1-methyl-l-sllabenzene Me Finally, silacyclopentadiene ring systems will be named as derivatives of silole. 0 fîS==\ /Me Si l-dimethyl-2,5-diphenylsilole ^Me 0 6 HISTORICAL The chemical endeavors and results of this thesis are In the area of reactive Intermediates In organoslllcon chemistry. The particular species that are Involved are sllylenes, sllenes, dlsllenes, and sllanones. The known chemistry of each of these species is reviewed separately. In addition, the various thermal migrations of silicon are reviewed briefly as they are utilized in new approaches to the generation of sllene and sllanones. Sllylenes It has been forty years since dlchlorosilylene became the first divalent silicon species to be prepared and observed spectroscopically. Even though Interest in carbenes began about the same time, development of the chemistry of sllylenes lagged behind that of carbenes because of the comparative dearth of methods for silylene generation avail­ able to the experimentalist. It was not until twelve years ago that Atwell and Weyenberg gave us the first convenient method for organosilylene generation that precipitated a flurry of activity in this area in the past decade (3). Sllylenes are more stable than their carbon analogs, however, no molecule incorporating a divalent silicon atom has yet been Isolated. Sakural and coworkers (5) have Just reported the preparation of 1, the first example of a 7 transition metal silylene complex. Me Me 3/Me Me-Si-Si-H + Fe-fCO). II 2 9 \ Me Me Me 1 The ground state of silylene (SlHg) has been shown to be a singlet (l4 kcal/mole below triplet) by fixed-frequency laser photoelectron spectrometry (6). The bond angle in silylene has been experimentally determined by double-flash ultraviolet spectroscopy to be 92°5' (7). These values are in good agreement with other experimental and theoretical results (8). The material covered in this review of silylenes will largely concentrate on developments In the last decade. The chemistry of silylenes prior to this time will only be briefly mentioned as it has been covered In several reviews (8-12). Prior to the report of Atwell and Weyenberg, the methods for generation of silylenes were both harsh and limited in the variety of silylenes that could be produced. Dlhalosilylenes can be produced by reduction of tetra- halosllanes with elemental silicon at temperatures in excess of 800°C (10).
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