St Andrews Research Repository

St Andrews University Home
View Item 
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  •   St Andrews Research Repository
  • Chemistry (School of)
  • Chemistry
  • Chemistry Theses
  • View Item
  • Login
JavaScript is disabled for your browser. Some features of this site may not work without it.

Triphenyl- and tetraphenyl cyclopentadienylides

Thumbnail
View/Open
MichaelSingerPhDThesis.pdf (34.56Mb)
Date
1968
Author
Singer, Michael Inglis Campbell
Supervisor
Lloyd, Douglas
Funder
University of St Andrews
Metadata
Show full item record
Altmetrics Handle Statistics
Abstract
The thermal decomposition of 2,3,4,5-tetraphenyldiazo cyclopentadiene in pyridine and methyl pyridines has been found to provide a route to the corresponding pyridinium 2,3,4,5-tetraphenyl-cyclopentadienylide. This procedure has been extended to include decomposition of the diazo compound in derivatives of Group V and VI elements and a route to a series of hitherto unreported tetraphenyloyclopentadienylides has been established. Triphenyl-phosphonium, triphenylarsonium, and triphenyIstibonium 2,3,4,5-tetraphenylcyclopentadienylides have been isolated as stable crystalline solids and evidence has been Sound for the existence of the triphenylbismuthonium analogue. Diphenylsulphoniumi methyIphenylsulphonium, and diphenylselenonium 2,3,4,5-tetra-phenyloyclopentadienylides have also been shown to have unusual stability. The mechanism of the decomposition reaction of 2,3,4,5- tetraphenyldiazocyclopentadiene is discussed and is considered to proceed by initial decomposition of the diazo compound to tetraphenyloarbenacyclopentadiene followed by eleotrophilic attack on a suitable heteror-atem group, containing a lone pair of electrons. A comparative study of the properties and the reactivities of the tetraphenylcyclopentadienylides with carbonyl compounds and nitrosobenzene has been made. The pKa's of some of the ylide conjugate acids were determined in 95% ethanol solution and it appears that for the similarly substituted ylidos there is no: consistent parallel between nucleophilicity and basicity. The thermal decomposition of other diazocyclopentadienes, including the 2,3,4,5-tetrachlora-, 2,3,4-tripheny1-1 5-bromo-2,3,4-triphenyl-, and 5-chloro-2,3,4-triphenyl- derivatives, occurred uncontrollably and attempts to obtain ylides failed when these diazo compounds were subjected to analogous conditions employed for 2,3,4,5-tetraphenyldiazocyclopentadiene. Phosphines were found to couple readily with substituted diazocyolopentadienes to form the corresponding phosphazines with the exception of the reaction between triphenylphosphine and 2,3,4,5-tetraphenyldiazocyclopentadiene. Evidence suggests that: these phosphazines, in acidic media, are protonated at the nitrogen atom rather than at the five-membered ring. Pyridinium 2,3,4-triphenyIcyclopentadienylide was prepared by alkylation of pyridine with 5-bromo-2,3,4-triphonyloyclo-pentadiene in a solution of nitromethane and subsequent basi-fication. In an attempt to prepare the analogous phosphomium ylide it was found that: triphonylphosphine in nitromethane led to reduction of the bromo compound. However when this reaction was carried out: in the absence of solventtriphenyl-(2,3,4-triphenyIcyclopentadienyl)phosphonium bromide was isolated. It has been found that tmiphenylarsine oxide and 2,3,4-triphenyloyclopentadiene undergo a reaction in triethylamine and phosphorus pentoxide to form triphenylarsonium 2,3,4- triphenyIeyclopentadienylide, and that' when the reaction is carried out in acetic anhydride the 5-acetyl ylide is formed. Some electrophilic substitution reactions on the triphenyl-phosphonium and triphenylarsonium 2,3,4-triphonyloyolopenta-dienylides have been done and the properties and nucleophilioity of these ylides have been investigated. A comparison has also been drawn between these ylides and their totmaphenylcyclopenta-dienylide analogues.
Type
Thesis, PhD Doctor of Philosophy
Collections
  • Chemistry Theses
URI
http://hdl.handle.net/10023/15155

Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.

Advanced Search

Browse

All of RepositoryCommunities & CollectionsBy Issue DateNamesTitlesSubjectsClassificationTypeFunderThis CollectionBy Issue DateNamesTitlesSubjectsClassificationTypeFunder

My Account

Login

Open Access

To find out how you can benefit from open access to research, see our library web pages and Open Access blog. For open access help contact: openaccess@st-andrews.ac.uk.

Accessibility

Read our Accessibility statement.

How to submit research papers

The full text of research papers can be submitted to the repository via Pure, the University's research information system. For help see our guide: How to deposit in Pure.

Electronic thesis deposit

Help with deposit.

Repository help

For repository help contact: Digital-Repository@st-andrews.ac.uk.

Give Feedback

Cookie policy

This site may use cookies. Please see Terms and Conditions.

Usage statistics

COUNTER-compliant statistics on downloads from the repository are available from the IRUS-UK Service. Contact us for information.

© University of St Andrews Library

University of St Andrews is a charity registered in Scotland, No SC013532.

  • Facebook
  • Twitter