Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se)
<p>This thesis examines the synthesis of novel acyclic silylenes with amido, boryl, gallyl and/or boryloxyl substituents, and their reactivities towards small molecules such as H<sub>2</sub> , CO<sub>2</sub> , H<sub>2</sub>O, NH<sub>3</sub> e...
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| Format: | Thesis |
| Language: | English |
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2021
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| _version_ | 1826316570338525184 |
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| author | Ying, L |
| author2 | Aldridge, S |
| author_facet | Aldridge, S Ying, L |
| author_sort | Ying, L |
| collection | OXFORD |
| description | <p>This thesis examines the synthesis of novel acyclic silylenes with amido, boryl, gallyl
and/or boryloxyl substituents, and their reactivities towards small molecules such as H<sub>2</sub> ,
CO<sub>2</sub> , H<sub>2</sub>O, NH<sub>3</sub> etc. The silylene systems were also used as precursors for compounds
featuring silicon-heteroatom double bonds, with a focus on the attempted synthesis of
molecules featuring a Si=O moiety (silanones). </p>
<p>Chapter 2 discusses the reactions between the gallyl anion [(DippNCH)<sub>2</sub>Ga] - and Si(II)
precursors such as IDipp·SiCl<sub>2</sub> and (NTMSDipp)(I<sup>i</sup>PrMe)SiCl. While an unexpected
silyl anion formed when IDipp·SiCl<sub>2</sub> is used, a novel NHC stabilized silylene can be
synthesized by metathesis between [(DippNCH)<sub>2</sub>Ga]<sup>-</sup> and (NTMSDipp)(I<sup>i</sup>PrMe)SiCl.
The gallyl-substituted silylene reacts with N<sub>2</sub>O, however, only a silyl migrated product
can be isolated instead of the expected silanone. The reaction between Cy<sub>2</sub>NSiBr<sub>3</sub> and
[(DippNCH)<sub>2</sub>B] - , in attempt to install an amido substituent on a potential silylene
system without a labile N-SiMe<sub>3</sub> moiety, results instead in a C‒H activation product. </p>
<p>Chapter 3 reports the synthesis of a novel bisboryloxysilylene, together with its heavier
Ge, Sn and Pb congeners (the latter in collaboration with Dr Ying Kai Loh). Structural
parameters of these tetrylenes obtained by X-ray crystallography, including the E‒O,
O‒B bond distances and O-E-O, E-O-B bond angles (E = Si, Ge, Sn or Pb) show a trend
consistent with expected periodic trend for group 14 elements, resulting from
relativistic effects and increasingly poor s-p mixing on descending group 14. Further
investigation involves studies of the reactivity of the bisboryloxysilylene fowards small
molecules possessing an E‒H bond (E = H, N or O). Although no reaction is detected
with H<sub>2</sub>, the silylene is able to activate the polar E‒H bonds in water, ammonia and tert-
butyl amine. Such processes most likely occur through a three-molecule transition state
as shown by DFT calculations. </p>
<p>Chapter 4 explores the possibilities of synthesizing Si=E (E = C, N, O or Se) containing
compounds using the bisboryloxysilylene as the precursor. The reaction between the
silylene and N<sub>2</sub>O generates the first example of a silahyponitrite, which can be regarded
as a masked silanone (by N<sub>2</sub>O) as the bound N 2 O can easily be substituted in reactions
with CO<sub>2</sub> and Ph<sub>3</sub>P=O. When the silylene is treated with an excess amount of selenium,
a novel tetraselenosilolane can be isolated. Three out of the four selenium atoms in this
compound can be removed by adding Ph<sub>3</sub>P to generate a silaselenone. Attempts have
been made to synthesize a Si=N or Si=C double bond. In the former case Me<sub>3</sub>SiN<sub>3</sub> was
used as the source of Me<sub>3</sub>SiN. However, this reaction only gives a two-fold addition
product, a silaazide. In the latter case Ph<sub>3</sub>P=CH<sub>2</sub> was utilized to act as a :CH<sub>2</sub>
transferring agent. The reaction proceeds instead via a [4+1] cycloaddition process,
yielding a dearomatized silaheterocyclic compound.</p> |
| first_indexed | 2024-03-06T21:46:51Z |
| format | Thesis |
| id | oxford-uuid:49e17da1-a44d-4cfe-a553-c150107424ab |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-12-09T03:47:25Z |
| publishDate | 2021 |
| record_format | dspace |
| spelling | oxford-uuid:49e17da1-a44d-4cfe-a553-c150107424ab2024-12-08T10:06:20ZSynthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se)Thesishttp://purl.org/coar/resource_type/c_db06uuid:49e17da1-a44d-4cfe-a553-c150107424abChemistry, InorganicEnglishHyrax Deposit2021Ying, LAldridge, S <p>This thesis examines the synthesis of novel acyclic silylenes with amido, boryl, gallyl and/or boryloxyl substituents, and their reactivities towards small molecules such as H<sub>2</sub> , CO<sub>2</sub> , H<sub>2</sub>O, NH<sub>3</sub> etc. The silylene systems were also used as precursors for compounds featuring silicon-heteroatom double bonds, with a focus on the attempted synthesis of molecules featuring a Si=O moiety (silanones). </p> <p>Chapter 2 discusses the reactions between the gallyl anion [(DippNCH)<sub>2</sub>Ga] - and Si(II) precursors such as IDipp·SiCl<sub>2</sub> and (NTMSDipp)(I<sup>i</sup>PrMe)SiCl. While an unexpected silyl anion formed when IDipp·SiCl<sub>2</sub> is used, a novel NHC stabilized silylene can be synthesized by metathesis between [(DippNCH)<sub>2</sub>Ga]<sup>-</sup> and (NTMSDipp)(I<sup>i</sup>PrMe)SiCl. The gallyl-substituted silylene reacts with N<sub>2</sub>O, however, only a silyl migrated product can be isolated instead of the expected silanone. The reaction between Cy<sub>2</sub>NSiBr<sub>3</sub> and [(DippNCH)<sub>2</sub>B] - , in attempt to install an amido substituent on a potential silylene system without a labile N-SiMe<sub>3</sub> moiety, results instead in a C‒H activation product. </p> <p>Chapter 3 reports the synthesis of a novel bisboryloxysilylene, together with its heavier Ge, Sn and Pb congeners (the latter in collaboration with Dr Ying Kai Loh). Structural parameters of these tetrylenes obtained by X-ray crystallography, including the E‒O, O‒B bond distances and O-E-O, E-O-B bond angles (E = Si, Ge, Sn or Pb) show a trend consistent with expected periodic trend for group 14 elements, resulting from relativistic effects and increasingly poor s-p mixing on descending group 14. Further investigation involves studies of the reactivity of the bisboryloxysilylene fowards small molecules possessing an E‒H bond (E = H, N or O). Although no reaction is detected with H<sub>2</sub>, the silylene is able to activate the polar E‒H bonds in water, ammonia and tert- butyl amine. Such processes most likely occur through a three-molecule transition state as shown by DFT calculations. </p> <p>Chapter 4 explores the possibilities of synthesizing Si=E (E = C, N, O or Se) containing compounds using the bisboryloxysilylene as the precursor. The reaction between the silylene and N<sub>2</sub>O generates the first example of a silahyponitrite, which can be regarded as a masked silanone (by N<sub>2</sub>O) as the bound N 2 O can easily be substituted in reactions with CO<sub>2</sub> and Ph<sub>3</sub>P=O. When the silylene is treated with an excess amount of selenium, a novel tetraselenosilolane can be isolated. Three out of the four selenium atoms in this compound can be removed by adding Ph<sub>3</sub>P to generate a silaselenone. Attempts have been made to synthesize a Si=N or Si=C double bond. In the former case Me<sub>3</sub>SiN<sub>3</sub> was used as the source of Me<sub>3</sub>SiN. However, this reaction only gives a two-fold addition product, a silaazide. In the latter case Ph<sub>3</sub>P=CH<sub>2</sub> was utilized to act as a :CH<sub>2</sub> transferring agent. The reaction proceeds instead via a [4+1] cycloaddition process, yielding a dearomatized silaheterocyclic compound.</p> |
| spellingShingle | Chemistry, Inorganic Ying, L Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title | Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title_full | Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title_fullStr | Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title_full_unstemmed | Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title_short | Synthesis of Si=E containing compounds using novel silylene precursors (E = O, N, C and Se) |
| title_sort | synthesis of si e containing compounds using novel silylene precursors e o n c and se |
| topic | Chemistry, Inorganic |
| work_keys_str_mv | AT yingl synthesisofsiecontainingcompoundsusingnovelsilyleneprecursorseoncandse |