Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes
Organic frameworks have been extensively studied during past decades for a myriad of applications. While inorganic frameworks, composed of non-carbon backbones, remain as mere chemical curiosities due to the much greater kinetic lability of the inorganic bonds. In particular, the instability of cycl...
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| Format: | Thesis |
| Language: | English |
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2018
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| Online Access: | http://hdl.handle.net/10356/73158 |
| _version_ | 1826110512830611456 |
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| author | Shi, Xiaoyan |
| author2 | Felipe García |
| author_facet | Felipe García Shi, Xiaoyan |
| author_sort | Shi, Xiaoyan |
| collection | NTU |
| description | Organic frameworks have been extensively studied during past decades for a myriad of applications. While inorganic frameworks, composed of non-carbon backbones, remain as mere chemical curiosities due to the much greater kinetic lability of the inorganic bonds. In particular, the instability of cyclodiphosphazane systems contain-ing saturated P-N frameworks, which are of significant interest to our group, has pre-viously undermined the exploration of their use in technological applications. In this thesis, the author firstly represents a convenient method to enhance the stabili-ties of these cyclodiphosphazanes by simply oxidizing them with chalcogen elements on the phosphorus centers (chapter 3). In addition, the author also reported the unexpected C-N bond activation occurred during the oxidation process. The experi-mental and theoretical studies demonstrate that steric factors, most probably steric strain release, play a crucial role in the metal-free activation of the C–N bonds herein described (chapter 4). Besides, conventionally, syntheses of cyclodiphosphazanes has no tolerance of protic solvents stemming from their high air- and moisture-sensitivities. Therefore, the con-cept of mechanochemistry has brought the prospect of avoiding the tedious processes associated with the demand of strict anhydrous conditions while synthesizing cy-clodiphosphazanes. In chapter 5, the first example of cyclodiphosphazanes synthesized by mechanochemical methodology is reported, further studies on the ap-plication of grinding to synthesize a series of new cyclic and acyclic cyclodiphos-phazane frameworks is investigated. More importantly, this method enabled the for-mation of previously reported as inaccessible arrangement adamantoid P4(NtBu)6. Lastly, a family of novel trimeric acyclic poly-cyclodiphosphazanes have been reported in chapter 6. For those structures, their special conformation might enable them as a potential large bite ligand with possible application of stabilizing the low coordination numbers and/or unusual oxidation states transition metal by applying the steric demanding principle. Finally moreover most importantly, inspired by the tri-meric structures, as far as we know, the ever big macrocycle with all P(III) centers, O-bridged hexamer {(μ-O)[P(μ-NtBu)]2}6, has been synthesized and fully characterized. |
| first_indexed | 2024-10-01T02:35:21Z |
| format | Thesis |
| id | ntu-10356/73158 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T02:35:21Z |
| publishDate | 2018 |
| record_format | dspace |
| spelling | ntu-10356/731582023-02-28T23:32:41Z Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes Shi, Xiaoyan Felipe García School of Physical and Mathematical Sciences DRNTU::Science::Chemistry Organic frameworks have been extensively studied during past decades for a myriad of applications. While inorganic frameworks, composed of non-carbon backbones, remain as mere chemical curiosities due to the much greater kinetic lability of the inorganic bonds. In particular, the instability of cyclodiphosphazane systems contain-ing saturated P-N frameworks, which are of significant interest to our group, has pre-viously undermined the exploration of their use in technological applications. In this thesis, the author firstly represents a convenient method to enhance the stabili-ties of these cyclodiphosphazanes by simply oxidizing them with chalcogen elements on the phosphorus centers (chapter 3). In addition, the author also reported the unexpected C-N bond activation occurred during the oxidation process. The experi-mental and theoretical studies demonstrate that steric factors, most probably steric strain release, play a crucial role in the metal-free activation of the C–N bonds herein described (chapter 4). Besides, conventionally, syntheses of cyclodiphosphazanes has no tolerance of protic solvents stemming from their high air- and moisture-sensitivities. Therefore, the con-cept of mechanochemistry has brought the prospect of avoiding the tedious processes associated with the demand of strict anhydrous conditions while synthesizing cy-clodiphosphazanes. In chapter 5, the first example of cyclodiphosphazanes synthesized by mechanochemical methodology is reported, further studies on the ap-plication of grinding to synthesize a series of new cyclic and acyclic cyclodiphos-phazane frameworks is investigated. More importantly, this method enabled the for-mation of previously reported as inaccessible arrangement adamantoid P4(NtBu)6. Lastly, a family of novel trimeric acyclic poly-cyclodiphosphazanes have been reported in chapter 6. For those structures, their special conformation might enable them as a potential large bite ligand with possible application of stabilizing the low coordination numbers and/or unusual oxidation states transition metal by applying the steric demanding principle. Finally moreover most importantly, inspired by the tri-meric structures, as far as we know, the ever big macrocycle with all P(III) centers, O-bridged hexamer {(μ-O)[P(μ-NtBu)]2}6, has been synthesized and fully characterized. Doctor of Philosophy (SPMS) 2018-01-08T06:05:13Z 2018-01-08T06:05:13Z 2018 Thesis Shi, X. (2018). Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/73158 10.32657/10356/73158 en 170 p. application/pdf |
| spellingShingle | DRNTU::Science::Chemistry Shi, Xiaoyan Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title | Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title_full | Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title_fullStr | Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title_full_unstemmed | Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title_short | Syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| title_sort | syntheses and characterization of cyclodiphosphazanes and macrocyclodiphosphazanes |
| topic | DRNTU::Science::Chemistry |
| url | http://hdl.handle.net/10356/73158 |
| work_keys_str_mv | AT shixiaoyan synthesesandcharacterizationofcyclodiphosphazanesandmacrocyclodiphosphazanes |