Synthesis and Coordination Chemistry of Functionalised Phosphazanes

This thesis focuses on the chemistry of novel phosphazane species derived from the chloro-phosphazanes [ClP(μ-NR)]₂ and their use as ligands and building blocks for macrocyclic compounds. The introduction (Chapter 1) surveys previous literature in the area, which is pertinent to the new studies. One of the most important issues is the various ways in which dimeric phosph(III)azanes can be employed as precursors for new ligands and in the design of new types of inorganic macrocycles. In Chapter 2 the synthesis of new chloro-dimers of the type [ClP(μ-NR)]₂ is described, which are the primary starting materials. Chapter 3 concerns the substitution at the chlorine atoms of [ClP(μ-NR)]₂ by LiSH to give a variety of sulfur-containing PV species [S=P(H)(μ-NR)]₂. The thermodynamic preference for the cis or trans isomers of the latter are explored by detailed NMR spectroscopic and DFT calculation investigations. Deprotonation of the ^tBu derivative [S=P(H)(μ-N^tBu)]₂ using organometallic bases (Chapter 3) led to the isolation of s-block salts (Mg²+, Na⁺, K⁺) of the P^III dianion [S-P(μ-N^tBu)]²₂-. The Mg²+ salt was found to form a mononuclear complex in the solid state whereas the Na⁺ salt formed a large cage comprising eight dianions and 16 Na⁺ ions built around a NaSH core. These s-block metal salts were shown to be useful transfer reagents for the dianion towards complexation with main group metals (e.g., Sn and Ge). Chapter 4 explores the oxidation of the P^III dianions [S-P(μ-N^tBu)]²₂- by chalcogens to give the more stable P^V species [(E=)P^V(-S)(μ-N^tBu)]²₂- (E = S, Se). The increase in stability and lower reducing ability of the P^V dianion allowed the formation of complexes with transition and main group metals. Reaction of [(E=)PS(μ-N^tBu)]²₂- with chloro-dimers [ClP(μ-NR)]₂ led to the formation of homo- and heteroleptic P^III-P^V phosphazane macrocycles of the type [{S=PV(μ-N^tBu)}2(u-E){P^III(μ-NR)}₂]. These can be oxidised to give air- and moisture-stable all-P^V species [{S=P^V(μ-N^tBu)}₂(μ-E){S=P^V(μ-NR)}₂] by reaction with elemental sulfur. Finally, in Chapter 5 the substitution of the chlorine atoms in [ClP(μ-NR¹)]₂ by amines (R²NH₂) is explored, to give a range of bis(amino) cyclophosphazanes [(R²NH)P(-NR¹)]₂ containing chiral and non-chiral R² and R¹ groups. These species were used in the formation of early transition metal (Zr, Ti, Hf) complexes which are potential pre-catalysts for alkene polymerisation studies.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2016

Author dc:creator

• Benson, Callum Giles Maxwell

Advisor dc:contributor.advisor

• Wright, Dominic

• Chemistry
• Inorganic
• Phosphazane
• Macrocycle

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/a1e1f9c9-87f9-41fc-aa3e-7fc529d98264/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

en

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.9901

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/264415