The synthesis and anion coordination chemistry of novel mono- and multi-functional borylmetallocenes

Day, Joanna 2008. The synthesis and anion coordination chemistry of novel mono- and multi-functional borylmetallocenes. PhD Thesis, Cardiff University.

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Abstract

The synthesis, characterisation and anion binding properties of a series of mono-, tris- and tetiukis-functional boronic esters of ferrocene are reported. Mono- borylated systems: (n5C5H5)Fe(ri5C5H4B02R) where 02R = ethane-1,2-diolato (la) and pinanediolato (lb) , tris-functional borylated systems: (r 5-C5H3EtB02R)Fe(r 5- C5H3(B02R)2 where 02R = ethane-1,2-diolato (3a), stilbenediolato (3b) and pinanediolato (3c) and tetrakis-functional borylated systems: (rj5-C5H3(B02R)2) 2Fe where 02R = ethane-1,2-diolato (4a), stilbenediolato (4b), pinanediolato (4c) and napthalenediolato (4d) have been synthesised and characterised by NMR, UV/Vis and IR spectroscopy, mass spectrometry and in most cases by X-ray diffraction. Electrochemical analyses of most of the above-mentioned boronic esters of ferrocene have demonstrated the influence of the number of boronic ester groups on the redox potential of the ferrocene backbone, and have allowed a comparison of the different substituents. The anion-binding properties of the above-mentioned boronic esters have been monitored by spectroscopic (including NMR and UV/Vis) and electrochemical methods. Bis-functionalised boronic esters of ferrocene have previously shown a colorimetric response to fluoride, and have been shown to bind two equivalents of fluoride per receptor. An analogous colorimetric response to fluoride is observed with the tris- and tetrakis-functionalised boronic esters, which also display a particular affinity for fluoride. The kinetics of the colorimetric response have been probed using time-resolved UV/Vis experiments, with the tris- and tetrakis-functionalised compounds shown to effect a more rapid response to fluoride. Kinetic experiments have revealed that the response to fluoride is greatly enhanced with tris- and tetrakis- functionalised receptors, and also revealed a binding stoichiometry of 2:1 (anion: receptor) in all cases thus the binding of more than two equivalents of fluoride by the additional boryl groups is not responsible for enhanced kinetics. The synthesis and characterisation of a range of dimeric, macrocyclic and polymeric ferroceneboronic esters has been undertaken. Dimeric ferrocene boronic esters (ti5-C5H5)Fe(r 5-C5H4)R(Ti5-C5H4)Fe(ri5-C5H5) where R = B02C8H1202B (7a), B(OCH2)2C(CH20)2B (8a) and B02(C6H2)02B (9a) , macrocyclic ferrocene boronic esters: (Ti5-C5H4)Fe(Ti5-C5H4)BRB 2 where R = B02C8Hi202B (7b) and B(OCH2)2C(CH20)2B (8b) , and the polymeric ferrocene boronic ester (rj5- C5H4)B02CgHi202B(r 5-C5H4)Fe n polymer (7c) have been synthesised and characterised by NMR and UV/Vis spectroscopy, mass spectrometry and in some cases by X-ray diffraction. Electrochemical analyses of some of the above-mentioned boronic esters of ferrocene have demonstrated the lack of electronic communication between iron centres with the saturated pentaerythritol and cyclooctanetetraol linker groups. Investigation into the factors controlling assembly of boronic ester units into poly-, oligomeric or macrocyclic products has been possible. The two different linker groups have revealed very different product distributions under analogous reaction conditions with ferrocene-bis-boronic acid. The pentaerythritol linker favours macrocycle formation, whilst the cyclooctanetetraol linker favours polymer formation. Thus reactions can be driven with high selectivity towards either macrocyclic or polymeric products depending on choice of linker group.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
ISBN:	9781303213007
Date of First Compliant Deposit:	30 March 2016
Last Modified:	12 Feb 2016 23:12
URI:	https://orca.cardiff.ac.uk/id/eprint/54700

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