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An investigation of the mechanism of chelate formation at group 6 metal carbonyl centres
Gallagher, Celia V
The reactions of M(CO)5(S) (M= Cr or W, S= solvent) with a senes of ligands, L, (L= dumine), were investigated In each case the appropnate chelate M(CO)4(L) compounds were formed The intermediates, M(CO)5(L), were also isolated and characterised by infrared, UV-visible and 'H n m r spectroscopy. The activation parameters for the formauon of the M(CO)4(L) species were determined, where possible. The subsequent reactions of the M(CO)5(L) intermediates were investigated and a mechanism for the chelate formation is proposed W(CO)5(2 ,2 '- bipyndylamine) was synthesised and structurally characterised by single crystal X-ray diffraction as a model for the monodentately coordinated dumine compounds. An investigation into the effect of conformational change on the pKa of the conjugate acid of 2,2'-bipyndine and related ligands was also conducted. Complete neglect of differential overlap (CNDO) calculations revealed that, for non-polar media, there was an increase in pKa of the conjugate acid of 2,2'-bipyndine when the angle (0) between the pyndine nngs was in the range 105-120°. In polar media the pKa of the conjugate acid of 2,2'-bipyndine was at a maximum when the ligand adopted the cis conformation (0= 0°). This study was also extended to include the conjugate acid of the dimethyldumine ligand. The results showed that, for non-polar media, there was an increase in the pKa of the conjugate acid of the dimethyldumine ligand when the angle between the two nitrogens was in the range of 90-105°. In polar media this angle was revealed to be in the range of 75-105°.
Keyword(s): Chemistry; Chelates; Ligands
Publication Date:
1993
Type: Other
Peer-Reviewed: Unknown
Language(s): English
Contributor(s): Long, Conor
Institution: Dublin City University
Citation(s): Gallagher, Celia V (1993) An investigation of the mechanism of chelate formation at group 6 metal carbonyl centres. PhD thesis, Dublin City University.
Publisher(s): Dublin City University. School of Chemical Sciences
File Format(s): application/pdf
Related Link(s): http://doras.dcu.ie/18740/1/Celia_V_Gallagher.pdf
First Indexed: 2013-07-31 05:28:12 Last Updated: 2019-02-09 06:33:06