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Title: Pentamethylcyclopentadienyl (Cp*) compounds of selenium and tellurium
Author: Bates, C. M.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Successful preparations were: (1) bis(pentamethylcyclopentadienyl)selenium, prepared by the reaction of selenium diethydithiocarbamate with lithiated pentamethylcyclopentadiene; (2) Cp*SenLi (n = 2,3,4), prepared by the reaction of elemental selenium with lithiated pentamethylcyclopentadiene in THF and its subsequent reaction with iodomethane to produce (3) methyl(pentamethylcyclopentadienyl)selenium or water to produce the polyselenide mixture (4) Cp*2Sen (n = 2,3,4). (4) was also produced by the low temperature reaction of selenium chloride with lithiated pentamethylcyclopentadiene. The compounds were characterised by conventional methods including 77Se NMR spectroscopy. The x-ray structural determination was obtained for compound (1) revealing the largest C-Se-C bond angle recorded for a simple diorganoselenide. The reactivities of the compounds (1) (3) and (4) were investigated in reactions with unsaturated transition metal fragments. In the reactions of (1) with sources of the tungsten and chromium carbonyl compounds [W(CO)5THF], [W(CO)3(CH3CN)3], [Cr(CO)5THF], [Cr(CO)4nbd] and [Cr(CO)3(CH3CN)3] the first example of reduction of a selenide to form a diselenide within the transition metal coordination sphere was observed. These produced the complexes [M(CO)2{Se2Cp*2}] (M = W, Cr). The x-ray structure determinations are included. These complexes contain the longest Se-C bonds recorded. A 1,2 metal shift was observed for the tungsten complex using the technique of two dimensional exchange NMR spectroscopy. (3) reacts with [W(CO5THF] or [Cr(CO)5THF] to produce the complexes [W(CO)5{Se(Me)Cp*}] and [Cr(CO)5{Se(Me)Cp*}]. The first recorded Se-W satellites are reported for the former. The compounds (1), (3) and (4) were reacted with diiron nonacarbonyl to produce the complex [Fe3Se2(CO)5]. Compound (1) was reacted with a half molar equivalent of [PdCl2(PhCN)2] to produce the complex [Pd2Cl4(SeCp*2)].
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available