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Towards the synthesis of transition metal derivatives of carbohydrates

University of British Columbia

The synthesis of organometallic derivatives of carbohydrates was approached in two different ways. The first method was nucleophilic attack by vitamin B₁₂s, cyclopentadienyl iron dicarbonyl and cyclopentadienyl tungsten and molybdenum tricarbonyl anions on the carbohydrate sulphonate in an attempt to synthesise direct metal linkage to the carbohydrate via a carbon metal bond. The reaction was found to be most successful when applied to primary carbohydrate sulphonates. Little success was encountered with secondary tosylates arid epoxides. The main problem enountered here was the difficulty in isolating the organometallic derivatives. Another series of compounds were synthesised in an attempt to extend this study of metal derivatives of carbohydrates, to metal-carbohydrate derivatives bonded through a heteroatom. Model systems were studied of six-membered thio complexes of tungsten, manganese and platinum. From the tungsten and manganese complexes it was found that the tungsten complex was 'locked' only by a t-butyl system, whereas the manganese complexes appeared to be 'locked' even without the t-butyl group. The six-membered rings in each case appeared to be puckered chairs. The configuration about the sulphur was not determined, although it appears to be either the diequatorial configuration, or a fast equilibrium between the axial-equatorial⇄diequatorial⇄equatorial-axial configurations. Studies on the platinum thio complexes indicate that for a six-membered ring, the average coupling constant of Pt-S-C-H was 58 Hz, while the trans coupling of platinum through sulphur was found to be at least 73 Hz, with J[formula omitted] + J[formula omitted] = 120 Hz.

Text

2011-04-06

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http://hdl.handle.net/2429/33338

Chemistry

University of British Columbia

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