This thesis describes the oxidative addition reactions of sulfur, oxygen and nitrogen containing organic molecules into triosmium clusters. The products were formed by C-H, O-H, N-H and S-S bond cleavage. The direct reaction of dibenzyl disulfide, di(2-thienyl)disulfide and di-tertiary-butyl disulfide with cluster Os3(MeCN)2(CO)io yielded their respective unsymmetrical thiolato derivatives: Os3(u-SCH2Ph)2(CO)io , Os3(p-StBu)2(CO)i0 and Os3(u- SC4H3S2)2(CO)io in high yields with the cleavage of the S-S bond. Only dibenzyl disulfide gave a second cluster Os3(u-H)(S2CH2Ph)(CO)io , which retained the S-S bond. Thermal treatment of Os3(u-SCH2Ph)2(CO)io gave the symmetrical isomer in which both sulfur ligands bridged the same pair of osmium atoms. The interconversion of isomers of the unsymmetrical form of Os3(u-SCH2Ph)2(CO)io , related by inversion at sulfur, gave Ea = 61.5 2.0 kJ mol"1, determined by NMR methods. The direct reaction of 8-hydroxyquinoline with Os3(MeCN)2(CO)io employing various reaction conditions yielded both mono-, tri- and tetra-nuclear compounds: 0s(C9H6N0)2(C0)2 , 0s3(C9H6N0)2(C0)8 , Os3(u-H)(C9H6NO)(CO)9 and Os4(u- H)(C9H6N0)(C0)ii . Three isomers of complex 0s(C9H6N0)2(C0)2 were observed. Reactions between osmium carbonyl and phenols substituted with both electron- donating or accepting substituents always gave the dienone structures 0s3(u-H)2(u- 0C6H4X)(C0)9 (X = OH, F, OMe) in preference to the alternative aromatic form. The variable-temperature NMR spectra of Os3(u-H)2(u-OC6H40Me)(CO)9 show both the hydrides and the carbonyl ligands are mobile. Attempts to link clusters were only successful with hydroquinone which gave Os6(u-H)3(u-OC6H30)(CO)i9 . However with aminophenol, reaction was always preferred at the amine in preference to the hydroxyl group. Benzoquinone gave a unique cluster Os3(u-H)(u- OC6H5O)(CO)10 . Finally we have shown how the direct reaction of Os3(MeCN)2(CO)io with 4,4- dipyridyl disulfide yields the linked cluster OseCu-HMp-CsCsNXCOo leaving the S-S bond intact. The S-S cleavage occurs by treating Os6(p-H)2(n- C5H3NS2C5H3N)(CO)2o further with Os3(MeCN)2(CO)i0 to give Os9(u-H)2 (NC5fi3S)2(CO)3o . The initial reaction always takes place at the pyridine ligands followed by S-S cleavage. The reaction of 4-mercaptopyridine gave a linked cluster Os6(u-H)2(NC5H3S)(CO)2o . All these reactions were carried out at room temperature.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:429501 |
| Date | January 2006 |
| Creators | Ali, Abul Basar |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1445285/ |
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