The incorporation of sulfur, oxygen and nitrogen containing organic molecules into triosmium clusters
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.