D.Sc. / This study involves the preparation and characterization of new amino(thio) carbene complexes of gold(I) and gold(III). In addition the reactivity of bis(thiazolyl) aurate and the above mentioned carbene complexes are also described. Various thiazolyllithium reagents reacted with [AuCl(tht)] to yield bis(thiazolyl) aurate complexes of gold(I) which were isolated in crystalline form. These crystals contained solvent of crystallization and no structural determination of these aurates were possible. The latter compounds readily reacted with elemental sulphur by insertion of a sulphur atom into one of the Au-C bonds thereof Subsequent reaction with one molar equivalent of CF 3S03CH3 or CF3SO3H produced either carbene, [Au(CNRYS)(SC=NY§)] (Y = CCH 3=CH, C4H6; R = H, CH3), or thione, [Au(S=h‘TRY)(C=NYS)], complexes of gold(I) which spontaneously decomposed into gold(I) polymers ([Au(C=NYS)]. or [Au(S&=NY)].) and organic products (C=NYS or S=CNRYS). In an attempt to isolate the above-mentioned carbene or thione complexes bis(thiazolyl) aurate complexes were treated with two molar equivalents of CF3S03CH3 or CF3SO3H after sulphur insertion. Rather than the expected mixed carbene thione complexes, [Au(elsTRY§)(S=eNRY§)]CF 3S03, homoleptic rearrangement produced bis(carbene) complexes of gold(I) with unexpected counterions (Cl instead of CF 3SO3). Reaction of lithiated mercaptobenzothiazole with [AuCl(tht)] yielded a bis(thiolate) complex of gold(I), [Au(SC=NC 6H4 S-0)2]Li. Alkylation or protonation of this modified aurate complex resulted in the formation of gold polymers, [Au(S=NC 6H4 -0)]„, and organic products, S=§NRC6H4§-o, R=H, CH3 ). Oxidative addition of halogens to bis(thiazolyl) aurate complexes produced no isolable organometallic complexes. [AuC1 1]Li probably formed after repetitive oxidation addition (C1 2) and reductive elimination reaction (2-chlorothiazole). However, oxidation of these aurate complexes with SOC12 limited the reaction to one oxidative addition and one reductive elimination step to produce [AuCl(CNHYS)] (Y=CCH 3=CH, C6H4) after acidification. Reaction of the neutral mono(carbene) complex [Au(CNCCH 3=CHS)(C=NCCH3=CHS)] with C12, Br2 or 12 produced carbene complexes of gold(I), [AuX(6NHCCH 3=CH§)] (X=C1, Br, I), after reductive elimination of 2-halogeno-4-methylthiazole. Cationic bis(thiazolinylidene) complexes of gold(I) react readily with C1 2 and 12 to produce stable Ms(carbene) complexes of gold(III). However, oxidative addition on the same carbene complex by I2 is followed by a novel reductive elimination of (ICNii)cF SO to produce carbene complexes of gold(I), [AuI(CMN7- TTA )]. Alkylation (CF3SO3CH3) of 4-methylthiazole, bensothiazole and methylimidazole, followed by deprotonation (BuLi) produced free carbenes. These carbenes were trapped by reaction with [AuCl(tht)] to form carbene-chloro complexes of gold(I). Chloro(1,3- dimethylimidazolinylidene)gold(I) react readily with NaN 3 or AgNO3 to yield [AuX(CNCH3CH=CH1:TCH3)] (X = N3 or NO3 ). As part of this study the structures of several carbene complexes were determined, including five carbene complexes of gold(I) and one carbene complex of gold(III). Au-C bond lengths of between 1.92-2.13A were found with the largest Au-C separation in the carbene complex of gold(III), [Au(aNCH3CH=CHNCH3)2]CF3S03 . Certain complexes of gold(I) exhibit interesting Au...Au interactions (3.19-3.51A) resulting in the aggregation of gold atoms to form dimers and chains of gold(I) atoms. The structures of two related complexes of iron were also determined to investigate the effect of protonation on a neutral carbene precursor, [Fe(CO) 2Cp(C=CHCH=NNPh)], to form the cationic carbene complex, [Fe(C0) 2Cp(aCH=CHNHI:IPh)JCF3S03. Small changes in bond lengths and angles resulted upon carbene formation.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:8961 |
| Date | 08 August 2012 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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