Ph.D. / This study comprises the preparation and characterization of new carbene complexes of iron, molybdenum, gold, copper and silver from azolyl and thienyl precursors. In addition, the syntheses of aminoacyl chelate and metallacyclic iron compounds as well as unique 6-membered dimeric and 18-membered trimeric thienyl gold compounds are reported. Furthermore, di(vinyl)carbene complexes, which are not yet known for gold and which are very rare for most other metals, are also described. In contrast to most other carbene complexes that result from precursors in which the heteroatom is situated a or y to the coordinated carbon atom, the new amino(organo)-, organo(thio)- and di(organo) carbene complexes are unique in that they have been prepared from azolyl or thienyl precursors in which the nucleophilic heteroatom is located outside the coordinated ring system and is separated from the coordinated carbon by several bonds. The complex [CpFe(CO)2C1] reacts with lithiated pyrazole, (thienyl)oxazoline or (thienyl)pyridine to form precursor pyrazolyl and thienyl iron(II) compounds which upon alkylation or protonation with CF3SO3Me or CF3SO3H afford amino(organo)-, organo(thio)- or heterometallacyclic alkoxy(amino)- and hydroxy(amino)carbene complexes as well as compounds which show pyridinium character. The heterometallacyclic complexes incorporate unusual ferropyridine or ferropyrole rings. ' 3C-{'}I} NAIR data of the above compounds show that the coordinated carbons of the azolyl and thienyl ligands are significantly affected upon carbene formation, although an X-ray crystallographic investigation indicates that carbene formation has little if any effect on bond distances in the azolyl ligand when it becomes a coordinated azolinylidene. The molecular structures of the pyrazolyl complex [CpFe(C0) 2{C=CHCH=NNPh}], the pyrazolinylidene complex [CPFe(C0) 2{CCHHNHI4P11}1[CF3S03], the 2-(2'-oxazolinyl)thien- 5-ylidene complex [CpFe(C0)2{CCHHC(1\1HCMe2CH26)}1[CF3S03] and the heterometallacyclic complex [CpFe(C0){CC(=&CMe 2CH2(5)SCH---9-1)] indicate small variations in iron-carbon distances of 1.981(2), 1.969(5), 1.99(1) and 1.959(7) A. Four equivalents of 2-(4',5'-dihydro-4',4'-dimethy1-2'-oxazolinyl)thien-3-yllithium reacts with the acetate [Mo2(O2CMe)4] to form the stable, neutral, quadruply bonded dimolybdenum complex [Mo2{C=C(6=NCMe2CH26)SCH2CH2} 2(02CMe)2], while 4-methylthiazoly1 lithium reacts with the same acetate to form the unstable, thiazolyl molybdate [Mo 2{6=NCMe—Cfg} 8]4". Reaction of [AuCI(tht)] (tetrahydrothiophene) with 2-(4',5'-dihydro-4',4'-dimethy1-2'-oxazoliny1)- thien-3-yllithium or 2-(4',5'-dihydro-4',4'-dimethy1-2'-oxazolinyl)thien-5-yllithium afforded dimeric and trimeric thienyl oligomers of gold(I). The molecular structure of the six-membered dimeric compound [Au{C=C(=NCMe 2CH2O)SCH=CH}li shows a Au...Au separation of 2.8450(6)A, while such interactions are absent in the trimeric compound [Au{C=C(C=NCMe2CH2O)SCH=CH}] 3 . Protonation of the former compound as well as the stable monomers obtained from [Au(tht)C 6F5] or [Au(Cl)PPh 3J afforded unique di(vinyl)carbene as well as imine complexes. Reaction of 2-(2'-pyridyl)thien-5-yllithium with [Au(COPPh 3] and subsequent alkylation yields an organo(thio)carbene compound. Finally, a series of cationic copper(I) bis(carbene) complexes were formed upon sequential treatment of copper(I) trifluoromethanesulfonate with thiazolyl- or pyrazolyllithium and CF3SO3Me. A similar reaction with 4-methylthiazol-2-yllithium and silver triflate produced the first amino(thio)carbene complex of silver.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:2637 |
| Date | 17 August 2012 |
| Creators | Desmet, Mieke |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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