M.Sc. / This study comprised the synthesis and characterization of new carbonyl carbene complexes of chromium, molybdenum and tungsten, prepared from thiazole precursors. In addition, the preparation and characterization of coordination compounds of chromium, tungsten and iron with new thiazole dithiocarboxylester ligands are reported.

This dissertation summarizes my research in the Roy group on the development, synthesis, and study of new N-heterocyclic carbene (NHC) based ligands and nickel phsophinidene core compositions of molecular clusters, also known as superatoms. Chapter 1 introduces superatoms as atomically precise and discreet building blocks for use in the design and synthesis of novel materials. A brief history as well as selected synthetic strategies of superatoms will be introduced. The relevant materials properties of superatoms as well as their dependence on core composition and ligand structure will be discussed. Next, the use of superatoms with specialized or functionalizable ligands to synthesize new materials will be demonstrated. This chapter details the importance of the superatom ligands and core composition is the foundation that the subsequent chapters builds upon in developing these two areas. Chapter 2 introduces a functionalized NHC as a potential superatom ligand. While not necessary for all superatom ligands, ligands that enable electronic access to the superatom core are attractive. In this chapter, the conductance of potential NHC based ligands are probed through the scanning tunneling microscope-based break-junction (STM-BJ) method. A novel method of forming single molecule junctions in situ was used and these ligands are found to display a length dependent conductance with strong coupling to the Au electrode, confirming their potential use as ligands for superatoms. Chapter 3 describes the nature of the NHC–M bond in self-assembled monolayers (SAMs) on a Au(111) surface using high-resolution spectroscopy and theoretical calculations. This study was performed as a result of challenges and questions encountered during the work of Chapter 2. The results obtained from this study explore an important structure-function relationship of NHC ligands and have broader impact in materials chemistry beyond superatoms. Chapter 4 explores the synthesis of superatoms with NHC ligands beyond simple imidazolium-based NHCs. This chapter describes the two primary synthetic techniques used and the synthesis of NHC-ligated superatoms. This work is also ongoing and characterization is limited to crude single crystal X-ray diffraction structures and select NMRs. Finally, Chapter 5 details the use of uncommon organocyclophosphine reagents to synthesis novel nickel-phosphinidene molecular clusters, a potential new superatom. In this chapter the synthesis of a family of nickel-phosphinidene molecular clusters is described and studied. A potential application of these molecular clusters is explored through the thermolytic conversion to the industrially relevant Ni2P.

This dissertation describes my efforts in the Nuckolls lab to expand synthetic methods of wet-chemistry superatom synthesis, superatom surface ligand and core modification, and assembly of superatoms into materials with useful, cumulative properties. This work builds off of previous work from the Nuckolls lab describing photolabile ligand substitution and use of this technique to covalently bind superatoms to form various materials such as polymers and weaved sheets. This work will focus on the Chevrel-type M₆E₈L₆ metal-chalcogenide cluster Co₆Se₈, modification of its outer stabilizing ligands, and fusion of its core with other Co₆Se₈ superatoms to form fused dimers. Chapter 1 consists of a review of background material that forms a foundational basis for this work. The field of superatoms and superatomic materials will first be covered to contextualize this work in the field at large. Then, the prior work on wet-chemistry synthesis of Co₆Se₈ superatoms with replaceable, photolabile carbonyl (CO) ligands will be discussed. Finally, previous dimensionally-controlled assembly of materials using these carbonylated superatoms will be covered. Chapter 2 consists of the discovery of a masking carbene ligand generated from trimethylsilyl diazomethane (TMSD) and its use to create a new, electronically-coupled superatom dimer species (Co₁₂Se1₆(PEt₃)₁₀) that shows evidence of quantum confinement akin to nanoparticles and nanoparticle assemblies. Chapter 3 consists of new ligand substitution and methods to synthetically functionalize the fused dimer introduced in Chapter 2. The reactive carbene-ligated cluster is used to add new functional groups that were previously inaccessible to these cobalt-selenide clusters. New multi-carbene clusters are demonstrated as well as the use of site-differentiated clusters to form functionalized fused dimers from bis-carbonyl clusters. Chapter 4 consists of an investigation of the carbene cluster and insights that may be used in the future to finally expand cluster fusion into a chain. A reversible bridging of the carbene ligand based on temperature and oxidation state is analyzed experimentally and computationally. This information is used to synthesize a series of new carbene clusters which are used to try and assemble electronically-coupled, fused Co₆Se₈ superatomic materials.

No description available.

Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: This study comprises the synthesis and characterisation of N-heterocyclic carbene complexes of group 10 metals with the main focus on such complexes with the nucleophilic N-atom in a position further than the α-position from the carbene carbon atom. These compounds were synthesised by the initial alkylation of quinoline- and acridine derivatives followed by the oxidative addition of the resulting salts to the complexes M(PPh3)4 (M = Ni, Pd, Pt). To complete the study an investigation of the catalytic activity and stability of such compounds in C,C-coupling catalysis was conducted. The carbene ligands used differed with respect to the position of the N-atom relative to the carbene carbon atom as well as with respect to substituents. The oxidative addition of the quinolinium- and acridiniumchloride salts to Ni(PPh3)4 was initially problematic. The desired product formed only in small amounts and could not be isolated easily. However, by replacing toluene with more polar THF as solvent, the nickel complexes could be synthesised in high yield without any indication of decomposition. Oxidative addition to Pt(PPh3)4 also yielded the desired product, although a number of by-products were formed as well. The molecular structure of trans-chloro(1,3-dimethyl-1,2-dihydroquinoline-2-ylidene)-bis(triphenylphosphine) platinum(II) trifluoromethanesulfonate could nevertheless be determined by X-ray crystallography. The new one-N, six membered, heterocyclic carbene complexes were all unambiguously characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. The carbene character of the complexes was corroborated by a large downfield chemical shift (δ 203 – 230) of the carbene carbon atoms in their 13C NMR spectra. The analyses furthermore indicated that with the exception of cis-chloro(1-methyl-3-phenyl-1,4-dihydroquinoline-4- ylidene)bis(triphenylphosphine)palladium(II) hexafluorophosphate, all the palladium, nickel and platinum complexes exhibit a trans arrangement of the PPh3 ligands. Both the cis- and the trans isomers of the complexes, chloro(1,3-dimethyl-1,2-dihydroquinoline-2-ylidene)- bis(triphenylphosphine)palladium(II) tetrafluoroborate and chloro-(1,3-dimethyl-1,2-dihydroquinoline- 2-ylidene)bis(triphenylphosphine)palladium(II) trifluoromethanesulphonate are, however, present in solution. The molecular structure of both isomers were determined by Xray crystallography. Crystallographic studies revealed that the new family of cationic complexes exist in a slightly distorted square planar environment with the carbene ligand orientated almost perpendicular to this plane. The metal-carbene bond lengths are insensitive to variations in the substituents on the carbene ligands and are therefore not a suitable parameter to distinguish between the strengths of these bonds. The N-heterocyclic carbene ligands with the N-atom removed from the carbene carbon atom by three bonds, exhibit a greater trans influence in the palladium complexes than those with the N-atom in the α-position. This is an indication of the better σ-donor ability of the former. A significant difference in the Ni-Cl bond lengths could, however, not be detected. The catalytic activity of the new synthesised palladium and nickel complexes in the Mizoroki- Heck and Suzuki-Miyaura coupling reactions, were investigated. The palladium complexes tested show potential as precatalysts for the Mizoroki-Heck reaction, although relatively high temperatures were needed to effect coupling, while coupling of aryl chlorides did not occur at all. The trans-chloro(1,2-dimethyl-1,4-dihydroquinoline-4-ylidene)bis(triphenylphosphine)- palladium(II) trifluoromethanesulphonate complex also displayed high activity in the C,Ccoupling of bromofluorene with arylboronic acids in the Suzuki-Miyaura coupling reaction. It even yielded high conversions in instances where sterically hindered aryl halides were used. The trans-chloro(1,2-dimethyl-1,4-dihydroquinoline-4-ylidene)bis(triphenylphosphine)- nickel(II) trifluoromethanesulphonate complex catalyses the coupling of sterically hindered arylbromides as well as arylchlorides to arylboronic acids. By further optimising the reaction conditions and increasing the streric bulk of the carbene ligands, even better results in both the Mizoroki-Heck and the Suzuki-Miyaura reactions are expected. / AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van N-heterosikliese karbeenkomplekse van groep 10 metale. Daar is veral gefokus op N-heterosikliese karbeenligande waarin die nukleofiele N-atoom verder as die α-posisie vanaf van die karbeenkoolstofatoom verwyder is. Die betrokke komplekse is gesintetiseer deur die alkilering van kinolien- en akridienderivate, gevolg deur die oksidatiewe addisie van die resulterende soute aan die komplekse M(PPh3)4 (M = Ni, Pd, Pt). Om die studie af te rond is die katalitiese aktiwiteit van dié komplekse in C,C-koppelingsreaksies ondersoek. Karbeenligande wat slegs een nukleofiele stikstofatoom besit en verskil ten opsigte van die posisie van dié atoom relatief tot die karbeenkoolstofatoom asook substituente aan die ligand, is gebruik. Die oksidatiewe addisie van die kinoliniumchloried- en akridiniumchloriedsoute aan Ni(PPh3)4 het aanvanklik probleme opgelewer, sodat slegs ’n klein hoeveelheid van die verlangde produk, wat moeilik isoleerbaar was, gevorm het. Deur egter ’n meer polêre oplosmiddel, THF, in plaas van tolueen te gebruik, kon die nikkelkomplekse met goeie opbrengs en sonder enige aanduiding van ontbinding, berei word. Oksidatiewe addisie aan Pt(PPh3)4 het die verlangde produk gelewer, alhoewel ’n aantal neweprodukte ook gevorm het. Ten spyte hiervan is daarin geslaag om die molekulêre struktuur van trans-chloro(1,3- dimetiel-1,2-dihidrokinolien-2-ilideen)bis(trifenielfosfien)platinum(II) trifluorometaansulfonaat kristallografies te bepaal. Die nuwe gesintetiseerde een-N, seslid, heterosikliese karbeenkomplekse is deur KMRspektroskopie, massaspektrometrie en X-straalkristallografie eenduidig gekarakteriseer. Die karbeenkarakter van die komplekse is bevestig deur die ver veldafwaartse chemiese verskuiwing (δ 203 - 230) van die karbeenkoolstofatoom in die 13C-KMR-spektra. Die analises toon ook dat, met die uitsondering van cis-chloro(1-metiel-3-feniel-1,4- dihidrokinolien-4-ilideen)bis(trifenielfosfien)palladium(II) heksafluorofosfaat, al die palladium-, nikkel- en platinumkomplekse ’n trans-rangskikking van die PPh3-ligande besit. Die cis- sowel as die trans-isomere van die palladiumkomplekse chloro(1,3-dimetiel-1,2- dihidrokinolien-2-ilideen)bis(trifenielfosfien)palladium(II) tetrafluoroboraat en chloro(1,3- dimetiel-1,2-dihidrokinolien-2-ilideen)bis(trifenielfosfien)palladium(II) trifluorometaansulfonaat, is in oplossing teenwoordig en die molekulêre struktuur van albei isomere is kristallografies bepaal. Dit is vasgestel dat al die kationiese komplekse in ’n effens verwronge vierkantvlakomgewing, met die karbeenligand byna loodreg op dié vlak, voorkom. Die metaal-karbeenbindingslengtes is onsensitief teenoor ’n variasie in die substituente gebind aan die karbeenligande en dit is nie ’n handige parameter om tussen die sterktes van dié bindings te differensieer nie. Die N-heterosikliese karbeenligande waarvan die N-atoom in ’n posisie drie bindings van die karbeenkoolstofatoom af voorkom, toon ’n effens sterker trans-invloed as die ligande met ’n α-stikstofatoom in die palladiumkomplekse. Dit is ’n aanduiding dat eersgenoemde ligande beter σ-donor eienskappe besit. Die nikkelkomplekse verskil egter nie betekenisvol ten opsigte van hul Ni-Cl bindingslengtes nie. Die katalitiese aktiwiteit en stabiliteit van die nuwe reekse palladium- en nikkelkomplekse is in Mizoroki-Heck en Suzuki-Miyaura-koppelingsreaksies ondersoek. Ofskoon relatief hoë temperature nodig is om koppeling te bewerkstellig en die komplekse nie koppeling van ’n arielchloried met butielakrilaat kataliseer nie, toon die palladiumkomplekse tóg potensiaal as prekatalisatore in die Mizoroki-Heck-reaksie. Die kompleks, trans-chloro(1,2-dimetiel-1,4- dihidrokinolien-4-ilideen)bis(trifenielfosfien)paladium(II) trifluorometaansulfonaat, toon ook uitstekende katalitiese aktiwiteit in die C,C-koppeling van bromofluoreen met arielboorsure in die Suzuki-Miyaura-koppelingsreaksie. Hierdie kompleks kataliseer selfs die koppeling van steries gehinderde arielhaliede met arielboorsure. Die kompleks trans-chloro(1,2-dimetiel- 1,4-dihidrokinolien-4-ilideen)bis(trifenielfosfien)nikkel(II) trifluorometaansulfonaat, bemiddel koppeling van arielbromied-, sowel as steries gehinderde arielchloriedsubstrate aan arielboorsure. Selfs beter resultate in die Mizoroki-Heck- sowel as die Suzuki-Miyaurakoppelingsreaksies word verwag deur verdere optimalisering van die reaksiekondisies en die inbouing van groter steriese hindering in die ligande.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This study comprises the preparation and characterisation of completely new Fischer-type carbene complexes of chromium and tungsten by deprotonation of (CO)5M=C(NMe2)(Me), (CO)5M=C(OMe)(Me) or (CO)5M=C(NMe2)C≡CH, and subsequent treatment of the formed anion with a variety of reagents, including reactive metal complexes. The deprotonation of the termodynamically stable complexes, (CO)5M=C(NMe2)(Me) (M = Cr or W) followed by reaction with the sulfonium salt, [Me2(MeS)S][BF4], yielded not only the expected products (CO)5M=C(NMe2)CH2SCH3, but also thioether complexes, (CO)5MS(CH3)2, disulfinated complexes (CO)5M=C(NMe2)CH(SCH3)2, S-bridged dinuclear compounds (CO)5M=C(NMe2)CH2S(CH3)M(CO)5, as well as the unique fourmembered- C,S-chelate carbene complexes (CO)4Cr=C(NMe2)CH(SCH3)SCH3 and (CO)4M=C(NMe2)CH2SCH3. Crystal structure determinations of (CO)5W=C(NMe2)CH(SCH3)2, (CO)5Cr=C(NMe2)CH2S(CH3)Cr(CO)5, (CO)4M=C(NMe2)CH2SCH3 (M = Cr, W) and (CO)4Cr=C(NMe2)CH(SCH3)SCH3 were successfully performed. The latter tetracarbonyl complexes have Cr-S bonding distances of 2.4531(9) and 2.4517(5) Å and a W-S distance of 2.577(1) Å. These relatively weak bonds contribute to the short M-C(O)-distances trans to it. The formed four membered chelate rings are essentially planar. The deprotonation of (CO)5Cr=C(NMe2)(Me) and sequential reaction with sulphur and CF3SO3Me does not yield the expected product, (CO)5Cr=C(NMe2)CH2SCH3, but (CO)5CrS=C(NMe2)CH3 resulting from a sulphur insertion was isolated. A single crystal structure determination of the latter complex shows a normal thione carbene complex. The reaction of methyl(methoxy)carbenepentacarbonylchromium(0) and the tungsten analogue with n-BuLi, followed by reaction with [Me2(MeS)S][BF4], afforded unexpected complexes via an unusual addition dissimilar to the above mentioned reactions of dimethylaminocarbene complexes. The formation of the products, (CO)5M=C(OMe)[CH=C(Me)NH(Me)] and (CO)4M=C(OMe)[C(SMe)=C(Me)NH(Me)] (M = Cr, W) can be ascribed to the influence of the heteroatom, oxygen, as well as the presence of acetonitrile in the sulfonium salt reagent [Me2(MeS)S][BF4]. An unusual alkylation by Me+ is also affected. The X-ray crystallographic structure determination of the complexes show hydrogen bonding between the alkoxy oxygen atoms and the protons on the nitrogen atoms. The latter four membered C,S-chelates show bonding distances and angles similar to these of the previously mentioned four membered chelates. Deprotonation of the alkynyl carbene complexes, (CO)5M=C(NMe2)C≡CH (M = Cr, W), with n-BuLi and subsequent reaction with PPh3AuX (X = Cl, NO3), initially afford the β-transmetalated products (CO)5M=C(NMe2)C≡CAuPPh3. In solution (CH2Cl2) the product isomerises through metal migration to Ph3PAuC(NMe2)=C=C=W(CO)5. The conversion was followed by means of 1H-NMR-spectroscopy and it appears that two first order reactions take place consecutively.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: See full text for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This study comprises the preparation and characterisation of various novel organometallic species of gold(I) by employing a range of anionic group 6 metal Fischer-type carbene complexes and group 6 metal-acyl complexes as synthons of the organic moieties introduced to the gold(I) electrophiles. The main objectives of this work are to develop the use of Fischer-type carbene complexes as synthons in the preparation of novel organometallic species along unusual reaction pathways and, in doing so, to expand the organometallic chemistry of gold(I), especially Au-C bond formation reactions. By reacting various β-CH acidic Fischer-type alkoxy/dialkylamino/ alkthio(methyl)carbene complexes, first with a base, and then with a gold(I) electrophile (Ph3PAu+), easy access to vinyl ether/dialkylamine/thioether complexes of gold(I) coordinated to M(CO)5 (M = Cr, Mo, W) fragments, is obtained. When methyl alkoxy- or dialkylaminocarbene complexes are employed, coordination of the novel alkoxyvinyl-gold(I)PPh3 and dialkylaminovinyl-gold(I)PPh3 species to the M(CO)5 fragments occurs in an asymmetrical fashion through the vinyl functionalities of the novel gold(I) species. This usually unstable coordination mode for vinyl ethers is stabilised by delocalisation of partial positive charges from the α-gold vinyl carbon atoms to either the gold(I)PPh3 fragment [for η2-{alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes] or the nitogen atoms of the vinyl amine group [for η2-{dialkylaminovinylgold( I)PPh3}M(CO)5 complexes]. In the latter complexes this delocalisation occurs to such an extent that these complexes are best described as zwitterions. The corresponding negative charges in the bimetallic complexes reside on the M(CO)5 fragments. As a representative example, uncoordinated ethoxyvinyl-gold(I)PPh3 was isolated in high yield via a ligand replacement reaction with PPh3. When Fischer-type alkthio(methyl)carbene complexes are employed in this conversion, novel sulphur coordinated {alkthiovinyl-gold(I)PPh3}Cr(CO)5 complexes are formed.The reaction mechanism involved in these conversions is believed to be the gold(I) analogue of the hydrolysis of Fischer-type carbene complexes. In this mechanism the bimetallic η2-vinyl ether coordinated {alkoxyvinyl-gold(I)PPh3}M(CO)5 complexes represent stabilised gold(I) analogues of postulated transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. The term aurolysis is conceived to describe the conversion when Ph3PAu+ is employed as electrophile instead of H+. The formation of the bimetallic η2-vinyl ether coordinated complexes in the current conversion, furthermore, strongly supports the existence of similar transition states in the hydrolytic decomposition of Fischer-type alkoxycarbene complexes. This mechanism is also accepted for the formation of analogous η2-{dialkylaminovinyl-gold(I)PPh3}M(CO)5 and {alkthiovinyl-gold(I)PPh3}-S Cr(CO)5 complexes when β-CH deprotonated Fischer-type dialkylamino- and alkthiocarbene complexes are employed in this reaction. The reaction of anionic group 6 metal-acyl complexes and their nitrogen analogues, N-deprotonated Fischer-type aminocarbene complexes, leads to the formation of acylgold(I) and novel imidoylgold(I) complexes coordinated to M(CO)5 (M = Cr, W) fragments. In the previous complexes poor stabilisation of the M(CO)5 fragments allows halide anions to readily form ionic adducts with these groups. This characteristic of these products provides a useful reaction pathway to the first example of a free acylgold(I) complex, benzoyl-AuPPh3. Coordination of the imine nitrogen atom to the M(CO)5 fragments in the analogous bimetallic imidoylgold(I)-M(CO)5 complexes is much stronger. These complexes are remarkably stable and could even be effectively isolated by means of low temperature silica gel chromatography. As a preliminary reaction mechanism for this conversion we propose a mechanism that is closely related to the aurolysis mechanism described above. The only difference is that, instead of formal reductive elimination of vinyl ethers/amine/thioether complexes of gold(I) from the M(CO)5 fragments, acyl and imidoyl complexes of gold(I) are produced in this step. Furthermore, the (Z)- stereoisomers of the bimetallic imidoylgold(I)-M(CO)5 complexes generated in this conversion are exclusively obtained.A second N-deprotonation-auration reaction sequence performed on suitable examples of the bimetallic imidoylgold(I)-M(CO)5 complexes yields, as the only isolable product, a novel triangular Au2Cr cluster complex, cis-{η2-(Ph3PAu)2} PPh3Cr(CO)4. This complex is the isolobal equivalent for the unstable molecular hydrogen complex, (η2-H2)PPh3Cr(CO)4, and exhibits the shortest known Au-Au separation between two gold atoms in cluster complexes of the type Au2M. Finally, two novel and vastly different molecular structures of closely related anionic benzoylpentacarbonyl tungstates, one with Li+ as counterion and another in which exactly half the Li+-cations have been replaced by protons, highlight the importance of hydrogen bonding and ion-dipole interactions in determining the solid state structure of such complexes. / AFRIKAANSE OPSOMMING: Hierdie studie behels die bereiding en karakterisering van verskeie nuwe organometaalkomplekse van goud(I). Hierdie komplekse is berei deur gebruik te maak van n wye reeks anioniese groep 6 metaal Fischer-tipe karbeenkomplekse asook anioniese groep 6 metaal asielkomplekse as sintetiese ekwivalente vir die organiese fragmente wat gedurende die sintese aan die goud atoom gebind word. Die hoofdoel van hierdie studie is om die gebruik van Fischer-tipe karbeenkomplekse as sintetiese voorgangers in die bereiding van nuwe organometaalverbindings te ontwikkel en om sodoende ook die organometaalchemie van goud verder uit te bou. Veral die ontwikkeling van nuwe sintetiese metodologieë vir die bereiding van Au-C bindings is hier van belang. Verskeie Fischer-tipe alkoksie-/dialkielamino-/alktio-(metiel)karbeenkomplekse met suuragtige waterstofatome geleë op die β-metallo-koolstofatoom is eers onomkeerbaar gedeprotoneer. Byvoeging van die goud(I) elektrofiel, Ph3PAu+, lei - volgens n ongewone reaksiemeganisme - tot die vorming van onderskeie vinieleter-, dialkielvinielamien- en vinieltioeterkomplekse van goud(I). Hierdie komplekse is verder ook op verskillende wyses aan M(CO)5 fragmente (M = Cr, Mo, W) gekoördineer. Die vinieleter- en vinielamienkomplekse van goud(I), wat vorm wanneer alkoksie- en dialkielaminokarbeenkomplekse onderskeidelik in hierdie sintese aangewend word, koördineer onsimmetries deur hulle viniel dubbelbindings aan die vrygestelde M(CO)5-groepe. Hierdie normaalweg onstabiele vorm van vinieleterkoördinasie, word gestabiliseer deur delokalisering van positiewe lading vanaf die α-goud viniel koolstofatoom na die AuPPh3-fragment [vir die η2-{alkoksievinielgoud( I)PPh3}M(CO)5 komplekse] óf na die stikstofatoom van die dialkielvinielamien groep [vir die η2-{dialkielaminoviniel-goud(I)PPh3}M(CO)5 komplekse]. Laasgenoemde komplekse kan as zwitterione beskryf word. Die onderskeie negatiewe ladings in hierdie komplekse bevind hulle hoofsaaklik op die M(CO)5 groepe. Sterk koördinerende ligande (bv. PPh3) verplaas die onsimmetriese viniel eter vanaf die M(CO)5-fragment. Só kon, as n voorbeeld, die vrye etoksievinielgoud( I)PPh3-kompleks met n hoë opbrengs berei word. Wanneer β-gedeprotoneerdeFischer-tipe tiokarbeenkomplekse met Ph3PAu+ reageer, vorm swawel gekoördineerde {tioviniel-goud(I)PPh3}Cr(CO)5 bimetalliese komplekse in stede van die π-komplekse. Dit word voorgestel dat in die bogenoemde reaksies die goud(I)elektrofiel dieselfde rol vervul as die proton gedurende die hidrolise van Fischer-tipe alkoksiekarbeenkomplekse. Die bimetalliese, η2-vinieleter-gekoördineerde {alkoksieviniel-goud(I)PPh3}M(CO)5-komplekse hier berei verteenwoordig dus stabiele goud(I) analoë van voorgestelde tusseprodukte in so ’n meganisme. Die term aurolise word voorgestel om die geval waar Ph3PAu+ in stede van H+ as elektrofiel aangewend word te beskryf. Die vorming van bimetalliese, η2-vinieletergeko ördineerde komplekse in die huidige reaksie ondersteun die moontlike vorming van die voorgestelde tussenprodukte tydens die hidrolise van Fischer-tipe alkoksie(metiel)karbeenkomplekse. ’n Soortgelyke meganisme kan ook gebruik word om die vorming van die η2-{dialkiellamienviniel-goud(I)PPh3}M(CO)5- en {alktioviniel-goud(I)PPh3}-S Cr(CO)5-komplekse vanuit β-CH gedeprotoneerde Fischer-tipe dialkielamino- en tiokarbeenkomplekse en Ph3PAuCl te interpreteer. Die reaksie van anioniese groep 6 oorgangsmetaal metaal-asielkomplekse en hulle stikstofanaloë, N-gedeprotoneerde Fischer-tipe aminokarbeenkomplekse, lewer onderskeidelik asiel- en imidoielkomplekse van goud(I) wat aan M(CO)5 fragmente (M = Cr, W) koördineer. Die goud(I)asiel-M(CO)5 koördinasie deur die asielsuurstofatoom is baie swak en die M(CO)5-eenheid in hierdie komplekse word maklik deur haliedanione en sekere oplosmiddel molekules verplaas. Die haliedanione vorm anioniese addukte met the M(CO)5 fragmente. Hierdie eienskap van die bimetalliese komplekse verskaf sodoende n gerieflike sintetiese roete na die eerste voorbeeld van n vrye asielgoud(I)-kompleks, bensoiel-AuPPh3. Koördinasie van die imienstikstofatoom aan M(CO)5-groepe in die bg. imidoielkomplekse is egter veel sterker. Die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse is verbasend stabiel en kan selfs effektief deur middel van lae temperatuur SiO2-kolomkromatografie geïsoleer word. n Soortgelyke reaksie meganisme as wat voorgestel word vir die aurolise van Fischer-tipe karbeenkomplekse word voorgestel vir hierdie reaksie. Die enigste verskil is dat die formele reduktiewe eliminasie van n viniel-eter, -amien of -tioeter vervang word met die vorming van asiel- of imidoielkomplekse van goud(I). Verder word die (Z)-isomere van die bimetalliese {imidoielgoud(I)}M(CO)5-komplekse uitsluitlik in hierdie reaksie verkry. Wanneer geskikte voorbeelde van bimetalliese {imidoielgoud(I)}M(CO)5-komplekse n tweede keer gedeprotoneer word en gereageer word met Ph3PAuCl, is die enigste isoleerbare produk van die reaksie n driehoekige Au2Cr troskompleks, nl. cis-{η2- (Ph3PAu)2}PPh3Cr(CO)4. Hierdie verbinding dien as n isolobale model vir die onstabiele molekulêre waterstof kompleks , (η2-H2)PPh3Cr(CO)4, en besit verder die kortste Au-Au afstand tussen twee goud atome in driehoekige troskomplekse wat nog tot dusvêr gerapporteer is. Laastens is die kristalstrukture van twee nou verwante anioniese {bensoiel}W(CO)5- komplekse bepaal. Die enigste verskil tussen die hierdie twee verbindings is dat die een slegs Li+ as teenioon bevat terwyl presies die helfte van die Li+-teenione in die tweede struktuur deur protone verplaas is. Hierdie klein verskil in samestelling veroorsaak egter drastiese verskille in die kristalstrukture van hierdie verbindings. Die belangrikheid van waterstof bindings en ioon-dipool interaksies in die bepaling van die vastetoestandstrukture van sulke verbindings word hierdeur beklemtoon.

Thesis (PhD)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Please refer to fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy