Phosphine complexes of nickel and palladium provide the best catalysts for the homogeneous catalysed carbon-carbon bond forming reaction between an organometallic nucleophile and an organic electrophile. Use of a homochiral ligand on the catalyst can lead to stereoselectivity in the cross-coupling reaction, with high ee's of coupled product being obtained. The processes of selectivity in the transmetalation step of the catalytic cycle have not been elucidated and the initial aim of the project was to study these processes. Initial experiments using organotin derivatives as the organometallic nucleophile highlighted the problems of selectivity and the forcing conditions needed in the attempted transfer of a benzyl group from the tin to the palladium catalyst. The compounds [8- (dimethylamino)-1-naphthyl]methyldiphenyltin (60) and [2-((dimethylamino)methyl) phenyl]methyldiphenyltin (70) were prepared and their reactivity in the palladium catalysed cross-coupling with 2-furoyl chloride, to give 2-benzoylfuran, was investigated. These molecules were found to undergo facilitated transfer of a phenyl group compared to transfer from control molecules. The effect was tested and attributed to the internal nucleophilic attack at the tin atom by the lone pair on the nitrogen atom. The compound [2- ((dimethylamino)methyl)-3-trimethylsilylphenyl]methyldiphenyltin (79) was prepared to test the effects of steric buttressing within the molecule, but was found to be of the same order of magnitude of reactivity as (60) and (70). All three molecules showed a reactivity of at least an order of magnitude greater than control compounds. The effect did not prove applicable to the transfer of a benzyl group or in other coupling reactions. The effect of palladium ligation was tested and the ligand triphenyl arsine found to increase the rate of the coupling reaction. The two facilitating processes were found to work in a co-operative fashion, giving a rate enhancement of ca. one hundredfold over control reactions. The nickel catalysed cross-coupling of α-substituted sp³ hybridised Grignard reagents with allylic esters was attempted, but proved unsuccessful. Stoichiometric reactions with nickel complexes were also found to be unsatisfactory in yielding coupled products. The synthesis of α-substituted diorganozinc reagents was attempted, but furnished only homocoupled products. The reaction of dibenzylzinc with aldehydes was found to proceed in the absence of catalyst, highlighting the reactivity of a benzylzinc moiety.

A number of organometallic transformations related to proposed elementary steps in the reductive polymerization of carbon monoxide are discussed. The use of isonitrile as model ligands for carbon monoxide, with which they are isoelectronic, is proposed. Investigations show that alkyl migration to isonitrile is preferred over migration to carbon monoxide. Iminoformyl products due to hydride migration to isonitrile are not, however, observed. Syntheses of a range of cationic complexes of the type [ (η⁵-C₅H₅)M(L)₂(CNR)]⁺, [(η⁵-C₉H₇)Ru(L)₂(CNR)]⁺ and [(η⁵-C₉H₇)M(L)₂(CO)]⁺ (M = Fe, Ru; L = CO, phosphine) are described. In two cases, addition of hydride to the isonitrile cations is followed by protonation on work-up to give aminocarbene complexes. These are inert to further reduction under the conditions employed. The majority of isonitrile cations lose the isonitrile ligand to give good yields of metal hydride complexes. A mechanism involving ring-slippage of the hydrocarbon ligand is implicated. Hydride addition to η⁵-C₉H₇ complexes results, in the majority of cases, in loss of the hydrocarbon ligand from the complex and recovery of indane. Evidence for the intermediacy of metal formyl complexes in a number of hydride donation reactions is presented. These formyl complexes are formed from carbonyl hydride complexes either under moderate CO pressure or in THF solution. Hydride complexes lacking a carbonyl ligand are found to be inert. Finally, two reactions, one involving an alkyl migration reaction catalyzed by silver(I) salts, and the other involving the reduction of a metal acyl ligand to metal alkyl, are combined to demonstrate a model for carbon chain growth at a metal centre. The synthesis of an iron pentanoyl complex, followed by a decomplexation reaction, gives pentanoic acid in which all the catbon atoms are potentially directly derived from carbon monoxide. This is the first synthesis of a single homologous acid from carbon monoxide.

This Thesis describes the synthesis and structural characterisation of a range of heterometallic cluster compounds of platinum. Chapter 1 reviews the current knowledge in this area and gives examples of the kinds of cluster compounds which have been characterised, with some emphasis on their mode of synthesis and their structural and spectroscopic characterisation. The structures of the cluster compounds are rationalised in terms of the triangular Pt₃ unit which dominates the cluster chemistry of platinum. The bonding in the simplest triplatinum cluster compounds is analysed and is used as a basis for understanding the interconversion of platinum cluster compounds and the formation of heterometallic platinum-gold cluster compounds. Chapter 2 describes the synthesis and characterisation of the homometallic platinum cluster compounds which are convenient precursors for the formation of heterometallic cluster compounds. A general synthetic route to the platinum carbonyl phosphine clusters has been developed and the exchange of bridging CO and S0₂ ligands in this type of cluster was investigated. The synthesis of a new type of anionic 44 electron triplatinum cluster, [Pt₃(μ-S0₂)₂(μ-X)(PR₃)₃]¯ described. The syntheses of heterometallic clusters from the trianguloplatinum cluster compounds are reported in Chapter 3. The use of [AuPR₃] as a capping fragment generates clusters with a tetrahedral Pt₃Au framework. The synthesis and characterisation of two novel "sandwich" compounds are reported in which a gold or copper atom is coordinated between two parallel triplatinum units. A full single crystal X-ray crystallographic study has been carried out on each of these compounds and their geometric parameters contrasted. Chapter 4 describes the reactions of the platinum-sulphide complex [Pt₂(μ-S)(CO)(PPh₃)₃]. This compound is found to be chemically robust. The pt-Pt bond has so far proved resistant to insertion reactions and only the ligands trans to the sulphur atom are readily exchanged. The bridging sulphido- group appears to have an extensive coordination chemistry which has lead to the synthesis of some heterometallic complexes. This property does not, as yet, provide a route into cluster formation but instead produces complexes which are aggregates of metal atoms. The application of ³¹P and ¹⁹⁵Pt NMR studies to the characterisation of platinum cluster compounds is discussed in Chapter 5. The solution NMR spectra of compounds synthesised in the course of this research are described and analysed in detail. A large amount of NMR data for homometallic triplatinum clusters has been gathered and it has been possible to characterise a number of such compounds having relatively low symmetry. The heterometallic complexes described in Chapters 3 and 4 have also been characterised using NMR spectroscopy by considering the extra MPR₃ fragments as perturbations on the spectra of the compounds from which they were derived. Analysis of the complex spectra obtained for such compounds was greatly assisted by the use of computer simulation techniques.

Two areas of organotransition metal chemistry and their potential application to organic transformations are discussed. The synthesis of cations of the type [Fe(η⁵-C₅H₅)(L)₂(CO)]⁺, [Fe(η⁵-C₅H₄CH₃)(L)₂(CO)]⁺, [Fe(η⁵-C₅(CH₃)₅)(L)₂(CO)]⁺ (where (L)₂=(CO)₂, (PPh₃)(CO), (PMe₃)(CO), (PPh₃)₂,(diphos) and (PMe₃)₂) and [Mo(η⁵-C₅H₅)(L)₃(CO)] (where (L)₃=(PPh₃)(CO)₂, (diphos)(CO) and (triphos)), many of them novel, is described. Investigations into the site of nucleophilic attack on the cations using hydride as a probe and the effect of varying the overall charge distribution of the cation are discussed. Hydride attack on a carbonyl ligand leads to the formation of metal formyl moieties and their detection by low temperature ¹H n.m.r. spectroscopy is described; furthermore, the fate of the metal formyls was found to be dependent upon the nature of the other ligands in the complex. A new criterion for establishing the stereoselectivity of nucleophilic attack on η⁵-C₅H₅ ligands is proposed. Hydride attack on an η⁵-C₅H₄CH₃ ligand was discovered to be regioselective occurring at the carbon atom alpha to the methyl-bearing carbon. The direct oxidation of alkenes to epoxides by hydrogen peroxide was shown to be catalysed by some of the metal carbonyl cations. The use of organotitanium reagents to convert vic-dibromides and epoxides to alkenes is discussed. (C₅H₅)₂TiCl₂ was shown to catalyse both a sodium amalgam debromination of disubstituted vic-dibromides and a zinc debromination of mono and disubstituted vic-dibromides. The latter reaction was developed into a synthetically useful procedure. Reduction of (C₅H₅)₂TiCl₂ by both sodium amalgam and zinc dust gave reagents which deoxygenated epoxides. Investigations into the regioselectivity and chemoselectivity of these reagents are discussed. During the synthesis of molecules containing both vic-dibromide and epoxide functionalities, a novel cyclisation was discovered which may have relevance to the biosynthesis of certain marine natural products.

This Thesis describes the synthesis, structural characterization and properties of some tin(II) and tin(IV) compounds containing bidentate ligands. Chapter 1 describes the main spectroscopic techniques used in the identification of tin(II) compounds; infra-red, ¹¹⁹Sn Mössbauer and n.m.r spectroscopy are outlined, and relevant examples given. A comprehensive listing is given of the main spectroscopic and structural properties of known tin(]3) compounds. Chapter 2 describes the general synthetic methods employed for the formation of tin(II)-oxygen heterocyclic compounds. A range of catecholate and related complexes of tin(II) were synthesized and the role of the substituent investigated with regard to their physical properties, especially their solubilities. The use of 4-nitrocatechol leads to a soluble product, {Sn[O-4-NO₂-C₆H₃O][OC₄H₈]}>sub>n</sub>, which enabled it to be studied spectroscopically and its solid state structure to be determined. The nature of the bonding in {Sn[O-4-NO₂-C₆H₃O][OC₄H₈]}_n was investigated using Extended Hiickel molecular orbital calculations. Chapter 3 describes the chemical reactivity of the novel, soluble, tin(II)-oxygen heterocycle {Sn[O-4-NO₂-C₆H₃O][OC₄H₈]}_n. Reaction with iodine gives SnI₂ [O-4-NO₂-C₆H₃O][OC₄H₈]<sub>2<sub>. Reaction with the Lewis base such as 1,2-diaminopropane gives Sn[NH₂CH₂CH(Me)H₂N][O-4-NO₂-C₆H₃O][OC₄H₈], whilst benzyltriethylammonium chloride gives {[Et₃BzN][SnCl(O-4-NO₂-C₆H₃O)]}_n. The solid-state structure of the compound consists of polymeric chains of [SnCl(O-4-NO₂-C₆H₃O)]^- and associated [Et₃BzN]⁺ cations. Reaction with BF₃.Et₂O gives the adduct F₃B.Sn[O-4-NO₂- C₆H₃O][OC₄H₈]. Reaction with W(CO)<sub>5_{thf gives {(OC)₃W.Sn[(O-4-NO₂- C₆H₃O)(OC₄H₈)]}₂ in which the tungsten atoms are believed to be bound η⁶ to the aromatic rings. Reaction with bis(triphenylphosphine)platinum-ethylene or tris(triphenylphosphine)platinum gives {PtH[PPh₃]₃}{[μ₂-O][μ₂-OH][Sn(O-4-NO₂- C₆H₃O)]₂}, the anion containing tin(II) and tin(IV) centres. Reaction with RhCl[CNC₈H₉]₃ gives {RhCl[CNC₈H₉]₃[μ₂-Sn(O-4-NO₂-C₆H₃O)]}₂. Reaction with Ph₃PAuCl gives the cluster Au₄(PPh₃)₄(μ₂-SnCl₃)₂, which is the first known example of a compound containing a μ₂-SnX₃ fragment. In comparison with SnCl₂, {Sn[O-4-NO₂- C₆H₃O][OC₄H₈]}_n only weakly inserts into the platinum-chlorine bonds of PtCl₂(dppe). Two molar equivalents of SnCl₂ reacts with PtCl₂(dppe) to give Pt(dppe)(SnCl₃)₂. Addition of a further equivalent of SnCl₂ in the presence of tetraethylammonium chloride gives [Et₄N][Pt(dppe)(SnCl₃)₃]. The platinum centre in this ion has a distorted trigonal bipyramidal geometry. Chapter 4 describes the synthesis of a number of tin(II)-sulphur heterocycles. The reaction between Sn[SC₆H₄S] and TMEDA gives a soluble adduct, Sn[SC₆H₄S]TMEDA. A number of tin(II)-nitogen heterocycles were also synthesized. Their intense colours and their instability towards air oxidation indicated that they were monomeric in the solid-state. Chapter 5 outlines the basis for non-linear optical properties, especially their SHG effects. A wide range of tris(catecholato)tin(IV) compounds were synthesized and tested for SHG activity. A number were found to have a significant SHG effect, especially [(O-4- NO,sub>2}-C₆H₃O)₃Sn][NHEt₃]₂, which has an SHG effect 1.33 x urea.

Several new late transition metal complexes containing P-O and P-N ligands derived from 2-dicyclohexylphosphinoacetaldehyde were synthesized. A facile one-pot template method is used for the synthesis of P-N complexes, where the phosphine aldehyde and amine can undergo a condensation reaction to form a phosphine-imine metal complex in the presence of a metal precursor. Metal complexes with phosphino-enolate, imine, and oxime ligands are synthesized. Ni(II), Pt(II), Rh(I) and Ir(I) metal centres were investigated. The Rh(I) and Ir(I) complexes contain a 1,5-cyclooctadiene ligand, thus resembling Crabtree’s hydrogenation catalyst [Ir(COD)(py)(PCy3)][PF6]. These complexes are also active catalysts for olefin hydrogenation. Furthermore, the synthesis of a new chiral amine functionalized NHC ligand is explored, which has potential applications as a ligand in the metal-catalyzed enantioselective hydrogenation of polar bonds. This ligand is inspired by previous achiral hydrogenation catalysts reported by Morris et al. that displayed high activity for a variety of unsaturated substrates.

The recovery of organometallic catalysts from polymer matrices is of great importance in promoting the application of homogeneous catalysts in industry. Such a green recovery technique will not only popularize the techniques of green catalytic hydrogenation of polymers by Rempel’s group, but also consummates the technique of heterogenization of organometallic catalysts. The high value product of hydrogenated nitrile butadiene rubber (HNBR) with dissolution of Wilkinson’s catalyst [RhCl(TPP)3] was selected as the model polymer matrix for developing a green separation technique. The supercritical carbon dioxide (scCO2) soluble fluorous Wilkinson’s catalyst [RhCl(P(p-CF3C6H4)3)3] was synthesized and shown exhibit a very limited activity in the catalytic hydrogenation of bulk HNBR. Its recovery from a HNBR matrix using scCO2 however failed. In spite of the assistance of the scCO2 dissolvable chelating ligand thenoyltrifluoroacetone (TTA), the weak compatibility of scCO2 with rhodium complexes failed again as an extraction solvent for the HNBR matrix. Inspired by the merits of CO2-expanded liquids (CXLs) and the versatility of CO2 in changing the physical properties of polymer melts, CXLs were tested as extracting solvents for separation of Wilkinson’s catalyst from bulk HNBR. CO2-expanded water (CXW) and CO2-expanded alcohols including methanol and ethanol (CXM and CXE) were examined with the assistance of a variety of chelating agents. The investigated chelating agents include ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA-Na2), diethylenetriamine (DETA), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA), and N,N,N’,N’-tetramethylethylenediamine (TMEDA). CXM and PMDETA were recognized as the optimal combination of extracting solvent and chelating agent for recovery of Wilkinson’s catalyst from HNBR. An extraction system consisting of CXM and PMDETA was carefully investigated with respect to the effects of temperature and pressure on the extraction performance over the temperature range of 40 to 100 °C and the pressure range of 20 to 200 bar. Increasing temperature effectively increased the extraction rate and became less influential when the temperature was above 80 °C. Increasing pressure at a fixed temperature was found to improve the extraction rate followed by suppressing it. Nevertheless, further increasing the pressure to an extreme high value above the respective critical point was able to promote the extraction rate again. The complex effects of pressure were thoroughly investigated by the means of analyzing the dissolution behavior of CO2 in HNBR and the variation of the extraction phase composition at different operational conditions. 0.14 g/mL was determined as the CO2 density by which the optimal pressure at a fixed temperature can be estimated. Based on a careful interpretation of the experimental results, an extraction mechanism was illustrated for interpreting the present extraction system. Additionally, the reactions involved in the extraction process were illustrated to reveal the principal challenges present in the extraction process and pointed out the potential solution for eliminating the obstacles. Two special operations-sequential operation and pressure varying procedure were tested for their effectiveness in enhancing the extraction ratio. A pressure varying procedure was found to be beneficial in further improving the extraction ratio, while sequential operation did not show any promise in enhancing the recovery. At last, the developed technique was shown to be highly efficient in applying it to HNBR particles coagulated from the HNBR latex. A residue of 59 ppm rhodium was obtained after 9 hours of operation. This study establishes a technology platform for separating the expensive catalyst from the polymer matrix, using “green” CO2-expanded liquids.

No description available.

Typescript (photocopy) / viii, 283 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1980

Typescript (photocopy) / 199 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1982