Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch,2005. / This study comprises the preparation and full characterisation of new carbene complexes of group 10 metals (Ni, Pd or Pt), the group 9 metal, rhodium, as well as group 6 metals (Cr and/or W). N-heterocyclic carbene (NHC) complexes of nickel and palladium were prepared via oxidative addition of the corresponding carbene precursors imidazolium-, imidazolinium-, pyridinium- and quinolinium chloride salts, to M(PPh3)4 (M = Ni or Pd). Three types of carbene complexes, namely the standard five-membered two-N carbene complexes, new six-membered NHC complexes and novel six-membered rNHC complexes received attention. In the rNHC complexes the heteroatom (N) is removed from the carbene carbon. These new square planar carbene complexes of the general formula trans-[(PPh3)2MCl(L)]X (M = Ni or Pd; X = BF4 or PF6) L = 1,3-dimethyl-2,3-dihydro-1Himidazol- 2-ylidene, 1,3-dimethyl-2,3,4,5-tetrahydro-1H-imidazol-2-ylidene, 1-methyl-1,2-dihydropyridin- 2-ylidene, 1-methyl-1,2-dihydro-quinolin-2-ylidene, 1,4-dimethyl-1,2-dihydro-quinolin-2- ylidene, 2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene, 1-methyl-1,4-dihydro-pyridin-4- ylidene) have been isolated and characterised. The preparation of the corresponding carbene complexes of platinum was complicated by the formation of [PtCl(PPh3)3]BF4 and the desired carbene complexes could not be isolated in pure form. The investigation of rNHC complexes was extended to include the synthesis of (CO)5M{CSC(CNCMe2CH2O)CHCH} (M = Cr and W). The molecular and crystal structures of thirteen of the new carbene complexes including the structures of both cis- (only formed below –20°C) and trans-chloro(1-methyl-1,2-dihydro-quinolin- 2-ylidene)bis(triphenylphosphine)palladium(II) tetrafluoroborate were determined. The metalcarbene bond distances in both the palladium and nickel carbene families do not differ significantly. The carbene ligands can be arranged in a series of increasing trans-influence, using the metalchloride bond distance as a guideline, as follows: 1,3-dimethyl-2,3-dihydro-1H-imidazol-2-ylidene and 1,3-dimethyl-2,3,4,5-tetrahydro-1H-imidazol-2-ylidene < 1-methyl-1,2-dihydro-pyridin-2- ylidene < 2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene, 1-methyl-1,4-dihydro-pyridin-4- ylidene. The crystal and molecular structures of two platinum compounds, cis-chloro(2-methoxy-1- methyl-1,4-dihydro-quinolin-4-ylidene)bis(triphenylphosphine)platinum(II) tetrafluoroborate and the byproduct [PtCl(PPh3)3]BF4 were also determined. Trans-chloro(2-methoxy-1-methyl-1,4-dihydro-quinolin-4-ylidene)bis(triphenylphosphine) palladium(II) tetrafluoroborate was found to be a very active catalyst, compared to simpler palladium carbene and phosphine complexes, in the Mizoroki-Heck and Suzuki-Miyaura coupling reactions. Quantum mechanical calculations indicated that the rNHC ligand in this complex is bound stronger to the palladium than a standard imidazole-derived NHC ligand. Further calculations suggested that the remote heteroatom carbene (rNHC) complexes of nickel(II) are significantly more stable when compared to the normal carbene (NHC) complexes. Energy decomposition analysis suggested that the rNHC ligands are strong s-donors and weak -acceptors. Unsymmetrical imidazolium-derived bis(carbene) complexes, [Rh(NHC)2COD]Br, bromomono( carbene) complexes, Rh(Br)COD(NHC), and chloro-mono(carbene) complexes, Rh(Cl)COD(NHC) where NHC = 1-R-3-methyl-2,3-dihydro-1H-imidazol-2-ylidene (R = ethyl, propyl or butyl), were formed in each reaction of the corresponding free carbene ligand with [Rh(Cl)COD]2. [Rh(Br)COD(NHC)] formed as a result of substitution of a chloride ligand by a Br-- anion. The carbonyl complexes, cis-[Rh(CO)2X(NHC)] (X = Br or Cl; NHC = 1-ethyl-3-methyl- 2,3-dihydro-1H-imidazol-2-ylidene) were isolated after the substitution of the COD ligand in Rh(X)COD(NHC) (X = Br or Cl) with CO. Isomerisation of these cis-carbonyl complexes to the trans isomers was observed. Cis-[(h4-1,5-cyclooctadiene)bis(1-butyl-3-methyl-2,3-dihydro-1H-imidazol-2-ylidene)rhodium(I)] bromide, bromo(h4-1,5-cyclooctadiene)(1-methyl-3-propyl-2,3-dihydro-1H-imidazol-2-ylidene) rhodium(I) and cis-[(h4-1,5-cyclooctadiene)bis(1-butyl-3-methyl-2,3-dihydro-1H-imidazol-2- ylidene)rhodium(I)]bromide were also characterised by single crystal X-ray diffraction. The synthesis and structural characterisation of a series of acyclic and heterometallacyclic Fischertype carbene complexes in which a soft donor atom (P) attached to the carbene side chain is either uncoordinated, (CO)5M=C(NMe2)CH2PPh2 (M = Cr or W), bonded to the original central metals (Cr or W) in four-membered chelates, (CO)4M=C(NMe2)CH2PPh2, or coordinated to a second M(CO)5 unit (only isolated for chromium) (CO)5Cr=C(NMe2)CH2P(Ph2)Cr(CO)5, were carried out. These compounds were produced by the reaction of the anionic Fischer-type aminocarbene complexes, [(CO)5Cr=C(NMe2)CH2]Li (M = Cr or W), with ClPPh2. The formation of the four-membered chelates, via cyclisation, occurs much faster for Cr than for W. The aminocarbene-phosphine chelates represent the first examples of structurally characterised, four-membered C,P-chelate carbene complexes.

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: In this study, a number of mono- and di-substituted acyl(aroyl)thioureas were investigated for potential application as specific carriers (ionophores) for the transport and extraction of Ag(l) from a mixture of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(lI) ions. The experimental arrangement for the transport experiments employed a liquid membrane set up involving a 3-phase system - 2 aqueous phases (source and receiving phase) separated by a chloroform membrane incorporating the ligand. Competitive metal ion transport experiments were conducted using the liquid membrane set up. The aqueous source and receiving phases were analyzed using Atomic Absorption Spectroscopy (AAS) and results were confirmed by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICPOES). The transport results show that the N,N-dialkyl-substituted-N'-acyl(aroyl) (HL) thioureas studied, with the exception of the N,N-di-(2-hydroxyethyl)-N'-benzoylthiourea (HL3 ) and N-piperidyl-N'-4-nitrobenzoylthiourea (HL9 ), were efficient and selective for Ag(I). HL9 was also selective for Ag(l) but not efficient. HL3 was selective for Cu(II). Under the experimental conditions employed, 13% Cu(lI) was transported by HL3 . Among the N,Ndialkyl- N'-aroylthioureas, maximum Ag(l) transport was obtained by using N,N-diethyl-N'-4- chlorobenzoylthiourea (HL5 ) and N,N-di-n-butyl-N'-benzoylthiourea (HL \ Under the experimental conditions employed, the percentages of Ag(l) transported by HL5 and HL 1 were 48% and 42% respectively. The transport selectivity and efficiency of 3,3,3' ,3'-tetraethyl-1 ,1'-isophthaloylbisthiourea (H2L12 ) and N,N-diethyl-N'-camphanoylthiourea (HL13)for Ag(l) were also studied. We were particularly interested, in comparing the Ag(l) transport and extraction efficiency of these ligands with that of the HL and H2L ligands. The experimental results reveal that, of all the ligands we investigated in this study, HL 13 was the most efficient and selective carrier for Ag(l) transport. The interesting result is that, depending on the ligand concentration used, HL 13 transported 71-81% of Ag(I). Competitive two-phase metal ion solvent extraction experiments were also performed under conditions similar to the transport studies. The results show that by varying the ligand concentration in the membrane phase, up to 100% Ag(l) can be selectively and efficiently extracted from the mixture of the seven metal ions. Finally, the N,N-di-(n)-butyl-N'-benzoylthiourea (HL1) ligand and its complex with Ag(l) were synthesized. Single crystals of the complex were grown for X-ray crystallography and the crystal and molecular structure of the complex was determined. The crystal structure showed that Ag(l) is bonded to the deprotonated ligand through the S,O atoms forming interesting cluster [Ag (L - S, 0)] 4 in the solid state. This structure is monoclinic and crystallizes in the space group P21!c with a = 17.805 (4) A, b = 21.759 (4) A, c = 36.438 (7) A, f3= 96.34(3)°, Z = 8 and a final R-factor of 5.4%. / AFRIKAANSE OPSOMMING: In hierdie proefskrif is 'n aantal mono- en di-gesubstitueerde asiel(ariel) tioureums ondersoek vir moontlike gebruik as ionofore (spesifieke draers) vir die transportasie en ekstraksie van Ag(l) vanuit 'n mengsel van Co(ll), Ni(II), Cu(II), Zn(II), Cd(II), Ag(l) en Pb(lI) ione. 'n Drie-fase selsisteem is gebruik vir die transportasie eksperimente, twee waterige fases (bron- en ontvang-fase) wat geskei is met die chloroform membraan fase wat die ligande bevat. Kompeterende metaalioon transportasie eksperimente is uitgevoer met behulp van hierdie vloeistof membraan stelsel. Die twee waterige fases is deur middel van Atoomabsorpsie Spektroskopie (AAS) ge-analiseer en resultate is bevestig met gebruik van Induktief-gekoppelde Plasma-Optiese Emissie Spektroskopie (IGP-OES). Die resultate het getoon dat elkeen van die N,N-dialkiel-gesubstitueerde-N'-asiel(ariel) (HL) tioureums, met uitsondering van N,N-di(2-hidroksie-etiel)-N'-benzieltioureum(HL 3) en Npiperidiel- N'-4-nitrobenzieltioureum(HL9 ), doeltreffend en selektief was vir Ag(l) transportasie. HL9 was selektief vir Ag(I), maar die transportasie waarde was nie hoog nie, dws. dit was nie doeltreffend nie. HL3 was selektief vir Cu(II). Met gebruik van ons eksperimentele kondisies is 13% Cu(lI) getransporteer deur HL 3. Van die N,N-dialkiel-N'- ariel tioureums, is maksimum transportasie van Ag(l) verkry met gebruik van N,N-dietiel- N'-4-chlorobenzieltioureum (HL5) en N,N-di-n-butiel-N'-benzieltioureum (HL1). Met gebruik van ons eksperimentele kondisies was die persentasie transportasie van Ag(l) deur HL5 en HL 1 48% en 42% onderskeidelik. Die selektiwiteit en doeltreffendheid van 3,3,3' ,3'-tetra-etiel-1 ,t-isoftaltelblstioureumtl+L 12) en N,N-di-etiel-N'-kamfonieltioureum (HL13) vir Ag(l) transportasie is ook onderneem. Ons was besonder ge-interesseerd om die Ag(l) transportasie en ekstraksie van hierdie ligande te vergelyk met dié van die HL en H2L tipe ligande. Die eksperimentele resultate het getoon dat van al die ligande wat bestudeer is, HL 13 die doeltreffendste en mees selektiewe ionofoor was. Van besondere, belang was dat, afhangend van die ligand konsentrasie wat gebruik is, HL13 71-81% Ag(l) getransporteer het. Kompeterende twee-fase metaalioon vloeistof-vloeistof ekstraksie eksperimente is ook uitgevoer onder toestande soortgelyk aan dié van die transportasie eksperimente. Die resultate toon dat met varierende ligand konsentrasie, tot soveel as 100% Ag(l) selektief en doeltreffend geëkstrakeer word vanuit 'n mengsel van die sewe metaal ione. N,N-di-n-butiel-N'-benzieltioureum (HL1 ) ligande en die kompleks daarvan met Ag(l) is ook gesintetiseer. Enkel-kristalle van die kompleks is verkry en X-straal kristallografiese analiese is onderneem. Die kristalstruktuur toon hoedat Ag(l) gebind is aan die gedeprotoneerde ligand deur die S en Q atome en toon ook interessante [Ag(L-S,Q)]4 groepe in die vaste toestand. Hierdie struktuur is monoklinies en kristaliseer in die ruimtegroep P21!c met a = 17.805(4) Á, b = 21.759(4)Á, c = 36.438(7)Á, P = 96.34(3t, z = 8 en 'n finale R-faktor van 5.4%.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy