Ph.D. / The main objective of the research described in this dissertation was the preparation and characterisation of hindered organophosphorus compounds. For this purpose, ionic and free radical mechanisms were applied in the synthesis of selected hindered organophosphorus compounds, some with interesting spectral properties. A brief background of the element phosphorus and the early development of organophosphorus chemistry is provided. The early development of the chemical nerve agents derived from phosphorus, their toxicity and illicit manufacture by terrorist groups is discussed. The vital role played by the organisation for the prohibition of chemical weapons in enforcing the prohibition of the development, production, acquisition, stockpiling and the use of chemical nerve agents and their destruction by the state party is highlighted. The methodologies such as Michaelis Arbuzov, Michaelis Becker, Perkow Pudovik, Abramov and radical protocol reactions used to synthesise phosphorus containing compounds, are reviewed. In the present research project, diphenylphosphonous chloride and phenylphosphonous dichloride reagents were used in nucleophilic substitution reactions with bulky alcohols. This resulted in the synthesis and characterisation by 1H, 13C, 31P NMR and GCMS spectroscopy of the compounds shown in Scheme 0.1, where R’ was derived from 2,2dimethylpropanol, 3methylbutanol, 1,2dimethylpropanol, 3,3dimethyl2butanol, 1,1dimethylethanol and 2methyl2butanol. (R)xPCl(3x) R'OH Et3N (R)xP(OR')(3x) H2O2 or S8 (R)xP(OR)(3x) Y R=Aryl, and Y=O, S The importance of using activated alcohols in the form of metal alkoxides in the cases of 1,1dimethylethanol and 2methyl2butanol for successful reactions was demonstrated. The influence of steric hindrance on the reactivity of these ionic reactions was studied by substituting diphenylphosphonous chloride, or phenylphosphosphonous dichloride, with tertbutylphosphonous dichloride or ditertbutylphosphonous chloride. This resulted in no nucleophilic substitution reaction taking place between tertbutylphosphonous dichloride and hindered alcohols in the presence of triethylamine. For successful reactions, the use of excess activated hindered alcohols in the form of either the lithium or potassium alkoxide was required. It was found that replacing both of the chlorine atoms in tertbutylphosphonous dichloride with hindered alcohols like 1,1dimethylethanol and 2methyl2butanol was sluggish, and in the present study this could not be realised. It was demonstrated that ditert butylphosphonous chloride is resistant to react with activated hindered alcohols due to enhanced steric hindrance in the organophosphorus reagent. The use of freeradical mechanisms in the phosphoruscarbon (PC) bond forming reaction is briefly reviewed. The importance of finding a nontoxic replacement of organotin reagents in radical protocols is also highlighted. The scope of the present work was limited to the reaction of phosphonylcentered radicals generated by the triethylboraneoxygen system with various alkenes ranging from less electron rich to more electron rich alkenes, including those containing a free hydroxy moiety. The reaction of diphenyl thiophosphite or diphenyl phosphite (Scheme 0.2) in the presence of triethylborane under aerobic conditions with enol ether alkenes afforded the expected antiMarkovnikov products.

The synthesis of 2:3-benzo-1,1-dimethyl-1-silacyclo-hex-2-ene has been reported. This compound was prepared by the simultaneous addition of 3-(o-bromophenyl)-propyl bromide and dichlorodimethylsilane to excess magnesium in tetra-hydrofuran. The six-membered ring organosilicon compound was readily brominated by N-bromosuccinimide to give the 4-derivative. Attempts were then made to synthesize the 4-cyano and the 4-carboxylate derivatives from this bromination product. Experimental data are also given for an attempted preparation of 2:3-benzo-4-(2-dimethylaminoethoxy)-1,1-dimethyl-1-silacyclohex-2-ene. / Pharmaceutical Sciences, Faculty of / Graduate

The novel bimetallic hydrides [(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)H₂]₂ can be prepared sequentially by the metathesis of [(n⁵-C₅H₅)W(N0)IH₂]₂ with Na[H₂Al(0CH₂CH₂0CH₃)₂]. Analyses of the ¹H NMR spectra of C[(n⁵-C₅H₅)W(N0)IH]₂ and [(n⁵-C₅H₅)W(N0)IH₂]₂ show the former contains hydride ligands bound to tungsten in a terminal fashion, while the latter possesses two terminal and two bridging hydrides. Addition of a Lewis base to [(n⁵-C₅H₅)W(N0)IH]₂ results in the formation of hydride species (n⁵-C₅H₅)W(N0)IHL (L = P(0Ph)₃, P(0Me)₃, PPh₃); in like manner, the dimer [(n⁵-C₅H₅)W(N0)IH₂]₂ is cleaved by triphenylphosphite to form the monomer cis or trans [(n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. A comparison is made of the reactivity of the tungsten-hydrogen link in the nitrosyl hydrides (n⁵-C₅H₅)- W(N0)IH[P(0Ph)₃], (n⁵-C₅H₅)W(N0)₂H, and (n⁵-C₅H₅)W(N0)IH₂[P(0Ph)₃]. The Mo(N0)₂²⁺ unit is obtained as the tetrakis-solvate via chloride abstraction from Mo(N0)₂Cl₂ by AgBF₄ or nitrosylation of Mo(C0)₆ by NOPF₆ in coordinating solvents such as nitromethane, acetonitrile, or tetrahydro-furan. The unsolvated complex [Mo(N0)₂(PF₆)₂][aub=n] is produced if the latter reaction is performed in dichloromethane; however, it readily converts to [Mo(N0)₂S₄](PF₆)₂ upon exposure to coordinating solvents (S). Hard Lewis bases (L = CH₃CN , 0PPh₃ or L₂ = 2 ,2-bipyridine replace the solvent molecules in [Mo(N0)₂S₄]X₂ (X = BF₄⁻, PF₆⁻) forming complexes [Mo(N0)₂L₄]²⁺ or [Mo(N0)₂L₂S₂]²⁺ depending upon the solvent employed. Reagents capable of being oxidized appear to reduce the dinitrosyl dication without permanent coordination to the molybdenum centre. Reduction of [Mo(NO)₂S₄](PF₆)₂ or [Mo(N0)₂(PF₆)₂][sub=b] is effected by sodium amalgam (one equivalent); addition of a ligand L₂ (L₂ = 2,2-bipyridyl, 3,4,7,8-tetramethyl-1,1O-phenanthroline) to the reaction mixture permits the isolation of [M(NO)₂L₂]₂(PF₆)₂. Addition of excess ligand results in the formation of non-nitrosyl containing species [Mp(L₂)₃]PF₆ (L = 0PPh₃ or L₂ = 3,4,7,8-tetramethyl-1 ,10-phenanthro- line). Decomposition of the nitrosyl species results from attempts to reduce [Mo(NO)₂S₄]²⁺ by two electrons. New complexes are identified by the aid of IR and ¹H, ¹⁹F, or ³¹P NMR spectroscopy and conductance measurements. Attempts to prepare thionitrosyl analogues of [Mo(N0)₂L₄]²⁺ have met with limited success; the only wel1-characterized thionitrosyls isolated in this study are the known (n⁵-C₅H₅)Cr(C0)₂NS and the new [(n⁵-C₅H₅)Mo-(N0)(NS)PPh₃]BF₄. Also discussed is the interaction of NOPF₆ with solvents. NOPF₆ has been found to react slowly with acetonitrile, a common solvent for nitro-sonium salts. / Science, Faculty of / Chemistry, Department of / Graduate

Mixed alkyllithium / lithium alkoxide aggregates in the form (RLi)n(ROLi)m were formed by addition of corresponding alcohol compounds at different Li/O ratios. Variable temperature 13C and 6Li NMR spectroscopy were used to verify the formation of the mixed aggregates and to study their behavior in hydrocarbon solution. Spectra for the lithium n-propoxide / n-propyllithium and iso-butyllithium / lithium iso-butoxide systems each indicated at least one mixed aggregate.

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