The acid catalysed aquation of potassium trismalonatochromium(III) and potassium bismalonatodiaquochromium(III) have been studied. Almost linear plots of log kobs against the Hammett acidity function were interpreted as being due to an A-1 mechanism operating. Two kinetically different types of co-ordinated oxygen were found in a study of the oxygen exchange between the trisoxalatocobalt(III) anion and 0-18 enriched water. The carbonyl, or outer, oxygen atoms are thought to exchange by an A-2 bimolecular mechanism, while the carboxyl, or inner, oxygen atoms are thought to exchange indirectly by co-ordination of enriched oxalate groups to the cobalt centre during the anation reaction of the bisoxalatodiaquocobalt(III) ion. Finally, oxygen exchange reactions between 0-18 enriched water and various carbonato-ammine cobalt(III) complexes were studied, and it was found that generally the three oxygen atoms of the co-ordinated carbonate exchanged at equal rates, an exception being in the case of the carbonatobis(o-phenanthroline)Co(III) ion where the outer, carbonyl, oxygen exchanged faster than the inner, metal-bound, oxygen atoms. The first of these two groups has been interpreted in terms of a fast, reversible one ended dissociation process occurring, which is much faster than oxygen exchange, and the latter case in terms of a rate determining one ended dissociation step.

Primary and secondary amines react with pentachlorocyclopropane to form a variety of novel products. Amidines, allyl and cyclopropenyl cations are easily reached by these reactions. The 1,1,3,3-tetra-aminoallyl cations of this series can be reversibly protonated at C(2) to give diamidinium ions. Action of KOH on the diamidinium species CH2[C(NHBut)2]2 2+ produces the diamidine CH2[C(NBut)(NHBut)]2 which hydrolyses to the formamidine CH(NBut)(NHBut). Bis- and tris-amino substituted Cyclopropenylium ions are formed by the action of secondary amines on pentachlorocyclopropane. The cations of this study are stabilised by electron back-donation from nitrogen atoms of substituent groups- The subject of back-bonding was probed in several ways. crystallographically determined structures of representative salts afforded bond length data from which deductions about back-bonding were made. The measurement of barriers to bond rotation is another way that this effect was investigated. Using the technique of variable temperatue NMR, VT-NMR, spectroscopy, energies of activation about unsaturated bonds of allyl, amidinium and cyclopropenylium cations were found. UV-spectra provided additional information concerning bonding in these species. Tautomerism of N,N’-disubstituted amidines was investigated by VT-NMR spectroscopy. Individual tautomers were identified in NMR spectra (13C,1H). Tris-alkylaminocyclopropenylium ions were oxidised to form intensely coloured radical dications. The first Raman spectrum of a cyclopropenyl radical dication was determined. Using the technique of pulse radiolysis we were able to reduce the cyclopropenylium cation, [C3(Net2)3]+, to the molecular radical. Further, pulse experiments enabled standard reduction potentials of representative [C3(NR2)3]2+ and allyl radical dications to be measured and compared. In general, tertiary amines reacted with pentachlorocyclopropane to generate product mixtures. Reaction of para-dimethylaminopyridine, DMAP, on pentachlorocyclopropane was a case in exception. The novel allylide product is the same as that formed via an alternative route. The direct reaction of ammonia on pentachlorocyclopropane product several products including the formamidine NC-N=CH-NH2. A polyamide was prepared from the hydrolysis of a diamidinium ion. The mechanism of formation and the characterisation of this glossy, thermoplastic material is discussed.

The present interest in organometallic nitrosyl complexes stems partly from their similarity with carbonyl analogues which are widely used as catalysts in industrial processes. The search for potential new catalysts among nitrosyl complexes is perhaps not surprising when it is realised that the nitrosonium ion (NO+), the species normally regarded as being co-ordinated, is isoelectronic with carbon monoxide. Further interest may be due to the fact that NO+ is also isoelectronic with molecular nitrogen and hence nitrosyl complexes may be suitable as models for co-ordinated nitrogen in the process of nitrogen fixation. In their own right nitrosyl complexes pose problems of chemical interest concerned with their structure and the bonding associated with the metal-nitrosyl bond. As part of an investigation into the geometry of co-ordinated nitrosyl this thesis presents structural data for several nitrosyl complexes of Group VIII metals .. In addition the mode of binding of the isocyanide group has been studied as well as the associated stereochemistry of the metals ruthenium, osmium and iridium. To date, structural studies have established three different modes of co-ordination for the nitrosyl group. Probably the most common involves a linear arrangement of metal, nitrogen and oxygen, the effective coordinating species being regarded as the diamagnetic nitrosonium ion (NO+).

The reactions between tritium gas and organic substrates sorbed on irradiated silica gel have been studied. It has been found that tritium gas, when admitted to gamma-irradiated silica gel, is adsorbed on radiation-induced sites on the solid and bleaches the blue colour of the solid. The sorbed tritium becomes activated to at least two forms; one capable of exchange with alkanes such as 2 methylbutane and both capable of exchange with toluene and 2 chloro2methylbutane. High levels of tritium were incorporated into 2 methylbutane, 2 chloro2methylbutane and toluene, up to 32±2%, 95% and 100% of the total tritium present, respectively, being incorporated (using 2 g SiO2, irradiated 15h), with high standards of radiochemical purity, (97±1% for 2 methylbutane). Yields of labelled hydrocarbons were found to be sensitive to the conditions under which the silica gel was degassed before irradiation; optimum degassing conditions being evacuation for one hour at 973 K. Yields were also found to be dependent on the quantities of silica gel and tritium used and on the radiation dose given the silica gel, all three of these being increased concurrently for maxim yields to be obtained. In a study of the labelling of hydrocarbons of different structures it was found that alkanes containing a tertiary carbon atom were labeled heavily compared to straight-chain hydrocarbons; activity yields of the substrate hydrocarbon decreasing with increasing molecular size, to insignificant values with hydrocarbons heavier than 2 methylhexane. Unsaturated hydrocarbons such as hex-1-ene were found to undergo hydrogenation on irradiated silica gel to produce labelled alkanes; branched-chain alkenes undergoing double-bond isomerization. Reaction mechanisms for tritium activation and exchange have been proposed, involving ionization of tritium by radiation-induced positive holes in the solid and exchange of the ionic species with carbonium ion intermediates. It has also been established that gamma-irradiated alkali halides do not promote exchange of tritium gas with alkanes.

Various systems for the formation of iodo-azide derivatives of alkenes have been examined. Iodine(I) azide, formed from sodium azide-iodine(I) chloride, has been found to exist in acetonitrile as a complex with sodium azide. The addition of iodine(I) azide to 5α-androst-2-ene in both dichloromethane and acetonitrile has been examined in detail, as well as the addition of thallium(I) azide-iodine in dichloromethane to the same substrate. Products were identified as those arising by diaxial opening of either α- or β-iodonium ions, or by cis-addition to the α-face of the alkene. Addition of iodine(I) azide in dichloromethane to 3-methyl-5α-androst-2-ene gave a cis-adduct as the major product, in addition to trans-diaxial adducts and a trans-diequatorial adduct. Formation of the products was rationalised as arising from c-3 carbocations or from trans-diaxial opening of either α- or β-iodonium ions. The major product from the reaction in acetonitrile was one of ring contraction. No cis product was formed in this reaction but an elimination product was present. Products from the latter reaction were postulated as arising from trans-diequatorial or trans-diaxial opening of either α- or β-iodonium ions. The reaction of sodium azide-iodine-crown ether with 3-methyl-5α-androst-2-ene in chloroform gave a high yield of the same product as those obtained in the reaction with iodine(I) azide in acetonitrile. The reaction of thallium(I) azide-iodine in dichloromethane with the above alkene gave products which could have all arisen via a c-3 carbocation. Solvolysis of the trans-iodo-azides of 5α-androst-2-ene with silver(I) acetate in acetic acid occurred with retention of configuration showing that azide acted as a neighbouring group in the reaction. Solvolysis of the trans-iodo-azide(94) of 3-methyl-5α-androst-2-ene gave, inter alia, a product where azide migration had occurred. Solvolysis of the trans-iodo-azide(95) gave mainly products of elimination. The action of iodine(I) azide on 3-methylene-5α-androstane and 1-mewthylene-4-tert-butylcyclohexane was examined and found to be non-regio- and non-stereo-specific. Iodo-azides were also formed from 3-tert-butylcyclohexene and 3-methoxycyclohexene. In each reaction the major product was that of trans-diaxial opening of the cis-iodonium ion, while the second major product arose by trans-diequatorial opening of the trans-iodonium ion. The ratio of diaxial to diequatorial product varied with the iodo-azide-producing system being used, and was larger in the case of 3-methoxy-cyclohexene, especially when the solvent was dichloromethane. A mechanism was postulated which involves reversible formation of iodonium ions as the fast step followed by rate-limiting attack by azide ions. Solvolysis of these iodo-azides was also investigated. Prior to the current work, both an AdE2 and an Ad3 mechanism had been postulated for the addition of iodine(I) azide to alkenes and in an attempt to distinguish between these possibilities a kinetic study was initiated. Preliminary results indicate that the reaction with cyclohexene is electrophilic and second order.

Complexes of tetravalent uranium and thorium have been prepared with the tetradentate ligands N, N’-ethylenebis(salicylaldimine), N,N’-o-phenylenebis(sali-cylaldimine) and the analogous ligands containing substituent groups in the salicylaldimine benzene rings (i.e. 3-MeO, 3-EtO, 5-Cl, 5-NO2). Attempts to form bidentate salicylaldimine complexes were impeded by hydrolysis and oxidation; however, the metal complexes with N-Mesalicylaldimine, N-Etsalicylaldimine and N-phenylsalicylaldimine have been isolated. X-ray powder patterns for these complexes are reported. X-ray structural studies have revealed the salicylaldehyde, N-Mesalicylaldimine, N-Etsalicylaldimine and N,N’-o-phenylenebis(salicylaldimine) complexes of thorium to be eight co-ordinate, with the salicylaldimine complexes having distorted square antiprismatic co-ordination and the salicylaldehyde complex displaying a dodecahedral configuration. U.V., visible and near-I.R. spectra of Schiff-base complexes of thorium, uranium, thallium and lithium are also reported and discussed.

The radiolysis of cysteine in both deaerated and oxygenated solution at pH 7 has been studied. In deaerated solution the mechanism of the reaction appears to be the same as that at pH 5 - 6. The rate constant for the reaction •OH + RSH → RS• + H2O has been measured by competition with paranitrosodimethylaniline. A value of 9 x 109 was found, which though not absolutely accurate (for reasons described in the text) is sufficiently accurate to that the reaction is fast. The rate constant of the reaction eaq + RSH → R• + SH- been measured by competition with oxygen, and a value of (4.0±0.2) 4 x 109 was found. This compares well with values found by other methods. From the values of G(-RSH), G(RSSR), and G(H2O2) in oxygenated solution, and from the effects of the scavengers nitrous oxide and acetone or these values a mechanism has been proposed in which RS radicals produced by attack of primary species on cysteine propagate a chain, the rate of the propagation reaction depending on the cysteine concentration. The autoxidation of cysteine has been studied briefly, the rate being found proportional to oxygen concentration. The mechanism is believed to be the same as that for the radiolysis.

Pauling (1931) introduced the concept of the hybridisation of (n - 1)d, ns and np orbitals to explain the two classes 'ionic' and 'covalent' into which co-ordination compounds of transition metals appeared to fall. These two classes in general have different numbers of unpaired spins, hence they will be distinguished by their magnetic moments. For a series of ferric salts a moment corresponding to either one or five unpaired spins was found, but not intermediate values. I the 'ionic' case the five d-electrons go into the 3d orbitals with their spins parallel giving a moment corresponding to five unpaired spins. I the octahedral case d2 sp3 hybridisation occurs, leaving three d-orbitals to hours the five d-electrons thus giving rise to a moment corresponding to one unpaired spin.

trans-1,2-Dichloro-1,2-dihydronaphthalene has been obtained as the major product of the photochlorination of naphthalene at low temperature, and is the first authentically described naphthalene dichloride. Its further reaction with chlorine, under heterolytic conditions gives, in part, a new naphthalene tetrachloride, whose configuration has been assigned, by 1H n.m.r., as being that of the r-1,c-2,c-3,t-4-isomer. The assigned configuration and conformation of the compound are confirmed by its behaviour on alkaline dehydrochlorination, which gives mainly trans-1,2,4-trichloro-1,2-dihydronaphthalene as an intermediate. The naphthalene dichloride, and its 4-chloro-derivative, have been found to undergo solvolysis in methanol - acetone (4:1), and it is further found that heterolysis of the carbon-chlorine bond at C- 2 is strongly favoured, leading largely to the 1-chloro-substituted elimination product. The former dichloride also gives a small amount of 1-methoxynaphthalene, which is possibly derived by unimolecular substitution at the 1-position. The presence of a chlorine atom at the 3-position of the structure is found to inhibit the solvolytic reaction. Bimolecular syn-elimination in these compounds is accelerated by the presence of additional chlorine substituents, and the increasing preference shown for attack at H- 2, which is further accentuated by the use of the powerfully basic reagent, potassium t-butoxide in t-butanol-dimethylsulphoxide (1:4), is interpreted as indicating a transition state tending toward the E1cB- like side of the E2 spectrum of transition states. The naphthalene tetrachlorides, and some derivatives, have been found to undergo aluminium trichloride-catalysed epimerization at the benzylic centres, which yields information on the relative thermodynamic stabilities of isomers with identical relative configurations at C- 2 and C- 3, and can also be of synthetic value. The photochlorination of 1-chloronaphthalene in CC14 at room temperature proceeds analogously with the reaction of naphthalene under the same conditions, giving five new tetrachlorides, four of which have been thoroughly characterized. The presence, in some tetrachlorides, of inter-ring non-bonded compressions between adjacent chlorines has been found to cause significant changes in the geometry of the alicylic ring, causing a tendency for the half-boat conformation to be adopted, provided this does not lead to 1,4-diaxially related chlorines. The strain present in these compounds is manifested by their very marked tendency to undergo isomerization in the presence of aluminium trichloride, and greatly increased rates of alkaline dehydrochlorination. The chlorination of l,5-dichloronaphthalene in chloroform, or dichloromethane, has been studied and has been found to be markedly catalysed by traces of iodine. The products are almost wholly derived by addition of chlorine in the first stage, and this has been interpreted as arising from a steric inhibition of proton-loss by the adjacent peri-chlorine.

Part I, The Hofmann Rearrangement. First-order rate constants and activation parameters were determined for the rearrangement of eleven N-halogenoamides. The structures of the N-halogenoamides (RCO.NHX) differed in the leaving group (X = chlorine or bromine) and the migrating group (R=ethyl, isopropyl, t-butyl, diphenylmethyl, benzyl, phenyl or p-tolyl). N-Bromoamides and the corresponding N-chloroamides rearranged at similar rates. When the leaving group was changed from bromide to chloride the activation energy was reduced by about one kcal. mole-1 and the activation entropy was reduced by about three cal. deg.-1 mole-1. Differences in the reactivity of halides as leaving groups from carbon and nitrogen are discussed. Changes in the structure of alkyl migrating groups resulted in small irregular changes in the activation parameters. The kinetic data were consistent with a stepwise rearrangement mechanism in which halide departed from nitrogen in the rate-determining step to give a short-lived nitrene intermediate which subsequently rearranged to an isocyanate. Other aspects of the Hofmann rearrangement were investigated. In the Hofmann reaction of amides and hypobromite, N-bromination of the amide was found to be much faster than the rearrangement of the intermediate N-bromoamide conjugate base. In contrast, when amides and hypochlorite reacted in alkaline solution N-chlorination was not fast by comparison with the rearrangement of the intermediate N-chloroamide conjugate base. Oxygen, iodide, and hypobromite did not inhibit the Hofmann rearrangement. Rearrangement of N-brmoacetamide N-bromopropionamide, N-bromoisobutyramide and N-bromopivalamide in the presence of oxygen gave traces of nitrite as a by-product. Nitrite may result from the capture of an intermediate nitrene by oxygen. Ionisation constants of six N-bromoamides and one N-chloroamide were measured. Of the N-halogenoemides which were investigated, the most acidic was N-chloroperfluorobutyramide (pK 2.45) and the least acidic was N-bromopropionamide (pK 7.95). There are no ionisation constants of N-halogenomides recorded in the chemical literature. Part II, The Rearrangement of N-Bromo-α-halogenamides and N-Bromoperhalogenoamides. Previous investigators of the rearrangement concluded that the conjugate base of the N-halogenoamide rearranged intramolecularly via a cyclic four-membered transition state to give an alkyl halide and cyanate ion. This mechanism is incompatible with evidence presented in this thesis. The arrangements of N-bromoperfluorobutyramide and N-bromo-α-chloroisobutyramide in alkaline solution were not first-order reactions. In neutral aqueous solution, the N-halogenoamide conjugate bases did not rearrange. However, in the presence of an excess of hydroxide ion, the N-halogenoamide rearranged readily. The rearrangement was catalysed by hydroxide ion and ammonia and inhibited by many reagents including oxygen, hypobromite, iodide, cupric hydroxide, silver oxide, and amides of carboxylic and sulphonic acids. Possible rearrangement mechanisms are discussed. The effects of small proportions of the inhibitors showed that the rearrangement was a chain reaction. Two probable steps in the chain reaction are the addition of hydroxide ion to the N-halogenoamide conjugate base to give a dianionic intermediate and heterolysis of the nitrogen-bromine bond in this intermediate to give a nitrene. Part III, The Reaction of Mandelamide and Hypohalite. In alkaline solution, mandelamide and hypohalite yield benzaldehyde, cyanate and halide. Several mechanisms which were postulated by previous investigators are excluded by evidence presented in this thesis. Evidence for an N-chloromandelamide intermediate in the reaction of mandelamide and hypochlorite was obtained. Chlorination of mandelamide in neutral or acidic solution gave N-chloromandelamide and N,N-dichloromandelmide. In alkaline solution, the N-chloromandelamides decomposed to give benzaldehyde and cyanate. This reaction was much faster than the reaction of mandelamide and hypochlorite to give the same products. The reactions of hypobromite and hypoiodite with mandelamide were also investigated. Neither oxygen nor an excess of hypobromite inhibited the reaction of mandelamide and hypobromite to give benzaldehyde and cyanate. Hypoiodite (prepared from the reaction of hypochlorite and iodide) and mandelamide also gave benzaldehyde and cyanate in high yield. The mechanism most consistent with the evidence involves the rearrangement of an intermediate N-halogeno-α-hydroxyamide conjugate base to an α-hydroxyalkyl isocyanate which subsequently decomposes to benzaldehyde and cyanate. Mechanisms involving dianionic intermediates were disproved. Stoichiometric similarities in the rearrangements of N-bromo-α-halogenoamides and N-halogeno-α-hydroxyamides were shown to be fortuitous and not the result of similarities in the rearrangement mechanisms. Part IV, Preparation of Amides, N-Bromoamides, and N-Chloroamides. Preparations of amides and N-halogenoamides used in this thesis are described. Some of the N-halogenoamides have not been reported previously. Methods for preparing N-bromo-perhalogenoamides which are described in the chemical literature involve the bromination of the silver salt of the perhalogenoamides in trifluoroacetic acid solution. A much simpler method for preparing N-halogenoperhalogenoamides is described in this thesis.