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The thesis is concerned with the synthesis, characterisation and reactivity of a variety of nickel(II) diphosphine complexes considered possible catalyst precursors for the copolymerisation of CO and ethene. [Ni(diphos)(o-tolyl)(py)]Y (1), [Ni(diphos)(_2)](Y)(_2) (2), and [Ni(diphos)(S)(_2)](Y)(_2) (3) {Y = OTs, OTf} are found to be catalyst precursors for the CO/ethene reaction (115 C, 1200psi, 1:1 CO: ethene) with high selectivity to polyketone formation, the activity depending on the phosphine ligand employed. However, the activity is low and attributed in part to the formation of the [Ni(diphos)(CO)(_2)] (4) complexes which are stable under the reaction conditions. The diphosphine hgand employed, particularly the nature of the backbone, is found to influence the synthesis and reaction chemistry of the complexes (1), (2) and (3).A series of complexes of the type [Ni(R(_2)P(CH(_2))(_a)PR(_2))(o-tolyl)Br] (5) {n = 2; R = Ph, Cy, 'Bu) have been synthesised and the complex [Ni(dppe)(o-tolyl)Cl] has been characterised by X-ray crystaliography. The influence of the chelating diphosphine on the structural characteristics and NMR parameters of these compounds has been investigated. When n > 2 the complexes of the type [Ni(diphos)(o-tolyl)X] were not isolated. The reaction of type (5) complexes with TIY (Y = OTs, BF(_4)) in pyridine led to the formation of complexes of the type [Ni(diphos)(o-tolyl)(py)]Y (1).A series of complexes of the type [Ni(diphos)Cl(_2)] (6) {diphos = dope, dBpe, dcpn} have been synthesised and characterised by X-ray crystallography. The influence of the chelating phosphine ligand on structural characteristics of these compounds has been investigated. Complexes of the type (2) and (3) can be synthesised from type (6) complexes. Detailed studies on the behaviour of a series of complexes of the type [Ni(diphos)(_2)](Y)(_2) (2) and [Ni(diphos)(Y)(_2)] (3) {Y = OTs and OTf), and the equilibrium between them in solution have been undertaken. The complex [Ni(dppe)(-2)](OTs)(_2) has been characterised by X-ray crystallography.

One particular aspect of the chemistry of the trifluoromethyl group is its high electron-withdrawing power which reduces the donor properties of normally strong bases. This investigation has been concerned with the chemistry of some phosphines containing this group. For this purpose, substituted phosphines containing methyl or phenyl and trifluoromethyl groups have been prepared. For the study of their donor properties, a series of addition compounds with boron trifluoride, platinum(Il) chloride and nickel(II) salts have been prepared. The reported methods for preparing the methyl-trifluoromethyl-phosphines do not produce a good yield; therefore, an attempt has been made towards a better understanding of the reactions. The phenyl-trifluoromethyl-phosphines have been prepared by reacting trifluoroiodo-methane with a phosphorus compound containing a P-P bond. Thus, a reaction with tetraphenylcyclotetraphosphine gives phenylbistrifluoromethylphosphine and phenyltrifluoromethyl-iodophosphine, and reaction with tetraphenyldiphosphine gives diphenyltrifluoromethylphosphine. The latter has also been prepared by reaction of trifluoroiodomethane with either triphenylphosphine or diphenylchlorophosphine. These new phosphines are colorless liquids (except phenyltrifluoromethyliodophosphine which is reddish-brown) of high boiling point. They are stable in air and cannot be hydrolysed with acid or water, except the iodophosphine C₆H₅CF₃PI, which reacts with water to give phenyltrifluoromethylphosphinic acid, a new oxyacid. Phenylbis-trifluoromethylphosphine can be hydrolysed with aqueous alkali to give fluoroform and phenylphosphonous acid. Diphenyltrifluoromethylphosphine, on the other hand, cannot be hydrolysed by aqueous alkali, but reacts slowly with alcoholic potassium hydroxide to give fluoroform and diphenylphosphinic acid. The phosphines form a further series of new compounds by reaction with halogens. Phenylbistrifluoromethylphosphine reacts with iodine to form trifluoroiodomethane, but forms phenylbistrifluoromethyldibromophosphorane with bromine. This compound also gives phenyltrifluoromethylphosphinic acid on aqueous hydrolysis, as obtained in the case of phenyltrifluoromethyliodophosphine. Besides forming the dibromophosphorane, diphenyltrifluoromethylphosphine is the first trifluoromethyl-phosphine known to form a diiodophosphorane. It is interesting to note that diphenyltrifluoromethylphosphine is difficult to hydrolyse, whereas the phosphoranes can be hydrolysed easily, giving fluoroform and diphenylphosphinic acid. By reaction with methyl iodide, this phosphine also forms a new phosphonium compound, methyldiphenyltrifluoromethylphosphonium iodide, which is readily hydrolysed by cold water with the loss of the trifluoromethyl group. In general, phosphines containing one trifluoromethyl group show similar properties to those of their parent compounds, trimethylphosphine and triphenylphosphine, while those containing two trifluoromethyl groups are very similar in their behaviour to tristrifluoromethylphosphine. The phosphines containing more than one CF₃ group do not form addition compounds with boron trifluoride. The phenyl-trifluoromethyl-phosphines form more stable complexes than the methyl-trifluoromethyl-phosphines. The phosphines containing up to two trifluoromethyl groups form complexes with platinum(II) chloride. A complex with tristrifluoromethylphosphine could not be obtained. Except dimethyltrifluoromethylphosphine, which forms mainly a cis isomer, the other phosphines, CH₃(CF₃)₂P,C₆H₅(CF₃)₂P, and (C₆H₅)₂ CF₃P form mainly trans isomers. The non-occurrence of the tristrifluoromethylphosphine complex and the production of mainly trans isomers of the above-mentioned phosphines has been interpreted in terms of steric phenomenon. The phosphines containing more than one CF₃ group do not form complexes with nickel(II) salts. The nitrato complexes of trimethylphosphine and dimethyltrifluoromethyl-phosphine are paramagnetic, while the dichloro, dibromo, diiodo, and dithiocyanato complexes are diamagnetic. A correlation of the various properties, for example boiling points and heats of vaporization, has shown that the trifluoromethyl substituted phosphines are not anomalous in the general family of phosphines. An attempt has also been made towards a study of the infra-red spectra of the phosphines and their compounds, and towards a correlation with the spectra of other phosphorus compounds. Finally, an approximate estimate of the "electronegativities" of a wide range of substituted phosphines gives values which are in good agreement with the observed order of reactivities of the phosphines studied, and assists in correctly placing the trifluoromethyl-phosphines in such a range of compounds. ` / Science, Faculty of / Chemistry, Department of / Graduate

The previously reported synthesis of dinuclear mixed-valence ruthenium complexes of general formula Ru₂Cl₅(P-P)₂, P-P = DPPP, DPPB, 5,5-CHIRAPHOS, or R.R-DIOP, has been extended to include other diphosphines: P-P = DPPN, DPPH, rac-DPPCP, rac-DPCYCP, S,S-BDPP, R- and S-BINAP, or S-PHENOP. The complexes are prepared by the reaction of RuCl₃P₂(DMA)-DMA, P = PPh₃ or P(p-tolyl)₃, with one equivalent of the appropriate diphosphine. The H₂-reduction of Ru₂Cl₅(P-P)₂ complexes in DMA, or in toluene in the presence of an added base, affords the corresponding dimeric Ru(II) complexes [RuCl(P-P)(µ-Cl)]₂, P-P = DPPN, R- or S-BINAP, or S,S-BDPP, which have been characterised by NMR spectroscopy. The [RuCl(P-P)(µ,-Cl)]₂ complexes (Structure I) show a great propensity to form trichloro-bridged dinuclear species (Structure II) in the presence of neutral coordinating ligands (L). A series of trichloro-bridged complexes of the type [(L)(P-P)Ru-(µ-Cl)₃RuCl(P-P)] (e.g. P-P = DPPB; L = NEt₃, NHBu₂, CO, DMA, PhCN, Mel) have been isolated or studied in situ and characterised spectroscopically. The molecular structure of the DMSO analogue shows an S-bonded DMSO ligand with an unsymmetrical arrangement of the chelating DPPB ligand (cf. Structure II). [ Formulas omitted ] The reaction of [RuCl(DPPB)(µ,-Cl)]₂ with H₂ has been investigated. In benzene or toluene, in the absence of an added base, dihydrogen adds reversibly to the ruthenium dimer to give the remarkably simple molecular hydrogen complex (L = η²-H₂; Structure II); the η²-H₂ ligand (with an H-H distance of 0.86 Å as estimated by ¹H NMR variable temperature spin-lattice relaxation data; T₁(min) - 12 ms at 300 MHz) is replaceable by N2. The reaction of [RuCl(P-P)(µ-Cl)]₂, P-P = DPPB or 5,5-CHIRAPHOS, with H₂ in the presence of NEt₃ as the added base yields the corresponding trinuclear Ru(II) hydride complex, [RuHCl(P-P)]₃, along with [(NEt₃)(P-P)Ru(u-Cl)3RuCl(P-P)]. The hydride complexes had been synthesised previously, albeit in low yields (<10%), and the crystal structure of the CHIRAPHOS derivative obtained. During the present work the original synthetic procedure has been modified to obtain the desired [RuHCl(P-P)]₃ complexes in ∼50% yield. In addition, these species have been characterised completely by NMR spectroscopy. The conversion of [RuCl(P-P)-((µ-Cl)]₂ to the corresponding hydride derivative likely proceeds via deprotonation by NEt₃ of the initially formed molecular hydrogen species. Under hydrogen atmosphere, [RuHClQDPPB)]₃ breaks down to form the dinuclear derivative [(η²-H₂)(DPPB)Ru(µ-H)(µ-Cl)₂RuH(DPPB)] containing a molecular hydrogen ligand, which has been identified by ¹H NMR T₁ measurements; similar complexes, but with a nitrile ligand (MeCN or PhCN) in place of the η²-H₂, have also been observed. Alternative routes to ruthenium complexes containing only one diphosphine per Ru ("RuII(P-P)") have been investigated. Some of the trichloro-bridged derivatives (e.g. L = amine, CO; Structure II, see above) are also accessible through reactions of the mixed-phosphine complex RuCl₂(DPPB)(PPh₃) with amines and aldehydes, respectively. Studies on the reactions of RuCl₂(DMSO)₄ or [RuCl(p-cymene)-(µ,-Cl)]₂ with one equivalent of diphosphines show that the nature and the distribution of product(s) (i.e. RuCl₂(P-P)₂ vs. "RuCl₂(P-P)") are greatly influenced by the chelate size of the diphosphine. The "RuCl₂(P-P)" species is observed only for those phosphines which form at least a six-membered ring upon coordination to the metal. Solid-state ³¹P NMR studies indicate that the structure of RuCl₂(DPPB)(PPh₃) is similar to that of RuCl₂(PPh₃)₃, which has been characterised previously by X-ray crystallography. Reactions of RuCl₂(DPPB)(PPh₃) with chelating ligands afford six-coordinate complexes of the type RuCl₂(DPPB)(L-L), L-L = PPh₂Py, DPPM, or norbornadiene; the corresponding hydridochloro derivatives are obtained when the reactions are conducted under an atmosphere of H₂ in the presence of Proton Sponge®. The dimeric [RuCl(P-P)(µ-Cl)]₂ and the trinuclear [RuHCl(P-P)]₃ complexes described in this study are effective catalyst precursors for the hydrogenation of various alkene, ketone, imine, and nitrile substrates under relatively mild conditions (30-100 °C, 1-12 atm of H₂). A detailed kinetic study on the hydrogenation of styrene catalysed by [RuCl(DPPB)(µ-Cl)]₂ shows a first-order dependence of the maximum rate on catalyst concentration, a first- to zero-order dependence on styrene concentration and a zero- to first-order dependence on the H₂ pressure. A mechanism involving formation of the molecular hydrogen (η²-H₂) complex (see above) followed by hydrogen transfer to the substrate is proposed to account for the observations, and the rate constants at 30 ºC for the various steps have been determined. Preliminary data on acetophenone and benzonitrile hydrogenation shows that the trinuclear hydride complexes are an order of magnitude more effective than the corresponding dimeric precursors. / Science, Faculty of / Chemistry, Department of / Graduate

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