Studies into the effects of hexa-hapto spectator ligands on the chemistry of ruthenium.

This thesis describes the results of investigations into the chemistry of ruthenium complexes of hexa-hapto spectator ligands. Two specific systems have been examined. Chapters 2-5 describe aspects of the chemistry of the ruthenium(IV) chloride bridged compound [{Ru(η3:η3-C10H16)Cl(µ-Cl)}2] which contains the n3:n3-bis(allyl) ligand 2,7-dimethylocta-2,6-diene-1,8-diyl, derived from the ruthenium trichloride mediated dimerisation of isoprene. In Chapters 6 and 7 the reactivity of arenes and cyclohexadienes is examined in ruthenium complexes of the polyaromatic η6-spectator [2.2]paracyclophane. Chapter 1 offers a general introduction to arene and allyl transition metal chemistry and attempts to place the results reported herein into a wider context. In Chapter 2 the reactions of the bis(allyl)ruthenium(IV) chloride bridged dimer [{Ru(η3:η3-C10H16)Cl(µ-Cl)}2] with amines and polypyridines are examined. Bridge cleaved amine adducts of formulae [Ru(η3:η3-C10H16)Cl2L] or [{Ru(η3:η3-C10H16)Cl2}2(?-L)] (L = PhNH2, o-pda, p-pda) are reported and the diastereoisomerism of the binuclear compounds examined. The mononuclear chelate compounds [Ru(η3:η3-C10H16)Cl(L- L)][Bp4] (L-L = 2,2'-diaminodiphenyl, 2,2'-bipyridyl, 1,10-phenanthroline) and [Ru(?3-?3-C10H16)(terpy)][BF4]2 are formed from treatment of the starting material with Ag[BF4] and the appropriate ligand. Chapter 3 reports a number of carboxylato compounds of ruthenium(IV). These products occur as either 1 : 1 bidentate chelates [RU(η3:η3-C10H16)CLO2CR)] (R = Me, CH2F, CH2Cl) or 1 : 2, monodentate carboxylato aqua complexes [Ru(η3:η3-C10H16)(O2CR)2(OH2)] (R = CH2CI, CH2F, CHCl2, CHF2, CCl3, CF3). The electronic properties of the carboxylato ligand are found to be crucial to the product stoichiometry. The analogous thiocarboxylato compounds [Ru(η3:η3-C10H16)]Cl(OSCR)] (R = Me, Ph, tBu) exhibit bidentate coordination and exist as two alternative geometric isomers with the sulphur located either axially or equatorially. In the case where R = Me coordination is found to proceed via a two step process involving the monodentate thioacetic acid adduct [Ru(η3:η3-C10H16)]Cl2(S(OH)CMe}]. The related nitrato compounds [Ru(η3:η3-C10H16)Cl(NO3)] and [Ru(η3:η3-C10H16)](NO3)2] are also reported. In the latter case the "semi-chelating" nitrato ligands readily become monodentate in the presence of two electron ligands to give adducts [Ru(η3:η3-C10H16)(NO3)2L] (L = CO, py). Chapter 4 reports a range of 2-pyridinol and pyridine-2-thiol compounds of ruthenium(IV) of form [Ru(η3:η3-C10H16))Cl(pyrX)] (X = O, S) and related species. These compounds all exhibit axial and equatorial geometrical isomerism and a method based on 1H NMR spectroscopy is described for distinguishing between the two forms. In Chapter 5 a range of bi- and trinuclear compounds of ruthenium(IV) are described and their inherent diastereoisomerism studied. The bridge-cleaved adducts [{Ru(η3:n3-C10H16)Cl2}2(µ-pyz)] and [{Ru(η3:η3-C10H16)Cl2}n(µ-tra)] (n = 1, 2, 3) are reported along with the thiocyanato, carboxylato and nicotinato bridged compounds [{Ru(η3:η3-C10H16)C1(µ-SCN)}2], [{Ru(η3:η3-C10H16)Cl}2(µ-O4R)] (R = C2, C3,H2) and [RU2(η3:η3-C10H16)2CL3(µ-NC5H4CO2)]. In Chapter 6 the single nucleophilic addition reactions of simple anions N- (N = H, CN, OMe, Me) to unsymmetrical bis(arene)ruthenium(II) compounds [Ru(η6-arene)(η6-[2.2]paracyclophane)]2+ (arene = C6H6, p-MeC6H4CHMe2, l,4-(CHMe2)2C6H4, C6Me6, C16H16) are examined. It is found that the cyclophane acts as a non-innocent spectator ligand, directing nucleophiles onto other arenes coordinated to the same metal centre to give the cyclohexadienyl compounds [Ru(η6-[2.2]paracyclophane)(η5-C6R6N)]+. Chapter 7 describes the extension of the work reported in Chapter 6 to double nucleophilic addition reactions to give ruthenium(0) compounds of general form [Ru(η6-[2.2]paracyclophane)(η4-diene)]. The reactivity of these Ru(0) species towards H[BF4] is examined resulting in a range of novel agostic compounds. Mechanistic aspects are investigated by a range of deuteriation studies. Finally, Chapter 8 offers some conclusions on what has been learned about the effects the two spectator ligands studied have on the chemistry of ruthenium

Anion Hydrogen Bonding from a ‘Revealed’ Urea Ligand

Hydrogen bonding from a urea group to hydrogen bond acceptor anions can adopt either R_2^1 (6) or R_2^2 (8) motifs depending on the proximity of hydrogen bond acceptor atoms. However, for the sterically bulky and weaker hydrogen bond acceptor triflate anion, hydrogen bond acceptor polymorphism is observe

The Impact of a Self-Avatar on Cognitive Load in Immersive Virtual Reality

The use of a self-avatar inside an immersive virtual reality system has been shown to have important effects on presence, interaction and perception of space. Based on studies from linguistics and cognition, in this paper we demonstrate that a self-avatar may aid the participant’s cognitive processes while immersed in a virtual reality system. In our study participants were asked to memorise pairs of letters, perform a spatial rotation exercise and then recall the pairs of letters. In a between-subject factor they either had an avatar or not, and in a within-subject factor they were instructed to keep their hands still or not. We found that participants who both had an avatar and were allowed to move their hands had significantly higher letter pair recall. There was no significant difference between the other three conditions. Further analysis showed that participants who were allowed to move their hands, but could not see the self-avatar, usually didn’t move their hands or stopped moving their hands after a short while. We argue that an active self-avatar may alleviate the mental load of doing the spatial rotation exercise and thus improve letter recall. The results are further evidence of the importance of an appropriate self-avatar representation in immersive virtual reality

Modulating the Hydration Behaviour of Calcium Chloride by Lactam Complexation

Complexation of calcium chloride with bis(lactam) ligand L1 allows the formation of both an unstable anhydrous complex, an aqua complex {[Ca2(μ-L1)2(H2O)9]Cl4]}n (1) and a related hydrate incorporating additional lattice water of crystallization {[Ca(μ-L1)(H2O)5]Cl2·H2O}n (2). Related mono(lactam) L2 does not form aqua complexes but the anhydrous complex {[CaCl2(μ-L2)2]}n (3), is highly deliquescent. An unusual ethanol solvate is also reported {[CaCl2(L2)(EtOH)]}n (4)

Guest inclusion by Borromean weave coordination networks

Reaction of N,Nʺ-ethylene-1,2-diylbis(3-pyridin-3-ylurea) (L) with AgNO3 in a variety of solvents gives a total of five 2-D Borromean weave coordination polymer networks that adopt three structural types depending on the interactions to the solvent pocket. The Borromean network is of formula [Ag2(L)3](NO3)2 ·solvent where the solvent is either a cluster of water molecules, mixtures of water and acetonitrile, water and methanol or chloroform and methanol. The Borromean structure is a thermodynamic sink and under fast crystallization conditions an alternative 2 + 2 metallomacrocycle forms that can result in metallogel formation. The metallogel structure transforms into the crystalline Borromean network over time