The chemistry of some simple tin hydrides (CH<SUB>3</SUB>)<SUB>4-x</SUB>SnH<SUB>x</SUB>(x=1-4) has been investigated with particular reference to their reactivity towards the reagents NaH, KH, alkyl lithium compounds, and the ylids Me<SUB>3</SUB>PCH<SUB>2</SUB> and Ph<SUB>3</SUB>PCH<SUB>2</SUB>. It has been found that the reaction between the stannanes and alkali metal hydrides or the ylids produces salts containing the respective stannyl anions, [Sn(CH<SUB>3</SUB>)<SUB>3-x</SUB>H<SUB>x</SUB>]<SUP>-</SUP> (X=0-3). These salts have been characterised by low temperature infrared spectroscopy, the results of which are in good agreement with the results of <I>ab initio </I>calculations. In contrast, reactions involving alkyl lithium compounds proceed by transmetallation with elimination of LiH and alkylation of the tin centre. The technique of <I>in situ</I> crystal growth at low temperatures has been used to obtain X-ray crystal structures of Me<SUB>3</SUB>PCH<SUB>2</SUB>. Me<SUB>2</SUB>SnH<SUB>2</SUB> and Me<SUB>3</SUB>SnH. The structure of the ylid in the solid phase has been shown to resemble the calculated structure of a transition state involving rotation of the CH<SUB>2</SUB> group about the P-C axis. The reaction between monochlorostannane and sodium metal produced small quantities of Sn<SUB>2</SUB>H<SUB>6</SUB>, detected by mass spectrometry. Attempts to increase the scale of this preparation were unsuccessful. Gas phase electron diffraction data were recorded for monochlorostannane but subsequent refinement showed that some decomposition of the sample had occurred giving rise to SnH<SUB>2</SUB>Cl<SUB>2</SUB>. The structure of Me<SUB>3</SUB>PbH was investigated by powder neutron diffraction and gas phase electron diffraction. Rietveld refinement of the neutron diffraction data based on an extant single crystal structure of Me<SUB>3</SUB>PbH was unsuccessful owing to inconsistencies between the two data sets, most probably stemming from the different temperatures at which they were collected. The gas phase experiment was partially successful, but data collected at the short camera distance, and crucial to an accurate structural determination, could not reasonably be refined in conjunction with that collected at the long camera distance. No reliable gas phase structure of Me<SUB>3</SUB>PbH has yet been determined.

This thesis describes research directed towards the synthesis, full chemical, spectroscopic and structural characterisation, and reactivity in selected cases of some ruthenium carbonyl clusters containing both π-donor and σ-donor ligands. Cluster nuclearities range between three and six metal atoms and are shown to display a variety of core geometries. Discussions centred on C-H and C-C activation, redox behaviour., magnetic susceptibility, solid state chemistry, mechanism and supramolecular chemistry are all presented. Chapter one contains some highlights of modern cluster chemistry and pays particular attention to redox, magnetic and C-H activation properties of clusters. The area of materials science is also touched upon in conjunction with the potential input from the cluster chemist. Chapter two describes the synthesis and characterisations of a range of compounds wherein a cluster moiety is bound to an extended polycyclic hydrocarbon framework, with a view to their incorporation into organometallic materials. Chapter three introduces the 'pseudo' arene fulvene in respect to its bonding interactions with clusters. A wide variety of compounds are presented isolated from substitution reactions with the parent cluster carbonyls. Chapter four introduces the concept of linking redox active clusters to a second redox active centre. The redox active centres chosen are based on ferrocene and cobaltocene and linked to the clusters by phosphine groups. Novel magnetic behaviour and reactivity has been observed in these systems. Chapter five contains a varied set of compounds which are essentially collections of clusters bound to more exotic π-donor ligands. This work focuses on the use of functional groups such as carboxylates and macrocycles for polymer precursors or host compounds or to give chirality to the cluster bound fragment. Chapter six presents the experimental details of the various methods of synthesis and characterisation used. It also contains spectroscopic and solid state data of the compounds.

1,3,5-triazine derivatives are considered as potentially polynucleating surface-ligands in chapter 2. Synthetic routes to novel hydroxy and thiol functionalised, alkylamino containing triazines developed. A range of such compounds with different subtitution patterns has been characterised. X-ray structure determination of 6-(diethylamino)-1,3,5-triazine-2,4-dithione (H₂SSta) and 6-(diethylamino)-1,3,5-triazine-2-thione-4-one (H₂OSta) showed them to be present in the thione/one tautomeric forms. All the crystallographically characterised triazines show strong intermolecular hydrogen bonding. Formation of transition metal complexes was found to be accompanied by ligand rearrangement. Condensation reactions, forming novel thioether bridged ligands <i>in-situ</i> have been observed in the crystallographically characterised complexes [Ni{Sta)S(S₂ta)}] and [Co₆NaO(OStaH)₇{S(Ota)₂}₂(O₂CPh)₂(H₂O)₂]. The instability of these compounds in solution in the presence of metal Lewis acids limits their study by isotherm determination and makes them poor candidates for the rational development of surface treatments for aluminium. The structurally related ligands 2-hydroxypyridine and uracil were shown by the isotherm studies to adsorb only weakly onto an A1(OH)₃ surface. Known carboxylic acid-based corrosion inhibitors for iron are considered in aluminium chemistry in chapter 3. Isotherm studies on the 3-ketocarboxylic acid, 3-(4-methylbenzolyl)-propionic acid and its non keto analogue 4-<i>p</i>-tolyl-butyric acid have reinforced the concept that secondary interactions, such as hydrogen bonding to surface hydroxides, can play an important role in determining the binding characteristics of surface ligands. In accordance with a survey of the Cambridge Crystallographic Database which revealed that there are few examples of carboxylic acids functioning as polynucleating ligands for aluminium(III), it was found impossible to isolate crystalline aluminium(III) complexes. However, the coordination chemistry of 3-ketocarboxylic acids was extended by the synthesis of two mixed ligand, 3-benzoyl-propionoic acid (Hbpa)/ 6-x-2-hydroxypyridine [Hxhp, where x = m (methyl) or c (chloro)], polynuclear nickel clusters, [Ni₃(chp)₄(bpa)₂(MeOH)₆].2MeOH and [Ni₆Na₂C1₂(OH)₆(Hmhp)₆(bpa)₆].

The solid-state structures of germane-d₄, GeD₄ and stannane-d₄, SnD₄, have been investigated by high resolution powder neutron diffraction. These structures have been compared with those found in the gas-phase. It was found that there are weak intermolecular interaction in the solid-state. These results confirm the findings of an earlier vibrational study which suggested a decrease in molecular symmetry on moving from the gaseous to condensed state. Several examples of a new class of organic chalcogenide donor ligand have been prepared and characterised. These new have been used in preparation of a variety of main group organometallic compounds including examples of mono, di- and tri-substituted compounds. The di- and tri-substituted compounds are the first to be subject structural characterisation by X-ray diffraction and the structures include trigonal bipyramidal geometries around gallium and indium atoms. Use of the <i>in situ </i>crystal growth technique has resulted in the structural characterisation of lead(IV) chloride that confirms the tetrahedral geometry and suggests a non-bonding Pb^...Cl contact that lies within the sum of the van der Waals radii. Preliminary investigations of PbCl₄ under high pressure indicate a phase change from discrete tetrahedral molecules to a layered structure similar to that of polymeric SnF₄. The chemistry of PbCl₄ is limited by the instability of the compound, but the loss of Cl₂ and reduction to Pb(II) occurs upon reaction with SbCl₅, leaving the unusual cation fragment [Pb(MeCN)₉]²⁺. The structure of (Me)₃PbCl has been determined by neutron diffraction and showed that the earlier investigations by X-ray analysis had erroneously determined the unit cell. The new data disprove the previous assertion that the Cl-Pb^...Cl angle was non-linear and confirms that it is in fact 180°, in common with the structures of (Me)₃PbBr and (Me)₃PbI.

The introduction begins with an out-line of the cluster surface analogy and looks at the importance of studying small organic molecules on clusters to attain a greater understanding of metallic surfaces. The Chapter goes on to look at the activation of alkynes upon coordination to a cluster and assesses the diverse behaviour of alkynes as ligands, some electron counting considerations are considered. Reaction procedures employed in the synthesis of cluster-alkyne complexes are compared highlighting pros and cons of the different routes. The Chapter concludes with a brief synopsis on the cluster [Ru<SUB>6</SUB>C(CO)<SUB>17</SUB>]. Chapter two is concerned with the synthesis and characterisation of a series alkyne substituted hexaruthenium carbonyl complexes. It is shown that through the utilisation of the oxidative decarbonylation reagent trimethylamine-N-oxide, Me<SUB>3</SUB>NO but-2-yne will successively displace carbonyl ligands to yield the complexes [Ru<SUB>6</SUB>C(CO)<SUB>15</SUB>(m<SUP>3</SUP>:h<SUP>2</SUP>:h<SUP>1</SUP>:h<SUP>1</SUP>-Me<SUB>2</SUB>C<SUB>2</SUB>)], 2, [Ru<SUB>6</SUB>C(CO)<SUB>14</SUB>(m<SUB>3</SUB>:h<SUP>2</SUP>:h<SUP>1</SUP>:h<SUP>1</SUP>:-Me<SUB>2</SUB>C<SUB>2</SUB>)(m:h<SUP>2</SUP>:h<SUP>2</SUP>-Me<SUB>2</SUB>C<SUB>2</SUB>)], 3. [(Ru<SUB>6</SUB>C(CO)<SUB>12</SUB>(m<SUB>3</SUB>h<SUP>2</SUP>:h<SUP>1</SUP>:h<SUP>1</SUP>-Me<SUB>2</SUB>C<SUB>2</SUB>)<SUB>3</SUB>], 5 and [Ru<SUB>6</SUB>C(CO)<SUB>10</SUB>(Me<SUB>2</SUB>C<SUB>2</SUB>)<SUB>4</SUB>], 6. It is observed that the octahedral array of atoms in complex 2 undergoes a polyhedral rearrangement when reacted to form 3 which exhibits a capped square based pyramid geometry, Complex 3 loses a carbon monoxide ligand to produce [Ru<SUB>6</SUB>C(CO)<SUB>13</SUB>(Me<SUB>2</SUB>C<SUB>2</SUB>)<SUB>2</SUB>], 4 via chemical and thermal activation. Complexes 3, 5 and 6 display unusual electron counts of 88 when according to polyhedral electron counting predictions such geometries should have counts of 86, this is discussed. The Chapter goes onto investigate the synthesis of complexes which have difference alkyne ligands bound to the cluster fragment. Complexes [Ru<SUB>6</SUB>C(CO)<SUB>14</SUB>(Me<SUB>2</SUB>C<SUB>2</SUB>)(Ph<SUB>2</SUB>C<SUB>2</SUB>), 7, [Ru<SUB>6</SUB>C(CO)<SUB>15</SUB>(MeC<SUB>2</SUB>Et)], 8, [Ru<SUB>6</SUB>C(CO)<SUB>14</SUB>(MeC<SUB>2</SUB>Et)(Me<SUB>2</SUB>C<SUB>2</SUB>)], 9 and [Ru<SUB>6</SUB>C(CO)<SUB>12</SUB>(MeC<SUB>2</SUB>Et)(Me<SUB>2</SUB>C<SUB>2</SUB>)(Ph<SUB>2</SUB>C<SUB>2</SUB>)], 11 are prepared and characterised. The Chapter closes with concluding remarks and an update of the current state of play of the research.

In this thesis we incorporate hydrogen bonding features NH₂ (Am), NHCH₂^tBu (Np), and NHCO^tBu (Piv) in the pyridine 6^th position of the tripodal ligand TPA (tris(2-pyridylmethyl)amine, L). Thus, thirteen ligands L^X-n (X = Am, Np, Piv; n = 0, 1, 2, 3) derived from and including TPA have been made. Also, one and two amino groups have been introduced in a similar position of the ligand <i>N,N</i>-Bis(2-pyridilmethyl)-<i>N</i>-(glycine)amine (BPG), (one amino group, APPG and two amino groups, BAPG) have been made. The structures of several [LMCl]^{0 or +1}complexes (M = Zn(II), Cu(I), Cu(II)) were determined by X-ray crystallography ([(L^Am-3)ZnCl]BPh₄, [(L^Piv-3)CuCl], and [(BAPG)CuCl]Cl). All these complexes exhibit intramolecular NH^…Cl hydrogen bonding. For the Zn(II)Cl complexes of the L^X-nligands, the main structural changes caused by hydrogen bonds are the lengthening of the Zn-Cl and the Zn-N_Pybonds and shortening of the Zn-N_Ax bond. In general, these changes are more significant when the number of hydrogen bonds increases, and vary according to their strength. In related Cu(I) and Cu(II) complexes, an important factor affecting the strength of the N-H^…Cl hydrogen bonds is the oxidation state of the metal centre. Thus, the N-H^…Cl interaction is stronger in the Cu(I) oxidation state. The [(L^X-n)CuCl]⁺ complexes were used to investigate the effect of the N-H^…Cl hydrogen bonding on the redox properties of the metal centre. Cyclic voltammetry studies showed that the reduced state of the metal centre is stabilised when stronger and more numerous hydrogen bonds are introduced. The half wave potential of the Cu(II)/Cu(I) redox couple shifted to more positive values by 58 mV in [(L^Am-1)CuCl]⁺ to 541 mV in [(L^Piv-3)CuCl]⁺ relative to the TPA complex. We estimated that in these complexes, hydrogen bonds can contribute as much as 30% to the stabilisation of the Cu(I) over the Cu(II) oxidation state. The individual contribution of each hydrogen bond towards stabilising the Cu(I) state is greater the fewer interactions. The effect of hydrogen bonding on the redox properties of zinc-bound DTBC (3,5-di-<i>tert-</i>butylcatechol) in [L^X-nZnDTBC) complexes was also investigated. The X-ray structure of [L^Am-1ZnDTBC] showed internal N-H^…O hydrogen bonding. Cyclic voltammetry and spectroelectrochemical studies showed that the reduction of DTBC complexes occurs at more positive potentials in the presence of hydrogen bonds. For [L^Piv-3ZnDTBC], the reduction of DTBC was facilitated by as much as 470 mV relative to the TPA complex, and is accompanied in this case by a binding enhancement of 3.9 x 10⁶ fold. These changes are compared with those obtained by changing the metal or its coordination sphere and with hydrogen bonds alone.

A series of complexes of general formula [OsX<SUB>3</SUB>L<SUB>3</SUB>] and [OsCl<SUB>3</SUB>L<SUB>2</SUB>L'] where X is a chloride or bromide and L and L' are different tertiary phosphines or arsines have been synthesised. The X-ray diffraction crystal structures of the complexes, <I>mer</I>-[OsCl<SUB>3</SUB>(PMe<SUB>2</SUB>Ph)<SUB>3</SUB>], <I>mer</I>-[OsCl<SUB>3</SUB>(PEt<SUB>2</SUB>Ph)<SUB>3</SUB>], <I>mer</I>-[OsBr<SUB>3</SUB>(PPr<SUP>n</SUP><SUB>3</SUB>)<SUB>3</SUB>], <I>mer</I>-[OsCl<SUB>3</SUB>(AsME<SUB>2</SUB>Ph)<SUB>3</SUB>], <I>mer</I>-[OsCl<SUB>3</SUB>(PPr<SUP>n</SUP><SUB>2</SUB>)<SUB>2</SUB>(AsPr<SUP>n</SUP><SUB>3</SUB>)], <I>mer</I>-[OsCl<SUB>3</SUB>(PPr<SUP>n</SUP><SUB>2</SUB>)<SUB>2</SUB>(PEtPh<SUB>2</SUB>)] and <I>mer</I>-[OsCl<SUB>3</SUB>(P(OMe)<SUB>2</SUB>Ph)<SUB>2</SUB>(AsPr<SUP>n</SUP><SUB>3</SUB>)] show them to have slightly distorted octahedral metal environments with the <I>trans</I> influence of the Group 15 ligands evident. The <I>mer</I> complexes have been studied electrochemically and all show two one-electron processes; an oxidation and a reduction process. Both couples involve the osmium metal centre. The one electron reduction step is rapidly followed by a chemical reaction resulting in the formation of an electroactive daughter product of general formula [OsCl<SUB>2</SUB>L<SUB>3</SUB>Y] where Y is a neutral coordinating ligand. The chemical reaction has been studied by kinetic and spectrochemical methods. The redox potentials of the <I>mer</I> species gives a good linear correlation with Tolmans electronic parameter for the tertiary phosphine. The electronic spectra of the compounds have been recorded and the peaks assigned to specific electronic transitions <I>via </I>the use of Extended Huckel Molecular Orbital Calculations. Electrochemical elucidation of these systems has shown that the redox potentials of the complexes are predominantly dependent on one ligand, namely the phosphine/arsine <I>trans</I> to the halide. The <I>fac</I> isomers also show two metal based one-electron couples at very different potentials from the analogous <I>mer </I>isomers. The reduction also produces an electroactive daughter product. The oxidation results in the isomerisation of the <I>fac</I> isomer to that of the <I>mer</I> isomer. The kinetic parameters of the reaction have been measured, and a mechanism is proposed for the isomerisation.

This work concerns the synthesis of a number of new metal derivatives of diphenylcarborane 1,2-Ph<SUB>2</SUB>-1,2-<I>closo</I>-C<SUB>2</SUB>B<SUB>10</SUB>H<SUB>10</SUB>, in which intramolecular crowding was expected to produce either unusual cage geometry or unexpected metal co-ordination. The (η<SUP>5</SUP>-C<SUB>5</SUB>Me<SUB>5</SUB>)Ir and several (η<SUP>6</SUP>-arene)Ru complexes of diphenylcarborane, and a less congested methylphenylcarborane derivative, were prepared and structurally characterised. These compounds are found to exhibit deviations from the usual <I>closo</I> geometry and in the former cases have been termed <I>pseudocloso</I>. Detailed analysis suggests that this distortion is accompanied by a significant loss of electron density at the boron cluster vertices. The relevance of these compounds to the '<I>isocloso/hypercloso</I>' debate is considered. During attempts to synthesise a truly <I>hypercloso</I> carbaruthenacarborane two new compounds were prepared. In one of these the carborane dianion was found to have undergone protonation, with the metal fragment, {(PPh<SUB>3</SUB>)<SUB>2</SUB>RuCl}, attached in an <I>exo-nido</I> fashion via three Ru-H-B bridges. This complex apparently exists as two species in solution and attempts are made to rationalise this behaviour in the light of detailed n.m.r. studies. The identical reaction in a non-protonic solvent gave a dicationic Ru dimer with two <I>nido</I>-carborane cages acting only as counterions. The failure to synthesise the intended <I>hypercloso</I> species is discussed. Three (η<SUP>6</SUP>-arene)Ru-carborane complexes of increasing steric congestion were exposed to elevated temperatures. All were unchanged at 65<SUP>o</SUP>C with the most crowded (<I>pseudocloso</I>) cluster rearranging [3,1,2-RuC<SUB>2</SUB>B<SUB>9</SUB> → 3,1,11-RuC<SUB>2</SUB>B<SUB>9</SUB>] at 110<SUP>o</SUP>C. This isomerisation is examined with respect to the metal fragment geometry. Attempts were made to incorporate a single {CuPR<SUB>3</SUB>} fragment into the Ph<SUB>2</SUB>C<SUB>2</SUB>B<SUB>9</SUB> polyhedron. Although this was unsuccessful, products containing two {CuPR<SUB>3</SUB>} units are achieved in high yield. In these complexes one metal atom is found to be bonded in an <I>exo-nido</I> fashion, while the other ligates the open five-membered face. In contrast with analogous complexes of less sterically demanding cages the metals are non-bonding and are found to be dramatically slipped from their preferred positions.

An introduction to macrocyclic coordination chemistry is presented and the general aims of the project are discussed. The syntheses and structural characterisation of the dimeric bi-octahedral complexes [Ni<SUB>2</SUB>(S<SUB>4</SUB>)<SUB>2</SUB>(μ-Cl)_2]^2+ (S_4 = [12]aneS_4, [14]aneS_4, of [Ni(H_2O)_6)]^2+ by [12]aneS_4 and [16]aneS_4 is discussed: [Ni[16]aneS_4)-(OH_2)_2]^2+ exhibits a <i>trans</i>-octahedral stereochemistry by x-ray crystallography. The syntheses and characterisation of the five-coordinate complexes [Ni([9]aneS_3)(PP)]^2+ (PP = diphosphine chelate) are presented. Four complexes in the series have been shown to adopt square-pyramidal geometries by single crystal x-ray analysis. The synthesis and single crystal structure of the square-pyramidal species [Ni([15]aneS_5)]^2+ is also described. [Ni([15]aneS_3)]^2+ forms six-coordinate adducts with Cl^-, CH_3CN and pyridine. An electrochemical study of the complexes [Ni([9]aneS_3)(PP)]^2+ is given. The reduction products [Ni([9]aneS_3)(PP)]^+ and [Ni([9]aneS_3)(PP)]^0 can be generated reversibly from the Ni^II precursors, and were assigned as square-pyramidal d^9 Ni^I and tetrahedral d^10 Ni^0 species respectively. The reaction of [Ni([9]AneS_3)(PP)]^+ with CO is investigated. The characterisation of the redox products of [Ni([9]aneS_3)_2]^2+ is also discussed: [Ni([9]aneS_3)_2]^3+ was formulated as an octahedral d^7 Ni^III complex. The synthesis and characterisation of the compounds [Rh([9]aneS_3)-(L)(L')]^+ (L,L' = C_2H_4, 0.5C_7H_8, 0.5C_8H_12, 0.5C_4H_6, CO, PR_3) is given. Single crystal x-ray analyses on four of these complexes show them to adopt a variety of five-coordinate geometries. The [Rh([9]aneS_3)]^+ fragment is shown to have high electrophilic character. Reactions of [Rh([9]aneS_3)-(L)(L')]^+ with electrophilic and nucleophilic substrates are discussed. The preparation and properties of the complexes [Ir([9]aneS_3)(L)(L')]^+ (L,L' = C_2H_4, C_8H_14, 0.5C_8H_12, 0.5C_4H_6, CO, PPh_3) are described. Three of these species are shown to have five-coordinate structures by x-ray crystallography. The electronic character of the species [M([9]aneS_3)(L)_2]^+ (M &61 Rh, Ir; L = C_2H_4, 0.5C_4H_6) is discussed. X-ray structural analyses of [16]aneS_4 show this ligand to adopt a rectangular conformation in the solid state. Molecular mechanics calculations on [16]aneS_4 and C_16H_32 are presented.

The crystal structures of several copper and mixed copper-lanthanoid complexes are reported, using the 6-chloro and 6-methyl derivatives of 2-pyridone as a ligand. With 6-chloro-2-pyridone, a novel dimeric copper complex results, which has been structually and physically studied. This species, under certain conditions, exhibits a dissociation reaction which has been examined using U.V.-vis. and E.P.R. spectroscopy and by cyclic voltammetry. Reaction of this dimeric copper compound with methanol and ethylene glycol results in the formation of tetranuclear and polymeric copper complexes respectively, which have both been structurally characterised. The reaction of this copper dimer with various lanthanoids results in the formation of a series of mixed copper-lanthanoid species based on four structural types. Reactions in methanol dichloromethane result in three structural configurations depending on size of the lanthanoid used (with La and Ce, LnCu<SUB>3</SUB> with five ligands; with Gd, Dy and Er LnCu<SUB>3</SUB> with eight ligands and for Yb Ln<SUB>2</SUB>Cu<SUB>2</SUB> with four ligands). The reaction of lanthanum with the dimeric copper species in a variety of solvents gave a further two structures, one of which (in ethanol) has a similar structure to those observed with Gd, Dy and Er in methanol, while in acetonitrile a fourth structural type occurs, based on La<SUB>2</SUB>Cu<SUB>2</SUB> with six ligands. With the 6-methyl-2-pyridone an unusual hexanuclear 'metallocrown' results, which has been characterised structually and by proton and sodium-23 NMR. The reaction of this species with lanthanoids in methanol yields a range of closely related mixed copper-lanthanoid compounds all based on Ln<SUB>2</SUB>Cu<SUB>2</SUB> (as seen for the product of Yb with the copper dimer in methanol). The only difference between the structures is a change in the coordination number of the lanthanoid between Sm and Gd to accommodate the contraction in lanthanoid size. The mixed phase reaction of this 'metallocrown' with lanthanum nitrate yields an extremely remarkable structure based on a La<SUB>8</SUB>Cu<SUB>12</SUB> core.