Several organic transformations are mediated by group(IV) metal alkoxides. The reactivity is based on the basic nature of alkoxide group, Lewis acidic nature of the group(IV) metals, insertion of unsaturated molecules into the M-OR bond and the reduction of M(OR)4 to low valent species. The thesis deals with insertion reactions and the reductive and metathetic coupling reactions mediated by group(IV) metal alkoxides. Titanium(IV) alkoxides and zirconium(IV) alkoxides promote insertion and metathesis of aryl isocyanates. It was observed that aryl isocyanates underwent double insertion in addition to mono insertion. At room temperature, head to tail double insertion is observed whereas at elevated temperatures, head to head double insertion occurred leading to metathesis. The reaction has also been extended to metathesis between heterocumulenes and heteroalkenes. Titanium and zirconium carry out these reactions with different efficiencies. The reasons for these differences have been sought through computational methods. New organic transformations promoted by group(IV) metal alkoxides that are reduced with Grignard reagents and silanes have been explored. Grignard reagents do show reactivity towards imines in the presence of group(IV) metal alkoxides. The reactions have been studied with stoichiometric and catalytic amounts of titanium(IV) isopropoxide and are shown to follow different pathways. Isotope labeling studies indicate that alkylated products formed in stoichiometric reactions arise due to metal-olefin intermediates. However in catalytic reactions, a metal-alkyl complex is responsible for alkylation. Titanium(IV) alkoxides when used in combination with silanes such as phenylsilane bring about the reductive coupling of imines. One of the interesting features is that this pinacol type coupling is diastereospecific.

Thesis (doctoral)--Helsinki University of Technology, 2001. / Includes bibliographical references. Also available on the World Wide Web.

The manipulation of molecular structures is an important enabling technology for future advances in nanotechnology. The ability to control the synthesis of nanostructured materials, such as the bond formation and geometry of a molecule is of great significance to nanoscience as nanosystems are constructed from these smaller units. Influencing the assembly of molecular structures at the early stages of material formation can modify the ensuing molecular aggregate structure with the potential for impact in a broad range of optical, chemical, and biological applications. Heteroleptic titanium metal alkoxides (OPy)₂Ti(4MP) ₂ and (OPy)₂Ti(TAP)₂, where OPy = OC₆H₆N, 4MP = OC₆H₄(SH)-4, and TAP = OC₆H₂(CH₂N(CH₃)₂)₃-2,4,6 were investigated as precursors for thin film and solution-based synthesis of oxide materials via the photoactivation of intermolecular reactions (e.g. hydrolysis/condensation) at selected ligand sites about the metal center. Manipulation of the molecular structure of these photosensitive metal alkoxides was achieved through the use of optical irradiation parameters, such as the tuning of the excitation wavelength, total optical fluence, and pulse energy intensity. Irradiating these metal alkoxides with UV-light was seen to cause photodisruption in the ligand groups leading to the formation of Ti-O-Ti linking via hydrolysis and condensation reactions. In spin-coated (OPy)₂Ti(TAP)₂ films, these photoinduced bridge bond formations resulted in an increase in refractive index and film densification as well as produced an insoluble film when rinsed in pyridine. By making use of these photoinduced film properties, the formation of physical relief structures from spin-coated (OPy)₂Ti(TAP)₂ films was demonstrated along with the ability to photopattern sub-micron and nanometer features. In addition, the micro- and nanostructure of thin films were optically manipulated through several deposition methods; a novel dip-coated in-situ photodeposition technique was utilized by illuminating at specific distances above the meniscus to further control the early stages of material formation due to changes in the mobility of the reactants from the evaporation and gravitational draining of the solvent. The ability to manipulate molecular development at the on-set of material formation through different deposition techniques and optical parameters allowed for the creation of several thin film optical devices, such as gratings, micro-optic lenslet arrays, and binary "on-off" patterned devices.

No description available.

Heterogeneous catalytic reactions that involve immiscible liquid-phase reactants are challenging to conduct due to limitations associated with mass transport. Nevertheless, there are numerous reactions such as esterification, transesterification, etherification, and hydrolysis where two immiscible liquid reactants (such as polar and non-polar liquids) need to be brought into contact with a catalyst. With the intention of alleviating mass transport issues associated with such systems but affording the ability to separate the catalyst once the reaction is complete, the overall goal of this study is geared toward developing a catalyst that has emulsification properties as well as the ability to phase-transfer (from liquid-phase to solid-phase) while the reaction is ongoing and evaluating the effectiveness of such a catalytic process in a practical reaction. To elucidate this concept, the transesterification reaction was selected. Metal-alkoxides that possess acidic and basic properties (to catalyze the reaction), amphiphilic properties (to stabilize the alcohol/oil emulsion) and that can undergo condensation polymerization when heated (to separate as a solid subsequent to the completion of the reaction) were used to test the concept. Studies included elucidating the effect of metal sites and alkoxide sites and their concentration effects on transesterification reaction, effect of various metal alkoxide groups on the phase stability of the reactant system, and kinetic effects of the reaction system. The studies revealed that several transition-metal alkoxides, especially, titanium and yttrium based, responded positively to this reaction system. These alkoxides were able to be added to the reaction medium in liquid phase and were able to stabilize the alcohol/oil system. The alkoxides were selective to the transesterification reaction giving a range of ester yields (depending on the catalyst used). It was also observed that transition-metal alkoxides were able to be recovered in the form of their polymerized counterparts as a result of condensation polymerization subsequent to completion of the transesterification reaction.

<p>Coordination compounds of europium and titanium with oxide, ethoxide (OCH₂CH₃), <em>iso</em>-propoxide (OCH(CH₃)₂) and <em>tert</em>-butoxide (OC(CH₃)₃) ligands have been studied. These belong to the general class of oxo-alkoxides, M<em>_x</em>O<em>_y</em>(OR)<em>_z</em>, with alkoxide ligands (OR) containing an organic, aliphatic part R. The R group can be systematically varied, permitting the investigation of the influence of electronic and steric effects on the coordination of metal and oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metal bridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gas phase-based synthesis of many technologically important materials.</p><p>The structure of a termetallic oxo-alkoxide of formula Eu₃K₃TiO₂(OH/OCH₃)(OR)₁₁(HOR) (R = C(CH₃)₃) was revealed by a combination of single-crystal X-ray diffraction and IR spectroscopy. Its unusual structure features a facial oxygen-centered Eu₃K₃O octahedron sharing one face with an oxygen-centered K₃TiO tetrahedron. Six-coordination of oxygen by a combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but the attachment of a tetrahedron to one of its faces provides a new dimension to the library of oxo-alkoxide structures. The structure was the result of incomplete metathesis in the synthesis attempt of europium-titanium oxo-<em>tert</em>-butoxides.</p><p>Eu₄TiO(OR)₁₄ and (Eu_0.5La_0.5)₄TiO(OR)₁₄ (R = CH(CH₃)₂) were found to be isostructural with previously published Ln₄TiO(OR)₁₄ structures (Ln=Sm, Tb_0.9Er_0.1). X-ray diffraction and UV-Vis absorption results show no site preference for La in either the solid state or hexane solution. The Ln₄TiO(OR)₁₄ structure forms part of an interesting group of Ln₄MO(OR)_{10+<em>z</em>}<em>­</em>(HOR)<em>_q</em> structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom, giving either a square pyramidal or a trigonal bipyramid-like coordination of the central oxygen atom, depending on the chemistry and size of M.</p><p>Eu₂Ti₄O₂(OR)₁₈(HOR)₂ (R = CH₂CH₃) was deduced from IR data to have the same molecular structure as Er₂Ti₄O₂(OR)₁₈(HOR)₂. UV-Vis measurements are also in agreement with the presence of one symmetry-unique europium site in the molecular structure. Structure determination by single-crystal X-ray diffraction has yet to be performed.</p><p> </p><p>Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), isopropoxide(OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. Thesebelong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR)containing an organic, aliphatic part R. The R group can be systematically varied, permittingthe investigation of the influence of electronic and steric effects on the coordination of metaland oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metalbridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gasphase-based synthesis of many technologically important materials.The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR)(R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IRspectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedronsharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen bya combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but theattachment of a tetrahedron to one of its faces provides a new dimension to the library of oxoalkoxidestructures. The structure was the result of incomplete metathesis in the synthesisattempt of europium-titanium oxo-tert-butoxides.Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructuralwith previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction andUV-Vis absorption results show no site preference for La in either the solid state or hexanesolution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z-(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom,giving either a square pyramidal or a trigonal bipyramid-like coordination of the centraloxygen atom, depending on the chemistry and size of M.Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the samemolecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreementwith the presence of one symmetry-unique europium site in the molecular structure. Structuredetermination by single-crystal X-ray diffraction has yet to be performed.</p>

Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), iso-propoxide (OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. These belong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR) containing an organic, aliphatic part R. The R group can be systematically varied, permitting the investigation of the influence of electronic and steric effects on the coordination of metal and oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metal bridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gas phase-based synthesis of many technologically important materials. The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR) (R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IR spectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedron sharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen by a combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but the attachment of a tetrahedron to one of its faces provides a new dimension to the library of oxo-alkoxide structures. The structure was the result of incomplete metathesis in the synthesis attempt of europium-titanium oxo-tert-butoxides. Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructural with previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction and UV-Vis absorption results show no site preference for La in either the solid state or hexane solution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z­(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom, giving either a square pyramidal or a trigonal bipyramid-like coordination of the central oxygen atom, depending on the chemistry and size of M. Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the same molecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreement with the presence of one symmetry-unique europium site in the molecular structure. Structure determination by single-crystal X-ray diffraction has yet to be performed.   Coordination compounds of europium and titanium with oxide, ethoxide (OCH2CH3), isopropoxide(OCH(CH3)2) and tert-butoxide (OC(CH3)3) ligands have been studied. Thesebelong to the general class of oxo-alkoxides, MxOy(OR)z, with alkoxide ligands (OR)containing an organic, aliphatic part R. The R group can be systematically varied, permittingthe investigation of the influence of electronic and steric effects on the coordination of metaland oxygen atoms. Their tendency towards hydrolysis and formation of metal-oxygen-metalbridges also makes (oxo)alkoxides interesting as precursors in liquid solution-based or gasphase-based synthesis of many technologically important materials.The structure of a termetallic oxo-alkoxide of formula Eu3K3TiO2(OH/OCH3)(OR)11(HOR)(R = C(CH3)3) was revealed by a combination of single-crystal X-ray diffraction and IRspectroscopy. Its unusual structure features a facial oxygen-centered Eu3K3O octahedronsharing one face with an oxygen-centered K3TiO tetrahedron. Six-coordination of oxygen bya combination of alkali metal and lanthanoid atoms is not uncommon for alkoxides, but theattachment of a tetrahedron to one of its faces provides a new dimension to the library of oxoalkoxidestructures. The structure was the result of incomplete metathesis in the synthesisattempt of europium-titanium oxo-tert-butoxides.Eu4TiO(OR)14 and (Eu0.5La0.5)4TiO(OR)14 (R = CH(CH3)2) were found to be isostructuralwith previously published Ln4TiO(OR)14 structures (Ln=Sm, Tb0.9Er0.1). X-ray diffraction andUV-Vis absorption results show no site preference for La in either the solid state or hexanesolution. The Ln4TiO(OR)14 structure forms part of an interesting group of Ln4MO(OR)10+z-(HOR)q structures where M is another lanthanoid (Ln) or a di-, tri- or tetravalent heteroatom,giving either a square pyramidal or a trigonal bipyramid-like coordination of the centraloxygen atom, depending on the chemistry and size of M.Eu2Ti4O2(OR)18(HOR)2 (R = CH2CH3) was deduced from IR data to have the samemolecular structure as Er2Ti4O2(OR)18(HOR)2. UV-Vis measurements are also in agreementwith the presence of one symmetry-unique europium site in the molecular structure. Structuredetermination by single-crystal X-ray diffraction has yet to be performed.

The present study involves the use of main group organometallics: organostannanes and organolithiums as precursors to chromium Fischer carbene complexes. Fischer carbenes are well stabilized by the π‐donor substituents such as alkoxy and amino groups and low oxidation state metals such as Group 6 (Chromium, Molybdenum or Tungsten). Carbenes are an important intermediate in the synthesis of a range of compounds through cyclopropanations, insertions, coupling and photochemical reactions. Synthesis and successful characterisation of three α‐alkoxystannanes was achieved via nucleophilic addition of tributylstannyllithium to the respective aldehydes, followed by an immediate MOM protection of the resulting alcohol. Six α‐aminostanannes were synthesised, consisting of N‐BOC, N‐acetyl and N‐ethyl derivatives of pyrrolidine and piperidine, via α‐lithiation and subsequent tinlithium transmetallation in the presence of TMEDA. The ¹³C NMR analysis highlighted an interesting phenomenon of tin‐carbon coupling that revealed unique structural information of both types of stannanes. DFT analysis was completed on the series of stannanes; a predicted frequency analysis was obtained which complemented the experimental Infra‐red data in elucidation of the compounds. The α‐alkoxy and α‐aminostannanes provided stable precursors to the organolithiums required for the synthesis of the novel Fischer chromium carbenes. The organolithiums were obtained via tinlithium exchange at low temperatures, followed by the addition of chromium hexacarbonyl to form the acylpentacarbonyl‐chromate salt. Alkylation of this intermediate using a Meerwein salt, Me₃OBF₄, gave rise to the novel Fischer chromium carbene complexes. Fischer chromium carbenes derived from the two isomeric butyl and isobutyl stannanes and the two N‐ethyl α‐aminostannanes were successfully synthesised. The difficulty encountered in the purification of the Fischer carbene complexes hindered the full characterisation, due to the presence of a by‐product, tetrabutyltin.

The Parkin group has recently synthesized tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]methane, [TismPriBenz]H, a bulky tetradentate tripodal ligand, which upon deprotonation can coordinated to form a variety of carbatrane metal complexes.The [TismPriBenz] ligand has been previously shown to stabilize metal hydride complexes, for example [TismPriBenz]MgH and [TismPriBenz]ZnH, and the ligand also has been incorporated in complexes featuring all of the non-radioactive Group 12 and Group 13 metals, as well as a large range of transition metals. However, the reactivity of these complexes towards carbonyl compounds is largely unexplored. Additionally, beyond [TismPriBenz]Li, there has been no attempt to introduce the heavier alkali metals into the [TismPriBenz] framework, which could potentially provide more reactive starting materials to generate other previously inaccessible metal complexes of the ligand; for instance, prior to this report, there has been no example of a lanthanide complex of [TismPriBenz]. In Chapter 1, the reactivity of [TismPriBenz]MgH and [TismPriBenz]MgMe towards ketones, aldehydes, and esters is explored. Generally, these magnesium complexes are able to insert a C=O double bond into a Mg–Me or Mg–H bond respectively, providing access to a large class of magnesium alkoxides. Specifically, [TismPriBenz]MgR (R = H, Me) can insert benzaldehyde and benzophenone to give [TismPriBenz]MgOCRHPh or[TismPriBenz]MgOCRPh₂ respectively. Additionally, [TismPriBenz]MgMe has shown rare reactivity towards methyl ketones, in that it forms the magnesium enolate compounds [TismPriBenz]MgC(Me)=CH₂ and [TismPriBenz]MgC(Ph)=CH2 upon treatment with acetone or acetophenone. In fact, [TismPriBenz]MgC(Me)=CH₂ is only the fourth acetone enolate complex to be structurally characterized, and the first such magnesium example. In the presence of the ester compounds methyl formate and ethyl acetate, [TismPriBenz]MgH and [TismPriBenz]MgMe are able to follow the insertion of the carbonyl with immediate elimination of either an aldehyde or ketone to yield the simple alkoxides [TismPriBenz]MgOMe and [TismPriBenz]MgOEt, a reaction with little precedence in the literature. [TismPriBenz]MgMe is also able to prompt the Claisen condensation of ethyl acetate, forming the first [TismPriBenz] complex with a 6-member chelating ring, [TismPriBenz]Mg(κ²-OC(Me)HC(O)OEt). These various alkoxides have demonstrated the ability to catalyze the Tishchenko reaction, the dimerization of an aldehyde to make an ester, and have also shown promise as catalysts for hydroboration and retro-aldol reactions. Lastly, the [TismPriBenz]Mg compounds have shown interesting reactivity towards O₂, leading to the isolation of both the rare peroxide dimer {[TismPriBenz]Mg}₂(μ-O₂) and the alkyl peroxide [TismPriBenz]MgOOMe. In Chapter 2, the reactivity of the complex [TismPriBenz]Tl is further developed, providing access to previously known methyl and iodide compounds of magnesium, zinc, and cadmium. Additionally, [TismPriBenz]Tl has been shown to react directly with the alkali metals sodium, potassium, and rubidium to form the novel alkali metal complexes [TismPriBenz]M (M = Na, K, Rb). Furthermore, [TismPriBenz]Li can react with CsF to afford [TismPriBenz]Cs, completing the non-radioactive Group 1 [TismPriBenz]M series. This makes [TismPriBenz] one of only a handful of organic ligands to have structurally characterized compounds with all of the alkali metals from Li to Cs, and the only ligand that formsmonomeric complexes in each case. [TismPriBenz]K was also used as a starting material to synthesize the first [TismPriBenz] lanthanide complexes, [TismPriBenz]YbI and [TismPriBenz]YbCl₂. [TismPriBenz]YbI itself can further react with KN(SiMe₃)₂ and NaCp to give [TismPriBenz]YbN(SiMe₃)₂ and [TismPriBenz]YbCp respectively. Lastly, the ability of the [TismPriBenz]Zn halide series to form ion pair complexes was investigated. [TismPriBenz]ZnI can react with ZnI₂ to afford {[TismPriBenz]Zn}₂[Zn₃I₈], which contains the novel zinc halide species [Zn₃I₈]²⁻. Additionally, all of the [TismPriBenz]ZnX (X = Cl, Br, I) complexes are able to react with excess ZnX₂ in THF to give the series {[TismPriBenz]Zn}[Zn(THF)X₃].

Dans ce manuscrit, un travail hautement multidisciplinaire, de la synthèse de ligands organiques à la caractérisation de couches minces, est présenté. L'objectif principal de cette étude était d'élaborer de nouveaux précurseurs de niobium, de titane et d'alcalino-terreux adaptés au procédé de dépôt de couches minces par CBVD développé par la société 3D-OXIDES. Afin de répondre aux exigences de ce procédé, deux classes innovantes de dérivés moléculaires à base de ß-amino-alcool ou de ß-dicétone ?-modifiée ont été élaborées grâce à la synthèse organique de nouveaux ligands. Les complexes métalliques ont ensuite été entièrement caractériser et leur intérêt respectif dans le processus de dépôt par CBVD a été étudié à travers la détermination des pressions de vapeur, les taux de croissance, les caractérisations spectroscopiques et analyses des couches minces / In this manuscript, a highly multidisciplinary work from organic ligand syntheses to thin films characterizations is presented. The main objective of this study was to elaborate new suitable niobium-, titanium-, and alkaline earth-based precursors for CBVD thin film deposition process developed by 3D-OXIDES company. In order to reach the requirements for CBVD deposits applications, two innovative classes of molecular derivatives based on either ß-amino-alcohol or ?-modified ß-diketone ligand have been elaborated, starting from the organic synthesis of new ligands, and thoroughly characterized. Their respective interest in CBVD deposition process was fully analyzed through the determination of vapor pressures, growth rates and spectroscopic and thin film characterizations