Academic literature on the topic 'Group-IV metal complexes'

AbstractCompared to the overwhelming prevalence of f-element-carbon, -nitrogen, -oxygen or -halide ligand linkages, the use of metal-based fragments as ligands is underdeveloped. This contrasts directly to the extensively developed fields of d- and p-block metal-metal complexes, which are still burgeoning. This review outlines the development of compounds that possess polarised covalent f-element-metal bonds. For this review, the f-element is defined as (i) a group 3 metal; (ii) a lanthanide metal; (iii) the actinide metals thorium or uranium. The metal is defined as: (i) a d-block transition metal; (ii) a group 13 metal (aluminium or gallium); (iii) a group 14 metal (silicon, germanium or tin); (iv) a group 15 metal (antimony or bismuth) metal. Although silicon, germanium and antimony are traditionally classified as metalloids, they are included for completeness. We focus on complexes that have been structurally authenticated by single crystal X-ray diffraction, and we highlight novel aspects of their syntheses, properties and reactivities.

Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35395

The thesis work aims at providing new insights and perspectives in the field of oligomerization/polymerization catalysis mediated by early metal complexes stabilized by ligands containing nitrogen donor groups. To make an additional step forward, widening the catalyst application range, most of the developed catalytic systems have been scrutinized with respect to their ability to promote different catalytic cycles related to the production of various materials and commodities. Accordingly, neutral and/or cationic catalysts capable to engage in highly efficient -olefin polymerization have also been successfully employed in the intramolecular hydroamination reaction of model primary and/or secondary aminoalkenes for the obtainment of pyrrolidine and/or piperidine heterocycles.

In this thesis a detailed ab initio theoretical study of organothorium chemistry is presented. The first part is devoted to examining both the bonding in and the reaction chemistry of various substituted thorium complexes. Using the chlorine ligand as a model for the usual cyclopentadienyl groups found in these systems, we examine the bonding of hydrogen and methyl ligands to thorium. Frequent comparisons with the experimental results on similar species are made. In addition, by contrasting the bonding in the thorium complexes with the bonding in the analogous Group IVB systems, a qualitative and quantitative picture of bonding, as the atomic number of the metal becomes larger, can be obtained. The reaction chemistry is studied via two different sets of processes. In the first, the deuterium (D₂) exchange reaction with a thorium-hydrogen bond is examined. Several studies have been done previously, both experimentally and theoretically, on the Group IVB exchange reactions. Hence, there is enough information to see trends and to make predictions about relative reaction rates. Also, from our investigation the effect that different types of ligands have on the activation barrier to reaction can be ascertained.

In the second part of the thesis, the factors that go into stabilizing bond formation are discussed concerning both main group elements and transition metals, including actinides. In particular, the process of bond formation between hydrogen atom and the alkali metals is compared with the same process in the Group IVB-hydrogen and thorium-hydrogen saturated complexes. The main difference between the alkali metal and the transition metal bonds with hydrogen is the bond strength trends with increasing atomic number. For the alkali metals the bond energies decrease down the column, yet for the transition metals and thorium it is the reverse. The conclusion is that the shape of the mostly d in character transition metal bonding orbitals is such that better overlap can be achieved with hydrogen as the orbitals become more diffuse. In the alkali metals the bonds can be described as s—s bonds whose overlap decreases with increasing diffuseness.

碩士
國立彰化師範大學
化學系
104
A series of main and transition metal complexes containing ketiminate ligand, [OCMeCHCMeNHC6H4-2-tBu] (L1), [OCMeCHCMeNHCH2C6H4-4-Me] (L2), [OCPhCHCMeNHCH2(C4H7O)] (L3), [OCPhCHCMeNHCH2Ph] (L4), [OCMeCHCMeNHCH2(C4H7O)] (L5), [OCMeCHCMeNHCH2Ph] (L6) and [OCMeCHCMeNHMes] (L7) were synthesized and characterized. Treatment of 1 equiv of AlMe3 with L1-L4 generates aluminum complexes [AlMe2(OCMeCHCMeNC6H4-2-tBu)]（1）, [AlMe2(OCMeCHCMeNCH2C6H4-4-Me)]（2）, {AlMe2[OCPhCHCMeNCH2(C4H7O)]}（3）, [AlMe2(OCPhCHCMeNCH2Ph] （4）. Treatment of 2 equiv of L1-L7 with ZnMe2 generates Zinc complexes [Zn(OCMeCHCMeNC6H4-2-tBu) 2] （5）, [Zn(OCMeCHCMeNCH2C6H4-4-Me) 2]（6）, {Zn[OCPhCHCMeNCH2(C4H7O)]2} （7）, [Zn(OCPhCHCMeNCH2Ph)2] （8）, {Zn[OCMeCHCMeNCH2(C4H7O)]2}（9）, [Zn(OCMeCHCMeNCH2Ph)2] （10）, [Zn(OCMeCHCMeNMes)2] （11）. Treatment of 2 equiv of L6 or L7 with MR4 generates group IV complexes ML2R2 (12, M=Ti, R1=CH2Ph, R=NMe2; 13, M=Zr, R1=CH2Ph, R=NMe2; 14, M=Zr, R1=CH2Ph, R=NEt2; 15, M=Hf, R1=CH2Ph, R=NEt2; 16, M=Ti, R1=Mes, R=OiPr; 17, M=Ti, R1=Mes, R=NMe2; 18, M=Zr, R1=Mes, R=NMe2; 19, M=Zr, R1=Mes, R=NEt2; 20, M=Hf, R1=Mes, R=NEt2). All the aforementioned complexes have been characterized by 1H and 13C NMR spectroscopy and have been determined by single X-ray diffractometry in solid state (except 2, 3, 4, 7, 8, 9, 11, 12, 13, 14, 15, 19 and 20). Complexes 16, 17, 18, 19 and 20 were tested as initiators for the ring-opening polymerization of ε-caprolactone.

碩士
國立彰化師範大學
化學系
107
應文摘要 A series of group 4 metal and main group complexes containing bi- or tri-dentate keto-amine, furanyl-amine or pyridyl-amine ligands are synthesized and characterized. Reacting furfural with 2-(aminomethyl)pyridine and (+/-)-tetrahydrofurfurylamine in the presents of NaBH4 result new tridentate amine ligands NC5H4CH2NHCH2C4H3O (L1H) and OC4H3CH2NHCH2C4H7O (L4H), respectively. Similarly, reacting Pyridine-2-carboxaldedehyde with 2-(aminomethyl)pyridine and (+/-)-tetrahydrofurfurylamine in the presents of NaBH4 result NC5H4CH2NHCH2C5H4N (L2H) and NC5H4CH2NHCH2C4H7O (L3H), respectively. In addition, adding 2,4-pentandione with one equivalent of 2-(1-cyclohexenyl)ethylamine in methanol gives a new keto-amine ligand MeC(OH)CHCMe(CH2CH2C6H9) (L6H). Similarly, adding 2,4-pentandione with one equivalent of 2-(aminomethyl)pyridine in methanol gives a new keto-amine ligand MeC(OH)CHCMe(NCH2NC5H4) (L5H). Ligands L1H-L6H have been characterized by 1H and 13C NMR spectroscopy. Reacting ligands L1H-L6H with main group and group 4 metal amide (M(NR2)4, M = Ti, Zr, Hf; R = Me, Et) yield corresponding ligand-metal amide complexes. Characterization of these metal complexes have been performed and related catalytic reactions will be performed.

The study is funded by Doha International Family Institute (DIFI), a member of Qatar Foundation, and is a collaboration between the Muslim Resource Centre for Social Support and Integration of London, Ontario; University of Guelph, Ontario; and University of Calgary, Alberta, all located in Canada; and the Doha International Family Institute, Qatar. The study received research ethics approval from the University of Guelph and the University of Calgary. This study aims to assess the impact of pre- and post-migration on marital relationships and family dynamics for Arab refugee families resettled in Canada. The study also examines the role of professional service providers in supporting these Arab refugee families. The unique experiences of Arab families displaced from their countries due to war and political conflict, and the various hardships experienced during their stay in transit countries, impact their family relations and interactions within the nuclear family context and their interconnectedness with their extended families. Furthermore, these families encounter various challenges within their resettlement process that interrupt their integration. Understanding the impact of traumatic experiences within the pre-migration journey as well as the impact of post-migration stressors on recently settled Arab refugee families in Canada provides insight into the shift in spousal and family relationships. Refugee research studies that focus on the impact of pre-migration trauma and displacement, the migration journey, and post-migration settlement on family relationships are scarce. Since the majority of global refugees in recent years come from Arab regions, mainly Syria, as a result of armed conflicts, this study is focused on the unique experiences of Arab refugee families fleeing conflict zones. The Canadian role in recently resettling a large influx of Arab refugees and assisting them to successfully integrate has not been without challenges. Traumatic pre-migration experiences as a result of being subjected to and/or witnessing violence, separation from and loss of family members, and loss of property and social status coupled with experiences of hardships in transit countries have a profound impact on families and their integration. Refugees are subjected to individual and collective traumatic experiences associated with cultural or ethnic disconnection, mental health struggles, and discrimination and racism. These experiences have been shown to impact family interactions. Arab refugee families have different definitions of “family” and “home” from Eurocentric conceptualizations which are grounded in individualistic worldviews. The discrepancy between collectivism and individualism is mainly recognized by collectivist newcomers as challenges in the areas of gender norms, expectations regarding parenting and the physical discipline of children, and diverse aspects of the family’s daily life. For this study, we interviewed 30 adults, all Arab refugees (14 Syrian and 16 Iraqi – 17 males, 13 females) residing in London, Ontario, Canada for a period of time ranging from six months to seven years. The study participants were married couples with and without children. During the semi-structured interviews, the participants were asked to reflect on their family life during pre-migration – in the country of origin before and during the war and in the transit country – and post-migration in Canada. The inter - views were conducted in Arabic, audio-recorded, and transcribed. We also conducted one focus group with seven service providers from diverse sectors in London, Ontario who work with Arab refugee families. The study used the underlying principles of constructivist grounded theory methodology to guide interviewing and a thematic analysis was performed. MAXQDA software was used to facilitate coding and the identification of key themes within the transcribed interviews. We also conducted a thematic analysis of the focus group transcription. The thematic analysis of the individual interviews identified four key themes: • Gender role changes influence spousal relationships; • Traumatic experiences bring suffering and resilience to family well-being; • Levels of marital conflict are higher following post-migration settlement; • Post-migration experiences challenge family values. The outcome of the thematic analysis of the service provider focus group identified three key themes: • The complex needs of newly arrived Arab refugee families; • Gaps in the services available to Arab refugee families; • Key aspects of training for cultural competencies. The key themes from the individual interviews demonstrate: (i) the dramatic sociocul - tural changes associated with migration that particularly emphasize different gender norms; (ii) the impact of trauma and the refugee experience itself on family relation - ships and personal well-being; (iii) the unique and complex aspects of the family journey; and (iv) how valued aspects of cultural and religious values and traditions are linked in complex ways for these Arab refugee families. These outcomes are consist - ent with previous studies. The study finds that women were strongly involved in supporting their spouses in every aspect of family life and tried to maintain their spouses’ tolerance towards stressors. The struggles of husbands to fulfill their roles as the providers and protec - tors throughout the migratory journey were evident. Some parents experienced role shifts that they understood to be due to the unstable conditions in which they were living but these changes were considered to be temporary. Despite the diversity of refugee family experiences, they shared some commonalities in how they experi - enced changes that were frightening for families, as well as some that enhanced safety and stability. These latter changes related to safety were welcomed by these fami - lies. Some of these families reported that they sought professional help, while others dealt with changes by becoming more distant in their marital relationship. The risk of violence increased as the result of trauma, integration stressors, and escalation in marital issues. These outcomes illustrate the importance of taking into consideration the complexity of the integration process in light of post-trauma and post-migration changes and the timespan each family needs to adjust and integrate. Moreover, these families expressed hope for a better future for their children and stated that they were willing to accept change for the sake of their children as well. At the same time, these parents voiced the significance of preserving their cultural and religious values and beliefs. The service providers identified gaps in service provision to refugee families in some key areas. These included the unpreparedness of professionals and insufficiency of the resources available for newcomer families from all levels of government. This was particularly relevant in the context of meeting the needs of the large influx of Syrian refugees who were resettled in Canada within the period of November 2015 to January 2017. Furthermore, language skills and addressing trauma needs were found to require more than one year to address. The service providers identified that a longer time span of government assistance for these families was necessary. In terms of training, the service providers pinpointed the value of learning more about culturally appropriate interventions and receiving professional development to enhance their work with refugee families. In light of these findings, we recommend an increased use of culturally integrative interventions and programs to provide both formal and informal support for families within their communities. Furthermore, future research that examines the impact of culturally-based training, cultural brokers, and various culturally integrative practices will contribute to understanding best practices. These findings with regard to refugee family relationships and experiences are exploratory in their nature and support future research that extends understanding in the area of spousal relationships, inter - generational stressors during adolescence, and parenting/gender role changes.

A detailed safety assessment of innovative Generation IV reactor designs with heavy-liquid metal coolants, such as lead and lead-bismuth eutectic (LBE), requires an evaluation of the maximum core temperature in several postulated scenarios. Considering the complex geometry of fuel assemblies (FAs), and the low Prandtl number of the coolants, this flow scenario is challenging for the models used in numerical simulations, e.g. for relating the turbulent transport of momentum and heat. Thus, reliable experimental data are needed for validation. In recent years, a series of comprehensive heat transfer tests in fuel pin bundle simulators was performed at ENEA (Italy) and KIT (Germany) in the framework of the European collaborative projects THINS and SEARCH. Both grid and wire spacer geometries are considered, in a wide range of operating conditions (temperature, flow velocity and power density) representative of the ALFRED and MYRRHA fuel assemblies, in natural and forced-convective flow regimes. Although different experimental approaches were followed by each group (e.g. thermocouple position and average data treatment), there is a relatively good agreement on results in the overlapping regions. These experimental studies indicate that the mean Nusselt number is in well agreement with the predictions of empirical correlations developed for sodium systems. In particular, for wire-spaced FA, heat transfer results show values close to the Kazimi-Carelli correlation both for low and high flow rates at ENEA and KIT respectively. For grid-spaced FA, results are more in agreement with Ushakov correlation. Furthermore, large temperature differences are measured by thermo-couples installed at selected rods and sub-channels. A discussion on the influences of the spacer design and bundle size is included. This wide comparison allows an overview of the research on the HLM cooled fuel assembly in Europe.