Periodic Reporting for period 1 - LoCo (Low Coordinate Transition Metal Single Molecule Magnets)
Période du rapport: 2017-02-13 au 2019-02-12
"There has been a remarkable (re)awakening of interest in the organometallic chemistry of the late 1st row metal elements Fe, Co and Ni in recent years as the need to find earth abundant alternatives to the rapidly depleting stocks of the heavier group 8-10 congeners (Ru, Rh and Pd) has gained recognition.
Magnets are ubiquitous in modern society, with applications that range from biomedical imaging and cancer therapy through information technology to defence and national security. In all of these aspects, miniaturisation is a highly desirable property. Chemists can achieve this by building families of molecule-based magnetic materials using a ""bottom-up"" approach to generate new materials with tuneable/designer physical properties. These can then (ultimately) be exploited in collaboration with condensed matter physicists, theoreticians and materials scientists for ‘real-world’ applications.
There are just a few two-coordinate, open-shell transition metal complexes (all of 1st row metals) in the literature. This remarkably small number results from (i) the difficulty in finding appropriate ligand sets that stabilise two-coordination and prevent aggregation to higher coordination numbers and (ii) the perceived extreme sensitivity of such species to air and moisture. As a result, a comprehensive understanding of the structures, physical properties and reactivity of very low-coordinate 1st row metal species remains embryonic at best. Given the enormous potential of such systems to exhibit novel reactivity and materials applications, a systematic study of new examples of two-coordinate metal complexes would lead not to only to major advances in understanding fundamental chemistry, but offer new opportunities for real-world applications.
The objectives are:
- Development of new two coordinate Ni complexes with different 6-/7-membered ring NHCs
- Study of their magnetic properties and potencial SMM behaviour
- Development of calculations of the properties of the prepared complexes
- Extension of the study to other first row metal NHC-complexes"
Magnets are ubiquitous in modern society, with applications that range from biomedical imaging and cancer therapy through information technology to defence and national security. In all of these aspects, miniaturisation is a highly desirable property. Chemists can achieve this by building families of molecule-based magnetic materials using a ""bottom-up"" approach to generate new materials with tuneable/designer physical properties. These can then (ultimately) be exploited in collaboration with condensed matter physicists, theoreticians and materials scientists for ‘real-world’ applications.
There are just a few two-coordinate, open-shell transition metal complexes (all of 1st row metals) in the literature. This remarkably small number results from (i) the difficulty in finding appropriate ligand sets that stabilise two-coordination and prevent aggregation to higher coordination numbers and (ii) the perceived extreme sensitivity of such species to air and moisture. As a result, a comprehensive understanding of the structures, physical properties and reactivity of very low-coordinate 1st row metal species remains embryonic at best. Given the enormous potential of such systems to exhibit novel reactivity and materials applications, a systematic study of new examples of two-coordinate metal complexes would lead not to only to major advances in understanding fundamental chemistry, but offer new opportunities for real-world applications.
The objectives are:
- Development of new two coordinate Ni complexes with different 6-/7-membered ring NHCs
- Study of their magnetic properties and potencial SMM behaviour
- Development of calculations of the properties of the prepared complexes
- Extension of the study to other first row metal NHC-complexes"
Results from work package 1:
1. Syntheses of N-heterocyclic carbenes 6-Mes, 7-Mes, 7-Xyl, IMes, SIMes and Ni(I) complex Ni(6-Mes)(PPh3)(Br).
2. Syntheses and characterisation of [Ni(6-Mes)(ANO-NHC)] (ANO-NHC = any other NHC) complexes [Ni(6-Mes)(7-Mes)]Br (1.1) [Ni(6-Mes)(7-Xyl)]Br, [Ni(6-Mes)(IMes)]Br (1.3) and [Ni(6-Mes)(SIMes)]Br.
3. Studies of the properties of complexes 1.1 and 1.3 through:
- EPR spectroscopy measurements at University of Cardiff, UK.
- Computational studies (collaboration with Dr V. Krewald (TU Darmstadt, Germany) and Dr E. Suturina (University of Bath)).
- Magnetic measurements (in collaboration with Prof Murugesu (University of Ottawa, Canada).
Results from work package 2:
1. Syntheses and characterisation of carbenes IBiox6 and IBioxMe4.
2. Synthesis and characterisation of Ni(I) compound [Ni(IBiox6)(PPh3)(Br)].
3. Synthesis of 1,1,3,3-tetramesitylquinobis(imidazolylidene) (abbreviated to bis-NHC).
4. Reaction of the bis-NHC with a range of 6- and 7-membered ring NHC complexes ([Ni(6-Mes)(PPh3)Br], [Ni(7-Mes)(PPh3)Br], [Ni(6-Xyl)(PPh3)Br] and [Ni(7-Xyl)(PPh3)Br]) to afford bimetallic Ni(I) complexes [(RE-NHC)Ni(bisNHC)Ni(RE-NHC]2+ (2.2 – 2.5).
5. Study of their properties:
- EPR spectroscopy at University of Cardiff.
- Theoretical models of paramagnetic NMR data (collaboration with Dr E. Suturina (University of Bath)).
- Ongoing magnetic measurements (in collaboration with Prof Murugesu (University of Ottawa, Canada).
- Electrochemistry (in collaboration with Prof F. Marken (University of Bath)).
Results from work package 3:
1. Syntheses of neutral two-coordinate Ni(I) complexes [Ni(6-Mes)X] (X = N{SiMe3}2 (3.1) NPh2 (3.2) O-2,6-tBu2-4-Me-C6H2 (3.3) and 2,6-Mes2-C6H4 (3.4).
2. Synthesis of neutral three-coordinate Ni(I) complexes [Ni(6-Mes)(PPh3)(NPh2)] (3.5) and [Ni(6-Mes)(PPh3)(C6H5)] (3.6).
3. Full crystallographic characterisation of complexes 3.1-3.6.
Results from work package 4:
1. Syntheses of carbenes IBiox6, IBioxMe4, IPr and IMes.
2. Synthesis and characterisation of new ruthenium complexes of the form [Ru(NHC)2(CO)HCl] and [Ru(NHC)2(CO)H]+ (NHC = IBiox6, IBioxMe4).
3. Study of the reactivity of these complexes towards ZnMe2.
4. Preparation of a family of heterobimetallic complexes [Ru(NHC)2(CO)ZnMe]+ (NHC = IPr, IBiox6).
5. Characterisation of all these new complexes and reactivity studies with H2.
6. Synthesis and characterisation of new platinum complexes of the form [Pt(NHC)2Me]+ (NHC = IBiox6).
7. Study of the reactivity towards organozinc reagents (ZnR2) (R= Ph, Et, H).
8. Preparation and characterisation of a family of T-shaped complexes [Pt(NHC)2R]+ (R= Ph, Et, H) by metathesis with organozinc reagents.
Results from WP1-WP3 remain to be completed due to the number of collaborators involved. Thus, they have yet to be disseminated in the form of published work. Some of the data from WP4 has been published (Dalton Trans. 2019) and has been disseminated at conferences (International School Marcial Moreno Mañas, in Oviedo (2018, Spain), ICOMC (International Conference on Organometallic Chemistry) in Florence (2018, Italy), July 2018, and the national conference of the specialised organometallic division in Zaragoza (2018, Spain). Aside from the conferences the fellow was an invited speaker on two occasions at the University of Bath to disseminate her results.
1. Syntheses of N-heterocyclic carbenes 6-Mes, 7-Mes, 7-Xyl, IMes, SIMes and Ni(I) complex Ni(6-Mes)(PPh3)(Br).
2. Syntheses and characterisation of [Ni(6-Mes)(ANO-NHC)] (ANO-NHC = any other NHC) complexes [Ni(6-Mes)(7-Mes)]Br (1.1) [Ni(6-Mes)(7-Xyl)]Br, [Ni(6-Mes)(IMes)]Br (1.3) and [Ni(6-Mes)(SIMes)]Br.
3. Studies of the properties of complexes 1.1 and 1.3 through:
- EPR spectroscopy measurements at University of Cardiff, UK.
- Computational studies (collaboration with Dr V. Krewald (TU Darmstadt, Germany) and Dr E. Suturina (University of Bath)).
- Magnetic measurements (in collaboration with Prof Murugesu (University of Ottawa, Canada).
Results from work package 2:
1. Syntheses and characterisation of carbenes IBiox6 and IBioxMe4.
2. Synthesis and characterisation of Ni(I) compound [Ni(IBiox6)(PPh3)(Br)].
3. Synthesis of 1,1,3,3-tetramesitylquinobis(imidazolylidene) (abbreviated to bis-NHC).
4. Reaction of the bis-NHC with a range of 6- and 7-membered ring NHC complexes ([Ni(6-Mes)(PPh3)Br], [Ni(7-Mes)(PPh3)Br], [Ni(6-Xyl)(PPh3)Br] and [Ni(7-Xyl)(PPh3)Br]) to afford bimetallic Ni(I) complexes [(RE-NHC)Ni(bisNHC)Ni(RE-NHC]2+ (2.2 – 2.5).
5. Study of their properties:
- EPR spectroscopy at University of Cardiff.
- Theoretical models of paramagnetic NMR data (collaboration with Dr E. Suturina (University of Bath)).
- Ongoing magnetic measurements (in collaboration with Prof Murugesu (University of Ottawa, Canada).
- Electrochemistry (in collaboration with Prof F. Marken (University of Bath)).
Results from work package 3:
1. Syntheses of neutral two-coordinate Ni(I) complexes [Ni(6-Mes)X] (X = N{SiMe3}2 (3.1) NPh2 (3.2) O-2,6-tBu2-4-Me-C6H2 (3.3) and 2,6-Mes2-C6H4 (3.4).
2. Synthesis of neutral three-coordinate Ni(I) complexes [Ni(6-Mes)(PPh3)(NPh2)] (3.5) and [Ni(6-Mes)(PPh3)(C6H5)] (3.6).
3. Full crystallographic characterisation of complexes 3.1-3.6.
Results from work package 4:
1. Syntheses of carbenes IBiox6, IBioxMe4, IPr and IMes.
2. Synthesis and characterisation of new ruthenium complexes of the form [Ru(NHC)2(CO)HCl] and [Ru(NHC)2(CO)H]+ (NHC = IBiox6, IBioxMe4).
3. Study of the reactivity of these complexes towards ZnMe2.
4. Preparation of a family of heterobimetallic complexes [Ru(NHC)2(CO)ZnMe]+ (NHC = IPr, IBiox6).
5. Characterisation of all these new complexes and reactivity studies with H2.
6. Synthesis and characterisation of new platinum complexes of the form [Pt(NHC)2Me]+ (NHC = IBiox6).
7. Study of the reactivity towards organozinc reagents (ZnR2) (R= Ph, Et, H).
8. Preparation and characterisation of a family of T-shaped complexes [Pt(NHC)2R]+ (R= Ph, Et, H) by metathesis with organozinc reagents.
Results from WP1-WP3 remain to be completed due to the number of collaborators involved. Thus, they have yet to be disseminated in the form of published work. Some of the data from WP4 has been published (Dalton Trans. 2019) and has been disseminated at conferences (International School Marcial Moreno Mañas, in Oviedo (2018, Spain), ICOMC (International Conference on Organometallic Chemistry) in Florence (2018, Italy), July 2018, and the national conference of the specialised organometallic division in Zaragoza (2018, Spain). Aside from the conferences the fellow was an invited speaker on two occasions at the University of Bath to disseminate her results.
During the period of the fellowship, there have been significant advances in the field of research (single molecule magnets (SMM)), with major developments relating to materials that function at higher temperatures (e.g. Science 2018, 362, 1400; Angew. Chem. Int. Ed. 2017, 56, 11445; Nature 2017, 548, 439). Most of this work remains conducted with lanthanides, rather than transition metals. Results from the project have suggested that having two ligands the same in [M(NHC)2]+ complexes is preferable. Studies from work package 4 on heterobimetallic chemistry have helped to underpin both further publications (e.g. Dalton Trans. 2019, 48, 14000) and (results pending) grant applications. Potential applications for both magnetic materials and heterobimetallic complexes (for catalysis applications) still remain far from true societal impact, but the studies performed by the fellow will contribute significantly to the development of both fields.
In terms of impact on the fellow (MEV), she has (i) developed a broad-range and high-level of expertise in organometallic chemistry, (ii) received advanced training in physical techniques (EPR, electrochemistry), in computational studies and in scientific dissemination (advanced courses, conferences). The fellow has enhanced her research management skills by forming links to new national and international collaborations and her people management skills (team working alongside undergraduate and postgraduate students). She has established contacts through planned secondments (EPR at Cardiff University) as well as new local and international collaborations that were unforeseen at the start of the project (calculations: Krewald (Darmstadt), Suturina (Bath); electrochemistry: Marken (Bath)).
In terms of impact on the fellow (MEV), she has (i) developed a broad-range and high-level of expertise in organometallic chemistry, (ii) received advanced training in physical techniques (EPR, electrochemistry), in computational studies and in scientific dissemination (advanced courses, conferences). The fellow has enhanced her research management skills by forming links to new national and international collaborations and her people management skills (team working alongside undergraduate and postgraduate students). She has established contacts through planned secondments (EPR at Cardiff University) as well as new local and international collaborations that were unforeseen at the start of the project (calculations: Krewald (Darmstadt), Suturina (Bath); electrochemistry: Marken (Bath)).