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Questions about Low-Valence Chemistry

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the what and talk so when we had prepared the magnesium 1 Daimler's offices we needed to prove the president of the middle middle upon their most specifically the absence of bridging hydride so you in the reduction of main group metal highlights with alkali metals which is what we were doing to access these systems it's often common than you get hydrogen abstraction from the solvent or all again and and you wind up with hydride against attached to the To the medallion to try and keep their oxidation state of what they like to be at and so the potential is there we had a and magnesium magnesium again to bridging hydroxide we really needed to prove that we didn't have any hard drive against them their notoriously difficult to detector Crystal graphically and sometimes spectroscopic clean and so we spent probably a year and a half trying to make the magnesium hydride ,comma because we thought that this would have different properties to the mechanism 1 company that if we could do that and that was approved and it is remarkable to me that making the magazine once systems of very of relatively easy making the magnesium hydride compounds which would expect probably as being the by-products in the register was a long time to do it but we we managed to do it and we showed that they're completely different properties and then we also obtained neutron diffraction studies on the magnesium 1 systems which shows the absence of hydride so that only proves the absence of hydraulic and it doesn't necessarily prove the absence all the oxidation state all magnesium compounds because because you could have a reduction of the for example and so we then and then use DFT calculations with collaborators in combination with these experimental charge density studies to try and locate and effectively see the electron density between the magnesium sentences and that's that's how we army can never totally fruitless this and the fact that we've always lived this situation we believe that the covalent bond albeit a very diffuse covalent bond between the 2 mechanisms certainly no hydride elegant presence well there more reactive and Grenier reagents but as I say there really remarkably or the reactivity is much less than we expected and when we set out to prepare these compounds we thought what we went terribly optimistic to tell you the truth we thought Well we're going to give it a go and will spend some time on this but if it doesn't work then we you wouldn't surprise us if it turned out that they really are very stable species and of course you can change the reactivity of the compounds by I'm changing the steric profile of the league ends the coordinated to the diet magnesium Frank and in fact if we use very bulky coordinated to the dominant religion fragments they almost a stable you can take the compounds and leave them in the air as good as crystal on solid insulation not mother solutions obviously but as a crystal on solid economic crystals of the compounds leave that we air for an hour or so come back and it's just a very thin layer of oxide material on this so really not terribly instance which is but certainly very stable as I say on some of these compounds that they don't decompose until 300 degrees Celsius when they do a disproportionate attention expects that generate magnesium metal and magnesium to compensate magnesium to compounds containing 2 of them against coordinated the magnesium sentences against you and in fact in 1 case the commitment sublime the company can sequence employment at a temperature of about 320 degrees Celsius going from being solid phase in the gas phase at this very high temperatures and wind conditions very stable compounds for what they are weak because of that we're looking at every activity where are we doing the reverse trying to reduce the steric of the compounds of the against coordinated to the dynamic fragments and that that makes them more reactive species so we try to find the limits of of balancing the a reduction in the steric a bulk of the league and to prepare stable magnesium 1 systems as opposed to a compensable disproportionate and we think we've done that now and we have had several compound types that set up a more reactive than the 1st systems that we prepared and we're using those as the reducing agents in the organic synthesis and the owner never metallic synthesis of things and we were also looking at trying to develop Kiraly against out to coordinate to the magnesium centers because we believe that on this might be able to give rise to an end to selectivity in the reductions that we carrying out of for example organic substrates and remember I said that a number of the products that we get from these reductions differ significantly from those the products that you get when you reduce the same substrates with with for example some into regions and so we think there's potentially using the systems for example in natural products since and that's that's another area that we're looking at no I think it
will it will develop quite rapidly and I'm sure the systems will be in the next generation of inorganic texts as as the 1st example of stable species containing low oxidation states from the ES block and the rights I think more than that I think they the chemistry will develop if we look at it we compared to the rapid development of low oxidation state people chemistry where that went and the applications those systems of funding I think we'll see a similar development in its block chemistry again it's that once the 1st realization that such species can be accessed and have remarkable and thermal stability and an oxygen was just ability then I think people will start to look at that at this area and indeed that's happening already found other examples of magnesium 1 compounds have been reported by Taiwanese groups and although they have looked for the chemistry versus India and indeed the 1st calcium 1 compound was reported last year by German chemist at best a house and do not emit it doesn't contain accounts calcium born but it's formerly accounts in 1 compound formed from the reaction of the highly activated calcium metal with trifle brands and this gives rise to assemblage which conflicts but we have a trifle benzene calcium on the top calcium and vitamins and th against calcium centers and is and the the bridging the gap is doubly reduced its apparent that existence obviously have some interesting reactivity doesn't really contain a true calcium Kelson covalent bond obviously we've tried to make such systems extend the chemistry of magnesium calcium and indeed to beryllium forming beryllium beryllium upon companies that industry obviously has its own problems with regard to the toxicity of Peruvian but we spent quite a bit of an effort to look at these compounds we haven't achieved yet we we think we know why that is so the moment we're developing I suppose the 2nd generation of ligand types to try and protect the eventual that metal metal bonds in the systems from attack this
communication that's that's the reason why we haven't been able to access Peruvian calcium 1 compounds with the least amount so that the magnesium magnesium bonds are about 2 . 5 Armstrong's it's been predicted that calcium calcium bonding and about 3 . 9 Engstrom said that very long and strong longer than mechanisms system and in the brilliant tasted much shorter that just a little over 2 so I I
believe the problem with beryllium is so far that the bond is too short in case a week when we have a popular game and attached to the Berlin fragments obviously when we reduced the that the league and beryllium highlight precursor that's going to generate a the league and beryllium radical Berlin 1 radical and 2 of those radicals linked to coupled to form the Berlin Berlin bonded system and and we've tried some some reductions and we see In the early stages of these reductions are very broad and deep blue collars to those reductions were almost certain that this is due to Berlin 1 radicals however the ligands using that don't allow the coupling of these 2 radicals to form Berlin 1 diamonds instead intramolecular ch activation reactions are going on effectively the Berlin radical is eating the and that's what gives rise to very complex reaction mixtures in in case we believe that begins on big enough so we reducing the the league and calcium highlight precursors and potentially the Thomas of forming but we have this very long bond accounts counts among about 3 . 9 and from it's also theory suggests going be weaker than the magnesium magnesium bonds using magnesium ponder about 45 tells them all I think the calcium Kelson bonds should that it to would so they're open for attack that also weaker so we need to protect those middle bonds upon formation so we're looking at more a three-dimensional again and if you like to 2 former Chubu Greece if you like around the magnesium around the constant constant belong to protected from attack and from the disproportionate but
think with respect to the reduction of organ metallic compounds used to generate low oxidation state lock systems in these generally involves the reduction of the gains metal highlight systems and the classical reducing agents that have been used for this purpose of the alkali metals that potassium metal certain mental quality metal or other systems like testing graphite and so these these reducing agents of firstly quite how much they have quite a quite strong reducing and they're also solids and so you're getting reactions at the surface of the metal potassium graphite so as not terribly control it's also sometimes difficult to deliver them still geometrically so you need to weigh out Sperry small amounts sometimes of of these alkali metals or testing graphite to stalking magically produce content was if you have an excess of these reagents you can perhaps generate the content you want that goes on to react further with the excess alkali metal that that is present so With the magnesium 1 systems firstly the I think the milder reducing agents the alkali metals there also soluble as they can do in coordinating role lies in on coordinating solvents solidly in Tolley wing where a lot of the precursor molecules are so you can carry out reductions at low temperature in a single phase with a milder reducing agent and he can still geometrically deliver electrons if you like to the substrates and I think that's the big advantage in systems and also the by-products so the period I kept inmates magnesium highlighted by-products of a dime Eric systems that can capture like the magnesium highlighted the light that's being generated and these these by-products are often I'm not very soluble so that precipitated out from the reaction mixture the Comptroller of the product and 6 crystal I think there more selective this story geometric model reducing agents and all these things together we like to call them despite producing while that of
course remains to be seen but I think we're just starting to get a hint of the potential uses of the money I they as I say they have we've now shown that we can prepare main group compounds with my group elements in a range of oxidation states not just 1 or 2 oxidation states and we can see that we can shuttle between those oxidation states for example in the reversible additional baffling to low oxidation state germanium systems as has been previously recently shown we can do the same with hydrogen and ammonia and other substrates we can use these compounds for catalysis and indeed this is starting to be shown already and manga compounds the so-called frustrated those newspapers that have been developed by adults Steffens group in in Canada and now being used as catalyst for example the hydrogenation of unsaturated organic substrates this this this is just the tip of the island but there are many many possibilities come I think and I think it's going to be
very optimistic we could say that I have paid lock systems could be used to replace many traditional catalysts in the future if this is the case then it will affect all of us because as we know everything around us is he's had some involvement with the transition of catalysts in their in their actions but of course it really does remain the same I think is also a good future for love oxidation states systems in I'm in the preparation of materials and the understanding of materials and just 1 example is the work of the National Bowling cultural values developed this huge the group 13 lost so he can form in clusters of for for example Aluminium atoms which contained 76 in 1 case in unit in his famous example 77 Aluminium atoms I think 57 of those only have Aluminium element a so it's effectively a blob of Aluminium Metal with an organic so what he's doing is is looking at how metal is building up
opponents promised deposition using these systems to model for example how medal was deposited in chemical vapor deposition processes which are important in microelectronics and another industry so I think it remains open to be seen what the future of this area is but I think it's a things quite exciting and I think even if even if some of the applications not realize the fundamental interest in the compound necessitate the use of the year future development having the rear of the US economy the head In the
Magnesiumhydrid
Stereoselektivität
Metallatom
Trennverfahren
Wursthülle
Verrottung
Hydroxide
Magnesium
Hydride
Konkrement <Innere Medizin>
Chemische Verbindungen
Lösung
Aktionspotenzial
Kristall
Isolierstoff
Spezies <Chemie>
Reduktionsmittel
Sterische Hinderung
Körpertemperatur
Reaktionsmechanismus
Nebenprodukt
Sekundärstruktur
Atombindung
Alkoholgehalt
Alkalimetalllegierung
Systemische Therapie <Pharmakologie>
Biosynthese
Hauptgruppenelement
Substrat <Chemie>
Biomolekül
Biologisches Lebensmittel
Hydrierung
Aktivität <Konzentration>
Oxidschicht
Reaktivität
Setzen <Verfahrenstechnik>
Mähdrescher
Energiearmes Lebensmittel
Elektronische Zigarette
Chemische Eigenschaft
Flüssigkeitsfilm
Oxide
Krankheit
Kompressionsmodul
Calcium
Chemische Forschung
Metallatom
Vitamin
Zusatzstoff
Magnesium
Ligand
Chemische Verbindungen
Computeranimation
Spezies <Chemie>
Atombindung
f-Element
Metallbindung
Systemische Therapie <Pharmakologie>
Metall
Reaktionsführung
Oxidschicht
Reaktivität
Querprofil
Setzen <Verfahrenstechnik>
Stromschnelle
Germane
Beryllium
Ligand
Pharmazie
Gap junction
Sauerstoffverbindungen
Calcium
Radikalfänger
Chemische Reaktion
Aktivität <Konzentration>
Wursthülle
Reaktionsführung
Komplexbildungsreaktion
Setzen <Verfahrenstechnik>
Magnesium
Ligand
Chemische Verbindungen
Azokupplung
Präkursor
Beryllium
Reduktionsmittel
Reaktionsmechanismus
Chemische Bindung
Systemische Therapie <Pharmakologie>
Diamant
Metallatom
Chemische Reaktion
Phasengleichgewicht
Magnesium
Chemische Verbindungen
Computeranimation
Kristall
Präkursor
Reduktionsmittel
Oberflächenchemie
Nebenprodukt
Vorlesung/Konferenz
Molekül
Graphit
Alkalimetalllegierung
Systemische Therapie <Pharmakologie>
Substrat <Chemie>
Kalium
Lösungsmittel
Elektron <Legierung>
Reaktionsführung
Oxidschicht
Organischer Halbleiter
Tieftemperaturtechnik
Redoxpotential
Bukett <Wein>
Chemische Verbindungen
Periodate
Insel
Biologisches Lebensmittel
Metallatom
Hydrierung
Germanium
Wursthülle
Oxidschicht
Ordnungszahl
Chemische Verbindungen
Werkstoffkunde
Ammoniak
Oxygenierung
Übergangsmetall
Atomcluster
Funktionelle Gruppe
Systemische Therapie <Pharmakologie>
Chemisches Element
Aluminium
Substrat <Chemie>
Hauptgruppenelement
CVD-Verfahren
Querprofil
Quellgebiet
Desublimation
Systemische Therapie <Pharmakologie>
Chemische Verbindungen
Chemischer Prozess

Metadaten

Formale Metadaten

Titel Questions about Low-Valence Chemistry
Serientitel Chymiatrie
Autor Jones, Cameron
Jerabek, Paul
Hegemann, Julian
Authmann, Andreas
Lizenz CC-Namensnennung - keine kommerzielle Nutzung - Weitergabe unter gleichen Bedingungen 3.0 Deutschland:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen und nicht-kommerziellen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/18755
Herausgeber Paul Jerabek, Julian Hegemann, Andreas Authmann
Erscheinungsjahr 2010
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Chemie
Abstract During our recording session with Prof. Jones (Monash University, Australia), he was so kind to answer a few additional questions concerning his research area. His answers are shown here.
Schlagwörter Vortrag
Anorganik

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