Modern Main Group Chemistry


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Modern Main Group Chemistry
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Jones, Cameron
Jerabek, Paul
Hegemann, Julian
Authmann, Andreas
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Paul Jerabek, Julian Hegemann, Andreas Authmann
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Prof. Jones (Monash University, Australia) talks about new approaches in the field main group chemistry.
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I don't know the they are around Of course I'm not sure we've been
involved in low oxidation states Maine group chemistry probably for 15 years old and in about 3 years ago and we began to wonder if we could extend this slow oxidation state chemistry of the people governments to be best locker rooms and nothing done before there were no examples of compounds containing 2 S block this block elements or to Hezbollah elements bonded to each other violently and we wondered if we could perhaps extend the chemistry the well-known chemistry blocks of agents that the people competence to this area and I suppose again this harks back to my undergraduate days where where I was looking at the at the formation of a new green reagents and and thinking about the mechanism of formation of Grenier reagents and the fact that magnesium magnesium bonded compounds had been proposed as intermediates in the formation of a new reality so we want to see if we could actually make such systems and we had we Jerusalem inspiration I suppose from another landmark study in 2004 by a Spanish chemist the minister Carmona Mendez to to prepare the 1st examples of zinc zinc on the competence formerly compounds containing zinc in the past 1 observation started in type and surprisingly he made these compounds of this particular compound which has has a seizing upon the teasing centers a coordinated each by painting therefore sought paint dying all began a book began to stabilize this system toward that is disproportionate nation but latest contacted by accident and 1 of the reagents that used in its preparation was titles the same company that Franklin alienating its intact so given the chemical similarities I suppose between zinc Group 12 medals and magnesium group to middle and and the fact that as examples could be stabilized we then thought well maybe we could use some of these some of alcohol people against the we'd had developed to stabilize low oxidation state people content for example gallium 1 compound germanium 1 continent and maybe these compounds could kinetically stabilized magnesium magnesium bond system and that's what we set out to do and that the main began talks that we used were died of serial killer lighting insulating model and ionic began systems such as the Baltic wanted tonight against which we developed in a laboratory and also beat kept Michael against which we found had similar stabilizing properties to help Baltic 1 of so we began by preparing magnesium to precursors to have target magnesium 1 compounds and these were magnesium iodide systems containing or incorporating the bulky quantitative writes all the care ligands we simply started by trying to reduce the systems with testimony at room temperature and to our surprisingly early experiments we managed care these magnesium magnesium bond since I think if we if we if we didn't have results early on we might have abandoned the study because we thought intuitively that these systems would be pretty hard to stabilize and pretty hard to to eventually access but that proved not to be the case so we managed to prepare a range of such systems they are quite reacted as you might expect of a not terribly air and moisture since this season against that we've used to stabilize them really to protect them from oxidation and hydrolysis Mary remarkably fairly stable theoretical studies have suggested that the magnesium mechanism farms in these systems are quite strong but must not remarkably so that 45 killer tells all that these compounds in some cases can be stable at 300 300 degrees Celsius which lost seemed really quite remarkable and we once we had prepared these compounds we thought we had we must really prove that we have magnesium 1 this is that the quarter of the claimant would not look good if we were wrong and so we spent long time trying to prove that the systems had magnesium magnesium covalent bonds and I'm not gonna go into what we didn't do that but we managed to do that and we published the work of finger last week of 2007 in science and after that time we thought well we we now have the systems we really must look at the further chemistry and their properties and really this work is still in its infancy but we have looked in some detail using experimental and theoretical techniques to try and analyze the metal metal bonding and the systems and again this work is only in its infancy but we've used a DFT calculations the theory sense an experimental charge density studies in experimental since this technique allows you effectively to see the electrons between the magnesium centers and and this shows that the system is do indeed contain magnesium magnesium covalent bonds albeit with rather diffuse electron density between the magnesium standards that is we believe that we can fall and said I we've also found this although there is electron density between shared between the 2 mechanisms as is really quite a few in fact very diffuse and and this has led to some strange properties for these compounds the magnesium magnesium bone is what we call deformable we can we can stretch it's quite significantly for example by coordinating the magnesium centers by other Lewis bases we can stretch the bonds by up to about 8 per cent so we can elongate and from about 2 . 5 inch drums in the uncoordinated Thomas to about 3 . 0 5 extremes in the quarter on which is which is a remarkable longer-range so that's 1 area that we've be looking at would also be looking at the use of magnesium once systems as reducing agents obviously with this elements in this unusual oxidation state you would expect that these dire merit systems would be able to deliver electrons to substrates and we are indeed looking at that with respect to their use as what we call the spoke reducing agents in both organic and will get a metallic synthesis so in organic synthesis we've shown that these dire Merit systems connectors very facile 2 center to electron reducing agents they can deliver if you like to electrons variously to unsaturated organic substrates will look at the many reactions and we found that we can we can induce carbon-carbon bond forming reactions nitrogen oxygen bond forming reactions we can carry out oxidative insertion reactions we can carry out reductive cleavage reactions and we've seen a whole range of reaction types within organic synthesis is if you like using these mechanisms wants this and I think most importantly many of the products of these reductions differ from those that you obtained by reducing the same substrates with more classical reducing agents used in organic synthesis such as Samarra to reagents and alkali metals and because of this we think that there is a potential use of the systems selective producing agents in organic synthesis and we are developing at the moment in collaboration with with organic chemicals With respect to in inorganic chemistry and were also investigating the use of these systems to as I was reducing agents to access a
previously unknown examples of low oxidation state the complexes so using these magnesium 1 reagents to try to prepare the systems that got us into this area in the 1st place without a quite a bit of early success in just 1 example of a compound was published but I think uh late 2009 we took and then hit psychic Cobain add up of germanium .period simple compound and we reduced without magnesium 1 compared this this stuff I worked and has generated a magnesium to Chloride system but the byproduct in the system was and was a compound containing 2 and had to start with operations coordinated to it you may need to correct no other substitutes and remained for this compound contains germanium in 0 oxidation states very unusual compound you could think of it as a soluble source of these elements of the moment we try to extend it to other elements in the people off and indeed in the block and we can see the NAC Addax all the elements if you like a soluble sources of those elements that can be delivering those elements to other reactants in synthesis and this is something that would really only just begun work
on there are a number of other groups working on this area chemistry around the world Greg Robinson's group in Georgia for example is really his excellent work got us into this so that's another area of chemistry that we've been looking out without magnesium 1 compounds the other main area that we are looking at is is using these magnesium 1 compounds as soluble model you like to examine the mechanisms for potentially examined the mechanisms in the kinetics of the hydrogenation of magnesium mess so magnesium metal reacts with die hydrogen to give magnesium hydride this is an important reaction it's a reversible reaction and it's important because magnesium .period hydride contains about 7 . 7 per cent by weight height hydrogen and so always finding used as a hydrogen storage system in a number of devices such as such as fuel cells so it's irreversible hydrogen storage system in the in the year the rapidly developing hydrogen economy subsystems .period important that this hydrogenation of magnesium metal To get magnesium hydride has problems in its it has Connecticut problems the kinetics of slow infecting made a temperature of about 300 degrees Celsius to hydrogenated magnesium and the hydrogen magnesium hydride unit at 300 degrees for greater than 3 resources as well so really it's obvious that you can use the systems and portable devices and so a lot of work is being carried out to try and improve the kinetics of the hydrogenation of magnesium metal for example by doping with transition metals allowing it with people of medals for example Al-Amin and this tends to work in some cases and the hydrogenation temperatures of magnesium alloys having been reduced into the hundreds of degrees which is a usable ranch but it's not really know what the mechanisms all the reasons behind the improvement in the medics of the hydrogenation magnesium and so we're beginning to what we beginning to wonder if we can use magnesium 1 systems of soluble sources of magnesium if you like to try and look at how the magnesium use hydrogenated in the presence of and in the presence of other metals and this is an area that we have looked at in the last 6 months or so we haven't published anything on it yet but hopefully we will be sending from more than you can do well enough to release that's all I wanted to talk about it I wanted to give you just a bit of an overview all of them this rapid development in manga chemistry in the last 30 years or so I think it's gone from being a rather staid and perhaps boarding area of chemistry to what I think is 1 of the most exciting areas of and rapidly developing areas of organic chemistry that is starting to die and I think this on this 1 renaissance in Lanka chemistry thing Intel is 1 lesson that is as chemists when we see rules in textbooks maybe we should question those rules because if we do question those rules that we can and we proved that they are they shouldn't be rules then we can access new areas of chemistry very interesting new compounds which have potential and and if they don't well they have enough fundamental fundamental interests to keep us excited talk Our it
was like that


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