 Welcome to this course on Transition Metal Organometallics in Catalysis and Biology. In this course, we have been exploring the depth and the breadth of organometallic chemistry, particularly with regard to the applications of organometallic compounds in large scale industrial processes. In this context, we have looked into various types of organometallic reactions, which have been practised in large industrial scales, and to start with, we have looked at the repicamistry, which is the conversion of C2 feedstock or acetylene to other functionalised forms. So, after repi, we have been looking into another very interesting reactions, which is olefin metathesis. We have looked at olefin metathesis followed by alkyne metathesis, and now we have been discussing about cross metathesis reaction, which was taken up in the previous lecture. Now cross metathesis reaction, as we have been discussing, has been developed in conjunction with the industrial process, particularly SHOP, which is better known as Shell Higher Olefin Process, and which was mainly used to utilise unwanted feedstock from this SHOP alpha olefin oligomerisation process. Let me just illustrate this, or Shell Higher Olefin Process would convert ethylene to alpha olefin using nickel catalyst. Now, these alpha olefins were primary source, which was from ethylene feedstock, and this was used or had used for making, had requirement making soft detergents, which has long chain fatty alcohols. Prior to these alpha olefins, they were accessed through cracking, as well as hydroformylation of alpha olefins, and they were synthesised from other methods. SHOP provided an easier and convenient access to this alpha olefin, other than the prevalent method of cracking or from alkyl halide sources, that gives alpha olefin, and then the hydroformylation acts to this. This was a better method to get alpha olefin, but the only problem which arose was that it was churning out alpha olefins of various fragments from C4 to C12 to C18 to C22, and so on. So, a large range of oligomers were obtained, and this was best represented by the Schultz flurry distribution C12 to C18, and the distribution was something of the type of this. Now, as for the requirement for detergent was in this region, which is about 40 to 50 percent, and they were for making detergent range. So, cross metathesis was then successfully crossed metathesis, actually cross metathesis followed by isomerisation, another reaction, so cross metathesis as well as isomerisation was used to convert the unwanted lower fragment and the unwanted higher fragment to make something of within the range of C12 to C18 for the use in soft detergent applications. So, this is where the cross metathesis reaction came into being applicable for using the distribution of alpha olefin, which otherwise at that point of time was not usable for any commercial purpose. So, this was an interesting development, which was practiced in a large industrial scale way back from 1977 in the shop plant, and this shows how this cross metathesis reaction was employed in large scale for commercial purpose. So, I am going to illustrate this cross metathesis has been used to shell higher olefin process in industry since 1977, and this is given nicely by this reaction, which is a C4 fragment plus C10H21, this is C22 fragment in presence of molybdenum trioxide, it is molybdenum oxide catalyst and L2O3 giving two of these C13 fragment, and this was actually both E and Z mixtures were obtained, and as mentioned that the process actually involved the industrial process involved indeed a three process combination of oligomerization, isomerization, metathesis reactions. Now, these three processes had been discussed in detail in our previous lecture, and the reference for this is by an article by Wilhelm Keim in Angukem International Edition 2038, 5212492212496. The catalyst was MOO3L2O3A for cross metathesis reaction, and then as we had observed that metal carbene species are usually involved in metathesis reaction, then the question which comes to mind that how does a metal oxide in terms of molybdenum oxide carry out cross metathesis. So, there is an interesting question in the sense that for the cross metathesis large scale reaction, the pre-catalyst was originally used as molybdenum trioxide, and it turns out that the active catalysis species of molybdenum carbene is generated through the following reaction as shown below. The active molybdenum carbene species is generated at the catalyst surface as depicted, and this is shown by the equation given here, this is molybdenum oxide reaction with olefin giving the molybdenum carbene species as shown here with the bound ketone, and this is the active species, and this is the pre-catalyst. What is seen over here is that the pre-catalyst of molybdenum oxide reacts with an olefin to generate the active species along with the metal carbene, along with the ketone, and this active molybdenum carbene species then it carries out this cross metathesis reaction, and this cross metathesis reaction had been developed with the intent to use the higher and lower alpha olefin oligomers to produce mid range alpha olefin oligomers, which could be converted to detergents like fatty acids or fatty alcohols as required through the process of another important industrial scale organometrics reaction, and which is hydroformylation. What we see is a chain of reactions, all of them are performed in large industrial scales, and they are effortlessly used for converting one feedstack to another to finally what is the valued target that is being achieved, so hydroformylation alpha olefins, which is of the range C12 to C18 would give fatty alcohols detergent applications. So, one thing to note here is that right now it may seem that something as trivial as application in detergent industry was brought about such utility of so many different reactions, so many different nice organometallic reactions for the large scale production of the feedstock for detergent industry. What we see is that the organometallic chemistry can cater to all aspects of societal need be it from detergent to polymers to so on and so forth, and all can be brought about by applying a very intriguing set of organometallic reactions. So, here we see that how cross metathesis along with isomerization, shop and hydroformylation four processes practiced in large scale would finally give a feedstock for producing detergent for the societal market. So, with these let me just talk a bit more about the advantage and disadvantage of cross metathesis reaction, and what it turns out is that the limitation of cross metathesis reaction arises due to the non selectivity in products in terms of not being able to exclusively form one of the products whether that be E or Z. So, one of the limitations of cross metathesis reaction is that both E and Z products are formed in a mixture and that gives rise to less selectivity in product formation and hence in more challenges in product isolation. So, this I will state by the equation as is given below cross metathesis has limited applications due to the formation of mixture of products like branching, like branching, homodimer is the mixtures. So, this is given by the equation as is shown here catalyst C2H4. Now, the cross metathesis of these two catalysts can result in so many different products as is shown here R2. So, it can be R1, R2 and that can be easy mixture and that is given by this veg bond plus R1, R1 this is a homodimer again easy mixture plus R2, R2 is a mixture. So, the drawback is what we see that the selectivity is less that all of these come at both easy olefinic mixture. This is the real cross metathesis product and so, this is the cross metathesis product and these are homodimers. So, the selectivity is a key issue of cross metathesis reaction and hence one of the important challenges is the ways to increase the selectivity of cross metathesis reaction challenges is to devise ways to increase the selectivity cross metathesis reaction and in this regard important is to mention that Grubbs find a way of increasing the production of heterodimer while starting with the homodimerization first. So, this is nicely illustrated by the equation over here Grubbs reported increased yield of heterodimer one of the starting olefin underwent homodimerization. This is best shown by the equation given here. So, R1 Grubbs catalyst. So, the first step is elimination of ethylene. This is nothing but a homodimer. Now, when this reacted with R2 which also eliminated ethylene then R1 which is a heterodimer. So, the point to note here is that in this sequential two-step process of introducing the olefin sequentially Grubbs reported increased yield of this heterodimer. So, this is one way of improving the selectivity of this cross metathesis reaction. Then the other way of increasing the selectivity of cross metathesis reaction is partially by carrying out the reaction through immobilizing by immobilizing one of the coupling partner. This is best given by this sentence the selectivity of cross metathesis can be improved by immobilizing one of the coupling partners coupling olefin with a polymer so that the cross metathesis product remain there and the soluble homodimer metathesis product is separated out. So, the other way of increasing the selectivity of cross metathesis product is by immobilizing one of the olefin so that the cross metathesis product remain in the polymer and the soluble homodimer product is separated out. So, with this I come to the conclusion of today's lecture. In this lecture we had looked into the application aspects of metathesis reaction with regard to the shop olefin polymerization process and what we had discussed is the fact that all these large scale industrial reactions have been used for making feedstock for soft detergents or fatty acids and how cross metathesis was developed to utilize the non-usable alpha olefin fragments of low and high molecular weights to produce alpha olefins of medium range molecular weight which could be used for applications as detergent. We have also looked at the issues which remain which play cross metathesis reaction and one of the main issue is the selectivity issue of selectivity because the metathesis does not distinguish between the two isomers E and Z and both are formed in the mixture for each of the products like cross metathesis products as well as homodimer, homometathesis products and then we had also looked at various attempts been made to overcome this lack of selectivity issue and two such methods that we have discussed is one by professor Grubbs who had reported increased yields of cross metathesis product by allowing homometathesis of the first olefin followed by the introduction of the second olefin to give the larger amount of the cross metathesis products. We have also looked at another strategy that implies immobilizing one of the coupling partners on a polymer so the cross metathesis products stay on the polymer surface whereas the soluble homodimer metathesis products are separated out. So, with these we come to conclusion of today's lecture we are going to be talking more on the aspects of cross metathesis as well as some other olefin metathesis reaction particularly the admitt reaction when we take up our discussion in the next class. Till then, goodbye and thank you.