Free Chemistry NEET Video Lectures for Coordination Compounds

00:00:01 [Music] [Music] [Music] good morning everybody so in this chapter we will be talking about our coordination compounds compounds and again there will be six classes so today we will basically introduce what we basically know about the different coordination compounds and the name basically about this coordination compound because all we know that there are chemical compounds as well so like that of our sodium chloride magnesium chloride all we know that they are typically metal salts and at the same

00:01:34 time we can consider them there as inorganic compounds so this is one example of an inorganic compound of sodium ion and second one is also an inorganic compound of magnesium ion but what else to be there which can define another group of compounds which will be calling as the coordinate compound or the coordination compounds or the complexes so in coordination compounds we will have a typical coordinate bond here in this class of compounds what we see that they are having ions in a plus c l minus

00:02:19 and at the same time magnesium two plus and two cl minus so they are packed in the lattices so they are forming some ionic bonds and these are ionic compounds and compared to that if a particular compound having some coordinate bond and coordinate bonds all we know that is particular bond is also known as a deity bond through some donation of electron charge so very simple molecule what we can consider to our life from the very existence of all life also and anywhere we know that this water molecule simple

00:03:09 water molecule and the covalent structure that means is the covalent molecule we all know and only there is partial charge separation as we all know that this is delta plus this is delta minus and this is also delta plus and this is also delta minus so basically what we find that dipoles are created along this o h bond and another one is also along this o h bond now if this lone pair of electron can be utilized for some bonding interaction to any species like say any metal ion so it is a particular donation unlike

00:03:53 that of shearing or the ionic compound formation here we have the two lone pair of electrons forming a bond between o and m that means we can have a om bond so what we are considering over here is a typical o m bond so o m bond if that particular o m bond is a coordinate bond or a dative bond where the lone pair of electrons utilized for the formation of that particular o m bond is coming from the oxygen atom of the water molecule so this oxygen is from the water so this is coming from the typical water

00:04:32 molecule so then if we can have at least one such interaction with that particular metal center or the metal ion center it can be a transition metal ion or a non transition metal ion as well so we can consider that we are just leading towards something where we are able to get some coordinate compounds or coordination compounds so that is there if we can see where we are able to develop a particular chapter which is devoted to coordination compounds and it is typically a backbone or spine or is the main thing

00:05:15 for modern inorganic chemistry so the latest one because is typically developed during the last 120 years so this particular development is say for 120 years following al fred noble alfred warner so alfred verner so alfred verner studied all these compounds during 1890s so and that particular type so during this last period that means we get the period where we can isolate the elements before that then when we identified that means the discovery of the elements we discovered the elements and afterwards we can put them in the

00:06:15 periodic table their positions and their electronic configuration structures and everything we studied in detail but this particular concept during the last 120 years has been so useful that the modern dates coordination chemistry is basically devoted to typical inorganic chemistry also so any inorganic compound if we just consider that we have a simple metal salt m is there having a charge of m n plus and that is a typical salt so what type of salt we know that the from earth crust we get something as the oxide

00:06:58 hydroxide or carbonate or sulfide ores and minerals so oats and minerals when we treat it with some mineral acid so acids are given and those acids are providing the corresponding anions so these are the anions which are coming from the acids during the treatment of these ore and minerals for isolating a typical metal salt cy nickel sulphate say iron sulphate or copper sulfate if we want to make because the copper will be present as copper two plus and the corresponding anion will be present as the

00:07:36 corresponding anionic salt but once we make that particular salt as i told you earlier that we can go for the corresponding solution that means we put that particular salt in water so we are putting that metal ion within water so all these informations and all these understandings can be there how our m n plus will be staying inside these water molecules in the solid state as well as in the solution state and sometimes if these salts in terms of the corresponding anions as isolated as the hydrates

00:08:19 that means dot n h two so if we isolate them as the hydrate so this how these water molecules are interacting with these soles as well as the corresponding ah metal cations also so this is also the very important thing that means the very backbone of our bioinorganic chemistry that means this particular thing that means the biologically if we have say iron we all know that iron in a particular oxidation state it is there in our blood where it is present it is present in our hemoglobin or it is present in our

00:08:58 myoclobin so the presence of this iron in form of a coordination compounds is also there in biology so that will see that how useful they are in studying the presence of iron as coordination compound in some biological species and it is also very useful in different chemical industry because chemical industry all we know that is very much dependent on the presence and usefulness on some good catalysts so catalysts will be there and those catalyst if they form some coordination compounds they can also be useful so

00:09:45 different types of organic transformations the industrial chemistry is not only devoted to inorganic industrial chemistry but it can be for organic industrial chemistry the medicinal industrial chemistry or the pharmaceutical industrial chemistry where you simply use some of these important coordination compounds say one important thing is that hydrogenation we all know that hydrogenation process can be utilized or can be done utilizing some randomical type of thing where the nickel is present as

00:10:19 nickel 0 and it is activating the hydrogen gas and that can be hydrogenated so what we see here that instead of that nickel as nickel 0 we can have some nickel complex or any other metal ion complex which can also be useful some useful for some specific hydrogenation reaction so these compound that means the coordination compounds will be useful for chemical industry as well then also we see that how these can be utilized for the different pigments this is also an application part so pollution blue all we know

00:11:01 and the oriolein is also another compound and the algerine red dye these are the three examples again have been taken from your cbse book so everything is there so what is this prussian blue definitely this color is highly intense and that prussian blue can be utilized as paint but why this is colored because of the when we study everything but this particular formulation because once we know the compound and its color and its usefulness then only we can immediately say what should be your corresponding formula

00:11:35 this is k f e f e f e c n whole six so what is that or this particular part that means some part we are writing in square bracket which is fe c n whole six so nature of that particular thing we just try to find out similarly another yellow compound yellow pigment which will be there which is oriolein which is also a cobalt compound and in this particular cobalt compound what we see that this is no2 this is no2 that means nitrite ion is there so nitrite can function as a ligand around covert so typically what i just told you that if

00:12:15 you have the corresponding anions which are coming from the mineral acids you get the simple sorts that of your ferric chloride nickel chloride or copper chloride as cubric chloride so chloride anions are coming from the corresponding mineral acid which is hydrochloric acid but if the corresponding anions are different here it is cn minus the cyanide ion here it is no2 minus the nitrite ion still we get some coloration for the presence of those anions as well as the corresponding central metal ion

00:12:50 but these are not very simple or the corresponding simplest possible example what we know for the corresponding metal salts these are not metal salt here we have written in square bracket here also we have written some part in square bracket and afterwards we will see what is that interpretation for writing these in terms of the corresponding square brackets will find why they are so colored and how they are utilized for the pigment another example is an algerine red dye which is nothing but an

00:13:20 compound of anthraquinone but the example of this red dye is telling us that we have something that means it is not the typical 1 2 dihydroxy 910 and we all know anthracene we all know quinoan so it is anthracene based quinone okay so and its two and one and two positions are also hydroxide groups so these hydroxide oxygen and this anthraquinone oxygen can be utilized for the formation of the coordinate bond to what to the aluminum aluminium has aluminium three plus so red lake or red dye is a billion red

00:14:00 coloration is only formed when it is forming a coordinate compound or a coordination compound to aluminium only so this can be utilized as again a red pigment so these are the typical example one is blue and there is yellow and another is red so these three useful colors we occasionally use all of them the way i have told you earlier that means ah the lead chromate how we can use in printing school buses so this is some red dye but the red dye is only obtained when we utilize this aluminum and aluminum is forming some

00:14:36 coordinate compound with this so we will define this one two dihydroxy 910 and sucuquinone as something where the oxygen atoms like our water molecules having lone pair of electrons can form bonds to the aluminum center and this is one more good example that we should not confuse ourselves that all the coordination compounds are forming from only the transition metal ions that means the 3d 4d and 5d elements it can be with other metal ions where you have filled d orbitals like zinc cadmium and mercury

00:15:16 similarly it can be with magnesium it can be with calcium and it can be with aluminum also so algerian red dye which is forming something that means the calcium you can have the calcium dye you can have the aluminium with the aluminum die so bound metal ions are important that means these are all present in the anionic form the cyanide is present as the anionic form that means the cyanide ion nitrite is formed as the nitrite ion similarly this anthraquinone hydroxy anthraquinone if they go for depotonation and hydroxy

00:15:49 groups are present as o minus of the phenol unit then it can bind either calcium or aluminum or both of them together to give some a red dye compound so the coloration again is due to the formation of this coordination compound so what we come to know from here is that the usefulness of this coordination compound where the different color we can generate due to the presence of these metal ions which is forming a coordinate compound or a complex species what is that because this metal atoms are ions so here iron cobalt calcium

00:16:27 aluminum all of them are present as metal ions but in some other cases also we will see that we can have the metal atoms also like nickel zero the nickel zero as just now we are discussing about our ranny nickel where the nickel as the fine powder having a very small size those are nickel atoms but those nickel atoms if it interact with some other species like carbon monoxide we all know that nickel can form very good compound where the nickel zero in zero oxidation state can bind to four carbon monoxide molecules so carbon

00:17:03 dioxide molecules are gaseous compounds so if the gas is bound to the metal center where the metal is in the zero oxidation state but due to this thing that means due to this definition the metal atoms that means the nickel atoms are bound to a number of neutral molecules here the carbon monoxide is the neutral molecule so that species which is forming out of nickel zero and the carbon monoxide is also termed as a coordination compound so it is not that the metal ions like iron in fe3 plus or covalent in cobalt three plus or calcium

00:17:39 in two plus or aluminum in two plus but the middle in the zero oxidation state as metal atoms can give rise to the coordination compounds and in the biology that means in bioinorganic chemistry what we study is basically we all know the typical names from our school days what is chlorophyll we all know we can define we can say the function we can so is reactivity similarly just now i told you about the hemoglobin and the vitamin b12 why they are important in terms of the coordination compound because they are

00:18:13 again a chlorophyll by definition is also a coordination compound hemoglobin as well as myoglobin which is present in our blood is also by definition a coordination compound similarly vitamin b12 is also a very interesting coordination compound where cobalt is present and not only a naturally occurring bioinorganic coordination compound but is also having some metal carbon bond is giving so it is a bio organometallic compound also so b12 is a vitamin b12 is also a bio organometallic compound of cobalt

00:18:51 so you have magnesium so if we if somebody asks you to identify the metal ions present so chlorophyll will be having magnesium hemoglobin or myoglobin will have iron and then vitamin b12 will have cobalt so we see that the typical definition a standard textbook definition we should always keep in our mind like knowing the periodic table what is then your coordination compounds so it basically contains one or more complex ions which is very important so afterwards we will define also like just now we have seen

00:19:30 that we can write a compound like k 3 f e c n whole six and from our school days we all know this is potassium ferry cyanide where iron is present in plus three oxidation state so this potassium ferric cyanide so this is the part which we write in square bracket is the complex part so this is again a compound so this is again a coordination compound it has a complex part so this part that on the right hand side we have a complex part so complex part is an ionic and the charge is balanced by the simple

00:20:20 potassium ion because the whole charge on this complex species is three minus so for potassium ferric cyanide you require three of the potassium ions to balance this particular charge the way we write we all know that the aluminum trichloride aluminum has a tri positive charge for charge neutralization we require three such chloride ions to balance it similarly this anionic coordination compound is trianic so we require three potassium ions to neutralize its charge overall this coordination compound is a

00:20:56 neutral one so is a neutral coordination compound and sometime you also see that this particular part that means the cationic part can also be a complex part similarly the anionic part can also be a cationic ah complex part so these two parts so this is complex and this is also complex and together these two we call them as your coordination compounds so that tells us that one or more complex sun which is important one or more complex science where we have the more complex ions that means at some time we can have both

00:21:40 the cationic part as complex entity and the anionic part is also a complex entity where we find that a small number of molecules or ions surround a central metal atom or ion just now the examples what we are looking for is that a small number of molecules so this what are those small number of molecules that means it can be your water molecules or it can be your cyanide ions so small number of those molecules or ions surround a central metal atom or ion usually of the transition metal family it can be

00:22:18 usually 3d 4d or 5d metals but it can beyond those transition metal ions so in a typical form either it can have the atom like nickel tetra carbonyl nico whole four will just discuss afterwards in detail or you can have k three fec n hole six where the cation is bound to some anions we get the coordination compounds and these coordination compounds also by definition they are very useful depending upon the number of groups the small groups number of small groups attaching to the central metal atom or ion

00:22:57 we get different coordination geometries so that we will just elaborate also these are the typical definitions how we define a coordination compounds and will be able to get a corresponding linear tetrahedral square planar or octahedral geometry so personality is very high apart from your typical organic chemistry where you know that the carbon center we have restricted geometries carbon can be planar carbon can be tetrahedral not beyond that but here we see that from a linear arrangement to a octahedral arrangement

00:23:29 a metal ion a specific metal ion can extend its geometry during the formation of your coordination compounds and not only our application in modern day inorganic chemistry by inorganic chemistry or industrial catalysis it has also some application in electroplating if we go for fine plating on some surface textile dye just now we have seen the corresponding ah dye for based on calcium or aluminium and in the medicinal chemistry some of these metal complexes or the metal compounds are very good ah

00:24:09 as the pharmaceutical history like overseas platinum which is a platinum based anti-cancer drug so when we go for these that means when we go for this processing we use a variety of metallurgical processes also that means the identification or the isolation of silver isolation of gold we use the cyanide as the typical process the cyanide process is basically based on the corresponding formation of the coordination entity or the coordinate species in solution then just now we discuss the industrial

00:24:44 catalyst and some analytical reagents so just now what we have discussed about that corresponding dye which is for giving you color to your calcium or aluminium so that can function as a very good reagent if that particular compound the anthraquinone that one two dihydroxyanthaquinone compound if itself is not so strongly colored in the anionic form when it is bound to aluminium or calcium we find that the color intensity is increasing and we get basically red dye dye is all are very colored very much

00:25:23 colored is a pigment what you use as a pigment or the dye the intensity for those colors are very high so what we can utilize it because it is not ah we will not be able to discuss all these in detail so this is the right time where we can say you about this analytical reagent so that particular reagent that anthaquinone dihydroxy anthraquinone can function as a very good analytical reagent to detect the presence of calcium ion or the aluminium ion in any unknown solution because the calcium ion or the aluminum

00:26:01 ion when it is present in aqua solution or water medium it is colorless as we put the reagent that reagent will develop some beautiful that red lake usually we go for the in the corresponding semi micro quantitative analysis even a spot plate the spot plate analysis is also very useful though in a drop of those reagent can give rise to some beautiful coloration or the lake formation for identification because you can have the shades of those two colors because when both of them are present together

00:26:37 it has a different color when only aluminum is present it has another color or when calcium is present though they are very close by but we can identify those coloration by knowing the thing the color that what particular coordination compound it is forming so in this particular analysis so analytical chemistry finds is typical application during the formation of these coordination compounds so we will now take the example of some ah compound which we all know from your laboratory classes also which is our

00:27:12 more salt so this more salt we consider it as a salt and we are asking ourselves whether we can level it as a coordination compound whether some coordinate bond is forming over there and when it is more salt we tag we definitely know that it is a ferrous compound of iron so more salt iron is present so there will be some small molecules or anions present also along with that and whether that particular anion or small molecules forming some coordinate bond to the iron center or not that will define whether your mod salt is a

00:27:58 coordination compound or not and analytically also we find that this more salt which is ferrous sulphate ammonium sulphate six water molecules since the name of this compound is ferrous ammonium sulphate or it is a double salt of ferrous sulphate and ammonium sulphate along with six water molecules of crystallization so it separate out or it crystallize out from the medium nicely as this formulation center dot is given so that's why these are all packed in the crystal lattice so there is no such interaction

00:28:36 with the iron center with that of your ammonia or the ammonium ion so we should be very much careful that no such coordination of ammonia as ammonium ion or ammonia as nh3 is to that of your iron center similarly another example is that your potassium alarm or potassium we call so which is potassium aluminium double salt so the potassium sulphate as well as aluminium sulfate double salt so double salts are two salts together they co-crystallize so is a co-crystallization process and in a single entity they are

00:29:09 crystallized out and they have the typical identity that when they dissolve it in water it can dissociate into the simpler ions so when we dissolve potassium ah salt of this that means the potassium alarm or the more salt what we get the more salt already i told you that this more salt we have fe two plus in the system similarly in solution whether this coordinate bond is present between iron so what we are expecting this ammonium ion we are expecting that means whether we can have a typical interaction like this

00:29:52 or when you dissolve it this can form or not so this can be derived from your ammonium ion so water can sometime be very useful to get this whether this is forming over there and the resulting some complex entity or the complex species is there which will not dissociate all together in the medium as fe as a v 2 plus or ammonia as the neutral ammonia molecule or ammonium ion but in actual practice when more salt is dissolved in water we are able to detect the presence of all all the cations and all the anions

00:30:36 what is present over there in the salt ammonium ion and the sulphate ion and large number of water molecules so will be about able to detect the ferrous ion will be able to detect sulphate ion will be able to detect ammonium ion not that will be getting something where we have the corresponding presence of these ah ammonia as this ammonium ion or some complex species so no complex species is there ammonium ion is also present as ammonium ion which can be detected over here as ammonium ion so is not a coordination compound it is

00:31:13 typical an example of a double salt so more salt like these salts are all double salt so will not get that but just now what we have told you that we are having potassium ferric cyanide now then another example is potassium ferro cyanide which is instead of k three it is now k four efficient whole six but this particular species if we take and if we try to dissolve it in water will not able to detect the presence of ferrous ion but the salties of ferrous will not be able to detect ferrous and in the medium or the cyanide in the

00:31:54 medium which is also highly poisonous so this particular part which is written in square bracket nowhere here we have written anything in square bracket so this part which under this square bracket thing we get that this particular entity due to the formation or due to the reaction or due to the bonding between iron and cyanide iron as ferrous and the cyanide ion forming a coordinate bond giving a typical entity or a separate entity whose nature is completely different which is the corresponding ferrocyanide

00:32:28 and ion so ferrocyanide anion is the corresponding complex species so we will able to generate something which is a complex compound so this is some typical example so this is the anionic part which is complex one similarly when we get this one which is the cationic part which is six ammonia molecules are bound to the cobalt center which is the cationic complex species here that is the example where we are saying that both cationic part as well as the anionic part are the complex pieces but we get the

00:33:00 corresponding coordination compound where the copper part is the cationic part and the platinum part is the anionic part similarly this compound that the medicinal value just now i told you can be your sis variety where two of these groups that means the same groups that means the nitrogen from the ammonia are 90 degree to each other as we know in the definition for in the organic chemistry the cis definition and the trans definition if this particular coordination compound has a geometry of a square plane

00:33:33 so if the cis variety is the corresponding medicine which is known as cisplatin but the trans variety is not so isomerism will also tell us or dictate us the very usefulness of those compounds but here also we see that three examples this is the cationic example of the complex part this both cationic and ionic and this is the neutral part for this corresponding compound so we should always be very much careful the nature of these compounds so nature of these compounds how we identify those natures

00:34:05 so these are typically the different salts so when you dissolve it in solution or water we find that this can be separated as the cationic part and these are the anions as three chloride ions so we can detect the number of chlorides you can get from this particular salt similarly here we are not able to get any chloride from these compounds whether it is present in the cationic part or the ionic part and obviously it is present in the corresponding ionic part but this chloride you cannot take out

00:34:38 so this has a typical example for the reactivity pattern or the reaction pattern if we try to immediately detect the presence of chloride similarly this will also behave differently so all three compounds if we try to treat it with a dilute solution of silver nitrate which we all know that silver nitrate is the reagent where you can detect the presence of chloride ion in sodium chloride say in aqua solution so if a aqua solution of silver nitrate is also added we get the precipitation which is very sparingly soluble or also also also

00:35:24 sometimes we say is insoluble if the volume of the medium or volume of the reaction is very less so in small volume medium is basically getting precipitated and silver as the precipitation of silver as the silver chloride which is a white compound and you can able to detect this as the presence of the chloride in the salt as the chloride as the anion so similarly the hexamine covalent three chloride when we see the systematic nomenclature also it is the name of this the naming also we should know how you

00:35:55 name it ok so is this hexa amines amines are the ligands we will also define what are those ligands so hexamine covalent three chloride when you react with silver nitrate it will also give rise to three agcl molecules so three agcl so amount of agcl we can take out we can filter it out we can take the weight of those and we can say that the quantitatively all the chlorides can be removed from this medium that means chlorides are not bound to the metal shelter so the chloride ions if we consider them

00:36:28 the species which is bound to the metal center as by definition will define them as the ligands why we call them ligand that will also see so in this particular case the chlorides are not ligands but here these are ligands here also these are ligands so we cannot eliminate chloride as silver chloride from these two compounds the way we are seeing the corresponding test of ferrous ion or the corresponding test of cyanide ion is missing in the ferrocyanide or the ferric cyanide ions ok so the analytical chemistry is always

00:37:00 very much helpful and the physical measurements also the physical chemical measurements also will also be helpful because we all know in the physical chemistry classes that these ions are very much helpful for giving you are the corresponding conductivity so the corresponding molar conductivity is also will be different if we just consider that this chloride is dissociating out and is found freely in the solution to conduct electricity or these chlorides are very strongly bound to the metal center and not available

00:37:35 for electrical charge conductance okay so it is that person what i was just telling in our first ah slide that it is alfred werner alfred werner during 1866 to 1919 so during 1890s basically he proposed this concept and he basically brought at this particular time that we are only basically at the beginning of this pm when nothing is known about the nature of the electron elect the proton neutron and all these things that the nature of these two valence one is primary valence and another is the secondary valence of the

00:38:10 metal ion so what we just see that instead of cobalt chloride as the salt we all know the cobalt chloride would be cocl3 so now what happens if we add some amount of ammonia to that cobaltic chloride so cobaltic chloride is the typical inorganic salt so like all other metal salt so cobalt chloride so cobaltic chloride if we can have so c should be always capital so cocl3 is the corresponding salt of cobaltic chloride where we know the cobalt is present as the three plus and the chlorides are as cl minor

00:38:48 then we bring something like water molecules sometime we can also use water so these are the species which can interact with the metal center and give rise to the complex species so the formula what we get we get this particular salt is there intact but these ammonias are also strongly bound not only a single ammonia but several ammonia will be bound to this particular species that means this ammonia molecules will be some entity which is directly attached to this cobalt center and if like that of

00:39:24 our water water having the lone pair of electron this ammonia also will have some lone pair of electron and if this lone pair of electron can be donated to our cobalt center the cobaltic center the trivalent cobalt center we get some species belongs to that corresponding coordination compounds so the primary valence will be there the charge neutralization and the secondary valence of the metal ion will be talking about when we have the complex species ok so these two things we are having so we can have several compounds like

00:40:00 this that means the cobaltic chloride we take and we react with ammonia and if we try to crystallize it so initially we get different solutions the first how we can identify them because all these transition metal ions the most important property of all these transition metal ions will be utilized for this purpose also and is also very much useful is the corresponding formation of the different colors so when covald3 chloride is reacting with ammonia and if we consider that in a different stoichiometry or in

00:40:31 different reaction condition the number of ammonia molecules reacting with this cobalt three chloride can be different and depending upon the nature of this color that means we can have different colors so this cobalt and these compounds with you have the n that means the n the way we say that the water of crystallizations these are not crystallization these are the molecules responsible for coordination to the central metal ion so if the n number is varying so different number of ammonia molecules

00:41:09 attached to this cobalt chloride will be separated out from the medium so what we get we get something that means the complex ion species where this complexion species are made up of this cobalt and ammonia so it is forming due to the presence of this cobalt and ammonia and these chlorides can be outside our coordinate sphere we call we will call them and depending upon the different number again that means it can also be x it can be three it can be two it can be one or it can be zero also so initially visually we can

00:41:51 check these as the different color so color reactions will be different as the stoichiometry is changing because you are having different complex species forming in the reaction medium so we see that when we try to do the reverse one that means the way we are identifying the chlorides the number of chlorides whether we can able to detect it by use of silver nitrate so the product of this reaction of cobalt three chloride with ammonia the presence of chlorides can be detected by the reaction of silver nitrate in excess

00:42:26 in solution we will see that the some of the chlorides can be precipitated out as silver chloride others are not so what are coming out as silver chloride those are the typical anionic chlorides which are present as the salt in cobalt chloride those can be taken out by the reaction of silver nitrate as silver chloride but other chlorides which are bound to the cobalt center cannot be taken out so those can not be separated out by the use of silver nitrate for the precipitation of silver chloride from

00:43:01 the reaction medium because this interaction with the silver ion that means a g plus reacting with c l minus giving rise to insoluble silver chloride is the ionic reaction and that ionic reaction is only giving rise to the presence of only chloride ion and due to this very ah low solubility that mean the corresponding value of the solubility product is very less so the solubility is also very less in water medium so they separate out as in soluble species so this silver as silver chloride will be separated out but it is not possible

00:43:38 if that chloride is directly attached to that cobalt center so first what we get is a yellow compound so very useful compound use yellow compound and this particular stoichiometry what we get yellow and sometimes depending upon the nature of the crystals it is a little bit of oranges also so this orange yellow in color or sometimes ah typically orange in color depending upon the size of those crystals what is forming so is a yellow coordination compounds as we go for a reaction of cobalt three chloride with ammonia so

00:44:19 and the stoichiometry of these because we all know that the typical stoichiometry is there because the reaction is with one of these and six of these ammonia so one is to six reaction product is giving us cocl three dot six h2o so we are not elaborating it like this we are talk taking the presence of these ammonia molecules as the corresponding ah presence as the corresponding solvent of crystallizations ammonia is also with ammonia in the liquid form so it is present in the corresponding species as

00:44:51 the corresponding solvents so if it is ammonia solvent then it is fine so this compound if we analyze it also for the percentage of cobalt percentage of nitrogen and percentage of chlorine also as chloride will find that this is the corresponding typical molecular formula so that typical molecular formula also corresponds to the corresponding this reaction what we just now told you that if the product of this that means the yellow compound dissolve it in water and react with some colorless and solution

00:45:26 of silver nitrate so silver nitrate in excess because we put excess silver nitrate such that all the chlorides which are present over here can be removed so three of these chlorides which are present in cobalt trees chloride and coc3 can be removed by reaction with a g plus as a g c l three a g c l as three chlorides of three molecules of agcl so what we find that all the chlorides present in cobalt chloride as the corresponding metal salt can be removed so these chlorides are not taking part into the corresponding

00:46:04 valance which is utilized for the direct cobalt chlorine bond for the complex species formation similarly the next compound will get is the purple compound where instead of three mole of agcl will be getting two mole of agcl and the stoichiometry is little bit different of one less ammonia we can have with the same c o c l three and the third one is the green compound where we get or we will be able to remove one mole of silver chloride so your stoichiometries again from six to five to four is down

00:46:42 and there is another violet compound so these two are pretty confusing to us right now having the same molecular formula but the colors are different one is green another is violet so this basically gives us some important idea that these two compounds the basic form of the corresponding complex part that means the coordination entity or the complex entity is same having one chloride outside the coordinate sphere and then another possibility we will also discuss that we are not able to detect any

00:47:19 removal of silver chloride from the compound which is a another category of compound which will be coc33nh3 so that is another possibility what we can have and that is the possibility where all of them are attached to cobalt and we are not able to get back any silver chloride precipitation from the reaction of silver nitrate so this is again a good thing which is the table which is taken from your textbook ncrt textbook which will again explain the presence of these that means why we are getting

00:47:56 yellow compound why you are getting purple compound why you are getting ah that a green compound and the violet compound so this formula what we just now we have seen these were the molecular formulas if we can think of the corresponding molecular formula of these as six n h three five and h three four and h three in two different cases will find that this can be present over here in the first case all the three that means all three chloride ions will be present over there as the corresponding anions in the typical salt so our

00:48:36 formula of this compound is c o n h three whole six c l three that means we have all the sex ammonia is attached to this particular cobalt so we can assemble we can cover it so in a typical form we can cover by all these ammonia so this is ammonia this is ammonia this is ammonia so how we know that so we will have all of them that means all six of the bonds basically six cobalt nitrogen bonds so we will have six cover nitrogen bonds and obviously this is forming due to the donation of this ammonia lone pair to

00:49:40 the cobalt orbitals and these bonds are what type of bonds these are coordinate bonds so if we are able to detect or if we are able to identify those coordinate bond the first category of compound will be these and these chlorides like that of or any others salt like aluminium chloride the typical example of aluminium chloride is that when you dissolve it in water it can dissociate all the chloride ions and you can ah you can remove them by addition of silver and silver ion for the formation of three silver

00:50:18 chloride precipitate three moles of silver chloride will be precipitated out similarly here also you get three silver chloride so your these will be there so six co n coordinate bonds are there and what about the cobalt chloride bond if we just consider so there is no coval chloride bond this chloride will be outside the coordinate sphere so no chlor cobalt chloride bonds so these are the two statements which are very useful and which are ah very immediately we should all know so this is the first compound what is

00:50:58 there the second compound which this is the yellow compound so this is the second compound is the purple compound and the difference is only thing that you now just change or manipulate the corresponding coordination environment so what we do the second compound if we write down the formula because everything is there in your textbook only you sit comfortably and write the corresponding form so here you have one cl and this nh3 is five in number and two of them are outside so think of the corresponding oxidation

00:51:39 state we should not forget the corresponding oxidation state is the trivalent one and the number of these so one of these so one of these bond that means one of these cobalt ammonia bond will not be there so will have five of them are nitrogens so these five of them are nitrogens of the ammonia and one of them is basically your chloride so this is the compound so that compound immediately tells us that if you have a charge of three one will be balance so overall charge of these complex pieces what we write

00:52:24 entire thing is in ah the square bracket so entire thing we write basically in square bracket so if this is we write so this charge basically sometimes we write is this small squared part to indicate the charge because the way we write that chloride as c l minus f e as two plus because the species is very small but when you write a huge species like this and we required some separation and then we write so plus three minus one so it is two plus so what will be there so you will have these two so the charge balance will be

00:53:06 therefore due to the presence of two cl minus so that is why you have two cl minus so in terms of this cover nitrogen and cobalt chlorine bonds now you can write it down nicely that will have five of the first category and one of the second category and when we go for the corresponding separation these two can only be separated these two chlorides can be separated as silver chloride so will have two agcl from the medium this will remain as the corresponding entity so the third one we are taking everything from your book

00:53:47 these examples are there in the book so the third variety is your green variety and the green variety we are moving one step forward where we have two cl bound to covald center so now you have the third one where you have co cl2 and obviously when two of the positions are occupied by these groups when two of them are occupied by these so obviously we will have four remaining ammonia so sorry this is ammonia so four remaining ammonia groups are there and thats why the stoichiometry of all these products in one case we have seen

00:54:32 that the stoichiometry for ammonia was six the next one it is five and the third case it is four so what basically we try to understand over here is that the number of cobalt chlorine bonds are increasing so the overall charge of this particular species two and three so it is one minus so outside you will have one chloride only and that chloride basically we can take it out so we can take it out as the corresponding one as the reaction of these with a g plus so we will get one agcl so that clearly differentiate depending

00:55:16 upon the number of agcl coming out number of moles of agcl coming out from the reaction in water medium so is very is all of them are we are lucky enough to see that all of them all of these compounds are water soluble so ah these things are there and the ammonia solution what we are using for the preparation are very dilute solutions because this ammonia we know that the ammonia in the laboratory is available as ammonium hydroxide which is also a weak base so that can also be available for the

00:55:50 production of h o minus so if more amount of hydroxide ions are there so the side reaction for all these reactions for all these complexion reaction can be the precipitation of cobalt hydroxide but which we should avoid so precipitation of this hydroxide and in fact also sometimes the removal of this hydroxides how we can manipulate this that will see afterwards that what is the corresponding product if we simply use ammonium hydroxide instead of some reaction where cobalt chloride is reacting with dilute

00:56:25 ammonia so this is there so one is coming so your difference is there three difference is two and the difference is one and this is also changing now you have four of them the cobalt nitrogen bonds and two of them are covered chlorine bonds so this quartz sphere and all these things are changing then the fourth one what we will just discuss in our next class that how we can go for the next one is the colour is different this is green but all other things are same that means is corresponding formula this reactivity

00:57:16 with silver chloride and its the corresponding conductivity measurement that i will see afterwards in the next class that how your the corresponding solution electrical conductivity ah how it can also detect the presence of chloride corresponding to the quadrosphere so what we see that the last two compounds having the same molecular formula but the colors are different that means what we should guess and the type of the electrolyte is also same is one is to one electrolyte and second one is also one is to an electrolyte only

00:57:49 possibility is that you have four ammonium groups and there are also four ammonia groups and the chlorides so what is the corresponding geometry until and unless we define this as the corresponding coordination number what is the typical coordination number we call and how the different number of these groups can be assembled around all these this will find it out then the corresponding positioning of these two groups so if we can have two different positions for the placement of these chlorides

00:58:21 along with these ammonia groups also will find that this will be responsible for one typical coloration and the second one is also responsible another different coloration but the nature of this electrolyte type is same but their corresponding positions will tell us something which is or another type of thing which will consider in terms of the corresponding isomerism ok so everything will say again in our next class thank you very much you.