 In the previous videos, we have been introduced to what coordination compounds are and we have also seen the various terms that are associated with the coordination compounds like the coordination entity, oxidation state, ligands, coordination polyhedra and so on. It is now time to familiarize ourselves with their naming conventions. You see, naming of coordination compounds can be very complex. In fact, coordination compounds themselves are quite complex. We have different types of ligands, we have different number of ligands and sometimes we have mono-dentate ligands, sometimes we have polydentate ligands and so on. And therefore it is absolutely essential that we come up with a set of rules that can help us distinguish one coordination compound from the other. So by simply looking at its name, we should be able to figure out what the central metal atom is, what its oxidation state is, what are the different types of ligands, whether ligand is a polydentate ligand or a mono-dentate ligand or an anionic ligand or a neutral ligand, etc., simply by looking at the name of this particular complex, okay? So if you are ready, let's quickly look at the rules that we need to follow while naming a coordination compound. Okay, so the first rule is that we first name the catnion which is followed by the name of the anion. For example, here we have CONS36Cl3 and CL3 is the anionic part and CONS36 plus is the catnionic part. So in this particular coordination compound, we will first name the catnionic part which is this coordination entity and then the anionic part. Now the coordination entity need not always be the catnion. For example, in this particular coordination compound, the catnion is a counter ion which is K plus and the coordination entity is anionic complex, right? Now in either case, in either of these cases, the important thing to remember here is that in the naming, we will always name the catnion first. It can be the coordination entity or the counter ion. It doesn't matter. What we need to do is simply name the catnionic part first and then the anionic part. Now within the coordination entity, we will first name the ligand and then the central metal ion. So as we saw before, the coordination entity can be anionic or catnionic as we can see in these two examples. But in either case, when we go about naming the coordination entity, we will first look at the ligand and then the central metal ion. So here the ligand is hydroxy group and the metal is zinc and here we will first name the ligand which is ammonia and then go about looking at the name of the central metal ion. As we already know, the ligands can be of different types. Some are anionic in nature while the others are neutral molecules. So obviously depending on the type of the ligands, their naming would also differ, right? So now let us quickly look at the naming of the ligands. When we have anionic ligands, the name will always end with an O. For example, when we have chloride ligands, the name would be chlorido. When we have bromide ligands, it would be bromido. And when we have hydroxy group, the name would be hydroxo. Now it doesn't really matter if it is a bidentate or a polydentate ligand. As long as we are talking about anionic ligands, the names would end with O. So here are the names of some of the anionic ligands. Let's now look at the neutral ligands. The names of the neutral and cationic ligands are the same except aqua for water, amine for ammonia, carbonyl for CO and nitrocell for NO. Except that if you look at these groups, you can see that the names are exactly the same. O2 is dioxygen, N2 is dinitrogen and NH2, CH2, CH2, NH2 is the name of ethylene diamine. Also named ethane 1, 2, diamine, correct? Now what do we do when we have more than one type of ligand? In that case, alphabetical order takes precedence. For example, in this coordination complex which is CR, NH3, CH2, CH3 plus, so here the name of ammonia would be amine and water would be aqua, right? So which one takes precedence alphabetically? So based on alphabetical order, we would prioritize amine over aqua. Now when we have many ligands of the same type, we use prefixes like dye, tri, tetra and so on. For example, if we have a complex like CR, NH3, thrice, H2O, thrice, 3 plus, then the naming of the ligands would be tri, amine because we have three ammonia groups and tri, aqua because we have three water molecules. Now as I mentioned before, amine takes precedence over water alphabetically. So the naming of the ligand would be tri, amine, tri aqua, chromium, chloride. Because as I said before, inside a coordination entity, we will first name the ligands and then we will name the central metal atom, right? And we will get to that later how the entire naming is done. But for now, understand that when we have monodentate ligands and when we have multiple of them, we first have to look at the alphabetical precedence and then we need to prefix dye, tri depending on the number of ligands that we have. Now remember, alphabetical precedence is for the ligands. We are not considering it after we use a prefix. Now when we have polydentate ligands, instead of dye, tri and tetra, we have a slightly different nomenclature, which is bis, tris and tetrakis. Bis for 2, tris for 3 and tetrakis is for 4. Now this becomes important when we have complexes where we have both polydentate as well as monodentate ligands. For example, in this particular coordination complex, we have a monodentate ligand as well as a polydentate ligand. So in order to avoid any confusion regarding the naming of these ligands, we actually keep them very distinct. For example, here we have dichlorido that corresponds to 2 chloride ligands and bis ethane-1-2-diamine which corresponds to 2 molecules of ethylene-diamine, which has been a polydentate ligand. So remember, this is purely to make it clearer or to avoid any kind of confusion between the naming of polydentate and monodentate ligands. So the naming of this particular complex would be dichlorido bis ethane-1-2-diamine which is the name of the ligand that we have followed by the name of the central metal ion. Now here we don't have any anionic group so we end the naming with the metal ion. Now another thing that we need to remember or keep in mind is that when we have polyatomic ligands like ammonia or water, we usually enclose them in brackets like this. For example, in this particular complex we enclose a polyatomic ligand ammonia within brackets but not chloride group. So this is again a small distinction that we need to keep in mind, okay? So that's pretty much about how to do the naming of ligands. Let's now look at the naming of central atom, right? After ligands comes the central atom. In the case of central atom we always need to write it along with this oxidation number. For example, when we have a neutral or cationic complex like this, the name of this particular complex would be triamine triaqua that which refer to the two different ligands chromium-3. We all know how to find the oxidation number of chromium here, right? Suppose x is the oxidation state of chromium then we have 0 and 0 because these are neutral ligands and then we have 3 chloride ions here and the overall charge is 0. So this would give x as plus 3. So here remember the central metal is always written along with the oxidation state. So this is when we have neutral or cationic complex. What about anionic complex? Suppose you have an anionic complex like K4, Fe, CN6. So this has the charge Fe, CN6, 4 minus, right? When we have anionic complexes the name of the central metal will end with 8. Okay, so let's try naming this coordination compound. So what was the first thing that we saw? The first thing is to write the name of the cation. And if you break up this coordination compound we know that this is the cationic part and this is the anionic part, right? So the name would be first potassium that refers to the cationic part. Now we need to focus on the anionic part which is our coordination entity. So within the coordination entity we said that first we have to name the ligands and then we have to name the central metal atom, right? Now here we have 6 synogrope and when we have anionic ligands the name ends with O, correct? So that would be potassium hexasino, hexasino would refer to 6 synogropes. And now that the ligands are over we have to look at the central metal ion. So the name of the central metal atom should end with an 8 because it is an anionic complex. So here it would be potassium hexasino ferrate and what is the oxidation state? 2. I am going to let you calculate that, okay? So the name of this particular complex is potassium hexasino ferrate 2. Now a small thing that you need to remember is that we don't put any space between the ligand and the metal atom, okay? Hexasino ferrate is almost like a single word. We have space only between the cationic and the anionic part, okay? So before we wrap up this video let's quickly look at one more example, alright? Okay so let's try to name this particular coordination compound. So first we have to name the cationic part, correct? The cationic part here is nothing but potassium and this is the anionic part, right? So the name here would begin with potassium. Now what we have here is an anionic complex. We saw that within any coordination entity we first have to name the ligand and then the central metal. Now if we have a negatively charged ligand then it would end with O and if it is a neutral or cationic ligand the name almost always remains same except in the case of few ligands like aqua for water, amine for ammonia and so on. So what is the ligand that we have here? OH group which as we know is a negatively charged group and how many such groups are there? We have four groups. So that means the name of the ligand here would be tetrahydroxyl, alright? So the ligands are sorted and now we need to move on to the metal. In an anionic complex we just saw that the name of the central metal atom would end with an 8. So here the metal is zinc and that means it should end with zincate. Okay, no space here, alright? No space here. And what is the oxidation state of zinc in this? We have 2 plus x plus 4 into minus 1 is equal to 0. So x is 2, okay? So the oxidation state is zinc 2. So the final name of this particular compound would be potassium, tetrahydroxyl, zincate 2. Remember no space between the metal atom and the ligand names, okay? So let's practice naming a few more compounds in the next video.