24. Transition Metals and Coordination Compounds
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Hey, guys, In this new video, we're gonna take a look at coordination compounds. Now we're gonna say here the most important or most prevalent aspect of transition metal chemistry is the interesting types of compounds they form. We refer to these compounds as coordination compounds or coordination complexes, and important things to know about them is that these coordination complexes or compounds they are usually colored, so they form very vibrant colors reds, greens, blues, purples, different types of colors because of the transition metal involved also, so they're usually colored and para magnetic. So the transition metal that's in the center of them usually has at least one electron, that is UNP aired. Now we're gonna say here within a coordination complex here, this is our coordination complex that we're talking about. It's made up of different things were going to say the coordination complex. Um, there is at least one thing that we call a complex ion, and we're gonna say complex ion is a species that is made up of a metal cat ion. So the transition metal in the middle that is connected to molecules that are neutral or it can also be connected to an ions negative ions. These neutral molecules that are connected to the metal or these negative ions that are connected to the metal are called Liggins. Now this is important to understand the metal can. Ion is gonna act as an electron pair except er, and we say it's acting as an electron pair. Except, er we're basically saying that it's acting as a Lewis acid and then here the Liggins, which could be neutral molecules such as ammonia or water. Or they could be negative ions such as chloride ion or fluoride ion. These Liggins they're acting as electron pair donors, so they have lone pairs on them that can donate electrons to the metal cat ion. Since they're acting as electron pair donors, they're acting as Louis Bases when you guys get to that section, if you haven't yet in terms of my videos about acid and base identification, realize that they're different types of acids and bases out there here. We're talking about Lewis acids and bases, and here we're talking about how they donate electron pairs. All right, so are complex ion when we're looking at this right here, this is our complex. Well, they start coordination complex or commit coordination on compound. It breaks up into a complex ion, and then also, in order to maintain the overall neutrality of the compound, we use counter ions. All right, so how do we look at this thing and figure out how it breaks up? Well, we're going to stay here First. Is we should calculate what is the oxidation number of nickel here? Here. We're gonna say that nickel is X ammonia has no charge because it's a neutral covalin compound. So it's oxidation number zero. Chlorine here is minus one. So it be X plus for ammonia, as each one is zero plus two chlorine. Each one is minus one equals zero. The charge of the compound this cancels out. So this is X minus two equals zero. So X equals plus two. So oh, should realize here's this thing breaks up into two ions. It breaks up into the nickel connected to the four ammonia us. We find out that the oxidation number of nickel is plus two. Ammonia is zero. So the overall charge of this thing is two. Plus, Then we have these two chlorine that are also involved. They break Frias Well, there's two of them, each one minus one. So we're starting out with our coordination complex on the left side of the era, it breaks up into two ions. This part here, this is our complex ion. And again you're complex. Ion is made up of basically two major things. It's made up of your metal. Can I on And then it's made up of your Liggins, Liggan or Liggins. Here are Liggins are ammonia, which are neutral. But there could have also been ammonia with bro mean there could be more than one type of Liggan attached to the transition metal in the middle. And then here the C L minus is here. There's two of them, so overall, this is minus two. So these negative negative to charge overall would cancel out this positive to charge overall. And that's why our coordination complex in the beginning was neutral. So since it's giving us a neutral compound when they're together, these represent our counter ions. So that's how we basically look at something and we break it down into its components. I know there's a lot involved here. This complex ion is made up of a bunch of things together not as simple as your basic Ionic compound, but it's still based on the principles of them. All right, so now, now that we've talked about the coordination complex and how it's made up of a complex ion and the counter ion, we have to talk about the coordination number involved. Now we're going to say the coordination number is the number of ligand atoms bonded to the central metal cat I'll and here, basically the number of ligand atoms that are usually attached to the central element. Usually 24 or six Liggins are attached to the central metal. These are the most common numbers there is, on rare occasion, very rare. Eight. But here we don't worry too much about that one. That one's way out there in terms of off the different types of coordination compounds we conform. So remember your coordination numbers. The number of Liggins attached to your metal cat ion. Now here we're going to say the coordination number is based on the size or charge off the metal cat ion, and it's also based on its electron configuration, because remember, these coordination complexes are para magnetic, so we have electrons that are not paired up the mawr unpaid electrons you have, the greater the chance of the number of bonds you conform because remember, forming bonds means you gain electrons, electrons that you can use to pair up with your unpaid electrons. And we're gonna say here we're gonna say that the most common coordination number is six. However, two and four also common six just happens to be the most likely number for a lot of these coordination complexes. So if we're talking about this, we have to talk about geometries. So we're gonna say the types of the geometries allowed are based on the coordination number of the central metal ion. So the first one is linear in terms of its geometry. This happens when we have a coordination number of too. So basically, we have our metal cat ion in the center, and it's connected to two Liggins thes Liggins could be, um, negative or they can be neutral. So good example here is we could have copper and it could be connected to maybe too bro means. And we should realize here is that when it comes to the complex ion, we draw brackets around it, so for the complex iron. We're always gonna put brackets around it. Now, Here, these next to both happened when we have four. Liggins connected, um, to the metal cat island. Okay, so four here could be either Tetra hydro or they could be, ah, square plane or planner. How do we determine which one's gonna dominate? Well, basically, we look at the metal cat ion, and if the metal can ion has on electron configuration that ends with D 10 for example, zinc zinc is are gone for us to three d 10. If it has a D 10 configuration, then it'll be Tetra Hydro. If it has a D eight configuration, for example, if we want to think of d A, we could think of nickel because nickel is are gone for us to three d eight. Then it'll be square plainer or planner. So good examples here. I could do zinc connected to four hydroxide. Overall charges minus two. And how am I coming up with the overall charge? Well, we know that zinc is a type one medal. It's always plus two, but we have four hydroxide ions. Each one is minus one. So if you think about it. You have plus, to hear you have minus four here. Really? Because there's each one is minus one. That's why the charge overall is minus two. And then he could just do nickel. But those four hydroxide as well, also minus two overall notice how again? I'm putting brackets around the complex ion because that's what you're supposed to do to write it correctly. And then octahedron is when you have six around here. So we could just do cobalt. We could use now a neutral licking if we want. So you have six of them. You could say, overall, this charges plus three. So again, these are the most common types of coordination numbers here. Eight is possible, but you're not gonna see it within your book. So don't worry too much about that. Um, six is the most common one. The Liggins can be either neutral or negatively charged. And as we go more and more until coordination complex will be taking a look at the different shapes, they can have the different types of ice tumors that exist as well as how do you name these different types of molecules? It's a bit different from the naming of normal ionic compounds and Covalin compounds, so it's gonna be a whole new set of rules that you have to remember. So just remember coordination complex looks at the complex on with its counter ion in the complex ion, we have our metal ion in the center connected toe Liggins, which can be either negative or neutral. The counter ion is just an ions that are used to balance out the overall charge of the complex ion that overall were neutral. Remember these principles when looking at coordination complexes?
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Yeah, So here were asked to find the geometry of the following complex ion. So here we have zinc connected to for ammonia molecules. These air the Liggins and the overall charge is plus two. Now, remember, zinc its electron configuration is are gone for us to three d 10. And remember, we said that if you have a D 10 configuration, near shape would be Tetra hydro. Okay, Right. So here the shape yet geometry would be Tetra hydro. And if we wanted to draw this out correctly, we'd have zinc in the center. Remember, Tetra Hydro means you're connected to four groups Now, Traditionally, you probably see it like this and H three here and H three here and h three here and here. It's the end that's connected, and that end is connected to three hydrogen. So he wrote it backwards to show the connection is between the zinc central element and the nitrogen because it's the nitrogen that has the lone pair being used to make the connection. Now, this is not the best way to draw Tetra Hydro. Technically, the best way to draw it will be drawing it like this. We still have sick in the center. We still have one ammonia molecule up here, but then the remaining three we draw kind of like that. This would be the Mork correct way of drawing this connection. And here because it has a charge, we put it in brackets and there'd be a plus to charge on the outside So that the correct way of drawing in we've seen this one. Let's see if you can draw the next one. Pause the video really quickly attempt to do it on your own. They come back and see if your answer matches up with mine.
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Alright guys, Hopefully positive video when you attempted to do it on your own. This one is fairly simple. We have gold here, but there are only two Liggins to bromide ions. So if you're coordination numbers too then your on leash. It can be linear. It's one. The coordination number is for that. We have to decide. Does it follow a teacher? He drill shape Or does it follow a square plainer or planner shape? So here we have gold in the center. Remember Linear 180 degrees in terms of its bond angle. Okay, so we put this in brackets and the negative charge on the outside. So that would be the way you should have drawn it. And remember, because there's a charge, you put brackets around it and the way the formulas presented tow us should have brackets in it. Now, now that we've done this one, try to attempt to do this practice one on your own, come back and see how best I draw Now, remember, just like Tetra Hydro, there is an ideal way to draw this particular shape, dry it first the way you would like to see it and then we'll see if your shape matches up with my shape. So good luck, guys.
Determine the geometry for the following complex ion:[Cr(NH3)4Cl2]2+
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Hey, guys, In this new video, we're gonna take a look at Liggins. So we're gonna say a ligand could be thought of is just simply a Lewis base. Because, remember, a Lewis base is an electron pair donor. So what happens here is that the transition metal in the middle is a cat ion, so it's positive, so it can easily accept negative electrons. The metal cat ion in the center is the Lewis acid, which is an electron pair. Except, er, the Liggan, which could be either neutral or negative, donates its lone pairs to the central metal. Now, I'm gonna say Liggins can be characterized by the number of elements in the molecule that can donate alone Pair. Now we're gonna say here that these compounds use their lone pairs to grab onto these metal cat ions and therefore they're referred to as key lading agents. Sochi lading, agents now key lading. Agents were gonna say that tequila is Greek and it means crab's claw. And basically, what happens here is that the lone pairs kind of act like teeth, that kind of chump into the metal cat aisles when it's donating its lone parents. Actually, um surrounding and holding on to that metal cat ion performing a strong bond. So that's where they'll turn key lading. Agent comes from Now we're gonna say Liggins that possess Onley one element able to donate a lone pair referred to as Mono Dent. Eight. Liggins. When we say Mano Dent eight Mono Dent, it means one tooth because again we think of them as claws or teeth that connect to the metal ion common ones. Here we have water, of course, Onley. One lone pair is being donated to form the bond, not both. Here. X X just stands for halogen. So we're talking about flooring, chlorine bro mean And I'd I or technically, since their negative. We're talking about fluoride, chloride, bromide and iodide. Now, when you get to organic, for those of you are brave enough to go into organic, you'll learn that X is just the default symbol to represent all halogen. So take note of that When you see X in chemistry, it really just refers to some type of halogen. Next we have our cyanide ion. Now Nitrogen also has a lone pair, but it's the carbon that possesses the negative charge. It's the carbon. That's going to be attacking with its lone pair. Here we have our hydroxide ion. Good. We have ammonia. Now. Here. This one is basically similar to Sinai ion. Except now we have the possession of a sulfur in in in this compound. We're gonna say here that when it comes to the structure, this is called your file Sign eight ion. And here's the thing. The sulfur or the nitrogen can be the attacker, not both. It's one or the other. So that's why it's mano dented here. This is our nitrite I on we should realize hears about our nitrate ion is that it's the nitrogen or the oxygen that can donate. And technically you're nitride. Ion has resonance. We'll call when we talk about lewis dot structures. Certain compounds can do resonance. So another way I could have drawn this is I could have still drawn that nitrogen in the center, but it could have been the oxygen that's on the right. That was single, bonded, and then the oxygen on the left now is double bonded. So here it's still one or the other, the nitrogen or the oxygen. So these air mono dented Liggins here. Legends that possess two elements able to donate a lone pair referred to as by Dent. Eight. We don't say die. Dent. Eight Die, Dent. It does not exist. Okay, it's by dented. So here, by means to what we have here is we have our aqsa late I on which will sometimes see written as C 204 to minus. So this is one where we could have drawn it. This also is resonances. Well, we could draw it a different way. We could draw still those carbons in the center. But now it's the oxygen's on top that are both single bonded, and then the oxygen's on the bottom are double bonded. Okay? Or we could just mix and match. Maybe this one here single, bonded and maybe that one there single bonded. So it all depends how you want to look at it, but just realize Oxlade ion is also residents. Um, stabilized here, this other one that we have here. This is called ethylene. Die a mean. Let me take myself out of the image guys. So that's ethylene. Die me. F a lien just means you have to ch two groups. And when we're saying a mean here. We're talking about nitrogen ins. But remember, Nitrogen likes to make three bonds. It's each one only making one bond right now. So each one will have to hydrogen is involved their in group five days. So they have five valence electrons. So that's where the lone pairs come from. Right here. We're gonna say that by Dent eight, and Polident Liggins Because they have more than one element with a lone pair, they conform rings when they attached to the metal cat ions. So we're gonna say that by Dent eight and Polident eight Liggins, would you be on the next page? They form rings in the complex Ion later on, we'll be seeing examples of this now. Here. If our Liggins possess mawr than to elements that are able to donate Ah, long pear Then they're referred to as Polident Tape Liggins, Polly Meaning many tooth. So here we have triphosphate now notice. Although these oxygen's here are also negative, it is not them that donate their electrons. It's these three here that donate their electrons. Then we have here die ethylene. So dai means to remember ethylene means ch two ch two So here goes one ethylene. Here goes a second ethylene. That's why it's diethylene. Tri means three. Three. What three means here goes. And a mean here goes in a mean and here goes into mean notice that here at the ends, nitrogen again wants to make three bonds. Each one's making one bond toe a carbon, meaning that they need to make two more bonds. So that's why each one has to hydrogen. This one here in the center, though, is already making to bonds one to this carbon and one to this carbon, so it only needs one more hydrogen to have three. Now, finally, this last one here, this is called Ethylene di amine tetra acetate ion or simply e d t. A. So let's look at the naming ethylene ethylene because we're going to say it's ethylene because we have, uh, this ethylene park right here. Here goes our ethylene die a mean dia mean means we have to nitrogen and then tetra means four tetra acetate. Here's our acetate ion. This part right here is acetate, and how many of them are there? There's four of them now. Technically, here there are six groups that can donate electrons, so this is technically a hex, a dent. Eight Liggan. But here's the thing. Usually what happens is it's these four. Since their negatively charged, they have an excess of electrons, so they're the ones most likely to donate electrons. Okay, these nitrogen is here are neutral so they're less likely to donate their electrons. They could, but more than likely it will be the acetate oxygen's that are negative that are donating their electrons now. E t A. You may say I've never heard of e d T. A. But the thing about E. T. A is e. D. T. A. Is found in a lot of every day. Um, products. You'll find it in processed fruits and vegetables, even if you look at certain shampoos in the grocery store. If you look at certain ones, they have e d. T. A. In them as an active ingredient, you'll see it in mayonnaise. You'll see it in salad dressings, your seat in sweeteners. It's in a lot of things that we either use, um, to clean ourselves or to clean our homes or to even eat. Here's the thing. Why, why they found in everything basically for example, if you have a can of fruits, right, What happens here is that during the process of packaging certain foods, there are trace amounts of metal shavings that can be found in the food, which isn't good. So how do you make sure you basically soak up these metal ions so that we don't? We don't get sick from them. You poor little bit of e d. T. A. In these processed cans. What happens here is that the DDT it binds to any traces of metals left behind in the food. And what it does here is it gets rid of those metal ions from your food and at the same time, it stops your food from spoiling too quickly. So it acts kind of like a preservative. It also acts as a way of protecting us from free floating metal ions. So there's a huge science involved in terms of this compound e t. It's found in ah lot of things. So it's a very, very, very important Liggan, um that you may not have heard of until today, but it's found in almost everything that we use. So remember we're talking about Liggins here. Liggins are just simply lewis basis. They connect to the metal ion in order to form are complex ion. Remember, your complex ion is made up of your metal ion in the center which acts as a lewis acid. And then you're Liggins that surround it. These Liggins can either be negatively charged or they could be neutral as in case off ethylene dia me. So just remember the different types we have mono bi and poly e t a. Being the most popular Polident ated like it.