Isomerism in Coordination Complexes - Video Tutorials & Practice Problems
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1
concept
Isomers
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Now recall that isomers are molecules with the same molecular formula but different connectivity or spatial orientation. Here. In the middle, we have our coordinations complex which is comprised of our coordinations a complex ion. And this counter ion of bromide with a structural isomer, you'd have the same exact formula overall formula, but different connections. The way we could do this is we could take one of the chlorine's here and this bromide and have them swap places. So now our bromine would be here and our chloride ion would be out here. Both structures have the same formula but they have different connectivity because now we're connected to the bromine instead of two chlorine with sterile isomers, we're talking about differences in spatial orientation. So the connections are the same, they're just represented differently in terms of spacing. So what I could do here is I have two chlorine on the same side here and two ammonia on the same side, I can just swap that. Now I have pneumonia on this side, ne chlorine. On this side, the connections are still the same. Our metal canine is still connected to two chlorides and two ammonium ammonia molecules it's just now they're not on the same side with each other. So this will count as a stereo isomer. So keep this in mind when we're talking about isomers overall, we'll take, taking a look at differences in connectivity or in spatial orientation.
2
concept
Structural Isomers
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Now, when we talk about structural isomers, we're gonna say it consists of two types. We have coordinations isomers or linkage isomers in coordinating isomers, we're gonna say these mole, these are molecules where the ann Liang and a counter ion have switched places. So if we take a look here at these two, what can make coordinations isomers? Well, we have an anion ligand, let's say our ligand here. That's antic is the bromide ion and it's gonna switch places with a counter ion. Now, the charges of them both have to be the same. So if I have a minus one here, I need to have a minus one Ln attached to the metal. So let's put a chlorine here for, for us to make its isomer, I just have those switch places. Now, my bromide ion has come here and my cord ion is out here. So we swapped in an anionic L again for another one. Now linkage isomers, these are molecules where the connectivity between the ligand and the metal is different. So one example we can have here is with thy cyan, remember thy cyan has resonance involved. And because of that, we could either have the nitrogen be the negative end or the sulfur being the negative end. When we talked about donor atoms, we said that the negatively charged atom within Alyan would act as the donor atom. And because nitrogen or sulfur can be negatively charged, either one could be the donor atom. This would result in linkage isomers. One where we have these Sulfurs directly connecting to our silver ion or one where the nitrogen directly connects to our silver ion. So these would be two linkage isomers. And as a result of the Ln itself possessing resonance, meaning multiple elements could be the donor atom, right. So just keep in mind when we talk about structural isomers, we're talking either about coronation isomers or linkage isomers.
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example
Isomerism in Coordination Complexes Example
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Draw one co-ordination isomer and one linkage isomer of the following complex. All right. So here we have our co ordination complex. If we want to draw a coordinations isomer, that means we have to substitute a counter ion for a Ln that's attached to the metal. Here, we could do that. We have still have our platinum here. It would still be connected to the ammonia. And it's the thiocyanate ion that's negatively charged like the bromide counter ion that's negatively charged. So I would just switch out the th cyanide or thiocyanate an ion and bring in the bromide and then your thy signing ion is on the outside. This would represent a co ordination isomer for linkage isomer. The ammonia are still there. And what we're doing here, remember, thy cyanide has resonance involved. Here we show the sulfur directly connecting to the metal cion, but I could easily have the nitrogen directly connecting to it instead. And the bromide ion would still be on the outside as a counter ion. So this here would represent a linkage isomer, right. So these are examples of a co-ordination isomer and a linkage isomer based on the original cordination complex given.
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concept
Geometric Isomers
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With geometric isomers. We're gonna say this is where a Ln has different spatial orientation around the metal. Now, this occurs in complexes of formula MX two Y two and MX two Y four. Here, we're going to say sis equals the liam pair on the same side and trans equals liam pair on opposite sides. So if we take a look here at MX two Y two here, we could say that X could represent the ammonia and then Y could represent the chlorine. If we wanna make this cyst, that means same side, we'd have to put a chlorine here so that they're both on the same side and we put an ammonia here. So they're on the same side trans here, they'd have to be opposite. So they have to be on different sides. So the chine would be here and now they're kind of opposite of each other, opposite sides. And the ammonia would be here again, opposite sides with MX two Y four here. Let's say we're using um as our X two chloride ions again, for them to be cyst, they'd have to be on the same side. So I put AC L here actually let me just make this, yeah, we'll put a seal here and AC L here, they're both on the same side and to make them trans to each other, they'd have to be on opposite sides. So a seal would go here and AC L would go here. Now, they're on opposite sides of each other. So again, geometric isomers, we're talking about different spatial orientation around the metal. And this happens when the formula is MX two Y two or MX two Y four. So keep that in mind when looking at different types of geometric isomers.
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example
Isomerism in Coordination Complexes Example
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Identify the following pairs of complexes as co-ordination linkage or geometric isomers. For the first one look for where the difference is the difference is here. And here in the first one, we have no two where the nitrogen is connecting directly to the Cobalt metal cion. But then next to it, it's the oxygen within the nitrite ion that's connecting to the metal cion. How is this possible through resonance? So we'd say the first one is a linkage pair or a pair of linkage isomers. For the next one look to see where is the change? Where is the difference here? Well, in both, they're connected to nickels connected to two waters and it's connected to, to ammonia. But as we can see in the first one, the waters are on the same side, the Am Moors are on the same side, but the iceberg next to it, they're opposite of each other. Now, so this would be a geometric pair of isomers. So next, let's see. Next, we have what, what's the difference? Well, the chorines here are next to each other, making them cysts and now they're opposites of each other, making them trans to each other. Also remember in this first example, if we look the formulas are what MX to Y two and these two are MX two Y four, they'll those tell us that these are geometric isomers as well. Then finally, the last one, what's the difference between these two? Well, it looks like we have a BR here and AC L here and it looks like they swapped places, we substituted out the counter ion and the um basically anionic ligand here. This is an example of cordination isomers. So that's what we can say about each of the following pairs given to us within this example problem.
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Problem
Problem
Which of the following complexes cannot have geometric isomers?
i) [PtCl2(NH3)2]
ii) K4[Fe(CN)4(OH)2]
iii) [Ag(NH3)2]Cl
iv) [Ni(H2O)2(NH3)2]Br2
A
i, ii, and iv
B
ii and iv
C
iii only
D
i and iii
E
iv only
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Problem
Problem
The complex [Fe(NH3)5OCN]2+ has two isomers. Draw their structures.
A
B
C
D
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Problem
Problem
How many isomers are possible for [Cu(H2O)2(NH3)2]SO4? Draw their structures.
A
2
B
2
C
2
D
3
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