Constitutional isomers of a ruthenium(II) coordination compound are shown below.

(a) Give the formula and name for structures 1-3.

(b) Which structures are linkage isomers? 

(c) Which structures are ionization isomers?

Video transcript

Hi, everyone. Welcome back. Let's look at our next question. Consider some of the following isomers of iron two co-ordination compound. We have three different structures given to us with a Cron consisting of an iron two compound and an a co a negative counter ion. I'll go into describing each of these in a few minutes. But meanwhile, our question asks, what are the names and formulas or the compounds? So that's what we're going to be looking to identify and our answer choices A through D offer different options for these names and formulas. So I won't read them all out loud. We'll go through each compound and talk about its name and then match it with an answer. So let's look at compound number one. Well, one thing to note as we start figuring this out is that we don't need to figure out the oxidation state of iron. In this case, it's given to us in our problem says we have iron two. So we know we have fe two plus as the form of iron in our compound. So in our formula, we're going to be writing the metal ion first, we have ac ion So we don't, the ion, the counter ion, excuse me will be named at the end. So we know that our formula, we'll start with a bracket to surround the complex. And then fe for our metal when we look at the name, however, we start with the ligands in alphabetical order. So let's take a look at the ligands. We have to in complex one, we have central iron with an octahedral structure. Six ligands, five of them are carbonyl, which is co so we'll write structure number one, all right, five carbonyl ligands. This is a neutral ligand. So we don't change the name in any way since it has no charge and it's mono dentate. We see and then our remaining ligand is the metal is bonded to a sulfur which then has CM and N carbon and nitrogen. Now, it's important to note that this grouping of carbon with a sulfur on one side and nitrogen on the other can bond with the iron in two ways. So, in this case, the metal is bonded to the sulfur atom and the bonding in that case, when it bonds to sulfur will remind you of cyanide and that you have a single bond from sulfur to carbon and then a triple bond from carbon to nitrogen. Something to note when the bonding is from the metal to the sulfur atom in this arrangement, this is thiocyanate by itself. And then, of course, when we have an anion as a ligand, an anionic ligand with a negative charge as this does, we have to change the ending to o so its name becomes bio sato. So thiocyanato, we've changed that cyan to cyano. And then in terms of our metal atom depends on whether our complex is a cion or an an our complex is a cion. So we just use the atom's name iron and then Roman numerals to indicate the charge. So as our problem says, iron to Roman numeral two, last of all, we name our anion chloride. So write that there. And then the only thing we have to do to get to our name finally is that we need to put our ligands in alphabetical order. So Carbel is going to come before Thio Cyano notice that we're not including our prefixes because they are not considered in terms of alphabetical order. So we're going to name this, starting with a ligand five. Carbs would be pentacarbonyl and then Thio Cyano iron two chloride. So let's look through our answer choices to see if the name is correct. We'll just look at the names and then we'll go back to our formula. So choice A number one has pentacarbonyl, bio cyano iron two chloride. So the name is correct in choice B we have PTO carbon, iso thio cyano iron two chloride. So this is incorrect. This is not Iso Cyano. If you recall, I talked about how that ligand could connect in two different ways. If it's iso thion, that means the bonding is between the metal and the nitrogen rather than the sulfur. So choice B will not be our answer because the name for number one is incorrect. Now, let's look at choice C, pentacarbonyl, thio cyano iron, two chloride. That's correct. But choice D for number one has that iso onto as well. So we can cross out choice D because number one is incorrect. So we're down to just two answer choices to go to. Now let's just double check our formula and make sure that's correct. We started off with I iron. Now we'll look at our carbon ligands. So we put in parentheses co and then a subscript of five and then we have our ion, excuse me. Now we have our second ligand. Sometimes this becomes like a tongue twister here, but we need to name it in order of the bonding. So we go from the bonded atom outward justice and Carbonel, we named it co because the carbon has the bond. So in this case, in parentheses, we would say SCN and then close parentheses, close the brackets because that's our complex. And then we write our cl chloride, the overall complex is neutral. So there's no charges indicated uh in our formula. So when we look at A and C here, we see that choice A has an incorrect formula for R thio cyano ligand. It's written N CS. But in this case, the bond is to the S and the S should be named first. So number one choice A is incorrect, eliminating choice A. When we go over to choice C, we see that formula has that ligand in the correct order SCN. So choice C, all we had to look at was one compound. If you want to test, you would be done, you'd have your answer answer choice C just because it's the only one that has compound compound number one named correctly. And with the correct formula, however, we'll be thorough and go on and just double check our other compounds and go through how to name them and write their formulas. So here we go to number two, we have iron, of course, in the center again, start by number two. And so our formula will begin again with brackets. And then fe we also have five carbonel leggings, which again, the name remains the same carbonel because they are neutral. And here we have that other version that other bonding of that ligand iron is bound to the nitrogen. And then we have a carbon and a sulfur. The bonding is actually different in this one. In this case, there are double bonds between the nitrogen and the carbon and between the carbon and the sulfur, not the triple bond in the other version. So when the bonding is to the nitrogen, this is iso pio sato again, that o ending since its an an I. Um and one way to remember that is thio, of course, indicates sulfur. So tho cyano has the bond to the sulfur, whereas isot cyano has the sulfur further out. So that's how you can keep those names straight. So we have our ligands and again, we have um in, in terms of alphabetical order carbonel will come before isot oyo. So when we look at our name, we should have Pena for the five carbon. Pentacarbonyl isot ino iron two. And our I our counter ion is again chloride. So let's look at choice C and make sure that's correct. And indeed, we see pentacarbonyl isothiocyanate iron two chloride. So our name is correct. When we write our formula, then we'll write in after the iron in parenthesis co and then subscript five. And then again, important to write in order here, starting with the atom bonded to the metal N CS, close the brackets and write CL for the ion. So when we look at our formula that's written, we see brackets feco five and then correct order N CS, low brackets and CL. So number two also correct, you can see that if you went back to choice A, they did the same thing with compound number two, naming it in the wrong order SCN. So reversing those two in the formula of that compound, finally, let's move on to complex number three. This one's a little different from the others. Again, we have iron we have our five carbonyl again, but our six ligand is not one of these N CS or SCN. It is bromide. Bromide is a negatively charged ligand. And so we change it to an O. So we say bromo, and we remember that this is negative one charge. And when we think about alphabetical order here, in this case, we have BROMO starting with B it come before Carbonel. So in this one, bromo needs to come first, there's only one. So it will be bromo pac carbonel iron two and our ion is different here. We have an oh minus is our counter ion. So hydroxide rather than chloride. So we can see in choice C number three, bromo. Pento Penta, excuse me, carbonyl iron two hydroxide. So correct name and the formula again will start with fe and then in brackets we start with the BROMO. So br and then in parentheses, co subscript five, close our brackets and then oh or our ion and that is written correctly in choice three. So I see the answer. Choice C is correct and having the correct formula for all three. And the correct names. Pentacarbonyl thio cyano iron two chloride, pentacarbonyl iso thio cyano iron two chloride and bromo pac carbon iron two hydroxide. See you in the next video.