(a) Identify the Lewis acid and the Lewis base in the reaction of ethylenediamine (H2NCH2CH2NH2) with Ni2+ to form [Ni(en)3]2+.

(b) Identify the ligands and donor atoms.

(c) Give the coordination number and geometry of the metal in the complex.

Video transcript

Welcome back, everyone. Here's our next problem. Consider the reaction of glycinate ion H two NC two co minus with co three plus to produce. And then we have a complex here in brackets with an overall charge of three plus. And that complex includes co and then in parentheses, lowercase gly subscript three. So it's a complex with an overall positive three charge consisting of Cobalt and three glycate ligands. We have to answer three questions. Number one, which is the Luis acid and the Lewis base in the reaction. Number two, which are the ligands and donor atoms in the complex. And number three, determine the co-ordination number and the geometry of the central metal ion. And then our multiple choice answers A through D are just different answers to these questions. So we'll walk through those as we look at the answers that we come up with. So first let's start out with which is the lowest acid and the lowest base in the reaction. Let's recall, Lewis acids are electron acceptors. I like to look at that letter A A for acceptor and A for asset while Lewis Bass is an electron donor. So when we think about which is which we've got a pretty straightforward answer because we have this Cobalt three plus and positively charged metals are Luit acids, they definitely accept electrons. So the luis acid is our Cobalt three plus and the Lewis base is R glycate ion, you can also tell it has a negative charge. And if we look at the structure glycinate, we have two carbons bonded together. And the first carbon has an NH two group on it. The mina group, second carbon has that double bond to an O and single bond to another O. So we have both a negatively charged oxygen which will be an electron donor. And we have a lone pair on our amino group, which is also happy to be an electron donor. So this is actually a bate ligand because it can form bonds with our central metal, both with the negatively charged oxygen and the nitrogen. So we've got our Lewis acid and Lewis base. Let's go ahead and look at our multiple choice options. In a long question like this, we can eliminate sometimes answer choices before we even work through everything. So we know that our luis acid will be the Cobalt. So choice A says Lewis acids, glycinate ion and Lewis bases Cobalt. So we can eliminate that right away. Choice B is the correct arrangement. Lewis acid being Cobalt, Lewis base being glycinate. So we can leave. Choice B. Choice C has the reverse arrangement. So we can eliminate choice C on the basis of its answer to number one. But choice D has the correct Lewis acid and base. So we're down to just two possible answer. Choices B and D. So let's move on to question. Number two. Number two says, which are the ligands and donor atoms in the complex? Well, we already answered that our donor atoms are nitrogen and oxygen and there's two of them in our ligand, our ligand is glycinate. Cobalt is our central metal atom and it's surrounded by three glycinate ligands. So let's go down to our answer. Choices. Just B and D left. Number two, in choice B says ligands are glycinate items. Glycinate ions, donor atoms are N and O. So B is OK. Choice D says ligands are glycinate ions and donor atoms are O and O. So only the negatively charged oxygen donates the electrons here. This is typical of carboxylate ions. So we can eliminate choice D as it has the incorrect donor atoms. So if I run a test, I'm already done. Choice B is my correct answer. And I move on. But to be thorough, we'll go ahead and look at question number three here, determine the co ordination number and geometry of the central metal ion. So we know what we have our Cobalt. We have three ligands, but this is a bent ligand. So the coordinating number will equal three legends times two bonds are multiplied by two bonds per ligand since it's bent eight. So the coordinating number will equal six with the coordinations of six, the geometry will be octahedral. So let's double check our choice. B make sure that's correct coordinations. Number six geometry octahedral. So therefore, we have our correct answer. Which is that our for number one, our luis acid is our Cobalt ion. Lewis base is the glycinate ion. For number two, our ligands are the glycinate ions with the donor atoms being nitrogen and oxygen. And number three, our co-ordination number is six and our geometry octahedral around our central Cobalt atom. See you in the next video.