The transmetalation step normally occurs after our oxidative addition step. We're going to say within this step we basically have the R₂ group of our coupling agent connecting to the transition metal complex while at the same time our X group leaves. Now our X group represents a good leaving group, so normally X is represented by chlorine, bromine, iodine or a triflate. If we take a look here, we have our R₂ group leaving, breaking this bond and connecting to our transition metal M. At the same time, this bond here breaks and X connects to our C group. So, as products, we're going to have still our R₁ group connected to our transition metal, which is connected to a set number of ligands, which, remember, is normally 2 or 4 at the beginning of the reaction where the X group left are R₂ attaches. Then as a byproduct, which we're really not concerned with but we're going to draw here just so that you know it's still around. We have our C group connected to our X group. So if you really want to think about transmetalation, it really just is one ligand coming in so that another ligand can leave. And those ligands are sometimes attached to 2 metals or to metalloids.

Now that we've seen this basic generic setup for the step, let's apply it to this image here. So, we created this structure here in the oxidative addition step. Now what we're going to do is we are going to expose it to a coupling agent. So here's my coupling agent here. So, the blue portion is my R₂ group. So, what's going to happen here is the bond between my R₂ group and the C group is broken and we're going to attach it to my transition metal, in this case palladium. While it does that, we're going to have this bond here break so that bromine can attach to the carbon. Okay. So, we're going to just have it attached to the carbon. And actually, let's redraw those arrows so it's not as messy. So, we have this bond here break, connect to the palladium, and this bond here breaks and attaches to the C. So what we wind up getting is we're going to have our 2 carbonyls still connected to palladium. And then we're going to still have this alkene group there. And there, where the halogen was, is now where we're going to place the R₂ group. And then we'd have our byproduct, which would just be our C group connected to our Br. So, that's basically how we would set up this transmetalation step. So, just remember, it all boils down to one ligand attaching to the transition metal of our complex so that the X ligand can leave. Okay. So our X group here could represent chlorine, bromine, iodine or a triflate group.