Heres the Monsanto process: I can't figure out how to determine the electron count for these rhodium complexes. Starting with the one at the top. Heres how I count its electrons: rhodium is a group 9 element so it has 2s electrons and 7d electrons which means it has 9 out of 18 valence electrons to begin with. The 2 CO ligands add an extra 4 electrons, bringing the total to 13. I'm a bit confused about how the iodide ligands work, do they also donate 2 electrons each? If so, that brings the electron count to 17. The ion has a charge of -1, bringing the total electron count to 18. How can this be a coordinatively unsaturated complex? If you add 2 more ligands to it then you end up with an electron count of 22.