The invention provides a process to form an ethylene/a-olefin interpolymer, comprising at least the following steps A) through C): A) polymerizing, in at least one reactor, at least one reaction mixture comprising ethylene and the a-olefin, in a solution polymerization, and in the presence of at least the following components I), II) and III): I) at least one compound of Structure 1, as described herein; II) at least one co-catalyst, as described herein; III) at least one compound of Structure 2, as described herein; B) separating the final polymer solution into at least a polymer-rich solution and a polymer-free solution; and optionally, at least a portion of the polymer-free solution is recycled back to the reactor; C) maintaining the level of the at least one compound of Structure 2 in the at least one reactor, from 100 ppm to 10,000 ppm, as described herein.