Final answer:
The two solutions mixed to create a metal ion complex are Fe2+ and 1,10-phenanthroline, forming a stable octahedral complex where the charge is balanced.
Step-by-step explanation:
The two solutions you will be mixing together to create the metal ion complex are Fe2+ and 1,10-phenanthroline. Based on the properties of the ions involved and the need to balance charges in forming complexes, it is important that the metal ion has a charge that complements the ligand, allowing for a neutral overall complex or one whose charge can be balanced by other ions in solution.
In the case of forming a typical complex with 1,10-phenanthroline, which is a bidentate ligand, we often use Fe2+. This is because 1,10-phenanthroline can effectively chelate, or bind to, Fe2+ to form a stable, octahedral complex. The iron(II) ion (Fe2+) is chosen over iron(III) (Fe3+) because the latter would result in a charge imbalance as 1,10-phenanthroline is a neutral ligand.