Science, Tech, Math › Science Complex Ion Definition in Chemistry Share Flipboard Email Print ANDRZEJ WOJCICKI / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated July 03, 2019 Complex Ion Definition: Complex ions are ions with a central metal ion bonded to one or more molecules or ions. They are a type of coordination complex. The central ion is the coordination center, while the molecules or ions bound to it are termed complexing agents or ligands. Examples: The copper ammine ion, Cu(NH3)62+ is a complex ion. Sources Cotton, Frank Albert; Geoffrey Wilkinson; Carlos A. Murillo (1999). Advanced Inorganic Chemistry. p. 1355. ISBN 978-0-471-19957-1.Lawrance, Geoffrey A. (2010). Introduction to Coordination Chemistry. Wiley. doi:10.1002/9780470687123. ISBN 9780470687123.