While the early work of Hillhouse focused on early-transition metal chemistry, his later career efforts were dedicated towards base metals. For example, in 2001 Hillhouse and co-workers synthesized a complex that refuted the notion that it was impossible for late transition metals like nickel to form multiple bonds with heteroatoms. The result was a molecule that he affectionately referred to as “Double Nickel,” which possessed an indisputable nickel-nitrogen double bond. Later the group published a study showcasing that one can also synthesize and isolated an electronically similar phosphinidine species. Additionally, using bulky N-heterocyclic carbene (NHC) ligands, Hillhouse and co-workers showed that one can stabilize a linear two-coordinate Ni-based imido species. His group has also showcased how some of these and similar complexes can undergo redox chemistry forming Ni(I) and Ni(III) species.