precursor complex

https://doi.org/10.1351/goldbook.P04806
May either indicate an @E02087@ or a @C01160@, but furthermore implies that this complex undergoes a reaction (e.g. @E02011@).
Source:
PAC, 1996, 68, 2223. (Glossary of terms used in photochemistry (IUPAC Recommendations 1996)) on page 2266 [Terms] [Paper]