Heterocyclic diketone derivatives with herbicidal action

Heterocyclic compounds of the formula (I) in which the variables are defined according to the description, the agriculturally suitable salts thereof, processes and intermediates for preparing the compounds of the formula I, compositions comprising them and the use thereof as herbicides, i.e. for controlling harmful plants, and a method for controlling unwanted plant growth, in which a herbicidally active amount of at least one compound of the formula I is allowed to act on plants, the seeds thereof and/or the habitat thereof.