On the Shirabe Jisho app for the iPhone, they have conjugation charts for verbs. It seems that with every る verb, there is no imperative when it is in ます form, but with every う verb, there IS an imperative when it is in ます form. Is this a mistake from the app, or is that just how it is, and if so, why?
So, I decided to take a look at the app (which is pretty nice, by the way) but I think there is a slight error going on.
For the る verbs and う verbs it is correctly showing an imperative form in the "positive" section. (Basically the short form of the verb).
For the う verbs it is listing the ～てください form as "imperative" but that is not, technically speaking, the "imperative" form. It is simply politely asking for someone to do something:
Please ___. So, I believe this has been mislabeled.
The る verbs do not show this form in the "ます" section but putting these verbs in the the "please" form is very simple. You just replace the る with てください.
Generally when one speaks of the "imperative" form, it is not in the formal ます category but is only in the short form of the verb (ie. the "Positive" section inside the app).