Lesson 11.7: Word order is different?

In Lesson 11.7, one of the sample sentences is: Ils n’en veulent acheter aucune.

However, that doesn't look like the normal word order. Doesn't the rule state that the pronoun should come before the infinitive? So it should be: Ils ne veulent en acheter aucune? 

Or is this an unmarked rule in informal speech? 

That word order is gramatically correct (according to my francaphone wife), with the emphasis on not buying a single one of ‘them’. A perhaps more fluid word order, used in spoken French, would be “Ils ne veulent en acheter aucune”.