label teams A - L,
events 1-6
A B C D E F G H I J K L
A . 1 3 5 . . . . . 6 4 2
B . . 2 3 6 . . . . . 5 4
C . . . 1 4 5 . . . . . 6
D . . . . 2 4 6 . . . . .
E . . . . . 1 3 5 . . . .
F . . . . . . 2 3 6 . . .
G . . . . . . . 1 4 5 . .
H . . . . . . . . 2 4 6 .
I . . . . . . . . . 1 3 5
J . . . . . . . . . . 2 3
K . . . . . . . . . . . 1
L . . . . . . . . . . . .
So in your first event, A pays B, C plays D, E plays F...
In the second event, B plays C, D plays E, ..., A plays L.
Following this kind of schedule, you can have up to 11 events (number of teams minus 1), but you need to have an even number of teams (which you do, so it's not a problem).