another key binding question

[kin techie com]

Hi,

I want to be able to bind the key sequence "control @" in emacs.
This sequence is again somehow hidden.

I ran xev, pressed and hold the control and shift keys, and saw
the key-down events for shift and control, but xev reported no
new events when I pressed 2.

I do not define it in the my .sawfishrc or sawfish's key
shortcuts.

Any idea who may be claiming the key sequence?

Thanks.

-kin