powersys,
Not if the transfer function represents a physical system, such as a control system or filter. Poles of a transfer function representing a physical system are either real, or occur in complex pairs. Of course, a pole can be complex, but since it does not represent a physical system, it would be of interest only to pure mathemeticians, not engineers.
Regards,
Kral
Added after 3 minutes:
powersys,
I meant to say "complex conjugate pairs" not "complex pairs".
Regards,
Kral