- IMC conditions
- Pilot flying is not IMC current
- Pilot flying is sole manipulator of the controls, and thus logs PIC
- Pilot not flying is acting PIC (required because the pilot flying
is
not IMC current) and so logs PIC

There is no provision for the pilot acting as PIC to log PIC in this
case. Only the flying pilot would be able to log PIC. The only way you
can log PIC is per 61.51(e). In this case the guy serving as PIC does
not meet the requirements of a "required crew member" since the
aircraft is legal to fly IFR with just one pilot (the fact that that
pilot isn't qualified doesn't change that).

-Robert