Nikon does not make an IR remote control that includes an interrupt trigger for the D5100. There is the ML3 for the more advanced Nikon dSLRs that interfaces through the wired trigger control so the camera can goto sleep and the IR remote will wake the camera when the IR beam from the transmitter is interrupted.
The IR for the D5100 has a time out feature so the ML-L3 or similar remote would not work.
You might look for a 3rd party product that uses the wired remote port of the D5100 and can trip the focus and then the shutter release. This would allow your camera to sleep between camera shots.