If I think about the normal refrigeration systems I've seen. You could get 120 degC out of the compressors discharge gas temperature, but then youd need to have another heat exchanger to lower the gas temperature further to be able to condense the refrigerant. You could end up with a large amount of heat at temperatures below 120 degC.

From what I hear about high temperature heat pumps, the compressors, valves and components dont like the high working temperatures. You might need to look at using parts outside of whats used in the everyday refrigeration.

To try and have the refrigerant condense up at 120 degC, Im thinking youd probably need to look for a refrigerant outside of the ones used in everyday heatpumps and refrigeration plant.