A/c Problem On 1997 Sebring Conv.

I just replaced the a/c compressor on a 1997 Sebring JXI convertable. I also replaced the drier and expansion valve, flushed the system, and added the correct amount of oil. I rotated the clutch 20 times to free the valves and push the oil out. I then pulled a vacuum for 1.5 hrs and sucked in about 3/4 of a can of freon. I then started the car to fire up the compressor so i could finish filling the system with freon. Here is my problem. The clutch will not engage to allow me to finish pulling in the freon. How do I get the clutch to engage? Any help with this matter will be greatly appreciated.