Another huge stumbling block is that you're looking at keys from two different generations of BMWs. You'll need to overcome the internal communication that is transmitted from each style of key.
The newer key comes from a generation of BMWs that doesn't even use the same type of communication bus as the diamond shaped key found in the e38/e39/e46/e53 generation of BMWs.
Your key uses 2 radio frequencies. A 125 KHz AM signal is used by EWS which sends a signal to the ring antenna around the ignition that powers up the EWS transponder chip....which then sends data back to the EWS control module and DME/ECU which allows the car to start. The FZV & DWA (central locking & anti-theft alarm siren) systems are sending a 315 MHz (433 Mhz in Europe) to a receiver (in the C pillar for sedans & in the rear roof spoiler/upper tailgate on the SAVs & Tourings)...which then sends that signal to the GM III which then sends a signal to lock/unlock or arm/disarm the car.
All the above is done over the K & P bus depending on which engine/model/options you have:
The new gen BMWs that use that newer style CAS (comfort access system) keys...have a different communication bus system (it's not like the one above. The CAS system uses a newer 128 bit encryption this is unlike your old style key. It also uses EWS 4 (which is the immobilizing system that shuts down ignition and fuel).
Perhaps someone has mocked up the new style key where you can insert the IC board from the diamond shaped key...you'll need all the innards from your old style key to make it work.
Newer Style CAS Key Info
