A series of η4-acyloxycyclohexadiene–Fe(CO)3 complexes was prepared and fully characterized by spectroscopic methods including single crystal X-ray diffraction. For this purpose a new synthetic access to differently acylated 1,3- and 1,5-dienol–Fe(CO)3 complexes was developed. The enzymatically triggered CO release from these compounds was monitored (detection of CO through GC and/or by means of a