Abstract The copper (I) and copper (II) complexes [Cu ((TMG et) 2 N et SEt)] BPh 4 (1· BPh 4) and [Cu ((TMG et) 2 N et SEt) Cl] Cl (2· Cl) with (TMG et) 2 N et SEt=((Me 2 N) 2 C= NCH 2 CH 2) 2 NCH 2 CH 2 SEt were synthesized and structurally characterized as a model system for the copper enzyme PHM, a monooxygenase involved in the activation of peptide hormones and neuropeptides. The reaction of the copper (I) complex 1· BPh 4 with ...