Copper complexes with multidentate ligands derived from l-proline. X-ray crystal structure of {[Cu(N,N′-bis[(S)-prolyl]ethylenediamine)]ClO4}2·(MeCN)2

The reaction of [Cu(CH3CN)4]X (X=ClO4, PF6) with multidentate ligands N,N′-bis[(S)-prolyl]ethylenediamine (1), N,N′-bis[(S)-N-benzylprolyl]ethylenediamine (2), N,N′-bis{[(S)-pyrrolidin-2-yl]methyl}ethylenediamine (3), N,N′-bis-{[(S)-N-benzyl-pyrrolidin-2-yl]methyl}ethylenediamine (4) gives copper complexes which were characterised by analytical (elemental analysis, and mass spectroscopy) and FT IR, NMR and electronic spectroscopies. The {[Cu(N,N′-bis[(S)-prolyl]ethylenediamine)]ClO4}2·(MeCN)2 complex was characterised by X-ray crystallography. This new family of Cu-complexes catalyse the cyclopropanation of styrene with ethyl and t-butyl diazoacetate to yield cis/trans 2-phenylcyclopropan-1-carboxylates in good yields and selectivity against dimerisation and low ee (<10%).