Two copper(Ⅱ) α,β-unsaturated carboxylate complexes with acetamide, Cu~2(CH~2＝CHCOO)~4(C~2H~5NO)~2(1) and Cu~2[CH~2＝C(CH~3) COO]~4(C~2H~5NO)~2(2), have been synthesized and characterized by elemental analyses, IR, ESR, electronic spectra and magnetic studies. The single crystal X-ray diffraction study of two complexes shows that complex 1 crystallizes in the monolinic space group with P2~1/c, a=1.5333(5) nm, b=1.0044(3) nm, c=1.6184(7) nm, β=115.28(3)°, Z=4, and R=0.0701, while complex 2 is triclinic, with space group P1, a=0. 93327(11) nm, b=1.12484(11) nm, c=1.3740(6) nm, α=94.90(2)°, β=108. 409(14)°,γ=110.556(5)°， Z=2 and R=0.0351. Two copper(Ⅱ) atoms are bridged by four α,β-unsaturated carboxylate groups, with each copper(Ⅱ) atom coordinated with an acetamide molecule in the axial position, forming a distorted square pyramidal configuration. The symmetric center is between the two copper(Ⅱ) atoms. The Cu－Cu bond distance is 0.26302(13) nm for the complex 1 and 0.26383(4)nm for the complex 2. The Cu－Cu distance and magnetic studies suggest that there exist antiferromagnetic interaction between two copper(Ⅱ) atoms.

Key words: COPPER COMPLEX, ACETAMIDE P, CRYSTAL STRUCTURE, METHYLPROPENOIC ACID P, ELEMENTAL ANALYSIS, INFRARED SPECTROPHOTOMETRY, ELECTRON SPIN RESONANCE