Axial-equatorial interactions in chelates of β-diones. Crystal and molecular structure of bis(3-nitro-2,4-pentanedionato) copper(II)

Abstract The IR spectrum and the structure of bis(3-nitro-2,4-pentanedionato)copper(II)], [Cu(O 2 N-acac) 2 ], are reported. The structure was determined by single crystal X-ray diffraction analysis (triclinic, space group P 1¯, Z = 1, a = 5.841(5), b = 7.843(7), c = 8.142(8)A, α = 80.40(7), β = 74.59(7), γ = 71.80(7)°, R 1 = 0.0335, w R 2 = 0.0809). The anion of 3-nitro-2,4-pentanedione, in addition to the commonly encountered bonds involving the carbonyl oxygens, also interacts with adjacent copper centres through one of the oxygen atoms of the −NO 2 group at a distance of 2.609(2)Aand the structure becomes polymeric. The axial interactions in the CuO 4 O 2 ′ chromophore are partly responsible for the elongation of the in-plane bonds. This is a rare example of a bis(β-dionato)copper(II) chelate in which copper(II) exists in a rhombically distorted octahedral environment.