Structure and magnetic exchange in poly-bis((μ-dialkylphosphinato)copper(II) compounds

The preparation, magnetic and thermal properties, electronic and infrared spectra, and molecular structure of poly-bis(μ-di-n-hexylphosphinato)copper(II) are described. Crystals of the compound are triclinic, a = 9.800(3), b = 12.336(6), c = 13.352(8) Å, α = 88.53(3), β = 74.02(4), γ = 82.33(3)°, Z = 2, space group [Formula: see text]. The structure was solved by Patterson and Fourier syntheses and was refined by full-matrix least-squares procedures to R = 0.045 and R w  = 0.056 for 3095 reflections with I ≥ 3σ(I). The crystal structure of Cu[(n-C 6 H 13 ) 2 PO 2 ] 2 consists of well-separated infinite chains of centro-symmetric spiro-fused eight-membered rings propagating along the crystallographic a axis.The magnetic susceptibility of Cu[(n-C 6 H 13 ) 2 PO 2 ] 2 was studied over the temperature range 4.2 to 300 K. The compound shows ferromagnetic behaviour and the data have been successfully analyzed according to the isotropic Heisenberg model for linear chains with g = 2.16 and J = 2.58 cm −1 . For comparison, the magnetic susceptibilities of Cu[(C 2 H 5 ) 2 PO 2 ] 2 and Cu[(n-C 4 H 9 ) 2 PO 2 ] 2 have also been measured over the range 4.2 to 300 K. The butyl derivative shows ferromagnetic exchange with g = 2.16 and J = 2.22 cm −1 while the ethyl derivative is antiferromagnetic with g = 2.19 and −J = 1.27 cm −1 . The structural details of all three compounds are examined in the light of the differing magnetic properties.