Inorganic Chemistry, Vol.42, No.4, 986-996, 2003
Structural and physical properties of the ferromagnetic tris-dithiooxalato compounds, A[(MCrIII)-Cr-II(C2S2O2)(3)], with A(+) = N(n-CnH2n+1)(4)(+) (n=3-5) and P(C6H5)(4)(+) and M-II = Mn, Fe, Co, and Ni
The structural and magnetic properties of the tris-dithiooxalato salts, A[(MCr)-Cr-II(C2S2O2)(3)], have been investigated with A(+) = PPh4+, N(n-CnH2+1)(4)(+), with n = 3-5, where M-II is Mn, Fe, Co, and Ni. With the exception of A[MnCr-(C2S2O2)(3)], all the salts are ferromagnets with Curie temperatures, T-c between 5 and 16 K. In contrast to the corresponding oxalates which are ferromagnetic, the A[MnCr(C2S2O2)(3)] compounds are paramagnetic above 2 K. Powder neutron diffraction studies of d(20)-PPh4[FeCr(C2S2O2)(3)] indicate that no structural phase transitions occur between 2.4 and 285 K and that the coefficient of linear expansion is four times larger for the c-axis than for the a-axis. The crystal structure refined from powder neutron diffraction data confirms the honeycomb layer arrangement observed in the related bimetallic tris-oxalate salts. The Mbssbauer spectra reveal that the iron(II) in PPh4[FeCr(C2S2O2)(3)] is coordinated mainly to six oxygen atoms of the dithiooxalato ligand but with a minor component of sulfur coordination that increases with aging of the sample; the iron(II) is high-spin in both cases. Powder neutron diffraction profiles of d(20)-PPh4[FeCr(C2S2O2)(3)] below T-c show magnetic intensity with a q = 0 propagation vector, confirming the presence of ferromagnetic order.