Structure and magnetic properties of the ferromagnetically coupled nickel dimer [Ni(terpy)(NCO)(H2O)]2(PF6)2

Summary The crystal structure of the dimeric [{Ni(C₁₅H₁₁N₃)(NCO)(H₂O)}₂](PF₆)₂ has been determined by x-ray diffraction methods. Crystal data are as follows: P 1,a=11.904(4) Å,b=10.392(4) Å,c=8.531(3) Å, =111.87(2)^o, =90.61(3)^o, =107.37(5)^o, U=926.7(4) ų, Z=2, D_m=1.77(2), D_x=1.78 g. cm^–3, (Mo-K)=12.1 cm^–1, F(000)=494. Least-squares refinement of 1230 reflections with I1.5(1) gave a final R =0.035 (R=0.038). The structure is formed by cationic [{Ni(C₁₅H₁₁N₃)(NCO)(H₂O)}₂]²⁺ and anionic PF₆^– units, linked through hydrogen bonds between the water molecule and the hexafluorophosphate ion. The resulting coordination geometry around each nickel(II) ion is ferragonally elongated octahedral. The N-bridging cyanate groups occupy simultaneously an equatorial position in the coordination sphere of one of the nickel atoms and an axial position in the other. The remaining axial positions are occupied by the water molecules. Powder susceptibility data, between 2.0 and 300 K, show the existence of ferromagnetic exchange between nickel centres. The magnetic parameters are J/K=6.6K, D/K =–17.6 K, zJ/K=0.57 and g-2.21.