From a newly synthesised tridentate ligand [pepci = N -(2-pyridin-2-ylethyl)pyridine-2-carbaldimine] two new octahedrally co-ordinated nickel(i1) dimers, [{Ni(pepci) (N3)z}z] 1 and [{Ni(pepci)(NCS),},] 2, have been prepared. The crystal structure 1 has been solved. It crystallizes in space group P2,lc with four formula weights in a cell measuring a = 9.1 98(3), b = 17.382(6), c = 19.356(7) A, and p = 99.57(1)". The structure consists of isolated dimeric units in which the nickel ions are linked by two azide bridging groups in an end-on fashion. Two pepci ligands and two terminal azide groups complete the co-ordination spheres. Inside the dimer, each Ni(pepci) ( N3)* entity is crystallographically non-equivalent. There are two different bridging angles Ni(A)-N(4A)-Ni( B) 102.2(2) and Ni(B)-N(4B)-Ni(A) 101.0( 2)". The co-ordination geometry at each nickel atom is approximately octahedral. The Ni(A) 0 . Ni(f3) distance is 3.297(1) A. For complex 2 a dimeric structure involving end-to-end thiocyanate bridging groups is proposed. Magnetic susceptibility data, measured from 4 to 300 K, were fitted to the Ginsberg equation, giving the parameters (cm-'): J = +36.3, D = -18.8, z'J' = 0.0 (N3); and J = +4.9, D = -9.8, z'J' = +0.33 (NCS). The magnetic behaviour of these and related complexes is discussed and some magnetostructural trends are given.

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Isomorphous compounds exhibiting the general formula [M(N 3 ) 2 (bpa)] n (M = Mn II 1, Co II 2 or Ni II 3; bpa = 1,2bis(4-pyridyl)ethane) have been prepared and magnetostructurally characterised. X-Ray diffraction analysis revealed a 2-D arrangement of octahedrally co-ordinated metal cations where di-µ-(1,3)-N 3 -bridged metallic chains are connected through bpa ligands. IR and UV-VIS spectra were consistent with this structural characterisation. Magnetic analysis carried out by means of ESR spectroscopy and susceptibility measurements indicated that the three compounds are antiferromagnetic, J values being Ϫ5.7, Ϫ14.0 and Ϫ80 cm Ϫ1 for 1, 2 and 3, respectively.

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The synthesis, crystal structure, and spectroscopic and magnetic properties of a new alternating ferro-and antiferromagnetic, one-dimensional manganese(II) azide complex, [Mn(dpa)(N 3 ) 2 ] (where dpa is the 2,2Ј-dipyridylamine ligand), are reported. The compound's crystal structure has been resolved at room temperature. The complex crystallizes in the monoclinic P2 1 /c space group, with a = 7.089(2), b = 19.090(4), and c = 9.682(4) Å , β = 104.61(2)°, and Z = 4. The structure consists of neutral chains in which each Mn II cation is alternatively bridged by two end-on and two end-to-end azido bridges. The octahedral coordination of the metallic [a]

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