Synthesis, structural, spectroscopic and magnetic studies of two azido and thiocyanato nickel(II) dinuclear complexes with ferromagnetic interactions

Abstract

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.

A Binuclear Copper(II) Complex with Two Symmetric End-on Azido Bridges. Synthesis, Spectroscopy, Crystal Structure and Magnetism

“…In fact, as shown in Scheme 1, in complexes with two symmetric end-on azido bridges, the Cu-N azido bond lengths are usually shorter than 2.10 Å and the interaction between the metal ions is often strongly ferromagnetic [4][5][6][7][8][9]. In contrast, complexes bridged by asymmetric end-on azido bridges with both short (£2.10 Å ) and long Cu-N azido bond lengths ( ‡2.20 Å ) are rare, and the interaction between metal centers is weakly ferromagnetic, or even antiferromagnetic [10][11][12][13].…”

Dinuclear Complexes of MII Thiocyanate (M = Ni and Cu) Containing a Tridentate Schiff‐Base Ligand: Synthesis, Structural Diversity and Magnetic Properties

“…When the N 3 -anion acts as bridging ligand, normally the end-to-end 1,3-coordination mode gives antiferromagnetic coupling, while the end-on 1,1-mode gives ferromagnetic coupling, but for very large M-μ 1,3 -N 3 -M bond angles the magnetic coupling may be reversed. [16][17][18][19] 2 ] cores have approximately the same angles and distances, and they generally show low ferromagnetic behavior, which was explained by Ginsberg et al [19d] and Duggan et al [19e] Ferromagnetic interactions have been found, generally, in octahedrally coordinated dimeric nickel(ii) complexes with 1,3-thiocyanate [16a,17] and -selenocyanate bridges. [18] When the phenolate acts as a bridging ligand through the oxygen atom in dinuclear nickel(ii) complexes, generally antiferromagnetic behaviour was found; [20][21][22][23] only three complexes showing ferromagnetic coupling have been described in the literature.…”

A novel 2D copper(II) coordination polymer with bidentate coligands and alternating double EO- and single EE-azido bridges

“…The CuÁ Á ÁCu separation in the dimer is 3.304 Å. These values lie in the typical range for double EO azido-bridging copper(II) complexes (2.9004-3.5034 Å) [12,23,[27][28][29][30]. In 1 each dinuclear unit is further linked through single EE azide bridges to four neighboring dimers, leading to a neutral 2D network with a pseudo-honeycomb (6, 3) topology (Fig.…”