Nickel pivalate complexes: structural variations and magnetic susceptibility and inelastic neutron scattering studies

Abstract

The synthesis and structural characterisation of three small nickel(II) cages are reported, all stabilised by pivalate ligands. The magnetic properties of the cages have been studied by a combination of susceptibility measurements and inelastic neutron scattering. For a dinuclear cage, [Ni2(mu-OH2)(O2CCMe3)4(HO2CCMe3)4] 1 the ground state is S=2, with a ferromagnetic exchange interaction between the Ni(II) centres of J=0.32 meV and D(S=2)=-0.09 meV in the ground state. For a tetranuclear heterocubane cage, [Ni4(mu(3)-OMe)4(O2CCMe3)4(MeOH)4] 2, two ferromagnetic exchange interactions are found and an S=4 ground state observed. While the zero-field splitting of this state cannot be determined unambigiously the most likely value is DS=4=-0.035 meV. For a tetranuclear nickel butterfly, [Ni4(mu3-OH)2(O2CCMe3)6(EtOH)6] 3, three exchange interactions are required, two anti-ferromagnetic and one weakly ferromagnetic; the resulting ground state is S=0. The data enable us to estimate the zero-field splitting of single Ni(II) ions involved in the cage as Di=+1.0 meV. Both and are therefore expected to be new single molecule magnets.

Dinuclear Nickel(II) Pivalate with Μ-Aqua and Di-Μ-Pivalato Bridges Showing a Ferromagnetic Interaction

“…This result shows that a considerable ferromagnetic interaction is operating between the two nickel atoms. Similar magnetic behavior was also reported by Eremenko [16] and Winpenny [17], although a smaller D value was found. The bridging angle between the two nickel atoms is 113.57(6)° for Ni1-O17-Ni2 in the present crystal structure.…”

“…Another hydrogen bonds can be found between the coordinating pivalic acid molecule and the bridging pivalato group or the neighboring pivalic acid molecule [O6(H)···O1 2.564(2) Å, O10(H)···O7 2.534(2) Å, O14(H)···O11 2.567(2) Å, O16(H)···O4 2.578(2) Å]. Almost same structure was reported by Eremenko et al [16] and Winpenny et al [17,18], although the preparative methods are different from the present preparation. The Eremenko's crystal structure was measured at 230 K and is almost same as the present crystal structure taken at 90 K, whereas the Winpenny's structure at 150 K belongs to different crystal system and space group, orthorhombic Pbca, irrespective of the similar dinuclear structure.…”

“…The bridging angle between the two nickel atoms is 113.57(6)° for Ni1-O17-Ni2 in the present crystal structure. The corresponding Ni-O-Ni angle is 112.8(2)° in Eremenko's crystal structure [16], whereas 111.24(11)° [17] or 111.53(10)° [18] in Winpenny's crystal structures. From the magneto-structural relationship between exchange interaction and Ni-O-Ni angle, the observed Ni-O-Ni angles prefer antiferromagnetic interaction rather than ferromagnetic interaction [15,19].…”

On the Possibility of Magneto-Structural Correlations: Detailed Studies of Dinickel Carboxylate Complexes

“…19 The compound contains two nickel( ) ions bridged by one water and two pivalate ligands ( Figure 1). 26 Structures of this type are well known for nickel and a host of other divalent metal ions.…”

Linking Rings through Diamines and Clusters: Exploring Synthetic Methods for Making Magnetic Quantum Gates

“…Lines are fitting curves obtained by diagonalizing the spin Hamiltonian of single {Cr 7 Ni} wheels, as described in the text. [14,15] were prepared according to published methods. , 0.6 mmol) was added.…”