2D and 3D Anilato-Based Heterometallic M(I)M(III) Lattices: The Missing Link

The
similar bis-bidentate coordination mode of oxalato and anilato-based
ligands is exploited here to create the first examples of 2D and 3D
heterometallic lattices based on anilato ligands combining M­(I) and
a M­(III) ions, phases already observed with oxalato but unknown with
anilato-type ligands. These lattices are prepared with alkaline metal
ions and magnetic chiral tris­(anilato)­metalate molecular building
blocks: [MIII(C6O4X2)3]3– (MIII = Fe and Cr; X = Cl
and Br; (C6O4X2)2– = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone,
H4C6O4). The new compounds include
two very similar 2D lattices formulated as (PBu3Me)2[NaCr­(C6O4Br2)3] (1) and (PPh3Et)2[KFe­(C6O4Cl2)3]­(dmf)2 (2), both presenting hexagonal [MIMIII(C6O4X2)3]2– honeycomb layers with (PBu3Me)+ in 1 or (PPh3Et)+ and dmf in 2 inserted between them. Minor modifications in the synthetic
conditions yield the novel 3D lattice (NEt3Me)­[Na­(dmf)]­[NaFe­(C6O4Cl2)3] (3),
in which hexagonal layers analogous to 1 and 2 are interconnected through Na+ cations, and (NBu3Me)2[NaCr­(C6O4Br2)3] (4), the first heterometallic 3D lattice
based on anilato ligands. This compound presents two interlocked chiral
3D (10,3) lattices with opposite chiralities. Attempts to prepare 4 in larger quantities result in the 2D polymorph of compound 4 (4′). Magnetic properties of compounds 1, 3, and 4′ are reported,
and in all cases we observe, as expected, paramagnetic behaviors that
can be satisfactorily reproduced with simple monomer models including
a zero field splitting (ZFS) of the corresponding S = 3/2 for Cr­(III)
in 1 and 4′ or S = 5/2 for Fe­(III)
in 3.