Coordination Polymers of Dicyanamide and Methylpyrazine: Syntheses, Structures, and Magnetic Properties

The crystal structures of M(dca)2(Mepyz)2·H2O, M = Co (1), Ni (2), dca = dicyanamide, N(CN)2-, and
Mepyz = methylpyrazine; [Mn(dca)2(Mepyz)2][Mn(dca)2(Mepyz)]2·2MeCN (3); and Mn2(dca)3(NO3)(Mepyz)2 (4) are
reported. Compounds 1 and 2 are isomorphous and consist of two-dimensional (2D) (4,4) sheets, with bridging μ1,5-dca ligands and trans-disposed monodentate Mepyz ligands. Compounds 3 and 4 were obtained as an intimate
mixture from the same reaction mixture. Compound 3 contains both one-dimensional (1D) chains, in which Mn
atoms are bridged by double μ1,5-dca bridges and the Mepyz ligands are trans and monodentate, and 2D (4,4) sheets,
in which similar 1D chains are connected by bridging Mepyz ligands. The structure of 4 contains two interpenetrating
4,6-connected three-dimensional networks, with bridging μ1,5-dca anions, bridging Mepyz ligands, and chelating
NO3- anions. Only very weak coupling and no long-range magnetic ordering intrinsic to these materials were observed
for 1 or 2, although traces of the ferromagnets α-Co(dca)2 and α-Ni(dca)2 were observable in very small applied
fields, with ordering temperatures at 9 and 21 K, respectively.