One- and two-dimensional coordination polymers of zinc(II) with pyrazine. Solid state reactions and decomposition kinetics of the interconversion reactions

The reaction of zinc(II) bromide with pyrazine yielded the two coordination polymers [ZnBr2(pyz)] 1 and [ZnBr2(pyz)2] 2. Crystal structures of these two compounds show that 1 is a 1-D zigzag chain polymer while 2 forms a regular square-grid (4,4) network. Adjacent grids in 2 are slipped in one direction so that the axial bromide ions on one layer project into the cavities of the grids in adjacent layers. The solid-state reaction of 1 with pyrazine yields 2, and 2 in its turn is readily converted into 1 by heating. The activation energy of the latter process has been determined as 99.8 kJ mol−1.