Synthesis and single crystal structure analysis of 3,3',5,5'-tetramethyl-4,4'-bipyrazolium tetrachlorocobaltate(ii) monohydrate [H 2 ME 4 BPZ][CoCl 4 ]·H 2 O

Slow evaporation of a solution of 3,3',5,5'-tetramethyl-4,4'-bipyrazolium chloride ([H 2 Me 4 bpz]Cl 2 ) with the cobalt chloride in concentrated aqueous HCl solution yielded block blue crystals and X-ray single crystal structure determination at 100K revealed that the molecule crystallized in the monoclinic system with a P2 1 /n space group. The asymmetric units consist of tetrahedral [CoCl 4 ] 2- anions and tetramethyl bipyrazolium [H 2 Me 4 bpz] 2+  dications and one water molecule which are connected through N—H····Cl and N—H····O hydrogen bond networks in the crystal lattice. Keywords : Crystal structure, Hydrogen bond and crystal engineering