Cobalt(II) chloride complexes with 1,1′‐dimethyl‐4,4′‐bipyrazole featuring first‐ and second‐sphere coordination of the ligand

In catena‐polydichloridocobalt(II)]‐μ‐(1,1′‐dimethyl‐4,4′‐bipyrazole‐κ²N²:N^2′)], CoCl₂(C₈H₁₀N₄)]_n, (1), two independent bipyrazole ligands (Me₂bpz) are situated across centres of inversion and in tetraaquabis(1,1′‐dimethyl‐4,4′‐bipyrazole‐κN²)cobalt(II) dichloride–1,1′‐dimethyl‐4,4′‐bipyrazole–water (1/2/2), Co(C₈H₁₀N₄)₂(H₂O)₄]Cl₂·2C₈H₁₀N₄·2H₂O, (2), the Co²⁺ cation lies on an inversion centre and two noncoordinated Me₂bpz molecules are also situated across centres of inversion. The compounds are the first complexes involving N,N′‐disubstituted 4,4′‐bipyrazole tectons. They reveal a relatively poor coordination ability of the ligand, resulting in a Co–pyrazole coordination ratio of only 1:2. Compound (1) adopts a zigzag chain structure with bitopic Me₂bpz links between tetrahedral Co^II ions. Interchain interactions occur by means of very weak C—H...Cl hydrogen bonding. Complex (2) comprises discrete octahedral trans‐Co(Me₂bpz)₂(H₂O)₄]²⁺ cations formed by monodentate Me₂bpz ligands. Two equivalents of additional noncoordinated Me₂bpz tectons are important as `second‐sphere ligands' connecting the cations by means of relatively strong O—H...N hydrogen bonding with generation of doubly interpenetrated pcu (α‐Po) frameworks. Noncoordinated chloride anions and solvent water molecules afford hydrogen‐bonded (Cl⁻)₂(H₂O)₂] rhombs, which establish topological links between the above frameworks, producing a rare eight‐coordinated uninodal net of {4²⁴.5.6³} ( ilc ) topology.