Two Cu II complexes of 3,4,5-tri-methyl-1 H -pyrazole.

The crystal structure of complexes of 3,4,5-tri-methyl-1 H -pyrazole with CuCl2 ·2H2 O and Cu(NO3 )2 ·2.5H2 O are presented, namely di-μ-chlorido-bis[chloridobis(3,4,5-trimethyl-1 H -pyrazole-κ N 2 )copper(II)], [Cu2 Cl4 (C6 H10 N2 )4 ] ( 1 ) and aquatetrakis(3,4,5-trimethyl-1 H -pyrazole-κ N 2 )copper(II) dinitrate, [Cu(C6 H10 N2 )4 (H2 O)](NO3 )2 ( 2 ), and compared to the previously determined structures for 3-methyl-1 H -pyrazole and 3,5-di-methyl-1 H -pyrazole. CuCl2 forms a 2:1 ligand-to-metal chloride-bridged complex with 3,4,5-tri-methyl-1 H -pyrazole, with a square-pyramidal coordination geometry about each copper(II) center. Similarly to the previously obtained 3,5-di-methyl-1 H -pyrazole complex with CuCl2 , the pyrazole ligands are cis to each other, with two chloride ions bridging the two copper(II) centers, and a terminal chloride ion occupying the axial position. Cu(NO3 )2 forms a 4:1 ligand-to-metal complex with 3,4,5-tri-methyl-1 H -pyrazole that is also arranged in a square-pyramidal geometry about CuII . The newly obtained copper(II) complex has the same coordination geometry as the 3,5-di-methyl-1 H -pyrazole complex, including an axial water mol-ecule, two nitrate ions hydrogen-bonded to the water mol-ecule, and four pyrazole ligands in the equatorial plane, suggesting that similar steric forces are at play in the formation of these complexes.