Supramolecular Structures of Cadmium(II) Coordination Polymers: A New Class of Ligands Formed by Linking Tripodal Tris(pyrazolyl)methane Units

Abstract

The new ligands C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2) (pz = pyrazolyl ring), 1 (ortho), 2 (meta), and 3 (para), that can potentially bond two or more metal centers were obtained in a single step from the reaction of the appropriate dibromoxylene, 2 equiv of tris-2,2,2-(1-pyrazolyl)ethanol, and excess NaH. Although the arrangement of the tris(pyrazolyl)methane units in the solid-state structures of 1 and 3 are similar, the orientation of these groups with respect to the phenyl ring are different, with 1 showing a twisted structure and 3 a stepped structure. The reaction of [Cd(2)(THF)(5)][BF(4)](4) with the appropriate ligand yields each of the three coordination polymers of the formula [C(6)H(4)[CH(2)OCH(2)C(pz)(3)](2)Cd](BF(4))(2)](n), 4 (ortho), 5 (meta), and 6 (para). In the solid-state structures of all three each tris(pyrazolyl)methane unit is tridentate, with each ligand bonded to two different cadmium(II) atoms, forming a coordination polymer containing 6-coordinate, pseudooctahedral cadmium(II) centers. Polymers 4 and 5 form wavelike chains whereas 6 is arranged in a stepped structure similar to the free ligand. The different connecting patterns of each ligand lead to very different supramolecular structures, structures organized by the BF(4)(-) groups through weak C-H...F hydrogen bonds. Crystallographic information: 1 is monoclinic, P2(1)/n, a = 16.3157(13) A, b = 8.5880(6) A, c = 21.9227(17) A, alpha = gamma = 90 degrees, beta = 100.134(2) degrees, Z = 4; 3 is monoclinic, P2(1)/n, a = 9.1965(9) A, b = 12.9185(12) A, c = 12.7306(12) A, alpha = gamma = 90 degrees, beta = 104.099(2) degrees, Z = 2; 4 is triclinic, P1, a = 10.7877(19) A, b = 12.582(2) A, c = 15.409(3) A, alpha =103.860(4) degrees, beta = 94.123(4) degrees, gamma = 92.573(4) degrees, Z = 2; 6 is monoclinic, C2/c, a = 23.023(3) A, b = 12.2588(14) A, c = 18.119(2) A, alpha = gamma = 90 degrees, beta = 121.281(2) degrees, Z = 4.