Supramolecular structures of cadmium(II) coordination polymers: A new class of ligands formed by linking tripodal tris(pyrazolyl)methane units

The new ligands C6H4[CH2OCH2C(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 I 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)][BF4](4) with the appropriate ligand yields each of the three coordination polymers of the formula {C6H4[CH2OCH2C(pz)(3)](2)Cd}(BF4)(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 BF4- groups through weak C-H . . .F hydrogen bonds. Crystallographic information: I is monoclinic, P2(1)/n, a = 16.3157(13) Angstrom, b = 8.5880(6) Angstrom, c = 21.9227(17) Angstrom, alpha = gamma = 90 degrees, 100.134(2)degrees, Z = 4; 3 is monoclinic, P2(1)/n, a = 9.1965(9) Angstrom, b = 12.9185(12) Angstrom, c = 12.7306(12) Angstrom, alpha = gamma = 90 degrees, 104.099(2)degrees, Z = 2; 4 is triclinic, P (1) over bar, a = 10.7877(19) Angstrom, b = 12.582(2) Angstrom, c = 15.409(3) Angstrom, 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) Angstrom, b = 12.2588(14) Angstrom, c = 18.119(2) Angstrom, alpha = gamma = 90 degrees, beta = 121.281(2)degrees, Z = 4.