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 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 [Cd2(THF)5][BF4]4 with the appropriate ligand yields each of the three coordination polymers of the
formula {C6H4[CH2OCH2C(pz)3]2Cd}(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:  1 is monoclinic, P2(1)/n, a
= 16.3157(13) Å, b = 8.5880(6) Å, c = 21.9227(17) Å, α = γ = 90°, β = 100.134(2) °, Z = 4; 3 is monoclinic,
P2(1)/n, a = 9.1965(9) Å, b = 12.9185(12) Å, c = 12.7306(12) Å, α = γ = 90° , β = 104.099(2) °, Z = 2; 4
is triclinic, P1̄, a = 10.7877(19) Å, b = 12.582(2) Å, c = 15.409(3) Å, α =103.860(4)°, β = 94.123(4)°, γ =
92.573(4)°, Z = 2; 6 is monoclinic, C2/c, a = 23.023(3) Å, b = 12.2588(14) Å, c = 18.119(2) Å, α = γ = 90°,
β = 121.281(2)°, Z = 4.