Synthesis of organotin bis(pyrazol-1-yl)methane-tetracarboxylates and tris(pyrazol-1-yl)methane-hexacarboxylates

Bis(pyrazol-1-yl)methane-tetracarboxylic acid and tris(pyrazol-1-yl)methane-hexacarboxylic acid, namely bis(3,5-dicarboxypyrazol-1-yl)methane (CH2[3,5-Pz(CO2H)2]2) and tris(3,5-dicarboxypyrazol-1-yl)methane (CH[3,5-Pz(CO2H)2]3), have been synthesized by the oxidation reaction of bis(3,5-dimethylpyrazol-1-yl)methane and tris(3,5-dimethylpyrazol-1-yl)methane with an excess of KMnO4. Reaction of CH2[3,5-Pz(CO2H)2]2 with (R3Sn)2O yielded the corresponding organotin polycarboxylates (CH2[3,5-Pz(CO2SnR3)2]2, R = Et (1) and n-Bu (2), respectively). The structures of these two complexes have been confirmed by X-ray structural analyses. Complex 1 formed a coordination polymer containing fused 22- and 24-membered macrocyclic units. While complex 2 created a double-layer macrocyclic structure by the bridging coordination of carboxylate groups to the tin atoms as well as the hydrogen bonds in coordinated waters. Reaction of CH[3,5-Pz(CO2H)2]3 with (Ph3Sn)2O yielded hexanuclear triphenyltin polycarboxylate CH[3,5-Pz(CO2SnPh3)2]3, which did not assemble into a supramolecular architecture like those in complex 1 or 2, possibly owing to the relatively large steric hindrance of the phenyl groups as well as the relatively large size of the hexabasic carboxylic acid.

Bis(pyrazol-1-yl)methane-tetracarboxylic acid and tris(pyrazol-1-yl)methane-hexacarboxylic acid as well as their organotin derivatives have been synthesized. These organotin complexes exhibited remarkably different supramolecular aggregates.Figure optionsDownload as PowerPoint slide