Crosslinking of the Pd(acacCN)2 building unit with Ag(i) salts: dynamic 1D polymers and an extended 3D network†
After deprotonation, the acetylacetonate moiety of the ditopic ligand 3-cyanoacetylacetone (HacacCN) acts as a chelating ligand towards Pd(II). The resulting square-planar complex Pd(acacCN)2 represents a suitable building unit for extended structures via coordination of Ag(I) cations to the peripheral nitrile groups. These target compounds have been structurally characterized: with silver salts of the anions BF4−, ClO4−, PF6− and CF3SO3−, chain polymers with an alternating sequence of Pd(II) and Ag(I) are obtained. Solvent molecules and counter anions fill voids close to the silver cations; more weakly coordinating anions are engaged in longer, the triflate anion in a shorter interaction to Ag(I). In contrast to powder samples, larger crystals of these one-dimensional polymers are rather stable with respect to desolvation. Two isomorphous 1D structures undergo a fully reversible k2 phase transition which can be monitored by single crystal diffraction. The phase transition temperature depends on the nature of the counter anion and may therefore be tuned as a function of chemical composition. The formation of chain polymers by linking Pd(acacCN)2 building blocks with Ag(I) salts of BF4−, ClO4−, PF6− and CF3SO3− follows chemical intuition whereas its reaction with silver nitrate leads to an unexpected and close-packed 3D structure in which layers of composition Ag(NO3) are connected by Pd(acacCN)2 linkers.