Group 12 metal coordination polymers of 1,2-bis(diphenylphosphino)ethane dioxide: A persistent 1D chain motif and consequent 2D and 3D architectures

A series of group 12 metal coordination polymers with 1,2-bis(diphenylphosphino)ethane dioxide (dppeO₂), {[ZnCl₂(μ-dppeO₂)]·CH₂Cl₂}_n (1·CH₂Cl₂), [ZnBr₂(μ-dppeO₂)]_n (2), [CdI₂(μ-dppeO₂)]_n (4), [(HgI₂)₂(μ-dppeO₂)]_n (5), [Zn(SCN)(μ-SCN)(μ-dppeO₂)]_n (6), and [Cd(NO₃)(μ-SCN)(μ-dppeO₂)]_n (7), have been synthesized and structurally characterized. The structures of the compounds are all based on an infinite 1D chain constructed by four-coordinate metal ions and dppeO₂ ligands adopting the trans bridging coordination fashion. In the coordination polymers 1, 2 and 4, the halide ions act as terminal ligands, leading to discrete 1D chains with alternative MX₂ and dppeO₂ repeating units. The mercury compound 5 features a unique square-wave-like inorganic chain -[Hg(1)-I-Hg(2)-I]-, and the 1D HgI₂(μ-dppeO₂) chains are further linked by HgI₂ bridges to form a 3D network. In the thiocyanate-containing compounds 6 and 7, the 1D chains are linked by one (6) or two (7) bridging SCN^- ions to result in 2D layered structures. Solid-state emission spectra of the coordination polymers show different variations compared to the free dppeO₂ ligand, such as enhancement (1, 2, 6 and 7), shift (3 and 4) and quenching (5) upon metal coordination.