Coordination versus spodium bonds in dinuclear Zn(ii) and Cd(ii) complexes with a dithiophosphate ligand

The important role of spodium bonding (SpB) in Zn(ii) and Cd(ii) complexes is highlighted in this feature article. SpB has been recommended to distinguish coordination bonds (high covalent character) from non-covalent contacts. Here, two new d(10)-metal dithiophosphate complexes, [M(L)(2)](2) {where M = Zn (1) and Cd (2); L = O,O '-bis(4-tert-butylphenyl) phosphorodithioate} have been synthesized in purely aqueous media and characterized by elemental and spectral analyses. The X-ray crystallography analyses indicate that both complexes are dinuclear, in which each metal atom is coordinated with four sulfur atoms in a distorted tetrahedral environment containing two four-membered chelate rings joined to a central eight-membered ring through metal (Zn/Cd) atoms. In complex 1 the eight-membered ring possesses a saddle conformation located on a two-fold axis of symmetry, C-2, while in complex 2 it possesses a centrosymmetric twisted chair conformation, C-i. In addition, the oxygen and sulfur atoms belonging to the bridging ligands form intramolecular SpBs with Zn(ii) in 1 and Cd(ii) in 2. The existence of intramolecular SpBs in both complexes is evidenced by DFT calculations by using the Bader's Quantum Theory of Atoms-in-Molecules (QTAIM) combined with the non-covalent interaction plot (NCI plot) index that is based on the reduced density gradient (NCI-RDG) method. A Hirshfeld surface study has been carried out to understand the intermolecular contacts in the crystal lattice.

Automated summary

The article highlights the important role of Spodium bonding (SpB) in Zn(ii) and Cd(ii) complexes, and presents the synthesis and characterization of two new d(10)-metal dithiophosphate complexes. X-ray crystallography analyses reveal that both complexes are dinuclear with a complex molecular structure.