Heterocyclic thione donors

Complexes of heterocyclic thione donors. Coord. Chem. Rev. 61, 115 (1984). 

An example of thione coordination is demonstrated with the thiocarbonyl donor ligand 2,6-dimethyl-4H-pyran-4-thione, that gives a complex with zinc chloride of the form ZnL2Cl2-The crystal structure shows the zinc is tetrahedrally coordinated by two chloride and two sulfur donors and the compound was further studied by 3H NMR and IR spectroscopy.573 Both monomeric and dimeric heterocyclic thione complexes have been formed with zinc.5 4,575... 

The formation of four-membered chelate rings involving N and S donors is not unusual and has been observed in several complexes of 2-thiol- or 2-thione-substituted N heterocycles. Foye and Lo reported this form of coordination for a variety of metal chelates of antibacterial heterocyclic thiones. 2-Mercaptobenzimidazole (35 X = NH) was reported to form such chelates with Cu , Al and Fe . Complexes of 2-thiouradl (36), and substituted forms, also have been reported with this bonding mode to these metal ions. The tetrakis chelate of W" with 2-mercaptopyrimidine has been shown to adopt a symmetrical dodecahedral geometry. The mercapto S atom is thought to act as the better t-electron donor with the corresponding aromatic N atom acting as a tc acceptor. 

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