Cyclopentadienylnickel thiolate complexes: synthesis, molecular structures and electrochemical detection of sulfur dioxide adducts

Simple reactions between Ni(η5-C5H5)(PR3)Br and the Schiff-base thiols, 4-HSC6H4NC(H)C4H2SBr-4′ (1) and 4-HSC6H4NC(H)C4H3S (2), or organothiols, HSC6H4F-4 and HSC6H4NH2-4, produced cyclopentadienylnickel thiolates of the formulae, Ni(η5-C5H5)(PR3)(SC6H4NC(H)C4H2SBr-4) (3), Ni(η5-C5H5)(PR3)(SC6H4NC(H)C4H3S) (4) or Ni(η5-C5H5)(PR3)(SC6H4X-4) (R=Ph, X=F (6) or NH2 (7) and R=Bu, X=F (5) or NH2 (8)) which were characterized by a combination of analytical techniques. Complexes 3, 6 and 7 were structurally characterized by X-ray crystallography, showing that they possess the familiar trigonal geometry around the nickel center. These complexes react with sulfur dioxide, with 5, 6, 7 and 8 exhibiting substantial differences between the redox potentials of the pre- and post-SO2 compounds to suggest that these complexes can be developed as potentiometric SO2 sensors.