Gallium(III) Tetraphenylporphyrinates Containing Hydrosulfide and Thiolate Ligands: Structural Models for Sulfur-Bound Iron(III) Hemes

Gallium­(III) tetraphenylporphyrinates (TPP) containing anionic sulfur ligands have been prepared and characterized in the solid state and solution. The complexes serve as structural models for iron­(III) heme sites containing sulfur coordination that otherwise prove challenging to synthesize due to the propensity for reduction to iron­(II). The compounds prepared include the first well-characterized example of a trivalent metalloporphyrinate containing a terminal hydrosulfide ligand, [Ga­(SH)­(TPP)], as well as [Ga­(SEt)­(TPP)], [Ga­(SPh)­(TPP)], and [Ga­(SSiⁱPr₃)­(TPP)]. The stability of these compounds toward reduction has permitted an investigation of their solid-state structures and electrochemistry. The structural features and reaction chemistry of the complexes in relation to their iron­(III) analogs is discussed.