Bis(benzimidazole)amino thio- and selenoether Iron(II) complexes as proton reduction electrocatalysts.

Two novel Iron (II) complexes featuring tetrapodal bis(benzimidazole)amino thio- and selenoether ligands (LS and LSe) were synthesized, characterized, and tested as electrocatalysts for the hydrogen evolution reaction. The bromide complexes [Fe(LS,LSe)Br2] (1-2) are highly insoluble, but their DMSO solvates were characterized by single crystal X-ray diffraction, revealing an octahedral coordination environment that does not feature coordination of the chalcogen atoms. The corresponding triflate derivatives [Fe(LS,LSe)(MeCN)3]OTf2 (1c-2c) were employed for electrocatalytic proton reduction, with 1c exhibiting higher activity, thus suggesting that the thioether may participate as a more competent pendant ligand for proton transfer.