Two heterodinuclear NiFe-based sulfenate complexes mimicking an S-oxygenated intermediate of an O2-tolerant [NiFe]-H2ase: synthesis, structures, and reactivity

The synthetic modelling of the S-oxygenated intermediate of an O-2-tolerant [NiFe]-H(2)ase has proven to be greatly challenging. Treatment of 1,4-bis(2-mercapto-2-methylpropyl)-1,4-diazacycloheptane with Ni(acac)(2)gave dithiolate complex [1,4-bis(2-mercapto-2-methylpropyl)-1,4-diazacycloheptanato]nickel(ii) or (bmmp-dach)Ni (1) and further treatment of complex1with 37% aqueous H(2)O(2)afforded sulfenate complex [1-(2-mercapto-2-methylpropyl)-4-(2-sulfeno-2-methylpropyl)-1,4-diazacycloheptanato]nickel(ii) or (mmp-sulfeno-dach)Ni (2) and sulfinate complex [1-(2-mercapto-2-methylpropyl)-4-(2-sulfino-2-methylpropyl)-1,4-diazacycloheptanato]nickel(ii) or (mmp-sulfino-dach)Ni (3). More interestingly, treatment of complex2with FeI(2)afforded the unexpected dithiolate/diiodine complex [(bmmp-dach)Ni][2I(2)] (4), while complex2reacted with Fe-2(CO)(9)or CpFe(CO)(2)(BF4) to give dinuclear Ni(ii)Fe(0) and Ni(ii)Fe(ii) complexes [(mmp-sulfeno-dach)Ni][Fe(CO)(4)] (5) and [(mmp-sulfeno-dach)Ni][Fe(CO)(2)Cp(BF4)] (6), respectively. Further reactivity studies demonstrated that (i) the reaction of complex5or6with decarbonylating agent Me3NO produced complex2, and (ii) the reaction of complex5with organometallic oxidant FcBF(4)afforded trinuclear Ni dithiolate complex [(bmmp-dach)Ni](2)[Ni(BF4)(2)] (7), unexpectedly. All the new complexes1-7were fully characterized by elemental analysis and various spectroscopic methods, and particularly the molecular structures of complexes2-5and7were further confirmed by X-ray crystallography.