Abstract
Complexes of the type (diphosphine)Ni(μ-SR)(2)Fe(CO)(3) are investigated with azadithiolate (adt, HN(CH(2)S(-))(2)) as the dithiolate. The resulting complexes are hybrid models for the active sites of the [NiFe]- and [FeFe]-hydrogenases. The key complex (dppv)Ni(μ-adt)Fe(CO)(3) (3) was prepared from the complex Ni[(SCH(2))(2)NCbz](dppv), which contains a Cbz-protected adt ligand (Cbz = C(O)OCH(2)Ph, dppv = cis-1,2-(Ph(2)P)(2)C(2)H(2)). This complex combines with Fe(2)(CO)(9) to give (dppv)Ni[(μ-SCH(2))(2)NCbz]Fe(CO)(3), which is readily deprotected to give 3. Complex 3 undergoes protonation at both Fe and N to give successively [(dppv)Ni(μ-adt)FeH(CO)(3)](+) ([H3](+)) and [(dppv)Ni(μ-adtH)FeH(CO)(3)](2+) ([H3H](2+)). The redox properties and dynamics of these complexes resemble previously reported analogues with propanedithiolate. Solutions of [H3](+) readily degrade to [(dppv)Ni[(μ-SCH(2))(2)NCH(2)]Fe(CO)(3)](+) ([4](+)), which features a methylene group linking N and Fe. Complex [4](+) can be made in high yield by reaction of [H3](+) with CH(2)O, and this conversion was also demonstrated with (13)CH(2)O. Complex [4](+) undergoes hydrogenolysis by photochemical reaction with H(2) to give [(dppv)Ni[(μ-SCH(2))(2)NMe]FeH(CO)(3)](+), the N-methylated analogue of [H3](+). Upon treatment ith Me(3)O(+), [4](+) undergoes quaternization, giving [(dppv)Ni[(μ-SCH(2))(2)N(Me)CH(2)]Fe(CO)(3)](2+). In contrast with the lability of [H3](+), the phosphine-substituted derivative [(dppv)Ni(μ-adt)FeH(CO)(2)(PPh(3))](+) did not degrade. Most complexes were characterized by X-ray crystallography.