Abstract
The dianion [Fe(2)[(μ-SeCH(2))(2)NH](CN)(2)(CO)(4)](2-) ([2](2-)) is of interest for the preparation of the selenide analog of the active site of the [FeFe]-hydrogenases. The obvious route for its synthesis by cyanation of Fe(2)[(μ-SeCH(2))(2)NH](CO)(6) (3) fails for reasons that this paper explains and resolves. We show that CN(-) cleaves Se-C bonds in 3. For example, treatment of Fe(2)[(μ-SeCH(2))(2)NH](CO)(6) with NEt(4)CN followed by CH(3)I gives substantial amounts of Fe(2)(μ-SeCH(3))(2)(CO)(6). Authentic [2](2-) can be obtained by cyanation of Fe(2)[(μ-SeCH(2))(2)NH](CO)(5)(pyridine). The (77)Se NMR data for [2](2-) and 3 are reevaluated and explained. Attempts to prepare Fe(2)[(μ-SeCH(2))(2)NH](PPh(3))(2)(CO)(4) (9) by Me(3)NO-induced decarbonylation of 3 also suffers from degradation of the organoselenium ligand. Complex 9 was prepared instead by photosubstitution. The protonation of [2](2-) and [Fe(2)[(μ-SCH(2))(2)NH](CN)(2)(CO)(4)](2-) are compared: the selenium compounds are more basic. The structure of [HFe(2)[(μ-SCH(2))(2)NH](CN)(2)(CO)(4)](-) was determined crystallographically.