title: Mononuclear five- and six-coordinate iron hydrazido and hydrazine species.
abstract: This article describes the synthesis and characterization of several low-spin iron(II) complexes that coordinate hydrazine (N(2)H(4)), hydrazido (N(2)H(3)(-)), and ammonia. The sterically encumbered tris(di-meta-terphenylphosphino)borate ligand, [PhBP(mter)(3)](-), is introduced to provide access to species that cannot be stabilized with the [PhBP(Ph)(3)](-) ligand ([PhBP(R)(3)](-) = PhB(CH(2)PR(2))(3)(-)). Treatment of [PhBP(mter)(3)]FeMe with hydrazine generates the unusual 5-coordinate hydrazido complex [PhBP(mter)(3)]Fe(η(2)-N(2)H(3)) (1), in which the hydrazido serves as an L(2)X-type ligand. Upon coordination of an L-type ligand, the hydrazido shifts to an LX-type ligand, generating [PhBP(mter)(3)]Fe(L)(η(2)-N(2)H(3)) (L = N(2)H(4) (2) or NH(3) (3)). In contrast, treatment of [PhBP(Ph)(3)]FeMe with hydrazine forms the adduct [PhBP(Ph)(3)]Fe(Me)(η(2)-N(2)H(4)) (5). Complex 5 is thermally unstable to methane loss, generating intermediate [PhBP(Ph)(3)]Fe(η(2)-N(2)H(3)), which undergoes bimolecular coupling to produce {[PhBP(Ph)(3)]Fe}(2)(μ-η(1):η(1)-N(2)H(4))(μ-η(2):η(2)-N(2)H(2)). The oxidation of these and related hydrazine and hydrazido species is also presented. For example, oxidation of 1 or 5 with Pb(OAc)(4) results in disproportionation of the N(2)H(x) ligand (x = 3, 4), and formation of [PhBP(R)(3)]Fe(NH(3))(OAc) (R = Ph (9) and mter (11)).
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Caroline T
authors.initials: CT
authors.lastname: Saouma
authors.forename: Connie C
authors.initials: CC
authors.lastname: Lu
authors.forename: Jonas C
authors.initials: JC
authors.lastname: Peters
mesh_terms: D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D005296:Ferrous Compounds; D006834:Hydrazines