title: Borane-protected cyanides as surrogates of H-bonded cyanides in [FeFe]-hydrogenase active site models.
abstract: Triarylborane Lewis acids bind [Fe2(pdt)(CO)4(CN)2](2-) [1](2-) (pdt(2-) = 1,3-propanedithiolate) and [Fe2(adt)(CO)4(CN)2](2-) [3](2-) (adt(2-) = 1,3-azadithiolate, HN(CH2S(-))2) to give the 2:1 adducts [Fe2(xdt)(CO)4(CNBAr3)2](2-). Attempts to prepare the 1:1 adducts [1(BAr3)](2-) (Ar = Ph, C6F5) were unsuccessful, but related 1:1 adducts were obtained using the bulky borane B(C6F4-o-C6F5)3 (BAr(F)*3). By virtue of the N-protection by the borane, salts of [Fe2(pdt)(CO)4(CNBAr3)2](2-) sustain protonation to give hydrides that are stable (in contrast to [H1](-)). The hydrides [H1(BAr3)2](-) are 2.5-5 pKa units more acidic than the parent [H1](-). The adducts [1(BAr3)2](2-) oxidize quasi-reversibly around -0.3 V versus Fc(0/+) in contrast to ca. -0.8 V observed for the [1](2-/-) couple. A simplified synthesis of [1](2-), [3](2-), and [Fe2(pdt)(CO)5(CN)](-) ([2](-)) was developed, entailing reaction of the diiron hexacarbonyl complexes with KCN in MeCN.
authors.affiliation: School of Chemical Sciences, University of Illinois , Urbana, Illinois 61801, United States.
authors.forename: Brian C
authors.initials: BC
authors.lastname: Manor
authors.forename: Mark R
authors.initials: MR
authors.lastname: Ringenberg
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Rauchfuss
mesh_terms: D001880:Boranes / Q000737:chemistry*; D020134:Catalytic Domain; D003486:Cyanides / Q000737:chemistry*; D006860:Hydrogen Bonding; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008958:Models, Molecular; D013055:Spectrophotometry, Infrared
chemical_list: D001880:Boranes; D003486:Cyanides; D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase