Borane-protected cyanides as surrogates of h-bonded cyanides in [FeFe]-hydrogenase active site models

Brian C. Manor, Mark R. Ringenberg, Thomas B. Rauchfuss

Research output: Contribution to journalArticlepeer-review

Abstract

Triarylborane Lewis acids bind [Fe2(pdt)(CO)4(CN) 2]2- [1]2- (pdt2- = 1,3-propanedithiolate) and [Fe2(adt)(CO)4(CN) 2]2- [3]2- (adt2- = 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(BAr 3)]2- (Ar = Ph, C6F5) were unsuccessful, but related 1:1 adducts were obtained using the bulky borane B(C6F4-o-C6F5)3 (BAr F3). 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 Fc0/+ 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.

Original languageEnglish (US)
Pages (from-to)7241-7247
Number of pages7
JournalInorganic Chemistry
Volume53
Issue number14
DOIs
StatePublished - Jul 21 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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