One-electron oxidation chemistry and subsequent reactivity of diiron imido complexes.
The chemical oxidation and subsequent group transfer activity of the unusual diiron imido complexes Fe((i)PrNPPh2)3Fe≡NR (R = tert-butyl ((t)Bu), 1; adamantyl, 2) was examined. Bulk chemical oxidation of 1 and 2 with Fc[PF6] (Fc = ferrocene) is accompanied by fluoride ion abstraction from PF6(-) by the iron center trans to the Fe≡NR functionality, forming F-Fe((i)PrNPPh2)3Fe≡NR ((i)Pr = isopropyl) (R = (t)Bu, 3; adamantyl, 4). Axial halide ligation in 3 and 4 significantly disrupts the Fe-Fe interaction in these complexes, as is evident by the >0.3 Å increase in the intermetallic distance in 3 and 4 compared to 1 and 2. Mössbauer spectroscopy suggests that each of the two pseudotetrahedral iron centers in 3 and 4 is best described as Fe(III) and that one-electron oxidation has occurred at the tris(amido)-ligated iron center. The absence of electron delocalization across the Fe-Fe≡NR chain in 3 and 4 allows these complexes to readily react with CO and (t)BuNC to generate the Fe(III)Fe(I) complexes F-Fe((i)PrNPPh2)3Fe(CO)2 (5) and F-Fe((i)PrNPPh2)3Fe((t)BuNC)2 (6), respectively. Computational methods are utilized to better understand the electronic structure and reactivity of oxidized complexes 3 and 4.
Department of Chemistry, Brandeis University , 415 South Street, MS 015, Waltham, Massachusetts 02454, United States.
Subramaniam
S
Kuppuswamy
Tamara M
TM
Powers
Bruce M
BM
Johnson
Carl K
CK
Brozek
Jeremy P
JP
Krogman
Mark W
MW
Bezpalko
Louise A
LA
Berben
Jason M
JM
Keith
Bruce M
BM
Foxman
Christine M
CM
Thomas
D005290:Ferric Compounds / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction
D005290:Ferric Compounds