Reactivity studies on [Cp′FeI]2: From iron hydrides to P4-activation

Abstract

Metathesis of [Cp 0 FeI] 2 (1) with KHBEt 3 affords the polyhydride iron complexes [Cp 0 FeH 2 ] 2 (2) and [Cp 0 2 Fe 2 H 3 ] (3). The ratio in which both 2 and 3 are obtained correlates to the applied H 2 pressure during synthesis. Complex 2 activates CH-or CD-bonds in aromatic compounds and shows slow H/D exchange in the presence of D 2 at room temperature in cyclohexane solvent. [Cp 0 FeH 2 ] 2 acts as a Cp 0 Fe (I)-synthon when reacted with white phosphorus (P 4 ) to give [Cp 0 Fe] 2 (m-P 4 ) (4) as the only P-containing product. This complex is best described as a triple-decker complex with a planar arrangement of a severely distorted kite-like cyclo-P 4 unit. This distortion persists in solution and solid state as evidenced by a small PP coupling constant in the 31 P{ 1 H} NMR spectrum and a long P-P distance of 2.53 A. Complex 4 is an isomer to the long-known [{Cp 0 Fe} 2 (m-h 4 :h 4 -P 4 )] ( 5) with a cistetraphosphabutadiene moiety and it thermally rearranges to 5, [{Cp 0 Fe} 2 (m-h 3 :h 3 -P 3 )] and [Cp 0 Fe (P 5 )]. All complexes described in this paper have been completely characterized including X-ray crystallography, variable temperature NMR studies and DFT calculations. Relaxed force constants (inverse compliance constants) are used as bond strength descriptors.

Selective P4 Activation by a Highly Reduced Cobaltate: Synthesis of Dicobalt Tetraphosphido Complexes

“…Nonetheless, its structure appears to be very sensitive to subtle changes in the oxidation state of the cobalt atoms and the presence of differently solvated potassium countercations. Similar observations were previously made for cyclopentadienyl complexes [Cp R 2 M 2 P 4 ] (Cp R =substituted cyclopentadienyl ligand, M=Fe and Co), where the substitution pattern on the cyclopentadienyl ligand has a profound effect on the structures of the P 4 x − fragment ,…”

The Interstitial Carbon of the Nitrogenase FeMo Cofactor is Far Better Stabilized than Previously Assumed

“…An analysis of the normal modes and the dipole moment derivatives allows the Fe À C inter frequencyt ob e expected in the range just below 600 cm À1 (see the Supporting Information). Although their value is still far from the value of atypical FeÀFe two-electron bond (well above 2Ncm À1 ), [20] these numbers are consistent with an assumed covalencyi nt he FeMo cofactor, which was suggested very early by H. Deng and R. Hoffmann. [19] Thee lastic strength within the iron cluster itself is also,a ccording to our calculations,m uch higher than hitherto assumed:w ith an Fe À Fe force constant of 1.23 Ncm À1 (older, empirical NRVS force constant:0 .27 Ncm À1 ,s ee Table 1), these bonds are much stronger than previously thought.…”

Reactions of the Lithiated Diphosphine tBu2P–P(SiMe3)Li with [(η6‐C6H6)RuCl2]2 in the Presence of Tertiary Phosphines

“…The presence of an Fe–Fe single bond was inferred for [{(Cp*Fe) 2 }(µ,η 2:2 ‐P 2 ) 2 ] (Cp* = C 5 Me 5 ) . The closely related species [{(Cp′′Fe)} 2 (µ‐P 4 )] (Cp′′ = 1,2,4‐ t Bu 3 ‐C 5 H 2 ) exists in two isomeric forms, one with a P 4 unit with a kite‐like distortion and no Fe–Fe bond and the second one with a trapezoidal P 4 unit and an Fe–Fe single bond . A trapezoidal P 4 unit and a Fe–Fe single bond were also found in [{(Cp′Fe)} 2 (µ‐P 4 )] (Cp′ = 1,3‐ t Bu 2 ‐C 5 H 3 ) .…”