Influence of N‐Substitution on the Oxidation of 2‐Pyridylmethylamines with Bis(trimethylsilyl)amides of Iron(III) – Synthesis of Heteroleptic Iron(II) 2‐Pyridylmethylamides

Abstract

The reaction of (thf)Fe[N(SiMe3)2]2Cl with (2‐pyridylmethyl)(diphenylphosphanyl)amine (1) in hot tetrahydrofuran (THF) yields dinuclear [(ClFe)2{μ‐N(SiMe3)2}{Ph2P(NCH2Py)2}] (2) and [ClFe{Ph2P(O)‐NCH2Py}]2 (3) with the oxygen atom stemming from THF degradation. The formation of 2 requires a P–N bond cleavage and reformation leading to the tetradendate diphenyl‐bis(2‐pyridylmethylamido)phosphonium ion. If this reaction of (thf)Fe[N(SiMe3)2]2Cl with 1 is performed at room temperature, no P–N bond cleavage is observed. Instead of that, ether degradation occurs yielding [Fe4(μ4‐O)(μ2‐Cl)2(Ph2P‐NCH2Py)4] (4) with a central oxygen‐centered iron tetrahedron as well as complex 3. Recrystallization of 3 from dichloromethane leads to addition of HCl and to the formation of [FeCl2·{Ph2P(O)‐N(H)‐CH2Py}] (5). The phosphonium ion of 2 is isoelectronic to the corresponding diphenyl‐bis(2‐pyridylmethylamino)silane (6). Lithiation of 6 followed by a metathetical reaction with (thf)2FeCl2 yields the trinuclear complex [Fe3Cl2{Ph2Si(NCH2Py)2}2] (7) with antiferromagnetic interactions.

[Fe4] and [Fe6] Hydride Clusters Supported by Phosphines: Synthesis, Characterization, and Application in N2Reduction

“…Even though the average oxidation state of Fe­(+1.5) is relatively low in cluster 4 , the assignment of the oxidation states of the Fe centers was not trivial. The terminal Fe–N­(SiMe 3 ) 2 distances (1.948(4)/1.949(3) Å) are comparable to those in 2a – c and 3 , and the Fe–{μ-N­(SiMe 3 ) 2 } distances (2.066(4)–2.082(4) Å) fall in the longer regions of previously reported Fe­(II)–{μ-N­(SiMe 3 ) 2 } distances (1.979(2)–2.099(3) Å). , The (η 6 -toluene)Fe moiety in 4 exhibits Fe–C distances (2.108(5)–2.132(6) Å) in the range of typical Fe–C­(η 6 -arene) distances reported for complexes of Fe(0), Fe­(I), Fe­(II), and Fe­(IV).…”

Synthesis of Iron and Cobalt Complexes of a Ferrocene-Linked Diphosphinoamide Ligand and Characterization of a Weak Iron–Cobalt Interaction

“…Complex 3 displays C i symmetry where the inversion center of the molecular structure sits in the middle of an elongated sixmembered heterocyclic ring composed of two Fe(II) centers and two phosphinoamide moieties. The bridging phosphinoamides in 3, (N1−P1 ≈ 1.67 Å), are similar to other iron N-Aryl phosphinoamides complexes, 46 all of which are longer than typical N-alkyl substituted phosphinoamides, 46,50 Other examples of trigonal planar iron phosphinoamide complexes have been reported by the Thomas group 46,55 and in all cases the N−P axes are perpendicular to the donor atom plane.…”

“…Complex 3 displays C i symmetry where the inversion center of the molecular structure sits in the middle of an elongated six-membered heterocyclic ring composed of two Fe­(II) centers and two phosphinoamide moieties. The bridging phosphinoamides in 3 , (N1–P1 ≈ 1.67 Å), are similar to other iron N-Aryl phosphinoamides complexes, all of which are longer than typical N -alkyl substituted phosphinoamides, , because of competing delocalization of the nitrogen-based lone pair into π* orbitals of the arene rings. The trigonal planar coordination geometry of 3 results in an unstrained ligand backbone characterized by a tilt angle of 0.13° − and a bite angle of 107.34° (see Figure for a depiction of Cp tilt and bite angles).…”

Understanding the directed ortho lithiation of (R)-Ph2P(NCO2Me)NHCH(Me)Ph. NMR spectroscopic and computational study of the structure of the N-lithiated species

“…10 The presence of additional coordination sites in the substituents of the phosphinimidic amide not involved in charge delocalization provides alternative possibilities of chelation. The pyridyl ring of complexes 3 11 and 4 12 determines that the anion acts as a tridentate and tetradentate ligand, respectively. Interestingly, N,N′-chelation in 3 and 4 takes place with one nitrogen of the [N-P-N] − backbone and the nitrogen of a pyridine ring.…”

“…Cryoscopic determinations on benzene solutions of complexes 7 and {Li[ t Bu 2 P(vNMe)NH]} suggested the existence of dimers 20 and trimers, 21 respectively. NMR spectra in C 6 D 6 have been measured at room temperature in a few cases (7,11,12). They only provide information about an average structure.…”