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

The reaction of (thf)Fe[N(SiMe 3 ) 2 ] 2 Cl with (2‐pyridylmethyl)(diphenylphosphanyl)amine ( 1 ) in hot tetrahydrofuran (THF) yields dinuclear [(ClFe) 2 {μ‐N(SiMe 3 ) 2 }{Ph 2 P(NCH 2 Py) 2 }] ( 2 ) and [ClFe{Ph 2 P(O)‐NCH 2 Py}] 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(SiMe 3 ) 2 ] 2 Cl with 1 is performed at room temperature, no P–N bond cleavage is observed. Instead of that, ether degradation occurs yielding [Fe 4 (μ 4 ‐O)(μ 2 ‐Cl) 2 (Ph 2 P‐NCH 2 Py) 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 [FeCl 2 · {Ph 2 P(O)‐N(H)‐CH 2 Py}] ( 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) 2 FeCl 2 yields the trinuclear complex [Fe 3 Cl 2 {Ph 2 Si(NCH 2 Py) 2 } 2 ] ( 7 ) with antiferromagnetic interactions.