Heterometallic iron(IV) μ-nitrido complexes supported by a tetradentate Schiff base ligand

Abstract

A nitrido-bridged heterometallic iron(IV) chloride complex supported by a tetradentate Schiff base ligand has been synthesized and its chloride substitution reactions have been studied. Treatment of the Fe(II) Schiff base complex [Fe(Br4saloph)(py)] (H2Br4saloph = N,N’-bis(3,5-dibromosalicylidene)-1,2-phenylenediamine; py = pyridine) with the Ru(VI) nitride [Ru(N)Cl2(LOEt)] (1, LOEt− = [(η5-C5H5)Co{P(O)(OEt)2}3]−) afforded the μ-nitrido complex [(LOEt)(py)ClRu(μ-N)Fe(Br4saloph)Cl] (2-Cl). The short Fe-N(nitrido) [1.668(4) Å] and Ru-N(nitrido) [1.709(4) Å] distances and the roughly linear Fe-N-Ru linkage [172.9(3)o] in diamagnetic 2-Cl are indicative of the Fe(IV)=N=Ru(IV) bonding picture. Salt metathesis of 2-Cl with [Ag(CF3CO2)] and [Ag(ReO4)] afforded [{(LOEt)(py)ClRu(μ-N)Fe(Br4saloph)(CF3CO2)}⋅Ag(CF3CO2)] (2-CF3CO2⋅Ag(CF3CO2)) and [(LOEt)(py)ClRu(μ-N)Fe(Br4saloph)(ReO4)] (2-ReO4), respectively. Chloride abstraction of 2-Cl with TlPF6, followed by recrystallization in air led to isolation of the μ-oxo complex [{2}2(μ3-O)Tl](PF6)2 (3), which is paramagnetic with a magnetic moment of 2.0 μB. Complex 3 features a [Ru-N-Fe-O(Tl)-Fe-N-Ru]2+ unit, the Tl atom of which is coordinated to the μ-oxo ligand and the oxygen atoms of the Schiff base ligands. The Ru-N(nitrido) (av. 1.709 Å), Fe-N(nitrido) (av. 1.659 Å) and Fe-O(oxo) (av. 1.991 Å) distances in 3 are consistent with M = N double bonds and Fe-O single bonds, respectively. Treatment of 2-Cl with [Tl(SC6F5)] afforded the Fe(III)/Ru(IV) nitrido complex [(LOEt)(py)ClRu(μ-N)Fe(Br4saloph)] (4) that has a longer Fe-N(nitrido) distance [1.753(4) Å] than the Fe(IV) congener 2-Cl does. The crystal structures of complexes 2-Cl, 2-CF3CO2⋅Ag(CF3CO2), 2-ReO4, 3, and 4 have been determined.