Nitrido bridges

High-valent iron also occurs in -nitrido bridged dimers with linear [Fe °-N=Fe" ]" and [Fe =N=Fe ] " cores [209, 210] (and references therein). Such compounds have been prepared first by thermolysis [247] or photolysis [248] of iron(III)-porphyrin complexes with an azide ligand, (N3). Mixed-valent iron-nitrido porphyrin dimers exhibit valence delocalization as can be inferred from the... 

An essential feature of [Tc=N] + complexes is the Lewis basicity of the nitrido group, which can react with strong Lewis acids such as trivalent boron compounds. Recently the first nitrido bridges between technetium and boron were produced by an acid-base reaction between... 

Ru L]. (120a) undergoes a reversible one-electron reduction to [Ru2(N)(L)2]" (120b) (Scheme 12), which contains an unpaired electron (/Ueff= 1.60//B at 293 K). The two nitrido-bridged complexes differ significantly in their bond distances. The Ru——Ru skeleton is linear in both cases, but the Ru— Nav distance changes from 1.768 A in Ru ——Ru to 1.826 A in Ruiv N-Ru ... 

A trinuclear nitrido-bridged osmium complex, [Os3(N)2(CN)io(OH2)4]", has been reported. 

In order to stabilize Os(IV), it is necessary to have either several ligands that are good tt bases (e.g., Cl- or Br-), or one ligand that is a strong7T base (e.g., O2-) (2,5,6). Many Os(IV) complexes contain one or more halo ligands. There is also a growing number of oxo- and nitrido-bridged complexes. 

The formation of the unsaturated intermediate Run(OEP) from the hydrido-complex RumH(OEP) is supposed to occur from a LMCT excited state. As a consequence, the dimeric [RuH(OEP)]2 with a metal-metal interaction is formed [245]. Irradiation of some systems containing Fein(Por)N3 leads to p-nitrido bridged binuclear mixed-valence complexes [(Por)Fem-N-Fe,v(Por)] [134, 162], In both cases photochemistry was used as a conventional preparative route for synthesis of the binuclear complexes. 

Scheme 11 Preparation of nitrido-bridged binuclear complexes 344...

In spite of the several different elements of the first transition series which form oxo bridged complexes including the many different iron compounds, nitrido bridges are almost unknown in that series. Although second and third transition series elements form nitrido bridged compounds39), the only example in the first transition series is (TPPFe)2N. 

The nitrido bridged hemin dimer was prepared by Summerville and Cohen40) by the anaerobic thermal decomposition of TPPFe(IH)N3... 

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