http://dx.doi.org/10.1039/c0dt00481b">
 

Document Type

Journal Article

Department/Unit

Department of Chemistry

Title

Formation of μ-dinitrogen (salen)osmium complexes via ligand-induced NN coupling of (salen)osmium(VI) nitrides

Language

English

Abstract

Treatment of [NnBu4][OsVI(N)Cl 4] with a stoichiometric amount of H2L (L = N,N′-bis(salicylidene)-o-cyclohexylenediamine dianion) in the presence of PF6 - or ClO4 - in MeOH affords [OsVI(N)(L)(OH2)](PF6) 1a and [Os VI(N)(L)(CH3OH)](ClO4) 1b, respectively. The structure of 1b has been determined by X-ray crystallography and the OsN bond distance is 1.627(3) Å. In the presence of a N-donor heterocyclic ligand in CH3CN, 1a reacts at room temperature to afford the mixed-valence μ-N2 (salen)osmium species [(X)(L)OsIII-NN-Os II(L)(X)](PF6), 2-14 (X = py 2; 4-Mepy 3; 4- tBupy 4; pz 5; 3-Mepz 6; 3,5-Me2pz 7; Im 8; 1-MeIm 9; 2-MeIm 10; 4-MeIm 11; 1,2-Me2Im 12; 2-Meozl 13; 4-MeTz 14). These complexes are formed by ligand-induced N⋯N coupling of two [Os VIN]+ to give initially [OsIII-N 2-OsIII]2+, which is then reduced to give the more stable mixed-valence species [OsIII-N2-Os II]+. Cyclic voltammograms (CVs) of 2-14 show two reversible couples, attributed to OsIII,III/OsIII,II and OsIII,II/OsII,II. The large comproportionation constants (Kcom) of (5.36-82.3) × 1013 indicate charge delocalization in these complexes. The structures of 3 and 14 have been determined by X-ray crystallography, the salen ligands are in uncommon cis-β configuration. Oxidations of 4 and 14 by [Cp2Fe](PF 6) afford the symmetrical species [(X)(L)OsIII-NN-Os III(L)(X)](PF6)2 (X = 4-tBupy 15; 4-MeTz 16). These are the first stable μ-N2 diosmium(iii,iii) complexes that have been characterized by X-ray crystallography. © 2010 The Royal Society of Chemistry.

Publication Date

2010

Source Publication Title

Dalton Transactions

Volume

39

Issue

46

Start Page

11163

End Page

11170

Publisher

Royal Society of Chemistry

ISSN (print)

14779226

ISSN (electronic)

14779234

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