A bis(μ-isocyanide diiron) complex as chelating ligand towards iron(II), palladium(II), zinc(II) and cadmium(II). X-ray structural assessment of a novel isocyanide bridging mode

Abstract

Reaction of 1,2-diisocyanobenzene with [Fe 2Cp 2(CO) 3NCMe] (Cp=η-cyclopentadienyl) (1:2) yields the tetranuclear complex [{Fe 2CP 2(CO) 2(μ-CO)} 2(μ 4-CNC 6H 4NC)] ( 2) which in solution appears to exist as a mixture of cis and trans isomeric forms. 2 may be diprotonated to yield [{Fe 2Cp 2(CO) 3} 2(μ 4-CN(H)C 6H 4N(H)C)](BF 4) 2 ( 3), monoalkylated to give [{Fe 2Cp 2(CO) 3} 2(μ 4-CN(R)C 6H 4NC)]BF 4 (R=Me ( 4), Et (5)) and oxidatively cleaved with one molecule of I 2 to give [FeCp(I)(CO) 2] and the asymmetric species [{Fe 2Cp 2(CO) 3}CNC 6H 4NC{FeCp(I)CO}] ( 6). In addition, 2 acts as a bidentate ligand towards the Lewis acidic metal halides FeCl 2, PdCl 2, ZnCl 2, ZnI 2 and CdI 2 giving rise to surprisingly stable pentanuclear supercomplexes ( 7a–e) which have been characterized by elemental analyses and IR and NMR ( 1H, 13C) spectra. Of 7c, an X-ray structure analysis has been carried out which for the first time assesses the μ 3-(C,C,N) bridging mode of isocyanide in a non-cluster molecule. The most striking stereochemical features are the various gross distortions and deviations from more idealized geometries which are undoubtedly governed by the steric overcrowding in the molecule.