A BIS(MU-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

Reaction of 1,2-diisocyanobenzene with [Fe2CP2(CO)3NCMe] (Cp = eta-cyc lopentadienyl) (1:2) yields the tetranuclear complex [{Fe2CP2(CO)2(mu- CO)}2(mu4-CNC6H4NC)] (2) which in solution appears to exist as a mixtu re of cis and trans isomeric forms. 2 may be diprotonated to yield [{F e2CP2(CO)3}2(mu4-CN(H)CH4N(H)C)](BF4)2 (3), monoalkylated to give [{Fe 2CP2(CO)3}2(mu4-CN(R)C6H4NC)]BF4 (R=Me (4), Et (5)) and oxidatively cl eaved with one molecule Of I2 to give [FeCp(I)(CO)2] and the asymmetri c species [{Fe2CP2(CO)3}CNCH4NC{FeCp(I)CO}] (6). In addition, 2 acts a s a bidentate ligand towards the Lewis acidic metal halides FeCl2, PdC l2, ZnCl2, ZnI2 and CdI2 giving rise to surprisingly stable pentanucle ar supercomplexes (7a-e) which have been characterized by elemental an alyses and IR and NMR (H-1, C-13) spectra. Of 7c, an X-ray structure a nalysis has been carried out which for the first time assesses the mu3 -(C,C,N) bridging mode of isocyanide in a non-cluster molecule. The mo st striking stereochemical features are the various gross distortions and deviations from more idealized geometries which are undoubtedly go verned by the steric overcrowding in the molecule.