The Interaction of 1,1'-Diisocyanoferrocene with Gold:Formation of Monolayers and Supramolecular Polymerization of an Aurophilic Ferrocenophane

摘要

Isocyanides are important ligands in coordination chemistry.They are of great current interest in surface chemistry,where their binding on gold and other metals has been addressed using bi- and tridentate isocyanides.However,despite their attractive properties,the number of oligodentate isocyanides has remained small in comparison to other prominent ligand families.Because of our interest in redox-functionalized ligands,1,1'-diisocyanoferrocene (1) has caught our attention.1 is a potentially bidentate ligand,whose chemistry,much to our surprise,has remained unexplored thus far.Its monodentate analogue isocyanoferrocene (2),however,has already been investigated in detail.2 behaves like an aryl isocyanide in complexes such as (2)Cr(CO)_5.IR data indicate that 1 behaves analogously.It readily forms (l)[Cr(CO)_5]_2 with 2 equiv of Cr(CO)_5(THF),whereupon the nu(NC) band shifts from 2118 to 2142 cm~(-1).This effect is similar to that observed in the case of (2)Cr(CO)_5.(l)[Cr(CO)_5]_2 was structurally characterized by X-ray diffraction.It exhibits an eclipsed orientation of the cyclopentadienyl rings with a synclinal arrangement of the two substituents.Spectroelectrochemical investigations have revealed that oxidation of the ferrocene unit of (l)[Cr(CO)_5]_2 (Edeg=0.55 V vs ferrocenium/ ferrocene) leads to a shift of the isocyanide band to 2017 cm~(-1),a fact that can be explained by a decreased net electron donor ability of 1~+