Reaction of bidentate isonitrile ligands with iron carbonyls

Abstract

Reaction of the bidentate isonitriles CN(CH₂)_nNC (n= 2, 3, 4, or 6) with [Fe₂(cp)₂(CO)₄](cp =η-cyclopentadienyl) yields exclusively [{Fe₂(cp)₂(CO)₃}₂{CN(CH₂)_nNC}] derivatives which are fluxional in solution and exist in three isomeric forms (bridged–bridged, bridged–terminal, and terminal–terminal with respect to the bonding mode of the bidentate isonitrile). The proportion of the isomers containing terminally bound isonitrile increases with the length of the alkyl chain. The complexes may be protonated to yield [{Fe₂(cp)₂(CO)₃}₂{CN(H)(CH₂)_n(H)NC}][PF₆]₂ salts (n= 2 or 6) and may be cleaved with I₂ to give [Fe(cp)(CO)₂l] and [{Fe(cp)(CO)l}₂{CN(Ch₂)_nNC}](n= 2 or 6). Reaction of CN(CH₂)_nNC (n= 2 or 6) with [Fe₂(CO)₉] or [Fe₃(CO)₁₂] yields exclusively [{Fe(CO)₄}₂{CN(CH₂)_nNC}] derivatives.