Synthesis of (μ 2 ,η 3 -allyl-η 5 -oxapentadienyl)diiron pentacarbonyl complexes, an unusual reaction product from η 4 -(vinylketene)Fe(CO) 3 complexes: structure and electron density distribution analysis.

The synthesis of a series of ferrocenylvinylketenes as stable η 4 -[Fe(CO) 3 ] complexes (3a-f) was successfully accomplished through the reaction of η 2 -[Fe(CO) 4 ] complexes under mild carbonylation conditions. The reactivity of 3a-f under thermal conditions afforded the unexpected formation of a novel family of (μ 2 ,η 3 -allyl-η 5 -oxapentadienyl)diiron pentacarbonyl complexes 5a-f proposed to be formed by a sequence metathesis-haptotropic rearrangement between the starting η 4 -vinylketene iron(0) complex 3 and a η 4 -vinylcarbene iron(0) complex trapped in situ after a reversible carbonylation process favored by the thermal conditions. An electron density distribution analysis (EDD) of 5e using high-resolution X-ray diffraction data in combination with the DFT framework was performed to understand the electronic communication between the two iron fragments.