1,3-Dipolar cycloaddition to the Fe-N=C fragment XVI. Reactivity of Fe(alkyl-NC) 3(iPr-DAB) complexes towards aromatic isothiocyanates as dipolarophiles. Insertion of isothiocyanate into the Fe-N bond

Article abstract of DOI:10.1016/0022-328X(95)05963-P

The reaction of para-substituted phenyl isothiocyanates (R³-C₆H₄-NCS; R³=H (a), Me (b), OMe (c), NO₂ (d)) with Fe(R²-NC)₃(ⁱPr-DAB) (7) (R² =^tBu or ^cHex) leads in a 1,3-dipolar cycloaddition reaction to novel [3.2.0] bicyclic compounds 10 into which two isothiocyanate molecules have been incorporated. A crystal structure determination revealed the unexpected insertion of an isothiocyanate via its C=S moiety and the lack of coordination of the unreacted imine nitrogen atom. Variable temperature NMR experiments showed a dynamic behaviour of 10, which involves interchanging coordination of the amino-and the imine nitrogen atoms to the iron atom. Complex 10cy is converted on silica gel to another complex 11cy. The structure of complex 11cy has been tentatively assigned, based on stoichiometry and spectroscopic properties. Probably two isothiocyanate molecules (c) have been cycloadded across both C=N-Fe moieties in complex 7y.