10.1021/om970703y.s001 Yuan-Te Fu Yuan-Te Fu Pei-Chi Chao Pei-Chi Chao Ling-Kang Liu Ling-Kang Liu Ring Opening of (Spiro[2.4]hepta-4,6-diene)tricarbonyliron:  A Revisit American Chemical Society 1998 Fe cation PPh 3 CO C 5 H 4 CPh 3 C 5 H 4 CH 2 CH 3 1998-01-19 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Ring_Opening_of_Spiro_2_4_hepta-4_6-diene_tricarbonyliron_A_Revisit/3780852 (Spiro[2.4]hepta-4,6-diene)tricarbonyliron (<b>2</b>) self-converts to the tethered acyl complex (CO)<sub>2</sub>FeC(O)CH<sub>2</sub>CH<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>) (<b>3</b>) when refluxed for 1 h in common organic solvents. The reaction of <b>2</b> with an external electrophile (CPh<sub>3</sub><sup>+</sup>, H<sup>+</sup>) opens the three-membered ring, resulting in the cation (η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>CH<sub>2</sub>CH<sub>2</sub>R)Fe(CO)<sub>3</sub><sup>+</sup> whose structure was determined by spectroscopic methods and confirmed by X-ray analysis of the PPh<sub>3</sub> derivative (η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>CH<sub>2</sub>CH<sub>3</sub>)Fe(CO)<sub>2</sub>(PPh<sub>3</sub>)<sup>+</sup>. The reaction of <b>3</b> with a strong electrophile (CPh<sub>3</sub><sup>+</sup>, Me<sup>+</sup>) affords the rotationally restricted Fe−(alkoxy)carbene cation (CO)<sub>2</sub>FeC(OR)CH<sub>2</sub>CH<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)<sup>+</sup>, which can be converted to the Fe−(anilino)carbene cation (CO)<sub>2</sub>FeC(NHPh)CH<sub>2</sub>CH<sub>2</sub>(η<sup>5</sup>-C<sub>5</sub>H<sub>4</sub>)<sup>+</sup>.