Circular Dichroism of Tricarbonyl(diene)iron Complexes. The Octant Rule Applied to Ketones Perturbed by Remote Fe(CO)3 Groups. Crystal Structure of (±)-Tricarbonyl[(1RS,4RS,5RS,6SR)-C5,6,C-η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octanone)]iron

The preparation and the CD spectra of optically pure (+)-trans-μ-(1R,4S,5S,6R,7R,8S)-C,5,6,C -η : C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo 2.2.2]octanone)]bis(tricarbonyliron) ((+)- 7 ) and (+)-tricarbonyl(1S,4S,5S,6R)-C-5,6,C-η-(5,6,7,8,-tetramethylidene-2-bicyclo2.2.2]octanone)]iron ((+)- 8 ), and of its 3-deuterated derivatives (+)-trans-μ-(1R,3R,4S,5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C-η-5,6,7,8-tetramethylidene(3-D)-2-bicyclo2.2.2]-(octanone)]bis(tricarbonyliron) ((+)- 11 ) and (+)-tricarbonyl(1S,3R,4S,5S,6R)-C-5,6,C- η-(5,6,7,8-tetramethylidene(3-D)-2-bicyclo2.2.2]octanone)]iron ((+)- 12 ) are reported. The chirality in (+)- 7 and (+)- 8 is due to the Fe(CO)₃ moieties uniquely. The signs of the Cotton effects observed for (+)- 7 and (+)- 8 obey the octant rule (ketone n→π*_CO transition). Optically pure (?)-3R-5,6,7,8-tetramethylidene(3-D)-2-bicyclo2.2.2]octanone ((?)- 10 ) was prepared. Its CD spectrum showed an ‘anti-octant’ behaviour for the ketone n→π*_CO transition of the deuterium substituent. The CD spectra of the alcoholic derivatives (?)-trans-μ-(1R,2R,4S, 5S,6R,7R,8S)-C,5,6,C-η : C,7,8,C- η-(5,6,7,8-tetramethylidene-2-bicyclo2.2.2]octanol)]bis(tricarbonyliron) ((?)- 2 ) and (?)-tricarbonyl- (1S,2R,4S,5S,6R)- C,5,6,C- η-(5,6,7,8-tetramethylidene-2-bicyclo2.2.2]octanol)]iron ((?)- 3 ) and of the 3-denterated derivatives (?)- 5 and (?)- 6 are also reported. The CD spectra of the complexes (?)- 2 , (?)- 3 , (+)- 7 , and (+)- 8 were solvent and temperature dependent. The ‘endo’-configuration of the Fe(CO)₃ moiety in (±)- 8 was established by single-crystal X-ray diffraction.