Synthesis and Structure of a New Type of Chiral Organoiron and Organoruthenium Complexes

The synthesis of 36 Fe(CO)₂L¹(η⁴-diene)], three Fe(CO)₂L¹(η⁴-encne)], and five Ru(CO)₂L¹(η⁴-diene)] complexes (L¹ = Ph₃P, Et₃P, (EtO)₃P, (MeO)₃p, C₆H₁₁NC) by thermal, selective CO ligand displacement in the corresponding tricarbonyl precursor complexes is described. In a second step, photochemical CO displacement by another phosphorus ligand L² leads to a new type of η⁴-diene complexes with a centre of chirality at the metal atom (Fe, Ru). 23 Fe and three Ru complexes of this type have been prepared and characterized. In the case of complexes with unsymmetrical dienes, racemic diastereoisomers are formed which can be separated by chromatographic methods. The molecular structures of Fe(CO)(Ph₃P)((MeO)₃P)(buta-1,3-diene)] ( 52 ), Fe(CO)(Ph₃P)((MeO)₃P)(isoprene)] ( 58 ) and Fe(CO)(Et₃P)(EtO)₃P(hexa-2,4-dienal)] ( 62a ) were determined by X-ray diffraction. All complexes were investigated by ¹³C-, ³¹P- and, in part, ¹H-NMR spectroscopy. At low temperatures, conformational isomers (rotamers) can be differentiated which probably arise from ψ rotation at the coordinated metal centre.