Some additional aspects of versatile starting compounds for cationic organoiron complexes: Molecular structure of the aqua complex [(eta(5)-C(5)Me(4)Et)Fe(CO)(2)(OH2)]BF4 and solution behavior of the THF complex [(eta(5)-C(5)R(5))Fe(CO)(2)(THF)]BF4

The structures of the versatile starting compounds for organoiron complexes, the cationic aqua complex [(eta(5)-C(5)Me(4)Et)Fe(Co)(2)(OH2)]BF4 (1b) and the halide complexes (eta(5)-C(5)Me(5))Fe(CO)(2)-I (2a), (eta(5)-C(5)Me(4)Et)Fe(CO)(2)-I (2b) and (eta(5)-C(5)Me(4)Et)Fe(CO)(2)-Cl (3b), are characterized by X-ray crystallography. Complex 1b [Fe-O: 2.022(8) Angstrom and 2.043(9) Angstrom, two independent molecules] is the first structurally characterized example of organoiron aqua complexes. Details of the synthetic procedures for the above complexes and the labile cationic THF complexes [(eta(5)-C(5)R(5))Fe(CO)(2)(THF)]BF4 (4) are disclosed, and the dissociation equilibrium of 4 is confirmed by means of variable temperature H-1-NMR as well as saturation transfer experiment.