Further exploration of the reaction between cis-[Fe(CO)4I2] and alkylamines: An aminium salt of fac-[Fe(CO)3I3]− or an amine-bound complex of fac-[Fe(CO)3I2(NH2R)]?

Four new monoiron (II) tricarbonyl complexes with the amine bound, fac -[Fe(CO) 3 I 2 (NH 2 R)] (R = Et, 1 ; n Pr, 2 ; n Bu, 3 ; n Pent, 4 ), were reported using cis -[Fe(CO) 4 I 2 ] as the precursor. All the complexes 1 – 4 were structurally confirmed by various techniques such as ultraviolet–visible (UV–vis), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectra and elemental analysis of which complexes 1 and 2 are crystallographically determined. The reaction of the precursor with alkylamines proceeded in two main parallel pathways to form both aminium salts of fac -[Fe(CO) 3 I 3 ] − and the amine-bound complexes ( 1 – 4 ). Their dominances altered with the reaction time. These complexes in DMSO undergo quick decomposition with complex 1 as the relatively most stable one ( t 1/2 = 7.3 min) although they are stable in solid status. Unlike the triiodo anion and pyridinyl analogs showing severe cytotoxicity due to the generation of iodine radical during the decomposition, no iodine radicals were detected from the fac -[Fe(CO) 3 I 2 (NH 2 R)] complexes. Therefore, the cell viability of RT112 cells was not affected by the presence of the amine-bound iron complex ( 1 ) up to 100 μmol L −1 .