Abstract
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•Homo and heterobimetallic complexes.•First cytotoxic investigations of diphosphine bridged (µ) diiron complexes.•DFT studies of the homo and heteronuclear complexes.•Comparison of DFT calculated and experimentally determined IR spectra.
A series of heterobimetallic [Fe,Ru] and homobimetallic [Fe,Fe] complexes, featuring µ -diphosphine bridges between the two metal centres, are reported along with their in vitro cytotoxicity activity on the A2780cisR cell-line. The known starting material [CpFe(CO)2(CH3)] (Cp = η5-C5H5) (1) was reacted with dppe (1,2-bis(diphenylphosphino)ethane) forming the known mononuclear κ1-dppe complex: [CpFe(CO)(COCH3)(κ1-dppe)] (2) and the known dinuclear complex: and [[CpFe(CO)(COCH3)]2(µ-dppe)] (3). Dimer cleavage reactions between complex 2 and two ruthenium arene complexes [(η6-p-cymene)RuCl2]2 and [(η6-benzene)RuCl2]2 formed two new heterobimetallic complexes: [CpFe(CO)(COCH3)(µ-dppe)Ru(η6-cymene)Cl2] (4) and [CpFe(CO)(COCH3)(µ-dppe)Ru(η6-C6H6)Cl2] (5). A homobimetallic system, [[CpFe(CO)(I)]2(µ-dppb)] (6) was obtained by the facile reaction between of [CpFe(CO)2I] and 1,4-bis(diphenylphosphino)butane (dppb). Complex 6 was methylated using MeLi to generate the more lipophilic complex [[CpFe(CO)(CH3)]2(µ-dppb)] (7). All of the complexes were fully characterized by spectroscopy (1H, 13C {1H}, 31P {1H} NMR; FTIR, UV–Vis), and high resolution mass spectrometry (HRMS). Density functional theory calculations (DFT) (Level of theory B3LYP, basis set for H, C, P, O, Cl is 6-31+G(d,p) and for Ru, Fe, I is DGDZVP) on complexes 5 and 6 are also reported. An excellent agreement between the DFT calculated infra-red (IR) spectra of the optimised geometries of 5 and 6 was found with the experimentally determined spectra. In vitro cytotoxicity studies of all complexes was carried out on A2780cisR (cisplatin resistant ovarian cancer cell-line) and compared to cisplatin as a positive control and RAPTA-C as a negative control. Although limited to only one cell-line, the results show that the heterobimetallic complexes 4 and 5 are the most cytotoxic (IC50 = 4.9 ± 0.4 µM and 6.5 ± 0.1 µM respectively), whilst the dinculear [Fe,Fe] complexes exhibit no, or very low cytotoxicity.