Herein, we describe
the synthesis, full spectroscopic characterization,
DFT (density functional theory) calculations, and single-crystal X-ray
diffraction analyses of a series of osmium arene σ-germyl, germanate,
σ-stannyl, and stannate complexes, along with their cytotoxic
(anticancer) investigations. The known dimer complexes [OsCl2(η6-C6H6)]2 (1) and [OsCl2(η6-p-cymene)]2 (2) were reacted with PPh3 to form the known mononuclear complex [OsCl2(η6-p-cymene)(PPh3)] (3) and the new complex [OsCl2(η6-C6H6)(PPh3)] (6); complex 3 was reacted with GeCl2·(dioxane) and SnCl2 to afford, by insertion into the Os–Cl bond, the neutral
σ-germyl and stannyl complexes [OsCl(η6-p-cymene)(PPh3)(GeCl3)] (7) and [OsCl(η6-p-cymene)(PPh3)(SnCl3)] (11), respectively, as a
mixture of enantiomers. Similarly, the reaction of complex 6 with GeCl2·(dioxane) afforded [OsCl(η6-C6H6)(PPh3)(GeCl3)] (9). Complex 2, upon reaction with 1,1-bis(diphenylphosphino)methane
(dppm), formed a mixture of [OsCl2(η6-p-cymene)(κ1-dppm)] (4) and
[Os(η6-p-cymene)(κ2-dppm)Cl]+Cl– (5) when
prepared in acetonitrile and a mixture of 4 and the dinuclear
complex [[OsCl2(η6-p-cymene)]2(μ-dppm)] (0) when prepared in dichloromethane.
By utilizing either isolated 4 or a mixture of 4 and 5, the synthesis of κ2-dppm germanate and stannate salts, [OsCl(η6-p-cymene)(κ2-dppm)]+GeCl3
– (8) and [OsCl(η6-p-cymene)(κ2-dppm)]+SnCl3
– (10), were
accomplished via halide-abstracting reactions with
GeCl2·(dioxane) or SnCl2, respectively.
All resulting complexes were characterized by means of multinuclear
NMR, FT-IR, ESI-MS, and UV/Vis spectroscopy. X-ray diffraction analyses
of 4, 8, 9, 10, and 11 were performed and are reported. DFT studies
(B3LYP, basis set LANL2DZ for Os, and def2-TZVPP for Sn, Ge, Cl, P,
C, and H) were performed on complex 9 and the benzene
analogue of complex 11, 11–benzene, to evaluate the structural changes and the effects on the frontier
molecular orbitals arising from the substitution of Ge for Sn. Finally,
complexes 3 and 7–11 were investigated for potential anticancer activities considering
cell cytotoxicity and apoptosis assays against Dalton’s lymphoma
(DL) and Ehrlich ascites carcinoma (EAC) malignant cancer cell lines.
The complexes were also tested against healthy peripheral blood mononuclear
cells (PBMCs). All cell lines were also treated with the reference
drug cisplatin to draw a comparison with the results obtained from
the reported complexes. The study was further corroborated with in silico molecular interaction simulations and a pharmacokinetic
study.
