A New Cyclometalation Motif: Synthesis, Characterization, Structures, and Reactivity of Pallada- and Platinacycles with a Bidentate {C(sp2,cyrhetrene),N}− Ligand

Novel multifunctional and multitarget homo- (Fe2) and heterobimetallic [(Fe,M) with M = Re or Mn] sulfonyl hydrazones

The synthesis and characterization of the novel ferrocenyl sulfonyl hydrazide [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-NH2}] (2) is reported. Additional studies on its reactivity using acetone or the ferrocenyl-, cyrhetrenyl- or cymantrenyl-aldehydes have allowed us to isolate and characterize [Fe(η5-C5H5){(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CMe2}] (3), the bis(ferrocenyl) derivative [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]Fe(η5-C5H5)}] (4) and the heterodimetallic compounds [Fe(η5-C5H5){[(η5-C5H4)-S(O)2-NH-N[double bond, length as m-dash]CH-(η5-C5H4)]M(CO)3}] with M = Re (5a) or Mn (5b). The X-ray crystal structures of compounds 3, 5a and 5b are also reported. A comparative study of their electrochemical and spectroscopic properties is also described. Additional computational calculations based on the DFT methodology have allowed us to elucidate the effect produced by the replacement of the terminal -NH2 (in 2) by the -N[double bond, length as m-dash]CMe2 (in 3) and -N[double bond, length as m-dash]CHR (in 4, 5a and 5b) moieties on the electronic distribution and to explain the differences detected in their electrochemical properties and absorption spectra. In vitro cytotoxicity studies of compounds 2, 4, 5a and 5b on the HCT-116 (colon), MCF7 and MDA-MB231 (breast) cancer cell lines reveal that compound 2 has no significant activity (IC50 > 100 μM), while its derivatives 4, 5a and 5b proved to be active in the three cancer cell lines selected in this study. The growth inhibition potency of compounds 5a and 5b against the triple negative MDA-MB231 breast cancer cell line is similar (or slightly) greater than that of cisplatin. Moreover, compounds 2, 4, 5a and 5b are less toxic than cisplatin in the normal and non-tumoral BJ fibroblasts, and the heterodimetallic complexes 5a and 5b with selective index >2.1 show an outstanding selective toxicity towards the MDA-MB231 cancer cells.

A novel type of organometallic 2-R-2,4-dihydro-1H-3,1-benzoxazine with R = [M(η5-C5H4)(CO)3] (M = Re or Mn) units. Experimental and computational studies of the effect of substituent R on ring-chain tautomerism

Novel 2-cyrhetrenyl and cymantrenyl-2,4-dihydro-1H-3,1-benzoxazines.

Isomeric and hybrid ferrocenyl/cyrhetrenyl aldimines: a new family of multifunctional compounds

Comparative experimental and theoretical studies of the properties and biological activities of the new aldimines 1 and 2 are reported.

Labile Pd-sulphur and Pt-sulphur bonds in organometallic palladium and platinum complexes [(COD)M(alkyl)(S-ligand)]n+-A speciation study

Reaction of various sulphur ligands L (SEt^-, SPh^-, SC₆F₄H-4^-, SEt₂, StBu₂, SnBu₂, DMSO, DPSO) with the precursors [(COD)M(R)Cl] (COD=1,5-cyclooctadiene, M=Pd or Pt; R=methyl (Me) or benzyl (Bn); DMSO=dimethyl sulfoxide; DPSO=diphenyl sulfoxide) allowed isolation and characterisation of mononuclear neutral (n=0) or cationic (n=1) complexes [(COD)Pt(R)(L)]ⁿ⁺. Reaction of l-cysteine (HCys) with [(COD)Pt(Me)Cl] under similar conditions gave the binuclear cationic complex in [{(COD)Pt(Me)}₂(μ-Cys)]Cl. Detailed NMR spectroscopy and single crystal X-ray diffraction in the case of [(COD)Pt(Me)(SEt₂)][SbF₆] and [(COD)Pt(Me)(DMSO)][SbF₆] reveal markedly labilised Pt-S bonds as a consequence of the highly covalent Pt-C bonds of the R coligands in these organometallic species. Cationic charge (n=1) seems to lower the Pt-S bond strength further. Consequently, most of these complexes are not stable long-term in aqueous DMF (N,N-dimethylformamide) solutions. This made the evaluation of their antiproliferative properties towards HT-29 colon carcinoma and MCF-7 breast adenocarcinoma cell lines impossible. Only the two complexes [(COD)Pt(R)(SC₆F₄H-4)] with R=Me or SC₆F₄H-4 coligands could be tested with the R=Me complex showing promising activity (in the range of cisplatin), while the R=SC₆F₄H-4 derivative is largely inactive, as were the phosphane complexes [(dppe)Pt(SC₆F₄H-4)₂] (dppe=1,2-bis(diphenylphosphino)ethane), cis-[(PPh₃)₂Pt(SC₆F₄H-4)₂] and cis-[(PPh₃)₂PtCl₂] which were tested for comparison. In turn, our findings might pave the way to new Pt anti-cancer drugs with largely reduced unwanted depletion of incorporated drugs and reduced side-effects from binding to S-containing biomolecules.