The potential of vinylferrocene Fc(CHCH 2 ) (1) as redox-active ene functional precursor for thiol−ene radical reaction has been successfully investigated for the first time. To this end, we initially studied thiol−ene model reactions of 1 with a variety of functionalized monothiols, including 2-mercaptoethanol, 1-thioglycerol, 3-mercaptopropionic acid, (3-mercaptopropyl)-trimethoxysilane, 2-aminoethanethiol hydrochloride, dithiol 2,2′-(ethylenedioxy)diethanethiol, and the tetrafunctional thiol pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). These reactions afforded the newly ferrocenyl-hydrothiolated smallmolecule models Fc(CH 2 ) 2 S(CH 2 ) 2 OH (2), Fc(CH 2 ) 2 S(CH 2 ) 2 COOH (3), Fc(CH 2 ) 2 S(CH 2 )CH(OH)(CH 2 )OH (4), Fc(CH 2 ) 2 S(CH 2 ) 3 Si(OMe) 3 (5), bimetallic Fc(CH 2 ) 2 S(CH 2 ) 2 O(CH 2 ) 2 O(CH 2 ) 2 S(CH 2 ) 2 Fc (6), and tetrametallic [Fc(CH 2 ) 2 S-(CH 2 ) 2 COOCH 2 ] 4 C (7) in relatively high yields. Furthermore, the hydrothiolation of the CC bond of vinylferrocene was successfully extended to the S−H-polyfunctionalized poly[(3-mercaptopropyl)methylsiloxane] (PMMS), which provided access to a new redox-active polysiloxane (Me 3 SiO){MeSi[(CH 2 ) 3 S(CH 2 ) 2 Fc]O} n (SiMe 3 ) (8) containing covalently attached electroactive ferrocenyl−thioether side groups. The thiol−vinylferrocene reactions have been initiated either thermally, in toluene solution with AIBN, or by UV light irradiation in THF in the presence of 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator. The outcomes of the hydrothiolation of vinylferrocene strongly depend on the thiol structure and on the experimental conditions. Thermogravimetric analysis (TGA) of 8 established that the incorporation of pendant thioether− ferrocenyl units within the Si−O−Si backbone significantly improves the thermal stability of polymethylsiloxane in comparison to the S−H-polyfunctionalized PMMS precursor. Electrochemical studies revealed that polysiloxane 8, containing sulfur-bridged ferrocenyl moieties attached along the main chain, exhibits unusual and excellent adsorption properties and spontaneously forms robust films on Pt and Au electrodes. The well-defined and persistent voltammetric waves of the surface-adsorbed 8 films display nearly ideal redox behavior and exhibit peak potential separations (ΔE peak ) and full width at half-maximum (E fwhm ) values close to those theoretically expected for stable, surface-immobilized electroactive layers.

A new family of heterometallic compounds 3-6 containing ferrocenyl and platinum(II) centers has been synthesized by reaction of 1-β-aminoethylferrocene (1) and 1,1'-bis(β-aminoethyl)ferrocene (2) with Pt(II) precursors. Using K(2)[PtCl(4)] as the Pt(II) source, the cis-square-planar neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)PtCl(2)] (3) and [{Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))}(2)PtCl(2)] (5) were obtained. Reaction of cis-[PtCl(2)(dmso)(2)] with 1 and 2 resulted in the displacement of dmso and chloride ligands from the platinum coordination sphere, affording the cationic and neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)Pt(dmso)Cl]Cl (4) and [Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))Pt(dmso)Cl(2)] (6). Compounds 3-6 were thoroughly characterized using multinuclear ((1)H, (13)C, (195)Pt) NMR, IR spectroscopy, ESI mass spectrometry and elemental analysis. Single-crystal X-ray analysis of heterometallic 6 confirmed the cis geometry of the molecule and revealed that the platinum atom is held in a perfect square-planar geometry. The electrochemical behaviour of the heterometallic compounds 3-6, which has been examined by cyclic (CV) and square wave (SWV) voltammetries in dichloromethane and dmso solution, is characterized by the reversible one-electron oxidation of the ferrocene moieties. The results of the biological activity studies revealed that the organometallic complex 5 is active against all cell lines with GI(50) values in the range 1.7-2.3 μM. When compared to the standard anticancer drug cisplatin, heterotrimetallic 5, possessing two aminoethylferrocenyl units coordinated to the Pt(II) center, showed a greater activity profile in the colon cancer cell line. Cell cycle studies revealed that the new mixed compound exhibits a mechanism of action different to cisplatin.

Redox-active, highly symmetrical cubic octasilsesquioxanes (OS) peripherally decorated with 24 ferrocenyl units, linked in threes around the periphery of a cubic cage, namely, [Fc 3 Si(CH 2 ) 2 Me 2 SiO] 8 Si 8 O 12 (6) and [Fc 3 Si-(CH 2 ) 2 ] 8 Si 8 O 12 (7) (Fc = (η 5 -C 5 H 4 )Fe(η 5 -C 5 H 5 )), have been synthesized. Such integrally ferrocenyl-functionalized cubic macromolecules 6 and 7, as well as the related smallmolecule models hexaferrocenyldisiloxane [Fc 3 Si-(CH 2 ) 2 Me 2 Si] 2 O (4) and dodecaferrocenyl cyclotetrasiloxane [Fc 3 Si(CH 2 ) 2 MeSiO] 4 (5), have been prepared by covalently linking, via Karstedt's-catalyzed hydrosilylation, triferrocenylvinylsilane (CH 2 CH)Si(Fc) 3 (3) around the surface of octasilsesquioxane cages T 8 (OSiMe 2 H) 8 and T 8 H 8 and linear [Me 2 SiH] 2 O and cyclic [MeSiHO] 4 siloxane scaffolds, respectively. All new polyferrocenyl oligosiloxanes have been thoroughly characterized using a combination of elemental analysis, multinuclear ( 1 H, 13 C, 29 Si) NMR spectroscopy, FT-IR, and MALDI-TOF mass spectrometry. The molecular structure of disiloxane 4, in the solid state, has been determined by single-crystal X-ray analysis. Hexametallic 4 shows a bent arrangement of the ferrocenyl-substituted disiloxane linkage (Si−O−Si angle of 147.6(5)°). Polyferrocenyl-OS 6 and 7 show good thermal stability and form iron-containing ceramics when pyrolyzed under nitrogen. The electrochemical behavior of polyferrocenyl OS and model linear and cyclic siloxanes has been examined by cyclic and square wave voltammetries, in dichloromethane solution using PF 6 − and B(C 6 F 5 ) 4 − as supporting electrolyte anions of different coordinating ability. The novel maximally ferrocenylfunctionalized oligosiloxanes exhibit a three-wave redox pattern, suggesting appreciable electronic interactions between the silicon-bridged triferrocenyl moieties as they are successively oxidized. OS 6 and 7 undergo remarkable oxidative precipitation in CH 2 Cl 2 /n-NBu 4 PF 6 and are able to form stable electroactive films on platinum electrode surfaces. They are the first redox-active OS showing significant electronic interactions between metal sites on the cage surface.

The potential of structurally new ferrocene-functionalized guanidines as redox-active precursors for the synthesis of heterometallic platinum(II)−guanidine complexes with anticancer activity was studied. To this end, an atom-economical catalytic approach was followed by using ZnEt 2 to catalyze the addition of aminoferrocene and 4-ferrocenylaniline to N,N′-diisopropylcarbodiimide. Furthermore, reaction of a platinum(II) source with the newly obtained guanidines Fc−NC(NH i Pr) 2 (3) and Fc(1,4-C 6 H 4 )−NC(NH i Pr) 2 (4) provided access to the heterometallic complexes [PtCl 2 {Fc−NC(NH i Pr) 2 }(DMSO)] (5), [PtCl 2 {Fc(1,4-C 6 H 4 )−NC(NH i Pr) 2 }(DMSO)] (6), and [PtCl 2 {Fc-(1,4-C 6 H 4 )−NC(NH i Pr) 2 } 2 ] (7). Electrochemical studies evidence the remarkable electronic effect played by the direct attachment of the guanidine group to the ferrocene moiety in 3, making its one-electron oxidation extremely easy. Guanidinebased Fe−Pt complexes 5 and 6 are active against all human cancer cell lines tested, with GI 50 values in the range 1.4−2.6 μM, and are more cytotoxic than cisplatin in the resistant T-47D and WiDr cell lines.

A new series of vinyl-functionalized polyferrocenyl organosilicon compounds, including triferrocenylvinylsilane, (CH2CH)Si(Fc)3 (7) (Fc = (η5-C5H4)Fe(η5-C5H5)), 1,3-divinyl-1,1,3,3-tetraferrocenyldisiloxane, [(CH2CH)(Fc)2Si]2O (8), and 1,3-divinyl-1,3-dimethyl-1,3-diferrocenyldisiloxane, [(CH2CH)(Fc)MeSi]2O (9), have been synthesized via the low-temperature salt metathesis reaction of monolithioferrocene and the chlorosilanes (CH2CH)SiCl3 and [(CH2CH)(Cl)MeSi]2O. Compounds 7−9 were characterized by elemental analysis, multinuclear (1H, 13C, 29Si) NMR spectroscopy, and MALDI-TOF mass spectrometry. The molecular structures of the vinyl-functionalized silane 7 and divinyldisiloxanes 8 and 9 in the solid state have been determined by single-crystal X-ray analysis. Whereas tetraferrocenyl compound 8 possesses a linear disiloxane skeleton (Si−O−Si bond angle of 180.0(2)°), biferrocenyl 9 shows a bent arrangement of the disiloxane linkage (Si−O−Si angle of 143.2(2)°). The oxidation electrochemical behavior of polyferrocenyl molecules 7−9 has been examined by cyclic voltammetry and square wave voltammetry in dichloromethane solution, using hexafluorophosfate, [PF6]−, and tetrakis(pentafluorophenyl)borate, [B(C6F5)4]−, as supporting electrolyte anions of different coordinating ability. Compound 7 can be reversibly oxidized in three consecutive steps to the trication 7 3+ . Divinyldisiloxanes 8 and 9 are reversibly oxidized in four and two one-electron-transfer steps, respectively, which suggests significant electronic interaction among the ferrocenyl redox centers linked by the short three-atom Si−O−Si bridge.