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We present a new synthetic strategy for obtaining mixed-valence triiron complexes where the metal centers are bridged by a novel, highly functionalized hydrocarbyl ligand. The alkynyl–vinyliminium complexes [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C(X–C≡CH)CHCNMe2}]CF3SO3 (X = 4-C6H4, [2a1]CF3SO3; X = (CH2)3, [2a2]CF3SO3) were synthesized in almost quantitative yields from the aminocarbyne precursor [Fe2Cp2(CO)2(μ-CO){μ-CNMe2}]CF3SO3, [1a]CF3SO3, and the di-alkynes HC≡C–X–C≡CH. Then, the ferracycle [Fe(Cp)(CO){C(NMe2)CH＝C(4-C6H4C≡CH)C(O)}], 4a1, was produced in 47% yield from the cleavage of [2a1]CF3SO3 promoted by pyrrolidine. Subsequent reactions of the acetonitrile adducts [Fe2Cp2(CO)(μ-CO)(NCMe){μ-CNMe(R)}]CF3SO3 (R = Me, [1aACN]CF3SO3; R = Xyl, [1bACN]CF3SO3) ([FeIFeI]) with 4a1 ([FeII]) at room temperature resulted in the formation of [FeIFeIFeII] complexes [Fe2Cp2(CO)(μ-CO){μ-η1:η3-C(X–C＝CHC(NMe2)＝FeCp(CO)C＝O)CHCNMe(R)}]CF3SO3 (R = Me, [5a1]CF3SO3; R = Xyl, [5b1]CF3SO3) in yields ranging from 56% to 64%. The new products were characterized by IR and multinuclear NMR spectroscopy, and the structures of [2a2]CF3SO3 and 4a1 were confirmed by single crystal X-ray diffraction. Cyclic voltammetry and spectroelectrochemical studies on [5a1]+ have revealed that reduction and oxidation events occur almost independently at the [FeIFeI] and [FeII] units, respectively. This observation underscores a minimal electronic interaction between the two fragments within the triiron complex. Accordingly, DFT studies pointed out that the HOMO and LUMO orbitals are predominantly localized in the two distinct compartments of [5a1]+. [ABSTRACT FROM AUTHOR]

Dimetallic complexes are suitable platforms for the assembly of small molecular units, and the reactivity of bridging alkenyl ligands has been widely investigated to model C–C bond forming processes. Here, we report the unusual coupling of an alkenyl ligand, bridging coordinated on a diruthenium scaffold, with a series of alkynes, revealing two possible outcomes. The diruthenium complex [Ru2Cp2(Cl)(CO)(μ-CO){μ–η1:η2-C(Ph)＝CH(Ph)}], 2, was prepared in two steps from [Ru2Cp2(CO)2(μ-CO){μ–η1:η2-C(Ph)＝CH(Ph)}]BF4, [1]BF4, in 69% yield. Then, the reaction of 2 with C2(CO2Me)2, promoted by AgCF3SO3 in dichloromethane, afforded in 51% yield the complex [Ru2Cp2(CO)2{μ–η3:η2-C(Ph)CH(Ph)C(CO2Me)C(CO2Me)}]CF3SO3, [3]CF3SO3, containing a ruthenacyclopentene-based hydrocarbyl ligand. On the other hand, 2 reacted with other alkynes and AgX salts to give the butadienyl complexes [Ru2Cp2(CO)2{μ–η3:η2-C(R)CH(R′)C(Ph)C(Ph)}]X (R = R′ = H, [4]BF4; R = R′ = Me, [5]CF3SO3; R = R′ = Ph, [6]CF3SO3; R = Ph, R′ = H, [7]CF3SO3), in 42–56% yields. All products were characterized by IR and NMR spectroscopy, and by single crystal X-ray diffraction in the cases of 2, [3]CF3SO3 and [6]BF4. DFT calculations highlighted the higher stability of [4–7]+-like structures with respect to the corresponding [3]+-like isomers. It is presumable that [3]+-like isomers initially form as kinetic intermediates, then undergo H-migration which is disfavoured in the presence of carboxylato substituents on the alkyne. Such hypothesis was supported by the computational optimization of the transition states for H-migration in the cases of R = R′ = H and R = R′ = CO2Me. [ABSTRACT FROM AUTHOR]

The room temperature reactions with internal alkynes, RC≡CR, of the μ-allenyl acetonitrile complex [Ru2Cp2(CO)2(NCMe){μ–η1:η2-C1H＝C2＝C3Me2}]BF4 (1-NCMe), freshly prepared from the tricarbonyl precursor [Ru2Cp2(CO)3{μ–η1:η2-C1H＝C2＝C3Me2}]BF4, 1, proceeded with alkyne insertion into ruthenium-allenyl bond and allenyl-CO coupling, affording compounds [Ru2Cp2(CO)2{μ–η2:η5-C(R)C(R)C1HC2(C3Me＝CH2)C(OH)}]BF4 (R = Ph, 2; R = CO2Me, 3; R = CO2Et, 4) in 83–94% yields. Deprotonation of 2–4 by triethylamine gave [Ru2Cp2(CO)2{μ–η2:η5-C(R)C(R)CHC(CMe＝CH2)C(O)}] (R = Ph, 5; R = CO2Me, 6; R = CO2Et, 7) in 75–88% yields, and 2–4 could be recovered upon HBF4·Et2O addition to 5–7. All the products, 2–7, were fully characterized by elemental analysis, IR and multinuclear NMR spectroscopy. The structure of 2 was ascertained by single crystal X-ray diffraction and investigated by DFT calculations, revealing a six-membered ruthenacycle with Shannon aromaticity index in line with related compounds. The formation of ruthenium-coordinated ruthenabenzenes from a preexistent diruthenium scaffold is a versatile but underdeveloped approach exploiting cooperative effects typical of a dimetallic core. [ABSTRACT FROM AUTHOR]

Single-crystal-to-single-crystal post-synthetic modifications (PSMs) of Lanthanide Organic Frameworks (LOFs) {[Ln2(H2L)3(DMF)4]·2DMF}n (Ln = Gd, 1 and Eu, 2; H4L = 2,5-dihydroxyterephthalic acid; DMF = dimethylformamide), carried out by treatment with (a) chloroform or (b) an imidazole solution in chloroform, yielded respectively isostructural {[Ln2(H2L)3(DMF)4]·CHCl3}n (Ln = Gd, 3; Eu, 4) or {[Ln2(H2L)3(Im)4][Ln2(H2L)3(Im)2(H2O)2]·6Im·2CHCl3}n (Ln = Gd, 5; Eu, 6). Single crystal X-ray diffraction studies of 5 showed two different regularly alternating dimeric units in the LOF and two regularly alternating cavities with different guest molecules. All compounds revert to the parent LOF, 1 or 2, when treated with DMF at 90 °C for 8 h. Europium-LOFs (2, 4 and 6) showed a faint red emission that progressively gained intensity upon cooling from RT to liquid nitrogen temperature. This behaviour was exploited to develop a family of luminescent thermometers whose characteristics were affected by the structural and coordinative modifications induced by PSMs. [ABSTRACT FROM AUTHOR]

We report an unprecedented mode of reactivity of carboxylic acids. A series of tertiary carboxylic acids, containing at least one phenyl α-substituent, undergo loss of carbon monoxide at room temperature (295 K), by a one pot reaction with 0.5–1 molar equivalents of WCl6 in dichloromethane. A plausible mechanism for the Ph3CCO2H/WCl6 reaction, leading to [CPh3][WOCl5] and Ph3CCl, is proposed on the basis of DFT calculations. The analogous reactions involving CEt(Ph)2CO2H, CMe(Ph)2CO2H and CMe2(Ph)CO2H selectively afforded stable hydrocarbons (alkene or indene, depending on the case), apparently resulting from the rearrangement of elusive tertiary carbocations. [ABSTRACT FROM AUTHOR]

The carbonic anhydrase inhibitor acetazolamide (AcmH2) reacted with [(η6-p-cymene)RuCl(μ-Cl)]2 to afford [(η6-p-cymene)RuCl2(κN-AcmH2)], 1A, in near-quantitative yield. In methanol, 1A exists in equilibrium with 1B, being probably a coordination isomer, as established by VT 1H-EXSY NMR spectroscopy. DFT calculations pointed to a higher stability of 1A with respect to 1B. [(η6-p-cymene)RuCl(κ2N,N′-AcmH)], 2, was obtained in 86% yield from [(η6-p-cymene)RuCl(μ-Cl)]2 and AcmH2 in the presence of NaOH. The reactions of 2 with AgNO3 (in water), pta/AgNO3 or pta/AgOTf/Et3N (in methanol) afforded the nitrate-coordinated complex [(η6-p-cymene)Ru(κO-NO3)(κ2N,N′-AcmH)], 3, the salt [(η6-p-cymene)Ru(κ2N,N′-AcmH)(κP-pta)]NO3, [4]NO3, and the zwitterion [(η6-p-cymene)Ru(κ2N,N′-Acm)(κP-pta)], 5, respectively, in high yields (pta = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane). The reactions of 5 with Brønsted acids yielded the protonated-pta species [(η6-p-cymene)Ru(κ2N,N′-Acm)(κP-ptaH)]X [6]X (X = NO3, TsO). All compounds were fully characterized by analytical and spectroscopic methods, and the structures of 1A, 2 and 5 were elucidated by X-ray diffraction. The stability of the compounds was investigated in aqueous media and 2 and 5 were evaluated for their cytotoxicity towards human ovarian A2780 and A2780cisR cancer cells and non-tumorigenic HEK-293 cells. [ABSTRACT FROM AUTHOR]

The new complexes [RuCl2(η6-p-cymene)(κP-Ph2PR)] [R = 4-C6H4OSiMe2tBu, 1; R = 4-C6H4Br, 2; R = OC(=O)CHCl2, 3; R = OPh, 4; R = O(2-C6H4SiMe2tBu), 5] and [Ru(C2O4)(η6-p-cymene){κP-Ph2PO(2-C6H4(SiMe2tBu))}], 6, were obtained in 83–98% yield from Ru(ii) arene precursors by three different synthetic strategies. The unprecedented phosphine Ph2P(O(2-C6H4SiMe2tBu)) was synthesized in 86% yield from 2-C6H4Br(OSiMe2tBu) and Ph2PCl, via intramolecular oxygen to carbon 1,3 migration of the silyl group (retro-Brook rearrangement). All the complexes were fully characterized by analytical and spectroscopic methods, and by single crystal X-ray diffraction in the cases of 3, 4, 5 and 6. Complexes 1–6 and the model compounds [RuCl2(η6-p-cymene)(κP-PPh3)] (Ru-PPh3) and [Ru(C2O4)(η6-p-cymene)(κP-PPh3)] (Ru-PPh3-O) underwent slow degradation in chloroform solutions upon air contact; the mixed valence complex [(η6-p-cymene)Ru(μ-Cl)3RuCl2(κP-PPh3)], 7, was isolated from a solution of Ru-PPh3 in CHCl3, and X-ray identified. The antiproliferative activity of 1–6 and Ru-PPh3, Ru-PPh3-O and [RuCl2(η6-p-cymene)(κP-PTA)] (RAPTA-C) was assessed towards the triple-negative breast cancer cell line MDA-MB-231, the ovarian carcinoma cell line A2780 and human skin fibroblasts (HSF). Complexes 1, 2, 5 and 6 displayed IC50 values significantly lower than that of cisplatin, with 2 providing a more potent cytotoxic effect on MDA-MB-231 and A2780 cancer cells compared to the noncancerous cell line (HSF). The stability of all complexes in DMSO/water solution was elucidated by NMR and conductivity measurements, and in particular 35Cl NMR spectroscopy was helpful to check the possible chloride dissociation. The stability studies suggest that the cytotoxic activity in vitro of the compounds is mainly ascribable to Ru(ii) species still bound to the phosphorus ligand. [ABSTRACT FROM AUTHOR]