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The reactivity of niobium and tantalum pentahalides with imines
Full text linkThe reactivity of NbCl5, NbF5 and TaCl5 with a selection of commercial imines was investigated for the first time by using dichloromethane as reaction medium. NbCl5 reacted with Ph2C=NH, in 1:2 molar ratio, affording [Ph2C=NH2][NbCl5(N=CPh2)], 1, in 55% yield, as result of imine self-protonation. The iminium salt [PhCH=NHtBu][NbCl6], 2, was isolated in 52% yield from NbCl5 and PhCH=NtBu (1:1 molar ratio), while a low yield of [tBu2C=NH2][NbCl6], 3, was identified from NbCl5/tBu2C=NH. The 1:1 reactions of NbF5 with Ph2C=NH and PhCH=NtBu were accompanied by electron interchange and led to the isolation of the salts [Ph2C=NH2][NbF6], 4, and [PhCH=NHtBu][NbF6], 5, respectively, in ca. 50% yields. Few crystals of [Ph2C=NH2]2[Ta2Cl10O], 6, were recovered from TaCl5/Ph2C=NH, the anion being probably generated by the action of adventitious water. Compounds 1-6 were characterized by elemental analysis, IR and NMR spectroscopy. The structures of 1, 4 and 6 were ascertained by X-ray diffraction studies
Photochemical Alkyne Insertions into the Iron-Thiocarbonyl Bond of [Fe2(CS)(CO)3(Cp)2]
No full textInternal alkynes (RC≡CR) react with [Fe2(CS)(CO)3(Cp)2] (1), under UV radiation, to give the complexes [Fe2μ-η1:η3-C(R)=C(R)C=S(μ-CO)(CO)(Cp)2] [R = Et, 2a; R = Ph, 2b; R = CO2Me, 2c], as a result of CO displacement and alkyne insertion into the metal-CS bond of 1. In addition, the reaction of 1 with EtC≡CEt affords the metallacycle species [Fe2μ- η2:η2-C(S)C(Et)=C(Et)C(O)(CO)2(Cp)2] (3) as secondary product. The molecular structures of 2a and 3 have been elucidated by X-ray diffraction studies. Compound 1 reacts with HC≡CCO2Me, affording the complex [Fe2μ- η1:η3-C(H)=C(CO2Me)C=S(μ-CO)(CO)(Cp)2] (2d) in modest yield. Complexes 2a,b undergo selective methylation at the sulfur atom, generating the cationic complexes [Fe2μ- η1:η3-C(R)=C(R)=C(SMe)(CO)(μ-CO)(Cp)2][CF3SO3] [R = Et, 4a; R = Ph, 4b]. The X-ray structure of 4a has also been determined. Finally, 4b undergoes nucleophilic addition of hydride and cyanide (from NaBH4 and NBun4CN, respectively) to form the vinylalkylidene complexes [Fe2μ- η1:η3-C(Ph)C(Ph)=C(X)(SMe)(CO)(μ-CO)(Cp)2] [X = H, 5; X = CN, 6]
Synthesis and characterization of new carbamates of early transition metals in high oxidastion state
No full textDeprotonation of diiron -vinylimminium complexes: a convenient route for the synthesis of mono- and poly-nuclear species containing novel multidentate ligands
No full textThe versatile chemistry of niobium pentachloride with aliphatic amines: Aminolysis, metal reduction and C–H activation
Full text linkThe reactions of NbCl5 with limited amounts (1-2 molar equivalents) of a series of primary, secondary and tertiary amines were investigated in dichloromethane as solvent. The 1:1 reaction of NbCl5 with NHEt2 cleanly afforded an equimolar mixture of [NbCl4(NEt2)]2, 1, and [NH2Et2][NbCl6], 2a; the former product constitutes the first example of structurally characterized Nb(V) chlorido-amido complex. The ammonium salts [NH3nPr][NbCl6], 2b, and [NH2iPr2][NbCl6], 2c, were isolated in 20-30% yields from the 1:1 reactions of NbCl5 with NH2nPr and NHiPr2, respectively. Cα-H bond activation and Nb(V) to Nb(IV) reduction took place in the reactions of NbCl5 with NR3 (R = Bz, Et; Bz = CH2Ph). The iminium salt [(PhCH2)2N=CHPh][NbCl6], 3, and the ammonium ion [NH(CH2Ph)3]+ were identified as the prevalent species generated from the 1:1 NbCl5/NBz3 interaction. [NHEt3][NbCl6], 4, and [NHEt3]2[NbCl6], 5, were isolated in moderate yields from, respectively, the 1:1 and 1:2 molar reactions of NbCl5 with NEt3. The solid state structures of 1, 2a, 3, 4 and 5 were ascertained by single crystal X-ray studies
Molybdenum(V) and Molybdenum(IV) coordination compounds from the reaction of MoCl5 with sulfones
Full text linkThe mononuclear complexes MoCl5L (L = 2,5-dihydrothiophene-1,1-dioxide), 1, and MoCl4L2 (L = dimethylsulfone, 2; diethylsulfone, 3; diphenylsulfone, 4) were obtained by the reactions of MoCl5 with the corresponding sulfones at room temperature in dichloromethane, and were characterized by analytical and magnetic data, and by X-ray crystallography in the cases of 1 and 2. The X-ray structure of 1 is the first one ever reported for an adduct of MoCl5 with a carbon-containing species
Enhanced DNA damage and anti-proliferative activity of a novel ruthenium complex with a chlorambucil-decorated ligand
No full textTriphenylphosphine substitution reactions of [RuCl(PPh3)2(tpm)]Cl, 3 ) 2 (tpm)]Cl, 1 , featuring tris(pyrazolyl)methane (tpm) as ligand, with the chlorambucil-decorated pyridine ligand PyCA, CA , 3-aminopyridine ( Py NH2 ) and 4-pyridinemethanol ( Py OH ) afforded the corresponding pyridine complexes 2-4 in high yields. PyCA CA was preliminarily obtained via esterification of 4-pyridinemethanol with chlorambucil. The new compounds PyCA CA and 2-3 were characterized by IR and multinuclear NMR spectroscopy. Additionally, the structure of 3 was ascertained by single crystal X-ray diffraction. The in vitro anti-proliferative activity of 2-4 and PyCA CA was determined against a panel of cancer cell lines, outlining 2 as the most performing compound. Targeted studies were subsequently undertaken using 2 to elucidate mechanistic aspects, including the assessment of ruthenium cellular uptake, cell cycle arrest, production of reactive oxygen species (ROS), western blotting and DNA damage (comet test). Overall, data highlight that the anticancer activity provided by 2 primarily affects the mitochondria pathway with a potential additional contribution from DNA damage
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