Some novel monoalkyl-N-aryl-substituted iminopyridine iron chloride complexes, differing in the nature of the substituent at the iminic carbon and at the ortho position of the aryl ring, were synthesized and characterized. For one of them, single crystals were obtained, which allowed for the determination of its crystalline structure, in which the iron center is coordinated to the chlorides and to the two nitrogen atoms of the ligand. The coordination around iron is distorted tetrahedral, a coordination mode rarely identified for FeCl2 adducts with bidentate nitrogen ligands. All the complexes were used, in combination with methylaluminoxane, for the polymerization of 1,3-butadiene and isoprene, providing syndiotactic 1,2 poly­(1,3-butadiene)­s and poly­(isoprene)­s with a predominantly cis-1,4/3,4 alternating structure, in which short cis-1,4 sequences of three or five units, whose length depends on the nature of the ligand on the iron atom, are present. A detailed NMR characterization (1H-, 13C-, and 2D experiments) of the resultant poly­(isoprene)­s is reported, and a tentative scheme for the formation of the novel isoprene polymers is proposed.

While ruthenium arene complexes have been widely investigated for their medicinal potential, studies on homologous compounds containing a tridentate tris(1-pyrazolyl)methane ligand are almost absent in the literature. Ruthenium(II) complex 1 was obtained by a modified reported procedure; then, the reactions with a series of organic molecules (L) in boiling alcohol afforded novel complexes 2 – 9 in 77–99% yields. Products 2–9 were fully structurally characterized. They are appreciably soluble in water, where they undergo partial chloride/water exchange. The antiproliferative activity was determined using a panel of human cancer cell lines and a noncancerous one, evidencing promising potency of 1 , 7 , and 8 and significant selectivity toward cancer cells. The tested compounds effectively accumulate in cancer cells, and mitochondria represent a significant target of biological action. Most notably, data provide convincing evidence that the mechanism of biological action is mediated by the inhibiting of mitochondrial calcium intake.

A series of titanium(IV) complexes of general formula TiCl3[N,N-(pyridin-2-ylalkyl)anilido, TiCl3L, 8-13, were prepared by reactions of TiCl4 with substituted (pyridin-2-ylalkyl)anilines, LH, and characterized by analytical and spectroscopic methods. Compound 10 was obtained by using TiI4 as titanium precursor. In the case of LH = 2,6-diisopropyl(pyridin-2-ylmethyl)aniline, 1, and 2,6diisopropyl(pyridin-2-ylethyl)aniline, 2, the intermediate formation of TiCl4LH, 6-7, was detected, undergoing HCl elimination on heating to finally give 8 and 9. The products are not stable in coordinating solvents (thf, CH3CN). Ligand dissociation was observed from TiCl3(N,N-2,6diisopropyl(pyridin-2-ylmethyl)anilido, 8, resulting in the formation of Ti2OCl6(CH3CN)4 and 2-(2,6diisopropyl-phenylaminomethyl)pyridinium hexachlorotitanate. By reaction of TiCl3(thf)3 or TiI3 with 1 and 2 at ca 100 °C, the air sensitive derivatives TiCl2L, 14, and TiI2L, 15, were afforded.All titanium complexes were evaluated as catalysts for the polymerization of 1,3-butadiene and isoprene, in association with methylaluminoxane (MAO). The results indicate that the catalytic activity is strictly dependent on the nature of the ligands and the oxidation state of the metal, while the nature of the titanium complex has negligible influence on the selectivity.

A combined DFT and experimental study indicates that one water molecule is allowed to enter the first coordination sphere of a one-site catalyst, thus activating water oxidation.

The substitution reactions of VCp 2 (CO) with some selected olefins have been studied. Tetracyanoethylene (tcne) and fumaronitrile (fn), containing electron-withdrawing substituents, promptly react with VCp 2 (CO) with quantitative formation of VCp 2 (tcne) and VCp 2 (fn), respectively, while acrylonitrile and diethyl fumarate (defu) gave partial displacement of coordinated carbon monoxide under a CO atmosphere. No CO displacement from VCp 2 (CO) was observed with cyclooctene and norbornene. The carbonylation of VCp 2 (defu) (VCp 2 (defu) + CO a VCp 2 (CO) + defu) has been studied gas volumetrically from both sides, and the equilibrium constant for the displacement of coordinated defu by carbon monoxide was estimated to be 55 ( 8 at 298.5 K. Variable-temperature experiments between 298.5 and 327.7 K have shown the enthalpy change to be -2.4 kcal mol -1 . The equilibrium constant for the addition of defu to VCp 2 (VCp 2 + defu a Cp 2 (defu)) has been evaluated spectroscopically to be 150 ( 11 at 298.5 K. From the available data, the equilibrium constant for the addition of carbon monoxide to VCp 2 (VCp 2 + CO a VCp 2 (CO)) has been calculated to be K a ) (8.2 ( 0.4) × 10 3 : i.e., about 2 orders of magnitude higher than that for the complexation of defu. The present data for the 3d 3 system of vanadium(II) (ν ˜CO in toluene 1881 cm -1 ) are compared with those exhibited by the 5d 10 system of AuCl(CO) (ν ˜CO in toluene 2153 cm -1 ), whose behavior consistently shows an opposite dependence, as far as the olefin/ CO competition is concerned, on the nature of the olefin.