Enrico Rotondo

Isoniazid-related copper(II) and nickel(II) complexes with antimycobacterial in vitro activity. Part 9

Isonicotinoylhydrazones 1, obtained by the primary antituberculous agent Isoniazid, have been used as monoanionic ligands (L) to prepare copper(II) 2 and nickel(II) 3 octahedral complexes of stoichiometry [MeL2(H2O)2]. Their antimycobacterial in vitro activity was evaluated against Mycobacterium tuberculosis H37Rv in comparison with the ligands. Complexes 2a, 2b, 2f, 3b, 3d and 3g displayed MIC values < or = 0.2 microg/mL.

Nickel(II) 2,6-diacetylpyridine bis(isonicotinoylhydrazonate) and bis(benzoylhydrazonate) complexes : Structure and antimycobacterial evaluation. Part XI

The reaction of 2,6-diacetylpyridine (dap) and isonicotinoyl- or benzoylhydrazide leads to bishydrazones H(2)dapin (1a) and H(2)dapb (1b), respectively. The condensation can either take place as a bimolecular kinetic process between the two reactants or as a monomolecular metal-templated synthesis in the presence of nickel(II) ions. In the latter case the reaction products are charged 2,6-diacetylpyridine bis(hydrazone) nickel(II) complexes, which can be easily deprotonated to neutral hydrazonates. Diffractometric analysis of one of these [Ni(dapb)](2) (8b) has shown a binuclear structure with two octahedral nickel(II) ions bridged by two helicoidal dap (bishydrazonates) in a spheroidal structure of C(2V) symmetry. The synthesized complexes 8 are promising as antimycobacterial agents against M. tuberculosis H37Rv. In particular, 8b displays significant activity (MIC=0.025 microg/mL) 10-fold higher than rifampin and equal to isoniazid, while its ligand is ineffective. Compound 8b is also capable of reducing HIV-induced cytopathogenic effect in human T(4 )lymphocytes.

Hydroformylation of styrene catalyzed by rhodium complexes with 2-diphenylphosphinopyridine

Abstract Mono- and binuclear rhodium complexes containing 2-(diphenylphosphino)pyridine, Ph 2 PPy 2 , as ligand have been examined as catalysts for the hydroformylation of styrene. All the species tested were good catalysts and the formation of the expected aldehydes took place selectively within several hours in mild conditions. The binuclear derivative [(η 5 -C 5 H 5 )Rh 2 (μ-CO)(μ-Ph 2 PPy)(CO)Cl], 1 , was an efficient catalysts only when the reaction was carried out under high pressure, whereas the in situ system obtained by addition of Ph 2 PPY to RhH(CO)(PPh 3 ) 3 , 4 , displayed a pronounced activity even in the low pressure reaction. 31 P{ 1 H} NMR shows that in solution Ph 2 PPy can easily displace one or two moles of PPh 3 from 4 , giving rise to mixed mononuclear phosphine-rhodium complexes that seem likely to be the most active catalytic species.

31P and 13C NMR investigation of the system tetracarbonyldi-μ-chlorodirhodium(I) — tertiary phosphine

13C and 31P{1H} NMR data at low temperature prompted us to characterize cis-[Rh(CO)2(PR3)Cl] (3) (3a, PR3  PPh3; 3b, PR3  PMe2Ph), as surprisingly stable products of the reaction between [{Rh(CO)2(μ-Cl)}2] (1) and tertiary phosphines in toluene (P : Rh = 1). Every attempt to isolate solid 3a led to the cis- and trans- halide-bridged dimers [{Rh(CO)2(μ-Cl)}2] (5a) and 6a which are formed from 3a by slow decarbonylation, a process which is greatly accelerated by the evaporation of the solvent under vacuum. The analogous reaction of 1 with dimethylphenylphosphine follows a similar pathway; in this case, however, low temperature NMR spectra allowed us to characterize the pentacoordinated dinuclear species [{Rh(CO)2(μ-Cl)}2] (2b) as the unstable intermediate of the bridge-splitting process. The reaction of 3 with a second equivalent of phosphine (P : Rh = 2) leads, at room temperature, to the well known product trans-[Rh(CO)(PR3)2Cl] (8) accompanied by evolution of CO; however our data show that when the reaction is performed at 200 K, decarbonylation is prevented and spectroscopic evidence of trigonal bipyramidal pentacoordinate [Rh(CO)2(PR3)2Cl] (7), stable only at low temperature, can be obtained.

Reactions of di-2-pyridyl sulfide with the palladium(II) and platinum(II) diene or methoxydiene complexes. Dynamic behaviour of the cationic compounds. Crystal structure of Pd(di-2-pyridyl sulfide)Cl2

Abstract The complexes [M(dps)Cl2] (MPdII (1); PtII (2)) and the labile compounds [M(MeOdiene)(dps)Cl] (MPdII, MeOdieneCH3OC8H12 (3) or CH3OC10H12 (4); MPtII, MeOdieneCH3OC8H12 (5) or CH3OC10H12 (6)) have been synthesized by reaction of dps (dps=di-2-pyridyl sulfide) with [M(diene)Cl2] (diene=cycloocta-1,5-diene or dicyclopentadiene) and the appropriate chloro-bridged methoxydiene complexes, respectively. The last reactions required drastic conditions. Also the reactions of dps with the solvento species [M(diene)(acetone)2]X2 and [M(MeOdiene)(acetone)2]X (X=BF4, PF6, ClO4) have been studied and the compounds [M(MeOdiene)(dps)]X (MPdII, MeOdieneCH3OC8H12 (7) or CH3OC10H12 (8); MPtII, MeOdieneCH3OC8H12 (9) or CH3OC10H12 (10)) were prepared. The structure of 1 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/n, with Z=4 in a unit cell of dimensions a=9.933(4), b=14.802(5), c=8.465(3) A, β=101.94(2)°. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full- matrix least-squares on the basis of 2163 observed reflections to R and R′ values of 0.0277 and 0.0348, respectively. In the square planar coordination around the Pd atom the dps molecule acts as a chelate ligand through the two pyridinic N atoms and adopts a N,N-inside conformation. The six-membered chelate ring shows a boat conformation with the Pd and S atoms out of the plane through the other four atoms on the same side. Although dissociation in the usual solvents prevents full characterization of 3–6 IR spectra suggest that the dps acts as monodentate ligand. The 1H NMR spectra, at variable temperature, and 13C NMR spectra of 7–10 show that the cationic complexes in solution undergo at least two dynamic processes; a ligand site exchange and a boat to boat inversion of the chelate dps ring. The ligand site exchange is fast, in the NMR time scale, at room temperature for palladium complexes and at higher temperature for the platinum complexes and makes equivalent the pyridine rings of dps. This process is interpreted in terms of formation of stereochemically non-rigid five- coordinate intermediates. The boat to boat inversion is fast at room temperature at least for platinum complexes. At low temperature the latter process is absent or occurs at markedly reduced rate for palladium complexes while the slow ligand site exchange results in equilibria between two conformers.

Some reations of the (π-C5H5)Rh(CO)L (L=CO, PPh3) complexes

The reactions of the complexes CpRh(CO)L (Cp = cycclopentadienyl; L = CO, PPh3) with Hl, ClCH2CN and C6H5SO2 l have been investigated. Inboth cases the reaction with hydrogen chloride gives products which do not contain the cyclopentadcienyl ring. Chloroa etonitrile reacts only with CpRh(CO)PPh3, and gives the cationic complex [CpRh(CO)(CH2CN)PPh3]+, which has been isolated and characterized. The sulphonyl chloride 6H5SO2l reacts with CpRh(CO)PPh3 to give a product which had not been fully identified and with CpRh(CO)2 to give CpRh (O)(C6H5SO2)Cl.

Antimycobacterial in vitro activity of cobalt(ii) isonicotinoylhydrazone complexes. Part 10

Octahedral cobalt(II) complexes of isonicotinoylhydrazones, which were obtained from the primary antituberculous agent isoniazid, have been synthesised and characterised. Their antimycobacterial in vitro activity has been evaluated against Mycobacterium tuberculosis H37Rv: they exhibit MIC values ranging from < 0.1 to 0.39 microg/mL, showing them to be generally more active than previously reported analogous Cu(II) and Ni(II) complexes.

Preparation and reactions of palladium(II) and platinum(II) dienyl complexes

Abstract The preparation of M(diene · OCH3)(L L)Y complexes (M = PdII, diene = 1,5-cyclooctadiene, endo-dicyclopentadiene, L L = 2,2′-bipyridyl, 1,10-phenanthroline, Y = hexafluorophoshate, diene = dicyclopentadiene, L L = 1,2-bis-(diphenylphosphino)ethane, Y = hexafluorophosphate; diene = 1,5-cyclooctadiene, L L = ethylenediamine, Y = Cl; diene = norbornadiene, L L = 2,2′-bipyridyl, phenanthroline, Y = Cl; M = PtII, diene = 1,5-cyclooctadiene, L L = 2,2′-bipyridyl, 1,10-phenanthroline, Y = hexafluorophosphate) is reported. For M = Pd, treatment of the dienyl complexes with hydrochloric acid in methanol gives Pd(L L)Cl2, while for M = Pt the products are Pt(diene)Cl2.

Crystal structure of [Pd(μ3-2-propenyl)(dps)][Pd(μ3-2-propenyl)Cl2]. NMR evidence of binuclear μ3-allyl palladium(II) species with bridging dps

Abstract The reactions of di-2-pyridyl sulfide (dps) with (μ3-allyl)palladium chloride dimers gave the ionic compounds [Pd(μ3-allyl)(dps)][Pd(μ3-allyl)Cl2] (allyl=2-propenyl (1), 2-methyl-2-propenyl (2), 2-butenyl (3)). The structure of 1 has been determined by X-ray diffraction methods. Crystals are triclinic, space groupP 1 , with Z=2 in a unit cell of dimensions a=8.840(1), b=8.928(1), c=12.317(2) A, α= 98.82(1), β=90.46(1), γ=95.46(1)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least-squares on the basis of 3855 observed relections to R and Rw values of 0.0269 and 0.0339, respectively. Compound 1 consists of discrete complex ion pairs, containing allyl groups coordinated to both the cationic and anionic palladium centres. In the cationic portion the dps acts as a chelate ligand and adopts an N,N inside conformation. The six-membered chelate ring shows a boat conformation. The cation and anion are connected by a short Pd2…Cl2 interaction (3.073(1) A) which determines pseudo-five-coordination for the cation. At low temperature the 1H NMR spectra in CD3OD of 1 and 2 confirm the presence of the cation and the anion while in CDCl3 they also indicate the presence of a binuclear species with bridging dps. The 1H NMR spectra, at variable temperature, show that 1, 2 and 3 in solution undergo dynamic processes. In CDCl3, a lower energy process makes the π-allyl groups equivalent at room temperature, a higher energy process determines the magnetic equivalence of syn and anti π-allyl protons at high temperature.

Phospholipid composition of plasma and erythrocyte membranes in animal species by 31 P NMR

The aim of this study was to provide basal values of phospholipid (PL) composition in different animal species by 31P NMR analysis using detergents. This fast and accurate method allowed a quantitative analysis of PLs without any previous separation. Plasma and erythrocyte membrane PLs were investigated in mammals (pig, cow, horse). Moreover, for the first time, the composition of plasma PLs in avian (chicken and ostrich) was performed by 31P NMR. Significant qualitative and quantitative interspecies differences in plasma PL levels were found. Phosphatidilcholine (PC) and sphingomyelin (SPH) levels were significantly higher (P < 0.001) in chicken plasma than all the other species tested. In erythrocytes, cow PC and phosphatidylcholine diarachidoyl were significantly lower (P < 0.001) than for pigs and horses, whereas pig PC presented intermediate values among cows and horses. Inorganic phosphate and 2,3-diphosphoglycerate levels were also significantly different between the species under investigation. The [SPH/total PLs] molar ratios in erythrocytes confirmed interspecies differences in phospholipid composition while the PC/SPH molar ratios could be related to a distinct erythrocyte flexibility and aggregability. Diet and nutrition may contribute primarily to the interspecies differences in plasma PL amounts detected. Significant differences between chicken plasma PC and SPH levels and those of the other animal species could be ascribed to a fat metabolism specific to egg production.