Maurizio Lanfranchi

Chiral Phosphoramidite Ligands Based on 8‐Chloroquinoline and Their Rhodium(III), Palladium(II), and Platinum(II) Complexes

The new chiral ligands 2-butyl-8-chloro-1-(4,8-di-tert-butyl-2,10-dimethoxy-5,7-dioxa-6-phosphadibenzo[a,c]cyclohepten-6-yl)-1,2-dihydroquinoline (BIPHENPHOSHQUIN, 3) and 2-butyl-8-chloro-1-(3,5-dioxa-4-phosphacyclohepta[2,1-a;3,4-a′]dinaphthalen-4-yl)-1,2-dihydroquinoline (BINAPHOSHQUIN, 4; 4a: SaRC, 4b: SaSC) have been synthesized starting from the rigid backbone of 8-chloroquinoline. The reactions of 3 and 4 with rhodium(I), palladium(II), and platinum(II) substrates are reported. The reaction of 3 with [Rh(CO)2Cl]2 in a 2:1 molar ratio in hexane afforded a binuclear chloro-bridged rhodium(III) species by intramolecular oxidative addition of the C–Cl bond of ligand 3 across the rhodium(I) centers. The rhodium(III) complex 5, incorporating the enantiomers SaRC-3 and RaSC-3, has been fully characterized by X-ray diffractometry. Reactions of [Pd(PhCN)2Cl2] with the ligands 3 and 4a in 1:2 molar ratio in toluene afforded the products cis-[Pd(3)2Cl2] (9) and cis-[Pd(4a)2Cl2] (10). Similarly, reaction of [Pt(COD)I2] with 4a in a 1:2 molar ratio afforded the complex cis-[Pt(4a)2I2] (11). An X-ray analysis has been carried out to obtain information on the effect of the ligand 4a on the overall structure of 11.

Synthesis, spectroscopic and structural characterization of chlorobis(methyl pyruvate thiosemicarbazone)copper(I) and chlorobis(triphenylphosphine) (methyl pyruvate thiosemicarbazone)copper(I) toluene solvate (2/1)

Abstract Two new compounds, chlorobis(methyl pyruvate thiosemicarbazone)copper(I), [Cu(Hmpt)2Cl] (A), and chlorobis(triphenylphosphine)(methyl pyruvate thiosemicarbazone)copper(I) toluene solvate (2/1), [Cu(PPh3)2(Hmpt)Cl]·0.5C7H8 (B) have been synthesized and characterized using spectroscopic studies and single-crystal X-ray diffraction methods at 293 K. Compound A crystallizes in space group C2/c, with a = 14.695(1), b = 13.775(1), c = 10.251(1) A, β = 113.38(1)°, V= 1904.7 A3; compound B crystallizes in space group P 1 , with a=17.871(7), b=10.681(2), c=11.695(7) A, α=74.90(1), β=86.65(4), γ=83.66(2)°, V=2141 A3. The crystal structures were solved by the heavy-atom method for A and by direct methods for B and refined to R values of 0.053 for both compounds. In A the copper and chlorine atoms lie on a crystallographic two-fold axis and the trigonal coordination around copper involves, besides chlorine, two sulfur atoms from two Hmpt molecules. In B the copper is tetrahedrally four-coordinated involving a chlorine atom, a sulfur atom from the Hmpt molecule and the phosphorus atoms of the two PPh3 molecules. In both compounds the ligand is neutral, monodentate through the sulfur atom and shows the configuration Z E Z about the C(2)N(3), C(1)N(2) and C(2)C(3) bonds (with respect to possible donating centres O(1), N(3) and S). The main vibrational bands are also reported and discussed.

Dansylated Polyamines as Fluorescent Sensors for Metal Ions: Photophysical Properties and Stability of Copper(II) Complexes in Solution

Protonation and the CuII complexation constants of the dansylated polyamines N-dansylethylenediamine (1), N-dansyldiethylenetriamine (2), N-dansyltriethylenetetramine (3), N′-[2-(dansylamino)ethyl]diethylenetriamine (4), and tris(2-dansylaminoethyl)amine (5) were determined by glass-electrode potentiometry in MeOH/H2O 9 : 1 (v/v) solution. For ligands 3 and 4, the determinations were also performed in aqueous solution. The complexes formed by these ligands in neutral form correspond to those observed for the analogous unsubstituted monoprotonated amines, whereas, when the ligands are deprotonated at the sulfonamide moiety, the species parallel those of the corresponding amines. The molecular structures of the complexes were deduced from the VIS absorption spectra. The crystal structure of the [CuL2H−2] complex 6 of ligand 1 (L) was determined by X-ray diffraction. The study of the photophysical properties of the ligands 3 – 5 showed that they are good fluorescent sensors for copper(II), which induced fluorescence quenching. Time-resolved fluorescence measurements allowed us to clarify the sensing mechanism. The pH dependence of the quenching effect demonstrated that it occurs for all Cu2+ complexes, even for species in which the sulfonamide moiety is not deprotonated. Sensing of Cu2+ was compared with that of other metal ions (Co2+, Ni2+, Zn2+, Cd2+, Hg2+), and selectivity was studied as a function of pH. Ligands 3 and 4 were found to be selective chemosensors for Cu2+ in weakly acidic solution (pH ca. 4 – 5).

Four-versus five-co-ordination in palladium(II) and platinum(II) complexes containing 2,9-dimethyl-1,10-phenanthroline (dmphen). Crystal structures of [PtCl2(dmphen)] and [Pt(η2-C2H4)Cl2(dmphen)]

The four-co-ordinate complexes with 2,9-dimethyl-1,10-phenanthroline [MX2(dmphen)](M = Pt, X2= Cl21, ClBr 2, Br23, or I24; M = Pd, X2= Cl25, ClBr 6, Br27 or I28) have been prepared for the first time. The crystal structure of [PtCl2(dmphen)]1, has been determined by X-ray diffraction methods. The complex has a square-planar geometry around the metal and the steric interaction between the methyl groups of dmphen and the cis chlorine ligands causes a narrowing of the Cl–Pt–Cl angle [85.8(1)°], a displacement of the two chlorine atoms from the N–Pt–N plane [0.286(4) and 0.372(4)A respectively], a bending of the phenanthroline (ca. 17°), and a rotation of the overall ligand plane with respect to the platinum co-ordination plane (ca. 28°). All interligand steric constraints are released in the five-co-ordinate complexes obtained from the four-co-ordinate species by direct uptake of olefins, [M(η2-olefin)X2(dmphen)](olefin = ethylene, a; propene, b; but-1-ene, c; cis-but-2-ene, d; trans-but-2-ene, e; or styrene, f). The structure of [Pt(η2-C2H4)Cl2(dmphen)]1a, has been determined by X-ray diffraction methods. The complex has a trigonal-bipyramidal geometry around the Pt atom; the phenanthroline ligand and the olefinic carbons occupy the equatorial plane while the two chlorine atoms are in axial positions. Bond distances and angles are similar to those found in other five-co-ordinate complexes of platinum(II). The rate of uptake of olefin by the four-co-ordinate complexes, the equilibrium constant (Kf) of the formation reaction [MX2(dmphen)]+ olefin ⇌[M(η2-olefin)X2(dmphen)], and the activation energy for olefin rotation in the five-co-ordinate complexes have been measured for different olefins and halogen ions. The uptake, in chloroform, takes place in a one-step process and the reaction rate increases by a factor of 104 going from the chloro 1 to the iodo 4 complex. The equilibrium constant for the formation reaction decreases by a factor of 103 going from ethylene to trans-but-2-ene and increases by a factor of 102 going from the chloro 1 to the iodo 4 species. The activation energy for olefin rotation (ethylene and propene)(ca. 20.5 kcal mol–1) is higher than any reported value for platinum complexes and does not appear to depend upon the nature of the halogen atoms.

Syntheses and structures of 2-diphenylphosphinomethylenide-6-diphenylphosphinomethylenepyridine complexes of palladium(II) and platinum(II); crystal structures of [PtCl2-(CHPPH2)-6-(CH2PPh2)pyridine] and [Pd(COOMe)2-(CHPPh2)-6-(CH2PPh2)pyridine]

The reactions of the palladium(II) and platinum(II) complexes of formula M(pnp)Cl2 (M  Pd, Pt; pnp = 2,6-bis(diphenylphosphinomethyl)pyridine) and Pt(dppf)Cl2 (dppf = 1,1′-bis(diphenylphosphinomethyl)ferrocene) with NaOMe in methanol under CO at room temperature and atmospheric pressure has been investigated. In contrast with the behaviour of the Pd(dppf)Cl2 complex, which gives the corresponding bis-methoxycarbonyl compound, the terdentate ligand of the M(pnp)Cl2 complexes is nucleophilically attacked by the methoxide ion to lose a proton and yield complexes of formula [MXC5H3N(CHPPh2)(CH2PPh2)] (M  Pt, X  Cl, COOMe; M  Pd, X  COOMe), which have been characterized by chemical and spectroscopic means. The crystal structures of [PtCl2-(CHPPh2)-6-(CH2PPh2)pyridine] (1) and [Pd(COOMe)2-(CHPPh2)-6-(CH2PPh2)pyridine] (2) have been determined by X-ray diffaction. In both complexes the terdentate anionic ligand chelates the metal to form two five-membered rings, and the PC and CC bond lengths in one of the chelate rings is in agreement with an sp2 hybridization of the formally anionic methylenidic carbon and with a large delocalization in the ring.

Simple, high-yields syntheses of nickel-osmium clusters. spectroscopic characterization of the new (η-C5H5)NiOs3(CO)9(μ2-H)3. The reactivity of (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3Ni3Os3(CO)9 towards H2, CO, alkynes and alkenes

Abstract The complexes (η-C5H5)NiOs3(CO)9(μ2-H)3 and (η-C5H5)3 Ni3Os3(CO)9 can be obtained in high yield by treating Os3(CO)12 or H2Os3(CO)10 with [(η-C5H5)-Ni(CO)]2 in refluxing hydrocarbons. The course of the reactions and the yields of the products can be modified by carrying out the reaction under nitrogen, hydrogen or carbon monoxide atmospheres. A preliminary report of an X-ray study of the hexametallic, 87 e− cluster was presented. The new tetrametallic derivative was characterized by spectroscopic techniques; a tetrahedral, tri-hydridic structure is proposed for this complex. The reactions of the heterometallic nickel-osmium complexes towards ligands, in particular alkenes and alkynes, are discussed. A preliminary investigation of homogeneous hydrogenation of these substrates is reported.

Non-apoptotic programmed cell death induced by a copper(II) complex in human fibrosarcoma cells

A0, a Cu(II) thioxotriazole complex, produces severe cytotoxic effects on HT1080 human fibrosarcoma cells with a potency comparable to that exhibited by cisplatin. A0 induced a characteristic series of changes, hallmarked by the formation of eosin- and Sudan Black-B-negative vacuoles. No evidence of nuclear fragmentation or caspase-3 activation was detected in cells treated with A0 which, rather, inhibited cisplatin-stimulated caspase-3 activity. Membrane functional integrity, assessed with calcein and propidium iodide, was spared until the late stages of the death process induced by the copper complex. Vacuoles were negative to the autophagy marker monodansylcadaverine and their formation was not blocked by 3-methyladenine, an inhibitor of autophagic processes. Negativity to the extracellular marker pyranine excluded vacuole derivation from the extracellular fluid. Ultrastructural analysis indicated that A0 caused the appearance of many electronlight cytoplasmic vesicles, possibly related to the endoplasmic reticulum, which progressively enlarge and coalesce to form large vacuolar structures that eventually fill the cytoplasm. It is concluded that A0 triggers a non-apoptotic, type 3B programmed cell death (Clarke in Anat Embryol (Berl) 181:195–213, 1990), characterized by an extensive cytoplasmic vacuolization. This peculiar cytotoxicity pattern may render the employment of A0 to be of particular interest in apoptosis-resistant cell models.

4-Amino-3-methyl-1,2,4-Δ2-triazoline-5-thione: an example of thione-thiol tautomerism and stabilization of Cu(I) and Au(I) complexes☆

Two complexes of Cu(I) (1) and Au(I) (2) with the ligand 4-amino-3-methyl-1,2,4-Δ2-triazoline-5-thione (HL) have been prepared. Potentiometric and spectrophotometric studies on the ligand show that the thiol is the prevalent form in solution while in the solid state the thione form is present. Preliminary ab initio calculations of the molecular electrostatic potential maps for the ligand HL are in good agreement with reactivity and studies in solution. Both compounds crystallize in the monoclinic system, 1 in the P21/m space group with unit cell parameters a = 6.829(2), b = 6.218(2), c = 8.540(3) A, β = 105.68(2)°, Dcalc = 2.180 g cm−3 and V = 349.1(2) A3 or Z = 2, 2 in the C2/m space group with unit cell parameters a = 15.902(6), b = 6.606(5), c = 6.707(3) A, β = 109.37(2)°, Dcalc = 2.462 g cm−3 and V = 664.7(6) A3 for Z = 2.5563 and 742 observed reflections for 1 and 2, respectively, were used in the refinement which converged to R and Rw values of 0.0388 and 0.0528 for 1 and 0.0432 and 0.0540 for 2. The structure of complex 1 presents an unusual phenomenon of disorder with the Cu atoms statistically distributed in two independent positions and the complex can be described as assuming a non-molecular cationic structure. The crystal structure of 2 consists of discrete [Au(HL)2]+ and Cl− ions.

Synthesis, molecular structure, solution equilibrium, and antiproliferative activity of thioxotriazoline and thioxotriazole complexes of copper(II) and palladium(II)

Preparations of copper(II) and palladium(II) complexes of 4-amino-5-methylthio-3-(2-pyridyl)-1,2,4-triazole (L(1)) and the copper(II) complex of 1,4-dihydro-4-amino-3-(2-pyridyl)-5-thioxo-1,2,4-triazole (HL) are described. These complexes have been characterized by means of spectroscopy and microanalysis. Molecular structures of HL (1), [CuCl(2)(H(2)L)]Cl.2H(2)O (2a), cis-[CuCl(2)(L(1))] (3), and cis-[PdCl(2)(L(1))] (4) have been determined by single-crystal X-ray diffraction. The HL ligand acts as a N,S bidentate through the thioxo moiety and the exo-amino group whilst the ligand L(1) forms N,N coordination complexes through the pyridine and triazole nitrogen atoms. Speciation in solution of the systems Cu/HL and Cu/L(1) have been determined by means of potentiometry and spectrophotometry as well as for the Cu/L(1)/A (HA=glycine) system in order to determine species present at physiological pH. Antiproliferative activity of these complexes and their ligands was evaluated, using the AlamarBlue Assay, on normal human fibroblasts (HF) and human fibrosarcoma tumor (HT1080) cells. The copper compounds cis-[CuCl(2)(H(2)L)]Cl and cis-[CuCl(2)(L(1))] exerted significant antiproliferative activity of both normal and neoplastic cells; although dose-response experiments revealed that the HT1080 cell line was more sensitive to the tested drugs than normal fibroblasts.

Ph3PSe as a convenient synthon for one-step syntheses of Ph3P-substituted selenido carbonyl iron and ruthenium clusters. Crystal structures of Fe3(μ3-Se)(μ-CO)(CO)7(PPh3)2, M3(μ3-Se)2(CO)7(Pph3)2 (MFe or Ru) and Ru4(μ4-Se)2(μ-CO)2(CO)7(PPh3)2☆

Abstract Ph3PSe reacts in toluene with Fe3(CO)12 or Ru3(CO)12 affording a variety of Ph3P-substituted selenido carbonyl clusters. In the case of iron the reaction is unselective, six products (1–6) having been obtained belonging to three different families of clusters. Fe2(μ-Se2)(CO)6−nLn (two products, 3, 5, n = 1, 2), Fe3(μ3-Se)2(CO)9−nLn (three products, 1, 2, 4, n = 0–2) and Fe3(μ3-Se)(μ-CO)(CO)9−nLn (one product, 6, n = 2). In the case of ruthenium, under certain conditions, the reaction is quite selective giving the disubstituted trinuclear cluster Ru3(μ3-Se)2(CO)7(PPh3)2 (8) in very high yield (> 90%). Minor products are the mono- and trisubstituted analogous derivatives 7 and 10 and the tetraruthenium cluster Ru4(μ4-Se)2(μ-CO)2(CO)7(PPh3)2 (9). The crystal structures of the clusters 4, 6, 8 and 9 are described.