Maria Angela Pellinghelli

Chiral modification of trinuclear ruthenium clusters with proline and cysteine derivatives. Synthesis, crystal structure, and catalytic properties of [(μ2-H)Ru3(CO)10- (μ2,η2-OCNCH2CH2CH2CHCH2OCH3)] and [(μ2-H)Ru3(CO)9(μ3,η2-NCCH2CH2CHCH2OCH3)]

Abstract Proline and cysteine derivatives have been used for the chiral modification of the trinuclear ruthenium cluster system. Whereas proline derivatives yield carbamoyl Ru3 clusters by NH activation, the cysteine derivatives react by SH activation to give mercapto Ru3 clusters. The chiral methoxymethyl pyrrolydine carbamoyl clusters catalyse the enantioselective isomerization of nerol to give citronellal with an enantiomeric excess of 12.4%. The structures of [(μ2-H)Ru3(CO)10(μ2,η2- OC NCH 2 CH 2 CH 2 C HCH2OCH3)] (R-2) and [(μ2-H)Ru3(CO)9(μ3,η2- NCCH 2 CH 2 C HCH2OCH3)] (S-3) have been determined by X-ray diffraction methods. Crystals of R-2 are monoclinic, space group P21 with Z = 2, in a unit cell of dimensions a = 8.662(4), b = 18.234(4), c = 7.662(2) A, β = 94.87(2)°. Crystals of S-3 are monoclinic, space group P21 with Z = 2 in a unit cell of dimensions a = 8.881(4), b = 16.720(6), c = 7.567(3) A, β = 112.15(2)°. Both structures have been solved by direct and Fourier methods and refind by full-matrix least-squares to R = 0.0581 (R-2) and R = 0.0239 (S-3) for 2366 (R-2) and 2454 (S-3) observed reflections. The structure of R-2 consists of a ruthenium triangle of unequal edges with both the hydride and carbamoyl ligands bridging the longest edge; the carbamoyl ligand interacts through the carbon and oxygen atoms. The structure of S-3 shows a metal triangle of unequal edges in which the dehydrogenated substituted pyrrolidine ligand interacts with all three Ru atoms through the C and N atoms of the imine group to form two σ-bonds with the two metals defining the longest edge (bridged also by the hydride ligand) and a π-bond with the third one.

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.

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.

Synthesis, X-ray and spectroscopic characterization of obtained throught the one-step reaction of mbit·2I2 with tin metal powder (mbit = 1,1′-bis(3-methyl-4-imidazoline-2-thione)methane)

Abstract The reaction of the adduct mbit·2I2 (mbit = 1,1′-bis(3-methyl-4-imidazoline-2-thione)methane) with tin metal powder produces Sn(mbit)2I9, in mild conditions. An X-ray diffraction study on a crystal showed that the compound consists of a cation [SnI2(mbot)2]2+ having two I2 as counterions, interacting with two disordered diiodine molecules. In the cation, the metal atom lying on a symmetry centre exhibits a slightly distorted octahedral coordination with the two iodides at the apices in trans position, and with the two mbit molecules acting as bidentate chelating ligands through the sulfur atoms and forming an eight-membered ring, the tin metal atom included. The counterions I1 are slightly bent (I(2)–I(3)–I(4) 176.0(1)) and so asymmetric (I(2)–I(3) 2.841(6) I(3)−I(4) 3.016(5) A) that they can be better described as I ·I2 adducts. The presence of the two independent, centrosymmetric and disordered diiodine molecules as guests in the channel running parallel to [III] brings about I82 units of the type I2·I✓I2✓I·I2, here two triiodide ions realted by a sym centre are linked only for one third to I(5)–I(510), that is one of the two disordered guest I2 molecules (I(4)✓I(5) 3.22(I) A). Two I82 units related by a symmetry centre are held together through a non-negligible interaction (I(4)✓I(6) 3.55(1) A) involving the other disordered diiodine molecule (I(6)–I(6m)) giving rise to an octadecaioddide. Crystallographic data for C18H24N8S4I90Sn are as follows: the crystal is trigonal. M = 1783.77 space group R3, Z = 3, V = 3146(4) A ′, a = 18.100(6) A , α = 115.55(2)°, R = 0.0584 . In accordance with a description of the counterions as a sequence of the type I2·I✓I2✓I·I2. FT-Raman spectra do not show the peaks generally found in conventional triiodides, but those related to perturbed diiodine molecules.

Anchoring rhodium(I) on thiourea-functionalized silica xerogels and silsesquioxanes part II. Matrix effects on the selectivity in the hydroformylation of styrene

Abstract Three thiourea-functionalized siloxane materials, 5SiO2 · SiO3/2(CH2)3NHC(S)NHPh (XGphtu), SiO3/2(CH2)3NHC(S)NHPh (XGphtu*) and p-{SiO3/2(CH2)3NHC(S)NH}2C6H4 (XGphenditu*) were prepared. They are able to anchor Rh(I) species giving supported complexes that are very active recoverable catalysts for the hydroformylation of styrene. Some of these materials show regioselectivity variation when used in consecutive catalytic runs. The recovered catalysts have been investigated by XPS and EDX and the change in regioselectivity has been ascribed to matrix effects. In fact, the surface rhodium leaching apparently forces the catalytic process to move in the inside of the materials causing the substrate to experience the inner matrix environment. Furthermore, the non-siloxanized thioureas PhNHC(S)NHPh (Phtu) and p-{PrNHC(S)NH}2C6H4 (Phenditu), which give discrete molecular Rh(I) complexes, were studied as models for the surface binding functions. The structure of [Rh(cod)Cl(Phtu)] (cod = 1,5-cyclooctadiene) has been determined by X-ray diffraction methods.

Evaluation of thermodynamic parameters for highly correlated chemical systems: a spectrophotometric study of the 1 : 1 and 2 : 1 equilibria between I2 and 1,1′-methylenebis(3-methyl-4-imidazoline-2-thione)(mbit) and 1,1′-ethylenebis(3-methyl-4-imidazoline-2-thione)(ebit). Crystal and molecular structures of mbit·2I2 and ebit·2I2

The reactions of I2 with 1,1′-methylene- and 1,1′-ethylene-bis(3-methyl-4-imidazoline-2-thione)(mbit and ebit) have been investigated in CHCl3 solution at different temperatures by spectrophotometry. The experimental data have been processed using two different procedures of computer analysis: SUPERSPEC based on the conventional Gauss–Newton–Marquardt least-squares method; and POWELSPEC, based on Powells direct search method for the refinement of ΔH° and ΔS°. The ability of the two methods to identify the involved equilibria correctly was compared. Evidence for the stepwise formation of the 1 : 1 and 1 : 2 adducts has been obtained by the two methods for the mbit case, while POWELSPEC only was able to solve the ebit case satisfactorily. The crystal structures of the adducts mbit·2I2 and ebit·2I2 have been determined. They show that the thionic sulfur atoms co-ordinate two diiodine molecules, with S–I 2.683(2)(mbit·2I2) and 2.642(3)(ebit·2I2)A and with I–I 2.897(1) and 2.903(2)A respectively, the two S–I–I groups beings related by a two-fold axis. The structural features of the S–I–I linear group are in accordance with Fourier-transform IR and Raman spectral data and can be taken into account with a three-centre two-electron axial orbitally deficient bonding scheme.

Stepwise Synthesis and Structural Characterization of Calix[4]- and Calix[5]arenes Bearing a Functionalized Arm on the Methylene Bridge

Abstract Calix[4]arenes 4 and calix[5]arenes 6 functionalized at the methylene bridge are synthesized starting from benzaldehydes 1. diphenylmethanes 2 and formaldehyde or 2.6-dihydroxymethylphenols 5 respectively. 1H NMR analyses of macrocycles 4 and 6 as well as crystal structure of the calix[5]arene 6by are reported.

Early-transition-metal ketene complexes: Synthesis, reactivity and structure of ketene complexes of bis(trimethylsilyl)niobocene, X-ray structure of [Nb(η5-C5H4SiMe3)2Br(Ph2CCOC,O)

Abstract The “carbenoid-like” complex [Nb(η 5 -C 5 H 4 SiMe 3 ) 2 Br] 1a reacts with 1 equivalent of several ketenes, R 1 R 2 CCO, to give the niobium(V) complexes [Nb(η 5 -C 5 H 4 SiMe 3 ) 2 Br(R 1 R 2 CCO C,O )] ( 2a , R 1 = R 2 = Ph; 3a , R 1 = R 2 = Me; 4a , R 1 = Ph, R 2 = Me; 5a , R 1 = Ph, R 2 = Et) with the expected CO bonding mode found in several early-transition-metal moieties. The protonation of these complexes with 1 equivalent of H + (an ethereal solution of HBF 4 ) affords the acyl cationic niobocene [Nb(η 5 -C 5 H 4 SiMe 3 ) 2 Br(R 1 R 2 HCCO)] + ( 6a , R 1 = R 2 = Ph; 7a , R 1 = R 2 = Me; 8a , R 1 = Ph, R 2 = Me; 9a , R 1 = Ph, R 2 = Et). The ketene complexes 2a and Nb(η 5 -C 5 H 4 SiMe 3 ) 2 Cl(R 1 R 2 C CO C,O )] 2b (hereafter b refers to the chloro-complexes) undergo a two-electron reduction without transformation of the ketene moiety to give the same anionic niobium(III) species [Nb(η 5 -C 5 H 4 SiMe 3 ) 2 (η 2 -(C,O)R 1 R 2 CCO)] − 10 by an ECE process. The structure of 2a was determined by X-ray diffraction methods. The crystals are triclinic, space group P 1 with Z = 4 in a unit cell of dimensions a = 16.063(7), b = 19.108(8), c = 10.696(6) A, α = 99.89(2), β = 94.64(2), γ = 111.95(2)°. The structure was solved from diffractometer data by Patterson and Fourier methods and refined by blocked full-matrix least-squares on the basis of 9706 observed reflections, to R and R w values of 0.0391 and 0.0567 respectively. The diphenylketene and the two Cp′ rings (Cp′ = C 5 H 4 SiMe 3 ) are η 2 (CO) and η 5 respectively. The niobium atom is also bonded to a Br atom. If the centroids of the Cp′ rings and the midpoint of the CO ketene bond are considered, the Nb atom displays a distorted tetrahedral coordination.

The structures of bis(1H+,5H+-S-methylisothiocarbonohydrazidium) di-μ-chloro-octachlorodibismuthate(III) tetrahydrate and tris(1H+-S-methylisothiocarbonohydrazidium) esachlorobismuthate(III)

Abstract The structures of bis(1H + ,5H + -S-methylisothiocarbonohydrazidium) di-μ-chlorooctachlorodibismuthate(III) tetrahydrate: (C 2 H 10 N 4 S) 2 (Bi 2 Cl 10 )· 4H 2 O (compound [I]) and of tris(1H + -S-methylisothiocarbonohydrazidium) esachlorobismuthate(III): (C 2 H 9 N 4 S) 3 (BiCl 5.67 I 0.33 ) (compound [II]) were determined from single crystal X-ray diffractometer data. Both compounds crystallize as triclinic (P 1 - ); crystals [I] with Z = 1 formula unit in a cell of constants: a = 10.621(3), b = 9.989(5), c = 7.439(3) A, α = 88.31(2), β = 84.51(2), γ = 68.88(2)°, final R = 0.0427 for 2229 unique reflections with I ⩾ 2σ(I); crystals [II] with Z = 2 and cell dimensions: a = 14.109(4), b = 12.209(9), c = 8.206(7) A, α = 103.54(3), β = 104.95(2), γ = 81.96(2)°, final R = 0.0411 for 3637 unique reflections (1 ⩾ 2σ(I)). The structure of [I] is built up of diprotonated organic cations, water molecules and dinuclear centrosymmetric [Bi 2 Cl 10 ] 4− anions held together by N-H⋯Cl, N-H⋯O, O-H⋯Cl hydrogen bonds and Van der Waals interactions. The [Bi 2 Cl 10 ] 4− complex consists of two edge-sharing octahedra in which three pairs of bonds of similar length are observed (Bi-Cl av = 2.602(5), 2.712(4), 2.855(5) A). The structure of [II] consists of monoprotonated cations and [BiCl 5.67 I 0.33 ] 3− anions held together by a tridimensional network of hydrogen bonds. Each bismuth atom is octahedrally surrounded by six chlorine atoms, one of which is statistically substituted by a iodine atom.