Joan F. Piniella

Ruthenium(II) complexes containing both arene and functionalized phosphines. Synthesis and catalytic activity for the hydrogenation of styrene and phenylacetylene

Abstract The [RuCl2(η6-arene)]2 complex reacts with PPh2R (R=H, Py, CH2Py, CCPh, CCtBu and CCp-Tol) ligands in CH2Cl2 to give neutral P-coordinated ruthenium(II) complexes [RuCl2(p-cymene)PPh2R]. The structure of [RuCl2(p-cymene)PPh2H] and [RuCl2(p-cymene)PPh2Py] complexes has been established by X-ray diffraction. The neutral P-coordinated complexes [RuCl2(p-cymene)PPh2Py] and [RuCl2(p-cymene)PPh2CH2Py] react with NaBF4 in CH2Cl2–MeOH mixture to give [RuCl(η6-p-cymene)PPh2Py]BF4 and [RuCl(η6-p-cymene)PPh2CH2Py]BF4 complexes, in which PPh2Py and PPh2CH2Py act as bidentate ligands. The structure of [RuCl(η6-p-cymene)PPh2Py]BF4 was determined by X-ray diffraction. The reaction of [RuCl2(η6-arene)]2 with PPh2CCPPh2 led to the [RuCl2(p-cymene)]2PPh2CCPPh2 complex, in which the diphosphine ligand bridges two [RuCl2(p-cymene)] units. [RuCl2(p-cymene)PPh2Py] and [RuCl(η6-p-cymene)PPh2Py]BF4 are suitable catalyst precursors for the hydrogenation of styrene and phenylacetylene.

Cobalt(II) complexes with pyrazole-derived ligands: crystal structure of {bis[3-phenyl-5-(2-pyridyl) pyrazole]aquachlorocobalt(II)}chloride monohydrate

Abstract The synthesis of the new pyrazole-derived ligands 3-phenyl-5-(2-pyridyl) pyrazole (HL0) and 3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole (HL1) and their Co(II) complexes is reported. Elemental analyses, conductivity measurements and IR and UV–Vis spectroscopies defined all complexes. 1H and 13C NMR spectroscopies were also used in the characterization of ligands. The crystal and molecular structures of [Co(HL0)2Cl(H2O)]Cl·H2O, consisting of discrete ions and water molecules linked by hydrogen bonds, are also reported. The hexacoordinated metal atom is bonded to two pyridinic nitrogens, two pyrazolic nitrogens (one of each nitrogen belonging to two different ligands), one chlorine atom and one water molecule, forming a distorted octahedral environment. The ligands are not exactly planar and the arrangement of ligands is cis, with a dihedral angle between the two mean planes of ligands of 89.21(6)°. The degree of distortion from regular octahedral geometry is compared to that of closely related structures.

Camphor-derived alcohols as chiral auxiliaries for asymmetric Pauson-Khand bicyclizations. Enantioselective synthesis of α-methoxyenones

Abstract The intramolecular Pauson-Khand reaction of enol and ynol ethers of Oppolzers camphor-derived neopentyloxy alcohols is described. Bicyclic products are obtained in yields of up to 65% and with diastereoselectivities as high as 94:6 under very mild reaction conditions. The absolute configurations of the major stereoisomers obtained when (1R, 2S, 3R, 4S)-3-neopentyloxy-1,7,7-trimethylbicyclo- [2.2.1]heptan-2-ol is used as a chiral auxiliary are rationalized on the basis of the theoretically predicted preferential conformations of model precursors. A simple procedure for obtaining auxiliary-free, enantiopure bicyclic α-methoxyenones is also presented.

Synthesis and structural characterisation of new binuclear Pd(II) complexes with both bridging and terminal pyrazolate ligands

Abstract Dinuclear pyrazolato-bridged Pd(II) complexes Pd2L40 and Pd2L41 have been prepared by reacting Pd(Ac)2 and one equivalent of HL0 (3-phenyl-5-(2-pyridyl)pyrazole) or HL1 (3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole. The new complexes have been characterised by elemental analyses, IR, 1H NMR and in the case of PdL14 by single crystal X-ray diffraction methods. This structure shows two palladium atoms bridged by two L1 ligands. The square-planar geometry of each Pd atom is completed by a bidentate chelating L1 ligand. The six-membered dipalladacycle formed by the two Pd atoms and the two bridging pyrazolato ligands adopts a distorted boat-like conformation.

The formation of [RuCl(p-cymene)(Me2HPz)(PPh2OR)]Cl (Me2HPz=3, 5-dimethylpyrazole; R=H, Me and p-Tol) complexes from the cleavage of the P-N bond of a P-coordinated P(Me2Pz)Ph2 ligand by ROH molecules in a ruthenium(II) complex. Crystal structure of [RuCl(p-cymene)(Me2HPz)(PPh2OH)]Cl

Abstract The complex [RuCl2(p-cymene)]2 reacts with 1-(3,5-dimethyl)pyrazolyldiphenylphosphine (P(Me2Pz)Ph2) to give the complex RuCl2(p-cymene)(P(Me2Pz)Ph2). This compound reacts with ROH molecules (R=H, Me and p-Tol) to give [RuCl(p-cymene)(Me2HPz)(PPh2OR)]Cl (R=H, Me and p-Tol) complexes, which contain both Me2HPz and PPh2OR coordinated molecules.

A Non-obvious Reaction Pathway in the Formation of 2-aminobenzene-1,3-dicarbonitriles From Alpha,Beta-unsaturated Ketones Or Aldehydes

Key intermediates demonstrating a non-obvious reaction pathway leading to 2-aminobenzene-1,3-dicarbonitriles from enones have been isolated and characterised in tire reaction between (E)-4-phenyl-3-butene-2-one and propanedinitrile in a basic hydro-alcoholic medium. (E)-4-Phenyl-3-butene-2-one reacts with three molecules of propanedinitrile to give a 6-amino-2-iminobicyclo[2.2.2]-5-octene-1,3,3,5-tetracarbonitrile system which evolves to a substituted cyclohexadiene by elimination of the sodium salt of 1,1,1-tricyanomethane. Further oxidation leads to the final 2-aminobenzene-1,3-dicarbonitrile. The proposed pathway involves more steps and more difficult transformations than previously presented for similar systems. We can not exclude a simpler reaction pathway derived from the double Michael and Knoevenagel adduct of (E)-4-phenyl-3-butene-2-one and propanedinitrile, however we have not found any evidence for this simpler process.

Synthesis and structure of a copper(II) tetranuclear complex of 3-(6-methyl-2-pyridyl)-5-(2-pyridyl)pyrazole ligand

Abstract The reaction of the ligand 3-(6-methyl-2-pyridyl)-5-(2-pyridyl)pyrazole (HL) with Cu(NO3)2·3H2O gives a complex of formula [Cu4L4(NO3)3](NO3), which has been characterised by elemental analyses, infrared and electronic spectroscopies and single-crystal X-ray diffraction. The molecular structure of this complex is tetranuclear. The Cu2+ ions are linked to four ligands, forming a macromolecular cyclic system. The co-ordination geometries of the Cu(II) are square pyramid. The formation of this complex implies a control of nuclearity by steric hindrance.

Ni(II) complexes with pyrazole-derived ligands. Crystal structures of [Ni(HL0)2ClH2O][Ni(HL0)2(H2O)2]Cl3·CH3OH·H2O and [Ni(HL1)2(H2O)2]Br2·2.5DMF (HL0=3-phenyl-5-(2-pyridyl)pyrazole and HL1=3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole

Abstract The reaction of 3-phenyl-5-(2-pyridyl)pyrazole (HL0) and 3-phenyl-5-(6-methyl-(2-pyridyl))pyrazole (HL1) with nickel(II) salts produces mononuclear coordination compounds. The new complexes have been characterised by elemental analyses, conductivity measurements and infrared and electronic spectroscopies. Two different forms of mononuclear nickel(II) complexes have been prepared and structurally characterised by X-ray crystallography: [Ni(HL0)2Cl(H2O)][Ni(HL0)2(H2O)2]Cl3·CH3OH·H2O and [Ni(HL1)2(H2O)2]Br2·2.5DMF. In the cationic complexes, the coordination of the Ni(II) is octahedral with two bidentate HL0 or HL1 neutral ligands in a cis disposition. The degree of distortion from regular octahedral geometry is compared to closely related structures. In the solid state, cations and anions are bonded by hydrogen bonding.

Unexpected chlorination of a pyrazole ligand. Structural characterisation of a new binuclear Cu(II) complex

Abstract Crystallisation of Cu(HL1)2Cl2·EtOH (HL1=3-phenyl-5-(6-methyl-2-pyridyl)pyrazole) in DMF affords [Cu2(ClL1)2Cl2(DMF)2], where the C-chlorination of the pyrazolyl ring and the formation of a dinuclear compound is observed. The deprotonated pyrazolyl ligands have three co-ordination positions (two pyrazole nitrogens and one pyridine nitrogen) and simultaneously act as chelate and bridging ligands.

Synthesis and structural study of a tetranuclear magnesium alkoxide: [Mg4(μ3, η2-OR)2 (μ2, η2-OR)4(OR)2] with OR-OCH(CH3)CH2OCH3

Abstract Direct reaction between magnesium and 1-methoxy-2-propanol yielded the title complex which has been characterized by X-ray crystallography. The molecular structure consists of a centrosymmetric tetrameric unit in which the Mg atoms are five- or six-coordinated by terminal, triple- and double-bridging chelating alkoxo ligands.