José Mahía

Lead(II) complexes with macrocyclic receptors derived from 4,13-diaza-18-crown-6.

Pages 5883, 5884, 5886, 5888. Several reference numbers in the text are incorrect. Page 5883: The reference number 14 should be 20; 15 and 16 near the bottom of the left-hand column should be 21 and 22; 21 should be 27. Page 5884: The 28 should be 34; 29 should be 35. Page 5886: The 31 should be 37. Page 5888: The 33 should be 39. The version with corrected reference numbers is available electronically.

Control of the Microarchitecture of a Double Helix − Electrochemical Synthesis and Characterisation of a Novel Dinickel(II) Helicate with Different Groove Sizes

Self-assembly of nickel ions and the N4 Schiff base H2PTs [H2PTs: N,N′-bis(2-tosylaminobenzylidene)-1,3-diaminopropane] in an electrochemical cell leads to the novel neutral double-stranded dinuclear helicate [NiPTs]2·CH3CN (1). Complex 1 was fully characterised by elemental analysis, IR and EPR spectroscopy, FAB mass spectrometry, and magnetic measurements. The single X-ray crystal structure of 1 shows that both ligands are asymmetrically positioned around the Ni−Ni axis, leading to a double-helical complex that presents a major and a minor groove.

β-Ferrocenyl-β-amino alcohols: a new class of central chiral ferrocene derivatives

Abstract An efficient procedure for the enantioselective synthesis of β-ferrocenyl-β-amino alcohols, a new class of central chiral ferrocene derivatives suitable for the elaboration of auxiliaries and ligands for asymmetric synthesis, is described. Key steps of the method are the catalytic asymmetric dihydroxylation of 1-ferrocenyl alkenes and the regio- and stereoselective azide substitution of the hydroxyl group adjacent to the ferrocene moiety. The stereochemistry of the substitution step has been established by X-ray diffraction analysis of a cyclic derivative. The first catalytic enantioselective synthesis of a β-ferrocenyl-β-amino acid derivative is also disclosed.

Chiral S,S-donor ligands in palladium-catalysed allylic alkylation

Abstract Chiral dithioether ligands have been tested in the model Pd-catalysed allylic alkylation reaction of (±)-3-acetoxy-1,3-diphenyl-1-propene with dimethyl malonate, giving high enantioselectivity (up to 81% e.e.) for the first time in this type of system. Pd(II)-allylic intermediates, [Pd(η3-1,3-Ph2-C3H3)(dithioether)]PF6 were prepared and characterised both in solution by NMR spectroscopy and solid state. The X-ray structure for [Pd(η3-1,3-Ph2-C3H3)(L)]PF6 (L=(R,R)-7,8-O-isopropylidene-1,5-dithia-cyclononane) was determined.

Copper complexes with bibracchial lariat ethers: from mono- to binuclear structures

Abstract Copper(II) complexes with a series of bibracchial lariat ethers are described. Independently of the nature of the counterion present (nitrate or perchlorate), the lariat ether N,N′-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 (L1) always forms mononuclear complexes, whereas the lariat ethers N,N′-bis(2-aminobenzyl)-4,13-diaza-18-crown-6 (L2) and N,N′-bis(2-salicylaldiminobenzyl)-4,13-diaza-18-crown-6 (L3) only give binuclear compounds. The X-ray crystal structure of [CuL1](ClO4)2 shows a seven-coordinated copper(II) ion in a distorted (axially compressed) pentagonal-bipyramidal geometry. The X-ray crystal structure of [Cu2(L3-2H)](ClO4)2 confirms the binuclear nature of the compound with both metal ions having identical coordination environments and each one placed out of the crown hole but efficiently encapsulated by the corresponding pendant arm; each copper(II) ion is five-coordinated with an intermediate geometry between trigonal-bipyramidal and square-pyramidal (τ=0.40). The EPR spectra in frozen solution samples are in accordance with a stable coordinate pattern for the metal centre of ligand L1, yielding a rhombic distorted complex with axial compression in solution, in agreement with the X-ray crystal structure of [CuL1](ClO4)2. For the binuclear complexes of L2 and L3, the Cu(II) centres in solution can be distorted from their tetragonally elongated structures via interaction with ethanol and/or the nitrate counterion, leading to more than one species.

Cadmium(II) and Lead(II) Complexes with Novel Macrocyclic Receptors Derived from 1,10-Diaza-15-crown-5

Two novel macrocycles, N,N′-bis(2-aminobenzyl)-1,10-diaza-15-crown-5 (L1) and a non-symmetric cryptand incorporating a pyridinyl Schiff-base spacer (L3), both derived from 1,10-diaza-15-crown-5, have been shown to act as receptors for lead(II) and cadmium(II) guests. The X-ray crystal structures reveal an anti conformation for the free ligand L1, but a syn arrangement in the lead(II) complex, [PbL1](ClO4)2. The corresponding cryptates of L3 can be prepared by simple transmetallation reactions starting from the barium cryptate, showing the preference of L3 for the heavy metal ions. The lead(II) ion, unlike cadmium(II), has been shown to be capable of acting as a template agent in the synthesis of L3. The X-ray crystal structures of the metal cryptates allow an insight into the influence of the nature of the metal ion guest on the conformation of the macrobicyclic receptor L3; the most significant changes are a different folding of the crown and variations in the distance between the two pivotal nitrogen atoms and the imine nitrogen atoms. The cryptand can thus expand or contract its cavity in order to accommodate the different metal ions.

Reaction between hydrazines and chiral α-acetylenic ketones: synthesis of novel enantiomerically pure pyrazolyl-β-amino alcohols

Abstract A simple and efficient methodology toward the stereoselective synthesis of novel, enantiomerically pure, pyrazolyl-β-amino alcohols is presented. Thus, when hydrazines 4a,b were allowed to react at 0°C with chiral α-acetylenic ketones of type 3, pyrazolyl oxazolidine derivatives 5a–d were formed with total regioselectivity in 92–97% yield. Subsequent oxazolidine ring opening by means of TFA, and re-protection of the amino group as the N-Boc derivatives, afforded enantiopure amino alcohols 7a–d.

Structure and magnetism of the first cyano-bridged hetero-one-dimensional GdIII–CrIII complexes

A reaction between Gd(NO3)3·6H2O, K3[Cr(CN)6] and dmf or bpy has allowed the synthesis of two new ferrimagnetic GdIII–CrIII chains which are the first low-dimensional 4f–CrIII systems; magnetic susceptibilty data indicate antiferromagnetic coupling between GdIII and CrIII.

A New CuI Complex that Mimics the Cresolase Reaction of Tyrosinase and the Crystal Structure of its Oxygenated CuII Complex

A new dinuclear CuII complex with a unique structural arrangement and containing a doubly bridged macrocyclic ligand has been prepared from two different routes, one of which involves the reaction of oxygen and a CuI precursor, thus mimicking the cresolase activity of tyrosinase

Addition compounds of MoO2Br2 from MoO2Br2(H2O)2. Molecular structure of MoO2Br2{OP[N(CH3)2]3}2 and MoO2Br2{CH2[P(O)(C6H5)2]2}

Abstract MoO2Br2L2 (L=dimethyl formamide (DMF), N-methyl pirrolidone (NMP), dimethyl sulfoxide (DMSO), methyl phenyl sulfoxide (MePhSO), diphenyl sulfoxide (Ph2SO), hexamethyl phosphorotriamide (HMPA), triphenyl phosphine oxide (OPPh3), tributhyl phosphine oxide (OPBu3), triocthyl phosphine oxide (OPOct3), methyl diphenyl phosphine oxide (OPMePh2), and 1/2 methylene bis(diphenyl phosphine) dioxide (dppmO2)) have been prepared by reacting a solution of MoO2Br2(H2O)2 in diethyl ether with the corresponding ligand. The molecular structures of MoO2Br2(HMPA)2 and MoO2Br2(dppmO2) have been established by X-ray diffraction analysis. The ability of MoO2Br2L2 to oxidize (CH3)3CSH to (CH3)3CSSC(CH3)3 has been determined by 1H NMR spectroscopy.