Pentafluoropyridine as a fluorinating reagent for preparing a hydrocarbon soluble β-diketiminatolead(II) monofluoride

A well-designed method for the preparation of a β-diketiminatolead(II) monofluoride has been developed using LPbNMe(2) (L = [CH{C(Me)(2,6-iPr(2)C(6)H(3)N)}(2)]) and pentafluoropyridine (C(5)F(5)N). The resulting LPbF was used for the synthesis of amidinatosilicon(II) monofluoride. Moreover the activation of a ketone was observed when the LPbF was treated with PhCOCF(3).     

Spectral characterization, cyclic voltammetry, morphology, biological activities and DNA cleaving studies of amino acid Schiff base metal(II) complexes

Metal complexes are synthesized with Schiff bases derived from o-phthalaldehyde (opa) and amino acids viz., glycine (gly) l-alanine (ala), l-phenylalanine (pal). Metal ions coordinate in a tetradentate or hexadentate manner with these N(2)O(2) donor ligands, which are characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic, (1)H NMR and EPR spectral studies. The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). Based on EPR studies, spin-Hamiltonian and bonding parameters have been calculated. The g-values calculated for copper complexes at 300K and in frozen DMSO (77K) indicate the presence of the unpaired electron in the dx2-y2 orbital. The evaluated metal-ligand bonding parameters showed strong in-plane sigma- and pi-bonding. X-ray diffraction (XRD) and scanning electron micrography (SEM) analysis provide the crystalline nature and the morphology of the metal complexes. The cyclic voltammograms of the Cu(II)/Mn(II)/VO(II) complexes investigated in DMSO solution exhibit metal centered electroactivity in the potential range -1.5 to +1.5V. The electrochemical data obtained for Cu(II) complexes explains the change of structural arrangement of the ligand around Cu(II) ions. The biological activity of the complexes has been tested on eight bacteria and three fungi. Cu(II) and Ni(II) complexes show an increased activity in comparison to the controls. The metal complexes of opapal Schiff base were evaluated for their DNA cleaving activities with calf-thymus DNA (CT DNA) under aerobic conditions. Cu(II) and VO(II) complexes show more pronounced activity in presence of the oxidant.     

Mixed-ligand complexes of nickel(II) involving sulphur-containing ligands and diaminocarboxylic acids

Summary Stability constants for mixed-ligand complexes of the types [NiABH₂], [NiABH] and [NiAB] formed by Ni^II with l-cysteine (cys), d-penicillamine (pen) or l-cysteic acid (cya) as ligand A and dl-2,3-diaminopropionic acid (dapa), dl-2,4-diaminobutyric acid (daba) or dl-ornithine (orn) as ligand B have been determined by the computerbased analysis of pH titration data obtained at 37 °C and I = 0.15 mol dm^–3 (NaClO₄). In the [NiABH] species, for all three secondary ligands (B), when A = pen or cya the labile proton appears to be attached to the terminal amino group of ligand B, whereas when A = cys it is not clear where the proton is located. In all the systems in the [NiABH₂] species, one proton resides with the primary ligand (A) and the other with the secondary ligand (B). In the [NiAB]-type complexes, cys and pen chelate through the amino and thiolato groups, while cya binds in a glycine-like mode and the secondary ligands (B) coordinate in a terdentate manner.Author to whom all correspondence should be directed.     

Multiple Cycloaddition Reactions of Ketones with a β‐Diketiminate Al Compound

A β‐diketiminate Al compound ( 1 ) with an exocyclic double bond reacts with two equivalents each of benzophenone and 2‐benzoylpyridine in a [4+2] cycloaddition to generate bicyclic and tricyclic compounds 2 and 3, respectively. Compound 2 consists of six‐ and eight‐membered aluminium rings, whereas 3 has two five‐ and one eight‐membered ring. Compounds 2 and 3 were characterized by a number of analytical tools including single‐crystal X‐ray diffraction. The quantum mechanical calculations suggest that the dissociation of the solvent molecule from 1 would lead to an active species 1A having two 1,4‐dipolar 4π electron moieties, in which the electrophilic site is the Al atom and the nucleophilic positions are polarized exocyclic and endocyclic C?C π bonds. The detailed mechanistic study shows that the dipolarophiles, benzophenone, and 2‐benzoylpyridine undergo double cycloaddition with two 1,4‐dipolar 4π electron moieties of 1A . Herein, the addition of one molecule of the dipolarophile promotes the addition of the second one.     

Elegant approach to spacer arranged silagermylene and bis(germylene) compounds

Herein we report on the reactions of the stable LSiCl (1) and LGeCl (2) [L = PhC(NtBu)(2)] with L(1)Ge, [L(1) = CH{(C[double bond, length as m-dash]CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}] (3) to yield 1-sila-5-germylene (4) and a 1,5-bis(germylene) (5). The reactions proceed through the 1,4 nucleophilic addition of the M-Cl (M = Si or Ge) to 3 without any modification of the oxidation state although the change of the oxidation state is thermodynamically more favorable. Compounds 4 and 5 were investigated by single crystal X-ray structural analyses, multi-nuclear NMR spectroscopy, and micro-analysis. Treatment of L(1)AlMe·thf (6) with 1 resulted in the formation of the 1-sila-5-aluminium complex (7). The complex contains a Si(II) and an Al(III) atom in the molecule. All reported reactions proceed without changing the oxidation states at the metal centers.     

Addition of Dimethylaminobismuth to Aldehydes,Ketones, Alkenes,and Alkynes

Bi? O chemistry : A direct regioselective route to bismuth bis(amino)naphthalene compounds, incorporating Bi? O and Bi? C bonds is described, in which an amide precursor is treated with aldehydes, ketones, alkenes, and alkynes, leading to insertion into the Bi? NMe₂ bond.

     

A new entry into aluminum chemistry: [L(1)AlMe]⋅THF, a versatile building block for bimetallic and polymetallic complexes

[L¹AlMe]?THF ( 1 ; L¹=CH[C(CH₂)](CMe)(2,6‐iPr₂C₆H₃N)₂) is prepared by a new method to test its reactivity towards metal complexes to give heterobimetallic or polymetallic complexes. The treatment of 1 with germanium chloride ([LGeCl]), tin chloride ([LSnCl]; L=CH(CMe2,6‐iPr₂C₆H₃N)₂), bismuth amide ([1,8‐C₁₀H₆(NSiMe₃)₂BiNMe₂]), and dimethyl zinc (ZnMe₂) gave the desired compounds with different functional groups on the aluminum center. All compounds have been thoroughly characterized by multinuclear NMR spectroscopy, EI mass spectrometry, X‐ray crystallography ( 2 , 3 , and 5 ), and elemental analysis.     

Synthesis and Characterization of Alkynyl Complexes of Groups 1 and 2

The synthesis of N‐heterocyclic carbene adducts of alkynyl lithium and magnesium is achieved, and different degrees of association are observed. Reaction of strontium amide nacnacSrN(SiMe₃)₂(thf) (nacnac=CH(CMe2,6‐iPr₂C₆H₃N)₂) with PhC≡CH in THF yields the dimeric alkynyl complex [nacnacSr(thf)(μ‐C≡CPh)]₂ which shows an interesting coordination geometry around the metal center. The compound retains the THF molecules, unlike its lighter congener, even in hydrocarbon solvents.     

Formation of silicon centered spirocyclic compounds: reaction of N-heterocyclic stable silylene with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine

Three silicon centered spirocyclic compounds 1-3, possessing silicon fused six- and five-membered rings have been prepared by the reaction of NHSi (L) [L = CH{(C=CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}Si] with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine, respectively, in a 1:1 ratio. The three spirocyclic compounds (1- 3) were obtained by three different pathways. The reaction of L with benzoylpyridine leads to the activation of the pyridine ring, and dearomatization occurred. Treatment of diisopropyl azodicarboxylate with L favors a [1 + 4]- rather than a [1 + 2]-cycloaddition product, and the azo compound was converted to hydrazone derivative. Finally the reaction of 1,2-diphenylhydrazine and L results in the elimination of hydrogen by activating one of the C-H bonds present in the phenyl ring. All three complexes 1- 3 were characterized by single crystal X-ray structural analysis, NMR spectroscopy, EI-MS spectrometry, and elemental analysis. In addition the optimized structures of probable products and possible intermediates were investigated using density functional theory (DFT) calculations.