Search results for "Transmetalation"
showing 10 items of 26 documents
C,N-chelated dicyclopentadienylzirconium complexes and their possible use as hydrogenation catalysts
2010
Abstract In situ generated Cp2Zr(n-Bu)Cl (6) reacts with {2-[(CH3)2NCH2]C6H4}2Pb to form exclusively {2-[(CH3)2NCH2]C6H4}Cp2ZrCl (7), [(CH3)2NCH2]C6H5, butene and elemental lead. The further derivatization of chloride (7) to fluoride (8), hydride (9), methyl derivative (10), and a reduction of 7 are also described. The crystal structures of 7–10 were determined. The catalytic activity of 9 and 10 in hydrogenation of styrene was also preliminarily tested.
“Cp*Ir(III)” Complexes with Hemicleaveable Ligands of the Type N-Alkenyl Imidazolin-2-ylidene. Reactivity and Catalytic Properties
2007
A series of Cp*Ir(III) complexes with N-alkenyl imidazole-2-ylidene ligands have been obtained by transmetalation of the previously obtained silver−carbene species. Two structural and electronic pa...
Gold nanostars co-coated with the Cu(II) complex of a tetraazamacrocyclic ligand
2015
The twelve-membered tetraazamacrocyclic ligand L1 bears an appended lipoic acid unit, whose disulphide ring is an efficient grafting moiety for the surface of gold nanostars (GNS). The GNS that were used featured a localized surface plasmon resonance (LSPR) absorption at ∼800 nm, i.e. in the near infrared (NIR). We investigated different approaches for coating them with the Cu(2+) complex of L1. While the direct reaction of [CuL1](2+) with as-prepared GNS led to aggregation, an initial coating step with polyethyleneglycol-thiol (PEG-SH) was found to be advantageous. Displacement reactions were carried out on pegylated GNS either with [CuL1](2+), directly generating [Cun(L1@GNS)](2n+), or wi…
Synthesis, structure and reactivity of trans-UO22+ complexes of OH-containing ligands †
2000
trans-Dioxouranium dinuclear complexes of a few OH-containing ligands possessing N-, O-binding sites were synthesized and characterised. Seven of these were also structurally characterised by single crystal X-ray diffraction. All these complexes exhibit symmetric U2O2 core structures in addition to having a seven-co-ordinated environment about each uranium centre. Even when the ligand possessed more than one CH2OH group, only one such group was found to be involved both in chelation as well as in bridging. These complexes exhibited facile transmetallation reactions with vanadium and molybdenum precursors. Though their core structures are alike, the complexes differ in their lattice arrangem…
Boron–nitrogen substituted dihydroindeno[1,2-b]fluorene derivatives as acceptors in organic solar cells
2019
The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron–nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized using standard Schlenk techniques and worked up and handled readily under atmospheric conditions. Through transmetallation via diarylzinc reagents a series of derivatives were synthesized which show broad visible to near-IR light absorption profiles that highlight the versatility of this BN substituted core for use in optoelectronic devices. The synthesis is efficient, scalable and allows for tuning through changes in substituents on the planar heterocyclic core and at boron. Exploratory evaluation in organic solar cell devices as non-ful…
Equilibrium, Kinetic and Structural Properties of Gallium(III) and Some Divalent Metal Complexes Formed with the New DATAm and DATA5m Ligands
2017
The development of 68Ge/68Ga generators has made the positron-emitting 68Ga isotope widely accessible and raised interest in new chelate complexes of Ga3+. The hexadentate 1,4-di(acetate)-6-methyl[amino(methyl)acetate]perhydro-1,4-diazepane (DATAm) ligand and its bifunctional analogue, 1,4-di(acetate)-6-pentanoic acid[amino(methyl)acetate]perhydro-1,4-diazepane (DATA5m), rapidly form complexes with 68Ga in high radiochemical yield. The stability constants of DATAm and DATA5m complexes formed with Ga3+, Zn2+, Cu2+, Mn2+ and Ca2+ have been determined by using pH potentiometry, spectrophotometry (Cu2+) and 1H and 71Ga NMR spectroscopy (Ga3+). The stability constants of Ga(DATAm) and Ga(DATA5m)…
Halogenomercury Salts of Sterically Crowded Triazenides - Convenient Starting Materials for Redox-Transmetallation Reactions
2010
Diaryl-substituted triazenides Ar(Ar′)N3HgX [Ar/Ar′ = Dmp/Mph, X = Cl (2a), Br (3a), I (4a); Ar/Ar′ = Dmp/Tph, X = Cl (2b), I (4b) with Mph = 2-MesC6H4, Mes = 2,4,6-Me3C6H2, Tph = 2′,4′,6′-triisopropylbiphenyl-2-yl and Dmp = 2,6-Mes2C6H3] were synthesized by salt-metathesis reactions in ethyl ether from the readily available starting materials Ar(Ar′)N3Li and HgX2. These compounds may be used for redox-transmetallation reactions with rare-earth or alkaline earth metals. Thus, reaction of 4b or 2b with magnesium or ytterbium in tetrahydrofuran afforded the triazenides Dmp(Tph)N3MX(thf) (5b: M = Mg, X = I; 6b: M = Yb, X = Cl) in good yield. All new compounds were characterized by melting poin…
Unique distal size selectivity with a digold catalyst during alkyne homocoupling
2015
Metal-catalysed chemical reactions are often controlled by steric hindrance around the metal atom and it is rare that substituents far away of the reaction site could be differentiated during reaction, particularly if they are simple alkyl groups. Here we show that a gold catalyst is able to discriminate between linear carbon alkynes with 10 or 12 atoms in the chain during the oxidative homocoupling of alkynes: the former is fully reactive and the latter is practically unreactive. We present experimental evidences, which support that the distal size selectivity occurs by the impossibility of transmetallating two long alkyl chains in an A-framed, mixed-valence digold (I, III) acetylide compl…
A doubly bridged isodicyclopentadienyl zirconium complex: bis{N-(3,5-dimethylphenyl)-N-[(η5-isodicyclopentadien-2-yl)dimethylsilyl]amido-κN}zirconium…
2002
Transmetallation of the dilithium salt of (3,5-dimethyphenylamino)(isodicyclopentadienyl)dimethylsilane by treatment with zirconium tetrachloride in a 2:1 ratio leads to the substitution of all four chloride ligands. With the applied stoichiometry, the title complex, [Zr(C(20)H(25)NSi)(2)].C(4)H(10)O, was obtained and crystallized from diethyl ether. X-ray diffraction characterization showed that both isodicyclopentadienyl ligands (alternatively called 4,5,6,7-tetrahydro-4,7-methano-1H-indene) are complexed to the metal on their exo face in a completely stereoselective manner and that they are eta(5)-bonded to the Zr atom.
Stereoselective Conjugate Addition of Mixed Organoaluminum Reagents to ?,?-Unsaturated N-Acyloxazolidinones Derived from Carbohydrates.
2005
The stereoselective synthesis of β-branched carboxylic acid derivatives was accomplished by conjugate addition of mixed organoaluminum reagents to chiral α,β-unsaturated N-acyloxazolidinones. Mixed organoaluminum reagentswere generated in situ by transmetalation of Grignard or organolithium compounds with methylaluminum dichloride. Efficient stereocontrol was achieved using different bicyclic glycosamine-derived oxazolidinones, yielding alternatively (R)- or (S)-configured β-branched carboxylic acid derivatives.