16733-97-4Relevant articles and documents
Electron-Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes
Mazzotta, Fabio,Zitzer, Georg,Speiser, Bernd,Kunz, Doris
, p. 16291 - 16305 (2020)
The synthesis of electron-poor mono-, di- and tri(imidazolium)-substituted Cp-ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X-ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH3CN)3Cp*](PF6). With mono- and di(imidazolium)-substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X-ray), whereas tri(imidazolium) cyclopentadienides are too electron-poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron-withdrawing imidazolium substituent at the Cp ligand by 0.53–0.55 V in an electrolyte based on a weakly coordinating anion. A reversible oxidation can be observed for the free 1,3-disubstituted ligand as well.
Syntheses and structures of lanthanoid(ii) complexes featuring Sn-M (M = Al, Ga, In) bonds
Zeckert, Kornelia
, p. 14101 - 14106 (2012)
The reactions of the tris(pyridyl)tin(ii) derivative [Li(thf)Sn(2-py R)3] (pyR = C5H3N-5-Me) (1) with the heavier group 13 alkyl compounds MEt3, M = Ga or In, have been carried out. These led to formation of [{Li(thf)Sn(2-py R)3}MEt3] adducts, which exhibit long Sn-M bonds and can be used for further lanthanoid metal coordination via the salt metathesis reaction with [Eu(Cp*)2(OEt2)] (Cp* = η5-C5Me5) to give complexes [Eu{Sn(2-pyR)3MEt3}2]. In contrast, addition of the lighter group 13 analogue, (AlMe3)2, to 1 resulted in a pyridyl transfer reaction, yielding dimeric [AlMe 2(2-pyR)]2. For comparison, the reaction of (AlMe3)2 with [Yb{Sn(2-pyR)3} 2] (pyR = C5H3N-3-Me) was explored, affording complex [Yb{Sn(2-pyR)3AlMe3} 2]. All complexes have been characterised by NMR spectroscopy and X-ray crystallographic studies. The Royal Society of Chemistry 2012.
The Photolysis of Cyclopentadienyl Compounds of Tin and Mercury. Electron Spin Resonance Spectra and Electronic Configuration of the Cyclopentadienyl, Deuteriocyclopentadienyl, and Alkylcyclopentadienyl Radicals
Barker, Philip J.,Davies, Alwyn G.,Tse, Man-Wing
, p. 941 - 948 (1980)
Cyclopentadienyl derivatives of tin(IV) and mercury(II) and alkylcyclopentadienyl derivatives of mercury(II) are photolysed in solution to show the e.s.r. spectra of the appropriate radicals RC5H4. (R = H, D, Me, Et, Pri, or But).The C5H5. radical is a planar ?-radical with average D5h symmetry, and its spectrum is broadened in the presence of organic bromides, perhaps by a charge-transfer mechanism.The introduction of alkyl groups breaks the degeneracy of the ψA and ψS molecular orbitals of the ?-system by electron release, destabilising the ψS MO, and the e.s.r. spectrum reflects the spin density distribution in the configuration ψA2ψS1.Deuterium has a small but detectable perturbing effect: the ψA MO is destabilised by ca. 100 J mol-1, and thermal mixing of the two energy levels results in the configuration ψS1.515ψA1.485.This is compatible with the model of a vibrational perturbation of the resonance integral β, rather than of the Coulomb integral α.
First tandem asymmetric conjugate addition of alkenyl nucleophiles and silyl trapping of the intermediate enolates
Westmeier, Johannes,Pfaff, Christopher,Siewert, Juergen,Von Zezschwitz, Paultheo
supporting information, p. 2651 - 2658 (2013/10/21)
The tandem asymmetric conjugate addition of alkyl or aryl groups to enones and subsequent silyl trapping has already been achieved and yields valuable silyl enol ethers. Herein, the first method for the respective addition of alkenyl groups is reported, which is based on a rhodium(I)-catalyzed addition of readily available alkenylzirconocenes. As prerequisite for silyl trapping, the initially formed enolates have to be transmetalated from zirconium to lithium by treatment with methyllithium prior to addition of the silyl chloride. Starting from 5- to 7-membered cycloalkenones, the respective silyl enol ethers were obtained in excellent yields and ≥93% ee; an acyclic substrate furnished a moderate enantioselectivity. Besides trimethylsilyl chloride, the silylation was also performed with tert-butyldimethylsilyl chloride, and the synthetic scope was evaluated by employing five different alkenyl groups. Moreover, the mechanism of this sequence was elucidated by 1H NMR studies, and the efficiency of catalyst control was exemplified by synthesis of a cis-3,5-disubstituted cyclohexanone which, due to strong substrate control, cannot be obtained by copper-catalyzed conjugate addition.
A method for the determination of the degree of association of organolithium compounds in liquid ammonia
Besten, Remco den,Harder, Sjoerd,Brandsma, Lambert
, p. 153 - 159 (2007/10/02)
A method for carrying out cryoscopy in liquid ammonia is presented.The degrees of association of some organolithium compounds in liquid ammonia have been determined.
Functionalized Keggin- and Dawson-Type Cyclopentadienyltitanium Heteropolytungstate Anions: Small, Individually Distinguishable Labels for Conventional Transmission Elactron Microscopy. 1. Synthesis
Keana, John F. W.,Ogan, Marc D.
, p. 7951 - 7957 (2007/10/02)
With an eye toward the development of a new series of small, highly electron dense labels for electron microscopy, we have synthesized several cyclopentadienyltitanium-substituted Keggin- and Dawson-type heteropolytungstate (HPT) ions that bear reactive organic groups on the Cp ring suitable for selective attachment to macromolecular sites.R-Cp-Ti(NMe2)3 derivatives 5a-f were prepared and then inserted into the Keggin defect HPT anion PW11O397- 7 to give TBA salts 10a-e.The major byproduct was shown to be oxotitanium compound 14.Ion exchange of 10a-d over acidic Al2O3 gave the corresponding moderately water soluble TMA salts 11.Conventional ion exchange then gave the corresponding water soluble K+ salts 13 and heteropoly acids 12.Amine 10e underwent methathetical exchange with Cs2B10Br10 and then ion exchange to give 12e and 13e, from which 11e was prepared.In the Dawson series, a suspension of HPT defect anion 16 in DMF was allowed to react with benzene solutions of 5c,e,f, giving, after anion exchange on acidic alumina, the corresponding TMA salts 17a-c which were then converted into K+ salts 18a-c.Oxotitanium HPT 21 was the major byproduct.Reaction 16 with potassium bis(oxalato)oxotitanium(IV) also led to 21, confirming the structure assignment.The new HPTs were characterized by elemental analysis of their TMA salts and by 1H, 31P, and 183W NMR spectroscopy on the water soluble K+ salts.
