scholarly journals Ligand influence on intramolecular cyclometalation in bis(phosphinimine) rare earth alkyl complexes

2016 ◽  
Vol 94 (4) ◽  
pp. 330-341 ◽  
Author(s):  
Kevin R.D. Johnson ◽  
Breanne L. Kamenz ◽  
Paul G. Hayes
Keyword(s):  
Rare Earth ◽  
Kinetic Analysis ◽  
Ancillary Ligand ◽  
X Ray ◽  
X Ray Crystallography ◽  
Alkyl Complexes ◽  
Ortho Metalation ◽  
Elimination Reactions ◽  
Alkane Elimination

The synthesis and reactivity of two new bis(phosphinimine)carbazole ligands (PippN=PMe2)2DMC (HLA, 3) and (PippN=P(C4H8))2DMC (HLB, 10), where Pipp = para-isopropylphenyl and DMC = 3,6-dimethylcarbazole, are reported. Dialkyl lutetium complexes of 3 and 10 were prepared in the presence of DMAP and THF by reaction of the proteo ligands with the new trialkyl reagent, Lu(CH2SiMe3)3(DMAP)2 (4) as well as Lu(CH2SiMe3)3(THF)2. For both ligands 3 and 10, the resulting lutetium complexes were prone to intramolecular cyclometalative alkane elimination reactions whereby the location of cyclometalation was influenced by the identity of the ancillary ligand coordinated to the metal. For ligand 3, cyclometalation of two PMe2 groups generated the complex (LA-κ3N,κ2C)Lu(DMAP)2 (5), whereas ligand 10 resulted in the single ortho-metalation of a para-isopropylphenyl ring to afford (LB-κ3N,κC)Lu(CH2SiMe3) (12). When complexed with scandium, ligand 10 behaved differently; double cyclometalation of two phospholane moieties resulted in the species (LB-κ3N,κ2C)Sc (15). The nature of the cyclometalation reactivity of ligands 3 and 10 is supported by X-ray crystallography and kinetic analysis, respectively.

Zirconium complexes of a cyclopentadienyl-amido ligand with a pendant amine donor via amine and alkane elimination

1996 ◽  
Vol 74 (9) ◽  
pp. 1696-1703 ◽  
Author(s):  
Ying Mu ◽  
Warren E. Piers ◽  
Donald C. MacQuarrie ◽  
Michael J. Zaworotko
Keyword(s):  
Lewis Acids ◽  
Methyl Chloride ◽  
Monoclinic Space Group ◽  
One Pot ◽  
Amido Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Zirconium Complexes ◽  
Alkane Elimination

Zirconium complexes of the multidentate ligand CpHNMeSiN(H)R (SiNR = -SiMe2N-t-butyl; NMe = -CH2CH2NMe2, 1) were prepared and characterized via amine and alkane elimination procedures. Reaction of 1 with Zr(NMe2)4 gave a mixture of bis-amido complexes 2 in which the ligand was 1,2 and 1,3 substituted. This mixture was converted to the analogous dichlorides 3 using Me2NH•HCl and 1,3-3 was purified at this stage; alternatively, 1,3-3 was obtained in one pot from 1 and Zr(NMe2)4 in ≈70% yield. Conversion of 1,3-3 to dimethyl compound (CpNMeSiNR)Zr(CH3)2, 1,3-4, was accomplished via reaction of the dichloride with methyllithium; methide abstraction with the Lewis acids B(C6F5)3 and [Ph3C]+[B(C6F5)4]− generated the cationic alkyls [(CpNMeSiNR)Zr(CH3)]+[R′B(C6F5)3]− (R′ = CH3, 6a; C6F6, 6b), which were characterized by NMR spectroscopy. Zirconium complexes containing 1 ligated as its 1,2 isomer were obtained from alkane elimination reactions between 1 and in situ prepared RnZrCl4−n (R = CH3, n = 3; R = CH2SiMe3, n = 2). 1,2-3 and the methyl chloride complex 1,2-(CpNMeSiNR)Zr(CH3)Cl, 5, were obtained in 18 and 30% yield, respectively. Complex 5 was characterized by X-ray crystallography (monoclinic, space group P21/a, a = 9.6951(10) Å, b = 14.3794(16) Å, c = 14.364(3) Å, V = 1990.3(5) Å3, Z = 4, R = 0.046, Rw = 0.041.) Key words: amine elimination, Cp-amido, zirconium complexes.

scholarly journals Near IR luminescent rare earth 3,4,5,6-tetrafluoro-2-nitrophenoxide complexes: Synthesis, X-ray crystallography and spectroscopy

Polyhedron ◽  
2008 ◽  
Vol 27 (5) ◽  
pp. 1503-1510 ◽  
Author(s):  
Youxuan Zheng ◽  
Majid Motevalli ◽  
Rendy H.C. Tan ◽  
Isaac Abrahams ◽  
William P. Gillin ◽  
...  
Keyword(s):  
Rare Earth ◽  
X Ray ◽  
X Ray Crystallography ◽  
Near Ir

scholarly journals Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

2015 ◽  
Vol 11 ◽  
pp. 1-8 ◽  
Author(s):  
Gert Kollenz ◽  
Ralf Smounig ◽  
Ferdinand Belaj ◽  
David Kvaskoff ◽  
Curt Wentrup
Keyword(s):  
Rare Earth ◽  
Crown Ether ◽  
Dft Calculations ◽  
Metal Ions ◽  
Rare Earth Metal ◽  
Alkaline Earth ◽  
Earth Metal ◽  
X Ray ◽  
X Ray Crystallography ◽  
Derivatives Of

The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray structures are reproduced very well by DFT calculations. Similar endo,endo conformations are calculated for the bisamide crown ether derivatives 7, where two proximate and nearly parallel crown ether units endow the molecules with a claw-like molecular cleft or tweezer structure as evidenced by an enhanced ability to extract some alkali, alkaline earth and rare earth metal ions.

scholarly journals Improved Deep-Red Phosphorescence in Cyclometalated Iridium Complexes via Ancillary Ligand Modification

2019 ◽  
Author(s):  
Evanta Kabir ◽  
Steven Sittel ◽  
Boi-Lien Nguyen ◽  
Thomas Teets
Keyword(s):  
Rate Constant ◽  
Quantum Yields ◽  
Iridium Complexes ◽  
Ancillary Ligand ◽  
Ancillary Ligands ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ligand Modification ◽  
Radiative Rate ◽  
Red Luminescence

In this work, we describe bis-cyclometalated iridium complexes with efficient deep-red luminescence. Two different cyclometalating (C^N) ligands‒1-phenylisoquinoline (piq) and 2-(2- pyridyl)benzothiophene (btp)‒are used with six strong π-donating ancillary ligands (L^X) to furnish a suite of 10 new complexes with the general formula Ir(C^N)2(L^X). Improvements in deep-red photoluminescence quantum yields were accomplished by the incorporation of sterically encumbering substituents onto the ancillary ligand, which can enhance the radiative rate constant (kr) and/or reduce the non-radiative rate constant (knr). Five of the complexes were characterized by X-ray crystallography, and all of them were investigated by in-depth spectroscopic and electrochemical measurements.<br>

A New, Simple, High-Affinity Glycosidase Inhibitor:  Analysis of Binding through X-ray Crystallography, Mutagenesis, and Kinetic Analysis

2000 ◽  
Vol 122 (17) ◽  
pp. 4229-4230 ◽  
Author(s):  
Spencer J. Williams ◽  
Valerie Notenboom ◽  
Jacqueline Wicki ◽  
David R. Rose ◽  
Stephen G. Withers
Keyword(s):  
Kinetic Analysis ◽  
X Ray ◽  
X Ray Crystallography ◽  
High Affinity ◽  
Inhibitor Analysis ◽  
Glycosidase Inhibitor

scholarly journals Improved Deep-Red Phosphorescence in Cyclometalated Iridium Complexes via Ancillary Ligand Modification

2019 ◽  
Author(s):  
Evanta Kabir ◽  
Steven Sittel ◽  
Boi-Lien Nguyen ◽  
Thomas Teets
Keyword(s):  
Rate Constant ◽  
Quantum Yields ◽  
Iridium Complexes ◽  
Ancillary Ligand ◽  
Ancillary Ligands ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ligand Modification ◽  
Radiative Rate ◽  
Red Luminescence

In this work, we describe bis-cyclometalated iridium complexes with efficient deep-red luminescence. Two different cyclometalating (C^N) ligands‒1-phenylisoquinoline (piq) and 2-(2- pyridyl)benzothiophene (btp)‒are used with six strong π-donating ancillary ligands (L^X) to furnish a suite of 10 new complexes with the general formula Ir(C^N)2(L^X). Improvements in deep-red photoluminescence quantum yields were accomplished by the incorporation of sterically encumbering substituents onto the ancillary ligand, which can enhance the radiative rate constant (kr) and/or reduce the non-radiative rate constant (knr). Five of the complexes were characterized by X-ray crystallography, and all of them were investigated by in-depth spectroscopic and electrochemical measurements.<br>

Structure and spectroscopy of uranyl salicylaldiminate complexes

2013 ◽  
Vol 101 (10) ◽  
pp. 631-636 ◽  
Author(s):  
A. L. Tamasi ◽  
C. L. Barnes ◽  
J. R. Walensky
Keyword(s):  
Schiff Base ◽  
Nmr Spectroscopy ◽  
Coordination Sphere ◽  
Ancillary Ligand ◽  
Schiff Base Ligands ◽  
Uranyl Complexes ◽  
X Ray ◽  
X Ray Crystallography ◽  
Chloride Ligand ◽  
C Nmr

Summary The synthesis of uranyl complexes coordinated to tridentate, monoanionic salicylaldiminate (Schiff base) ligands was achieved by the reaction of UO2Cl2(THF)3, 1, with one equivalent of the corresponding sodium salicylaldiminate salts affording [(C9H6N)N=C(H)C6H2t Bu2O]UO2Cl(THF), 2, [(NC5H4)N=C(H)C6H2 t Bu2O]UO2Cl(THF), 3, and [(C6H4SCH3)N=C(H)C6H2tBu2O]UO2Cl(THF), 4. These are uncommon examples of uranyl complexes with a monoanionic ancillary ligand to stabilize the coordination sphere and one chloride ligand. Compounds 2-4 have been characterized by 1H and 13C NMR spectroscopy as well as IR and UVVis spectroscopy and their structures determined by X-ray crystallography.

Synthesis and Characterisation of Two Lithium Tetramethylberyllate Salts and a Series of β-Diketiminato Beryllium Alkyl Complexes

2020 ◽  
Vol 73 (12) ◽  
pp. 1144
Author(s):  
Albert Paparo ◽  
Caspar N. de Bruin-Dickason ◽  
Cameron Jones
Keyword(s):  
Titration Method ◽  
Alkyl Complexes ◽  
Elimination Reactions ◽  
Synthetic Studies ◽  
Alkane Elimination

A safer route than that previously published for the synthesis of [BeI2(OEt2)2] has been developed. Reactions of beryllium dihalide complexes [BeX2(OEt2)2] (X=Br or I) with either LiMe or LiBun lead to mixtures of products, which have been shown to act as sources of ‘BeR2’ (R=Me or Bun) in previous synthetic studies. Here, a titration method has been developed to determine the quantity of metal alkyl residues in these ‘BeR2’ mixtures that are available for subsequent alkane elimination reactions. Treating ‘BeMe2’ mixtures with N,N,N′,N′-tetramethylethylenediamine (tmeda) gave two lithium tetramethylberyllate compounds, [{(tmeda)Li}2(μ-BeMe4)] and [{[(tmeda)Li](BeMe4)(μ-Li)}∞], which were crystallographically characterised. Treatment of insitu-generated ‘BeR2’ solutions with several β-diketimines (HC{C(Me)=NR}{=C(Me)N(H)R}, NacnacH, R=aryl or alkyl) yielded a series of β-diketiminato beryllium alkyl complexes, [(Nacnac)BeR], including the first chiral example of such a compound. Crystallographic studies of these reveal them to be monomeric, with planar three-coordinate beryllium centres.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

Sign in / Sign up

Export Citation Format

Share Document