Nature of the active silane alcoholysis catalyst in the RuwClx(CO)y(PMe3)z (w, x, y, z = 1 or 2) system; Ru2(µ-Cl)2Cl2(CO)4(PMe3)2 as a new catalyst for silane alcoholysis in a polar solvent

2001 ◽  
Vol 79 (5-6) ◽  
pp. 949-957 ◽  
Author(s):  
Mee-Kyung Chung ◽  
George Ferguson ◽  
Valerie Robertson ◽  
Marcel Schlaf
Keyword(s):  
Dynamic Behaviour ◽  
Polar Solvent ◽  
Variable Temperature ◽  
Model System ◽  
Dimeric Complex ◽  
X Ray ◽  
H Nmr ◽  
Nonpolar Solvents ◽  
Solid State Structures ◽  
Silane Alcoholysis

The dimeric complex Ru2(µ-Cl)2Cl2(CO)4(PMe3)2 (1) forms an active silane alcoholysis complex in the polar solvent N,N-dimethylamino-acetamide (DMA). The dynamic behaviour of 1 in DMF-d7 solution has been investigated by variable temperature (VT) 1H NMR. The solid state structures of 1 and cis,cis,trans-RuCl2(CO)2(PMe3)2 (3) have been determined by single crystal X-ray diffractometry. Using ethylene glycol - triethylsilane as a model system, the catalytic activity of 1 in DMA is compared to that of a series of known silane alcoholysis catalysts, including RhCl(PPh3)3, PdX2 (X = Cl-, OAc-), and cis,cis,trans-[IrH2S2L2]SbF6 (L = PPh3, S = THF). Complex 3 is not an active silane alcoholysis catalyst in this solvent, but is active in nonpolar solvents. Its structure and spectroscopic signature is, however, different from that of a previously reported catalyst of the same composition.Key words: silane alcoholysis, polar solvent, ruthenium catalyst.

Synthesis, characterization, and dynamic behaviour of pseudoferrocene complexes

1990 ◽  
Vol 68 (11) ◽  
pp. 1923-1931 ◽  
Author(s):  
Michael D. Clerk ◽  
Michael J. Zaworotko ◽  
Bozena Borecka ◽  
T. Stanley Cameron ◽  
Donald L. Hooper ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Variable Temperature ◽  
Grignard Reagents ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
H Nmr ◽  
Ring Rotation ◽  
Methyl Phenyl

Carbanion sources (organolithium and Grignard reagents) react with [(mesitylene)2Fe]2+ and [(mesitylene)(Ch)Fe]+ cations (Ch = cyclohexadienyl) to afford neutral Ch2Fe and ChCh′Fe ("pseudoferrocene") complexes, respectively. Addition of R− (R− = methyl, phenyl, benzyl, and t-butyl) occurs stereospecifically via exo addition at an unsubstituted carbon atom of the arene ring. The synthesis and characterization of these complexes is detailed and the structure of bis(η5-exo-6-phenyl-1,3,5-trimethylcyclohexadienyl)iron(II), 3b, has been determined by single crystal X-ray diffraction analysis. 3b crystallizes in the triclinic space group [Formula: see text], with a = 11.947(2), b = 12.784(1), c = 8.865(2), α = 108.59(1)°, β = 108.19(1)°, γ = 84.91(1)°, and Dcalcd 1.227 g cm−3 for Z = 2. Least-squares refinement gave a conventional R value of 0.0452 for 2080 independent observed reflections. The structure reveals that the complex adopts a gauche-eclipsed conformation. The variable temperature (vt) 1H NMR spectra of pseudoferrocenes are interpreted in terms of restricted ring rotation around the ligand—metal—ligand axis. Keywords: arene, cyclohexadienyl, pseudoferrocene, variable temperature NMR, X-ray diffraction.

Metallkomplexe mit biologisch wichtigen Liganden, CXLVI [1]. Bis(allyl)-N,O-α-Aminocarboxylat-Rhodium-Komplexe / Metal Complexes of Biologically Important Ligands, CXLVI [1]. Bis(allyl)-N,O-α-Aminocarboxylate-Rhodium Complexes

2002 ◽  
Vol 57 (7) ◽  
pp. 810-818 ◽  
Author(s):  
Walter Ponikwar ◽  
Peter Mayer ◽  
Wolfgang Beck
Keyword(s):  
Amino Acids ◽  
Metal Complexes ◽  
Dynamic Behaviour ◽  
Rhodium Complexes ◽  
X Ray Diffraction ◽  
X Ray ◽  
H Nmr

The reactions of [(η3-C3H5)2Rh-μ-Cl]2 with the anions of α-amino acids (glycine, L-alanine, L-valine, L-isoleucine, L-proline, L-phenylalanine, L-phenylglycine, L-thyrosine) afford the N,O-chelates (η3-C3H5)2Rh(α-amino carboxylate). For complex (η3-C3H5)2Rh(glycinate) dynamic behaviour in solution could be observed by 1H NMR. The structure of (η3-C3H5)2Rh(L-prolinate) was determined by X-ray diffraction.

Dynamic stereoisomerization in inherently chiral bimetallic [2]catenanes

2015 ◽  
Vol 51 (27) ◽  
pp. 5840-5843 ◽  
Author(s):  
Thirumurugan Prakasam ◽  
Matteo Lusi ◽  
Elisa Nauha ◽  
John-Carl Olsen ◽  
Mohamadou Sy ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Variable Temperature ◽  
Redox Processes ◽  
Metal Translocation ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Inherently Chiral

Stereoisomerization and the unprecedented phenomenon of metal translocation in the absence of redox processes were probed in two inherently chiral bimetallic [2]catenanes by using a combination of variable-temperature 1H NMR and CD spectroscopies, X-ray crystallography, and DFT calculations.

scholarly journals Unique Digoldgermanes: Structural Characteristics, Dynamic Behaviour and Distinctive Reactions

2021 ◽  
Author(s):  
Liliang Wang ◽  
Guorong Zhen ◽  
Yinhuan Li ◽  
Mitsuo Kira ◽  
Liping Yan ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Dynamic Behaviour ◽  
Structural Characteristics ◽  
Bond Formation ◽  
Gold Atom ◽  
Addition Product ◽  
X Ray ◽  
Ambient Temperatures ◽  
X Ray Crystallography ◽  
H Nmr

Abstract Digoldgermanes with a gold coordinated by a dialkylgermylene ligand, R’2Ge(AuPR3)(AuGeR’2) (3a; R = Me, 3b; R = Et), were synthesized as green solids through the reactions of stable dialkylgermylene 1 with R3PAuCl followed by the reduction with KC8 at ambient temperatures. The structural characteristics of 3a and 3b were elucidated using NMR spectroscopy, X-ray crystallography, and DFT calculations. An intense absorption maximum was observed at 590 nm in the UV-vis spectrum of 3a in hexane. A pendular motion of AuPR3 group between Ge(IV) and Ge(II) of 3a and 3b occurring in the NMR time scale was found by the dynamic 1H NMR analysis, suggesting that the Ge(II) ligand has an enhanced electrophilicity to be attacked by the nucleophilic gold atom which closes to ‒1 oxidation state. DFT calculations of 3a revealed the existence of high-lying σ(Ge-Au) type HOMO and low-lying LUMO with germylene pπ nature. We show the bond formation and activation alternatively at Au or Ge atom, a methylation of digoldgermane 3a with MeOTf affords methylgermane 5. Moreover, the digoldgermane 3a reacts with Cl− ion of Ph4PCl and CH3C(O)Cl smoothly to form the corresponding chloride-addition product 7 and chlorogoldgermane 9, respectively. Cyclic trimerization reactions of aromatic isocyanates were high-efficiently catalyzed by 3a giving the corresponding 1,3,5-triaryl isocyanurates.

Thiophenophane metal complexes IV. Effects from ligand changes outside the coordination sphere

1996 ◽  
Vol 74 (11) ◽  
pp. 2340-2348 ◽  
Author(s):  
C. Robert Lucas ◽  
Shuang Liu
Keyword(s):  
Magnetic Susceptibility ◽  
Variable Temperature ◽  
Cyclic Voltammograms ◽  
Ferromagnetic Coupling ◽  
X Ray ◽  
H Nmr ◽  
Variable Temperature Magnetic Susceptibility ◽  
Structural Differences ◽  
Coordination Spheres ◽  
Temperature Responses

Preparation of two thiophenophane polythioether macrocycles and 11 of their complexes of Cu(I), Cu(II), Ag(I), and Pd(II) is described. The single crystal X-ray structure of [(CuBr)2(L1)x is reported: space group Pcma, a = 8.7120(6), b = 10.7791(5), c = 12.0929(5) Å, Z = 2, Rf = 0.052, Rw = 0.036 for 521 reflections. Variable-temperature magnetic susceptibility measurements for [(CuCl2)2(L1)] and [(CuCl2)2(L2)] reveal weak antiferromagnetic and weak ferromagnetic coupling, respectively. Cyclic voltammograms of these compounds display two unequal waves in acetonitrile solvent but only one in nitromethane or dimethyl sulfoxide. 1H NMR spectra of {[(η-C3H5)Pd]2(L1)}{PF6}2 and {[(η-C3H5)Pd]2(L2)}{PF6}2 in various solvents show different temperature responses. These magnetic, electrochemical, and NMR effects are discussed in the light of structural differences at sites in the two ligands that are outside the coordination spheres. Key words: magnetic susceptibility, copper, thioether, electrochemistry.

scholarly journals [3.3]Dithia-bridged cyclophanes featuring a thienothiophene ring: synthesis, structures and conformational analysis

2009 ◽  
Vol 5 ◽  
Author(s):  
Sabir H Mashraqui ◽  
Yogesh Sanghvikar ◽  
Shailesh Ghadhigaonkar ◽  
Sukeerthi Kumar ◽  
Auke Meetsma ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Energy Minimization ◽  
Elevated Temperatures ◽  
Variable Temperature ◽  
Energy Difference ◽  
Nmr Analysis ◽  
Stable Conformation ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr

The synthesis of [3.3]dithia-bridged cyclophanes 7, 9 and 11 incorporating a fused heterocycle, thieno[2,3-b]thiophene is described. The structures are established by 1H NMR analysis and, in the case of 11, also by single crystal X-ray crystallography. Conformational analysis by variable temperature NMR suggests that cyclophanes 7, 9 and 11 exhibit conformationally rigid bridges and rings at least up to 130 °C. Energy minimization of 11 revealed anti -11 to be the most stable conformation. Although, the computed energy difference between the most stable conformation anti -11 and the next higher energy conformation syn-anti -11 is only 2.98 kJ/mol, it is intriguing that 11 does not exhibit thia-bridge inversion even at elevated temperatures.

Titanocene and ansa-titanocene complexes bearing 2,6-bis(isopropyl)phenoxide ligand(s). Syntheses, characterization and use in catalytic dehydrocoupling polymerization of phenylsilane

2011 ◽  
Vol 76 (1) ◽  
pp. 75-94 ◽  
Author(s):  
Michal Horáček ◽  
Jan Merna ◽  
Róbert Gyepes ◽  
Jan Sýkora ◽  
Jiří Kubišta ◽  
...  
Keyword(s):  
Variable Temperature ◽  
Titanocene Dichloride ◽  
Spectroscopic Methods ◽  
Rotation Barrier ◽  
X Ray Diffraction ◽  
Hindered Rotation ◽  
Catalytic Behavior ◽  
X Ray ◽  
Catalytic Activities ◽  
H Nmr

Aryloxychloro and bis(aryloxy) titanocenes of general formula L2TiCl2–x(OAr′)x where L = η5-C5H5 (x = 1 (1) and 2 (2)), L2 = SiMe2(η5-C5H4)2 (x = 1 (3) and 2 (4)), and Ar′ = 2,6-(CHMe2)2C6H3 were prepared by the reaction of corresponding titanocene dichloride with LiOAr′ and characterized by spectroscopic methods and compound 3 by single crystal X-ray diffraction analysis. The bulky aryloxy ligand in 1 and 3 exerts a hindered rotation around the Ti–O bond on the 1H NMR time scale, resulting in its dynamic behavior in CDCl3 solution. Variable temperature NMR measurements proved the rotation barrier in 3 (ΔG‡298 = 13.9 ± 0.3 kcal/mol) to be lower than that in 1 (ΔG‡298 = 14.7 ± 0.2 kcal/mol) as a consequence of the more open titanocene shell in the ansa-structure of 3. The catalytic behavior of complexes 1–4, [(η5-C5H5)2TiCl2] and [{SiMe2(η5-C5H4)2}TiCl2], was examined in dehydrocoupling polymerization of phenylsilane under comparable conditions, showing a remarkable higher activity for the titanocene complexes with regards to the ansa-titanocene ones. The order of catalytic activities 2 ~ 1 > [(η5-C5H5)2TiCl2] >> [{SiMe2(η5-C5H4)2}TiCl2] ~ 3 ~ 4 reveals the aryloxy ligands to have an enhancing effect on activity in the titanocene series.

Tris-triphenylsiloxy compounds of aluminium

1992 ◽  
Vol 70 (3) ◽  
pp. 771-778 ◽  
Author(s):  
Allen W. Apblett ◽  
Alison C. Warren ◽  
Andrew R. Barron
Keyword(s):  
Variable Temperature ◽  
Molecular Structures ◽  
Water Ligand ◽  
X Ray ◽  
X Ray Crystallography ◽  
H Nmr ◽  
Phenyl Rings ◽  
Coordinated Water ◽  
Hydrolysis Of ◽  
Solvent Complex

The reaction of AlMe3 with three equivalents of HOSiPh3 in THF results in the formation of the solvent complex Al(OSiPh3)3(THF) (1). Hydrolysis of 1 yields the stable water complex Al(OSiPh3)3(H2O)(THF)2 (2) in which the THF molecules are hydrogen bonded to the coordinated water ligand. Compounds 1 and 2 have been fully characterized by 1H, 13C, 17O, 27Al, and 29Si NMR and IR spectroscopy. In addition, variable temperature 1H NMR of 2 has been employed to investigate the steric interactions between the phenyl rings of adjacent siloxide ligands. The molecular structures of the solvates 1•(THF) and 2•(THF)1.25 have been determined by X-ray crystallography. 1•(THF): monoclinic P21/c, a = 10.03 (1), b = 23.758 (6), c = 23.294 (7) Å, β = 101.13 (6)°, Z = 4, R = 0.084, Rw = 0.094. 2•(THF)1.25: cubic [Formula: see text], a = 23.034 (3) Å, Z = 4, R = 0.093, Rw = 0.099. Keywords: aluminium, siloxide, hydrolysis, complex, NMR spectroscopy.

Phenylsilane dehydrocoupling and addition to styrene catalyzed by (R-indenyl)Ni(phosphine)(methyl) complexes

2009 ◽  
Vol 87 (1) ◽  
pp. 280-287 ◽  
Author(s):  
Yaofeng Chen ◽  
Davit Zargarian
Keyword(s):  
Solid State ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Structural Parameters ◽  
Catalytic Cycle ◽  
Synthesis And Characterization ◽  
H Nmr ◽  
Solid State Structures ◽  
Indenyl Complexes

This report describes the synthesis and characterization of the Ni–Me complexes (R-indenyl)Ni(PR′3)Me (R = 1-i-Pr, 1-SiMe3, and 1,3-(SiMe3)2; R′= Me, Ph) and outlines their catalytic reactivities in the dehydrogenative oligomerization of PhSiH3 and its addition to styrene in the absence of initiators/activators. Observation of higher hydrosilylation activities for PPh3-based compounds featuring bulky substituents on the indenyl ligand confirms earlier suggestions that phosphine dissociation is an important component of the catalytic cycle for this reaction. In contrast, oligomerization of PhSiH3 is more facile with PMe3-based precursors and independent of the steric bulk of the indenyl ligand, implying that this reaction does not involve phosphine dissociation. These conclusions are consistent with the variable-temperature 1H NMR spectra of {1,3,-(SiMe3)2-indenyl}Ni(PR′3)Me and various structural parameters observed in the solid-state structures of {1,3,-(SiMe3)2-indenyl}Ni(PPh3)Me, {1,3,-(SiMe3)2-indenyl}Ni(PMe3)Cl, and {1-SiMe3-indenyl}Ni(PMe3)Me.Key words: nickel-indenyl complexes, hydrosilylation, hydrosilane oligomerization.

Iridium(I) complexes containing bidentate pyrazolylgallate ligands. X-ray crystal structures of [Me2Gapz2]Ir(COD), [Ir(μ-pz)(CO)2]2, and [Ir(μ-3,5-Me2pz)(CO)2]2

1985 ◽  
Vol 63 (3) ◽  
pp. 692-702 ◽  
Author(s):  
Sophia Nussbaum ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Crystal Structures ◽  
Variable Temperature ◽  
Hydrogenation Reaction ◽  
Synthesis And Characterization ◽  
Nmr Studies ◽  
X Ray ◽  
H Nmr ◽  
Measurable Activity

The synthesis and characterization of a number of Ir(I) complexes incorporating bidentate, chelating, pyrazolylgallate ligands are described. Non-rigidity for some of the complexes in solution has been demonstrated by variable temperature 1H nmr studies. Crystal structures of three complexes, [Me2Gapz2]Ir(COD), [Ir(μ-pz)(CO)2]2, and [Ir(μ-3,5-Me2pz)(CO)2]2 are reported and confirm the expected boat conformations for the six-membered M—(N—N)2—Ir rings (where M = Ir or Ga) in the compounds. One of the complexes studied has exhibited measurable activity as a catalyst in the hydrogenation reaction of cyclohexene.

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