Synthesis of 16-Electron (η3-Cyclooctenyl)metallacarboranes of Rhodium(III) and Iridium(III) with the New Sterically Demanding [(4‘-MeC6H4)2C2B9H9]2-Carborane Ligand. Molecular Structures of [3-{(1−3-η3)-C8H13}-1,2-(4‘-MeC6H4)2-3,1,2-pseudocloso-MC2B9H9] (M = Rh, Ir) and [(η6-MeC6H4)Rh(C2B9H9C6H4Me)Rh(η4-C8H12)]2, a Dimeric Byproduct Containing Distorted 13-Vertex {4,9,1,10-Rh2C2B9} Cluster Units

2007 ◽  
Vol 26 (15) ◽  
pp. 3868-3873 ◽  
Author(s):  
Leonid S. Alekseev ◽  
Fedor M. Dolgushin ◽  
Alexander A. Korlyukov ◽  
Ivan A. Godovikov ◽  
Evgenii V. Vorontsov ◽  
...  
Keyword(s):  
Molecular Structures ◽  
Sterically Demanding ◽  
Carborane Ligand

Molecular structures of tris(1-tert-butyl-2-mercaptoimidazolyl)hydroborate complexes of titanium, zirconium and hafnium

2016 ◽  
Vol 72 (11) ◽  
pp. 806-812 ◽  
Author(s):  
Yi Rong ◽  
David Sambade ◽  
Gerard Parkin
Keyword(s):  
Coordination Chemistry ◽  
Olefin Polymerization ◽  
Metal Center ◽  
Molecular Structures ◽  
Direct Influence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polymerization Catalysis ◽  
Sterically Demanding ◽  
Titanium Zirconium

Cyclopentadienyl and tris(pyrazolyl)hydroborate have found much use as supporting ligands in the chemistry of titanium, zirconium and hafnium, especially with respect to applications involving olefin polymerization catalysis. In contrast, closely related tris(1-alkyl-2-mercaptoimidazolyl)hydroborate, [TmR], ligands have so far found little application to the chemistry of these elements, despite the fact that such ligands are currently used extensively in coordination chemistry. In view of the fact that a substituent in the 2-position exerts a direct influence on the steric environment of the metal center, we report here the application of the sterically demanding tris(1-tert-butyl-2-mercaptoimidazolyl)hydroborate [Tm^{{\rm Bu}^{\rm t}}] ligand to these metals. Dichlorido(η5-cyclopentadienyl)[tris(1-tert-butyl-2-sulfanylidene-2,3-dihydro-1H-imidazol-3-yl)borato-κ3S,S′,H]zirconium(IV) benzene hemisolvate, [Zr(C21H34BN6S3)(C5H5)Cl2]·0.5C6H6, (I), dichlorido(η5-cyclopentadienyl)[tris(1-tert-butyl-2-sulfanylidene-2,3-dihydro-1H-imidazol-3-yl)borato-κ3S,S′,H]titanium(IV) benzene hemisolvate, [Ti(C21H34BN6S3)(C5H5)Cl2]·0.5C6H6, (II), [bis(1-tert-butyl-2-sulfanylidene-2,3-dihydro-1H-imidazol-3-yl)borato-κ3S,S′,H]dichlorido(η5-cyclopentadienyl)zirconium(IV), [Zr(C14H24BN4S2)(C5H5)Cl2], (III), (1-tert-butyl-2,3-dihydro-1H-imidazole-2-thione-κS)(1-tert-butyl-2-sulfanylidene-1H-imidazol-3-ido-κ2N3,S)dichlorido(η5-cyclopentadienyl)zirconium(IV) benzene monosolvate, [Zr(C7H11N2S)(C7H12N2S)(C5H5)Cl2]·C6H6, (IV), and tribenzyl[tris(1-tert-butyl-2-sulfanylidene-2,3-dihydro-1H-imidazol-3-yl)borato-κ3S,S′,S′′]hafnium(IV) benzene tetrasolvate, [Hf(C7H7)3(C21H34BN6S3)]·4C6H6, (V), have been structurally characterized by X-ray diffraction. The [Tm^{{\rm Bu}^{\rm t}}^{{\rm Bu}^{\rm t}}] ligand coordinates to Ti and Zr in Cp[κ3S2,H-Tm^{{\rm Bu}^{\rm t}}]MCl2[M = Zr, (I), and Ti, (II)] in a κ3S2,Hmode, while the benzyl compounds [Tm^{{\rm Bu}^{\rm t}}]M(CH2Ph)3[M = Zr and Hf, (V)] exhibit κ3S3coordination.

scholarly journals Methanediide Formation via Hydrogen Elimination in Magnesium versus Aluminium Hydride Complexes of a Sterically Demanding Bis(iminophosphoranyl)methanediide

2017 ◽  
Author(s):  
Christian P. Sindlinger ◽  
Samuel R. Lawrence ◽  
David B. Cordes ◽  
Alexandra M. Z. Slawin ◽  
Andreas Stasch
Keyword(s):  
Diethyl Ether ◽  
Elevated Temperatures ◽  
Chemical Properties ◽  
Molecular Structures ◽  
Hydride Complexes ◽  
Hydrogen Elimination ◽  
Sterically Demanding ◽  
Central Carbon ◽  
Acidic Compounds ◽  
H2 Elimination

Substituted bis(iminophosphoranyl)methanes are CH acidic compounds that can form complexes with formally dianionic central carbon centres. The reaction of H2C(Ph2P=NDip)2 (≡ H2L), Dip = 2,6-diisopropylphenyl, with one equivalent of di-n-butylmagnesium afforded the methanide complex [HLMgnBu] 1. Treatment of complex 1 with phenylsilane in aromatic solvents at elevated temperatures afforded the methanediide complex [(LMg)2] 2 presumably via the MgH intermediate [(HLMgH)n] (n = 1 or 2). The reaction of 1 with LiAlH4 in diethyl ether yielded the AlH complex [HLAlH2] 3. Alternatively, this complex was also obtained from the reaction of H2L with AlH3∙NMe3. The molecular structures of [HLMgnBu] 1, [(LMg)2] 2, and [HLAlH2] 3 are reported. Complex 3 shows no sign of H2 elimination to a methanediide species at elevated temperatures in contrast to the facile elimination of the putative reaction intermediate [(HLMgH)n] (n = 1 or 2) to form [(LMg)2] 2. The chemical properties of complex 2 were investigated and this complex appears to be stable against coordination with strong donor molecules.

Synthesis and characterization of intramolecularly coordinated alanes with new sterically demanding trisyl-based ligands

2007 ◽  
Vol 85 (7-8) ◽  
pp. 483-490 ◽  
Author(s):  
Clinton L Lund ◽  
Olimpiu Stanga ◽  
J Wilson Quail ◽  
Jens Müller
Keyword(s):  
Solid State ◽  
Molecular Structures ◽  
Synthesis And Characterization ◽  
Ortho Position ◽  
Donor Group ◽  
Pyridyl Group ◽  
X Ray ◽  
Sterically Demanding ◽  
Derivatives Of

Five new intramolecularly coordinated aluminum species, whose molecular structures have been elucidated in solution by NMR spectroscopy and in the solid state by single crystal X-ray analysis, are described. All species are equipped with a trisyl-based ligand with a pyridyl donor group [Pytsi stands for -C(SiMe3)2SiMe2(2-C5H4N)]. While the compound (Pytsi)AlMeCl was accessible either from Li(THF)(Pytsi) and MeAlCl2 or from (Pytsi)AlCl2 and LiMe, the tert-butyl derivative (Pytsi)AltBuCl could only be obtained from Li(THF)(Pytsi) and tBuAlCl2. Attempted synthesis of (Pytsi)AltBuCl from (Pytsi)AlCl2 and LitBu or from (Pytsi)AlCl2 and tBuMgCl failed. Three other compounds (3-5) were synthesized and can be described as derivatives of (Pytsi)AlMe2 with additional groups in the ortho position of the pyridyl group. Compound 3 carried a Me group in the ortho position, while compounds 4 and 5 were equipped with Ph and 2,6-diisopropylphenyl moieties, respectively.Key words: aluminum, trisyl ligands, methyl alanes.

Zirconium alkyl and borohydride complexes stabilized by a sterically demanding anionic organic amide. The crystal structures of ZrMeL3 (2) and Zr(BH4)L3 (3) (L = (3,5-Me2Ph)N(Ad); Ad = adamantyl)

1997 ◽  
Vol 75 (11) ◽  
pp. 1494-1499 ◽  
Author(s):  
Aparna Kasani ◽  
Sandro Gambarotta ◽  
Corinne Bensimon
Keyword(s):  
Crystal Structures ◽  
Molecular Structures ◽  
Crystal Data ◽  
Lithium Amide ◽  
X Ray ◽  
X Ray Crystallography ◽  
Sterically Demanding

The lithium amide [3,5-Me2PhN(Ad)]Li•Et2O (L) reacts with ZrCl4(THF)2 to give ZrClL3. Reactions of ZrClL3 with MeLi and NaBH4 produce the corresponding ZrMeL3 (2) and Zr(BH4)L3 (3), respectively. The molecular structures of 2 and 3 were determined by X-ray crystallography. Crystal data are as follows. 2: C55H75N3Zr, FW 869.45, orthorhombic, Pcab; a = 19.2436(3) Å,b = 45.9342(4) Å, c = 21.2935(3) Å, V = 18822.2(4) Å3Z = 8; 3: C54H76BN3Zr, FW 869.25, orthorhombic; Pbc21, a = 11.5399(3) Å,b = 19.4091(4) Å, c = 20.4471(5) Å,V = 4579.72(19) Å3Z = 4. Keywords: zirconium, amide, alkyl, borohydride, structure.

Electron Microscopy in Molecular Biology

1967 ◽  
Vol 25 ◽  
pp. 2-3
Author(s):  
Cecil E. Hall
Keyword(s):  
Electron Microscopy ◽  
Molecular Biology ◽  
Noise Level ◽  
Molecular Structures ◽  
Material Structure ◽  
The Arts ◽  
Shadow Casting ◽  
Electron Image ◽  
High Degree ◽  
Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

Molecular architecture and functions of the neuronal cytoskeleton

1990 ◽  
Vol 48 (3) ◽  
pp. 2-3
Author(s):  
Nobutaka Hirokawa
Keyword(s):  
Major Elements ◽  
Molecular Structures ◽  
Organelle Transport ◽  
Molecular Architecture ◽  
Neuronal Morphogenesis ◽  
Microtubule Associated Proteins ◽  
Associated Proteins ◽  
And Function ◽  
Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

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