3-Hexyne Complexes of Molybdenum(II) and Tungsten(II). Crystal Structures of [WI2(CO)(PPh3 )2 (η2-EtC2 Et)] and [WI2(CO){Ph2P(CH2)3PPh2}(η2-EtC2Et)]

1999 ◽  
Vol 54 (2) ◽  
pp. 171-178 ◽  
Author(s):  
Mutlaq Al-Jahdali ◽  
Paul K. Baker ◽  
Michael G. B. Drew
Keyword(s):  
Molecular Structure ◽  
Crystal Structures ◽  
Equatorial Plane ◽  
Octahedral Geometry ◽  
Equimolar Amount ◽  
The Other ◽  
And Tungsten

Treatment of [Ml2(CO)3(NCMe)2] (M = Mo, W) with two equivalents of EtC2Et in CH2CI2 at 0°C yields the bis(3-hexyne) complexes [MI2(CO)(NCMe)(η2-EtC2Et)2] (1 and 2). Complexes 1 and 2 react with two equivalents of PPh3 in CH2CI2 to give the complexes [Ml2(CO)(PPh3)2 (η2-EtC2Et)] (3 and 4). The molecular structure of 4 (M = W) has been crystallographically determined and has a pseudo-octahedral geometry with the two PPh3 ligands trans to each other with the two cis-iodo-ligands, which together with the carbonyl and 3-hexyne ligand are occupying the equatorial plane. Reaction of 1 and 2 with an equimolar amount of Ph2P(CH2)nPPh2 (for M = Mo, n =1; for M = W, n = 1 to 6 ) in CH2CI2 affords the mono(3-hexyne) complexes [Ml2(CO){Ph2P(CH2)nPPh2}(η2-EtC2Et)] (5 - 11). The tungsten complex [Wl2(CO){Ph2P(CH2)3PPh2}(η2-EtC2Et)] (8 ) has also been crystallographically characterised and has cis-phosphorus atoms in the equatorial plane with the carbonyl and one of the iodo-ligands, with the other iodo-ligand and the 3-hexyne occupying the axial sites.

scholarly journals Die Kristallstrukturen der Dysprosium-Komplexe [DyCl3(DME)2] und [DyCl2(THF)5]+[DyCl4(THF)2]- / Crystal Structures of the Dysprosium Complexes [DyCl3(DME)2] and [DyCl2(THF)5]+[DyCl4(THF)2]-

1996 ◽  
Vol 51 (4) ◽  
pp. 531-535 ◽  
Author(s):  
Stefan Anfang ◽  
Kurt Dehnicke ◽  
Jörg Magull
Keyword(s):  
Molecular Structure ◽  
Crystal Structures ◽  
Chlorine Atom ◽  
Octahedral Geometry ◽  
Space Group ◽  
Structure Determinations ◽  
Bipyramidal Structure ◽  
Chloride Ligands ◽  
Oxygen Atoms

Abstract [DyCl3(DME)2] (DME = 1,2-dimethoxyethane) has been prepared from the known tetrahy-drofuran complex [Dy2Cl6(THF)7] in boiling DME. Both complexes were characterized by structure determinations. [DyCl3(DME)2]: Space group P21/c, Z = 4, lattice dimensions at -70 °C: a = 1141.9(6), b = 884.2(4), c = 1558.3(6) pm, β = 104.83(4)°. The complex has a molecular structure with a distorted pentagonal bipyramidal geometry in which the oxygen atoms of the chelating DME molecules and one chlorine atom occupy the pentagonal plane. [DyCl2(THF)5]+[DyCl4(THF)2]-: Space group C2/c, Z = 4, lattice dimensions at -70 °C: a -1241.4(9), b = 1139.4(6), c = 2735.1(19) pm, β = 91.19(4)°. The complex contains a seven-coordinate cation with axial chloride ligands in a pentagonal bipyramidal structure and a six-coordinate anion with a trans octahedral geometry.

Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

1966 ◽  
Vol 16 (01/02) ◽  
pp. 018-031 ◽  
Author(s):  
S Sherry ◽  
Norma Alkjaersig ◽  
A. P Fletcher
Keyword(s):  
Molecular Structure ◽  
Methyl Ester ◽  
Comparative Studies ◽  
Esterase Activity ◽  
Methyl Esters ◽  
Hydrolytic Activity ◽  
The Other ◽  
Other Hand

SummaryComparative studies have been made of the esterase activity of plasmin and the streptokinase-activator of plasminogen on a variety of substituted arginine and lysine esters. Human plasmin preparations derived by different methods of activation (spontaneous in glycerol, trypsin, streptokinase (SK) and urokinase) are similar in their esterase activity; this suggests that the molecular structure required for such esterase activity is similar for all of these human plasmins. Bovine plasmin, on the other hand, differs from human plasmin in its activity on several of the substrates studied (e.g., the methyl esters of benzoyl arginine and tosyl, acetyl and carbobenzoxy lysine), a finding which supports the view that molecular differences exist between the two animal plasmins. The streptokinase-activator hydrolyzes both arginine and lysine esters but the ratios of hydrolytic activity are distinct from those of plasmin and of other activators of plasminogen. The use of benzoyl arginine methyl ester as a substrate for the measurement of the esterase activity of the streptokinase-activator is described.

The pseudomalachite-ludjibaite-reichenbachite conundrum: OD description

2019 ◽  
Vol 57 (5) ◽  
pp. 571-581
Author(s):  
Emil Makovicky
Keyword(s):  
Crystal Structures ◽  
Current Knowledge ◽  
The Other ◽  
Crystal Chemical ◽  
Layer System ◽  
Coordination Polyhedra

Abstract Crystal structures of the three polymorphs of Cu5(PO4)2(OH)4, namely pseudomalachite, ludjibaite, and reichenbachite, can be described as being composed of rods perpendicular to their crystal-chemical layering. Two different sorts of rods can be defined. Type 1 rods share rows of Cu coordination polyhedra, forming a series of slabs. Slab boundaries and slab interiors represent alternating geometric OD layers of two kinds, with layer symmetries close to P21/m and , which make up two different stacking schemes of geometric OD layers in the structures of ludjibaite and pseudomalachite. Such OD layers, however, are not developed in reichenbachite. Type 2 rods are defined as having columns of PO4 tetrahedra in the corners of the rods. In the Type 2 slabs composed of these rods, geometric Pg OD layers of glide-arrayed tetrahedra alternate with more complex OD layers; in ludjibaite this system of layers is oriented diagonally with respect to the Type 1 OD layer system. Two different OD stackings of Type 2 OD layers form the ludjibaite and reichenbachite structures but not that of pseudomalachite. Thus, ludjibaite might form disordered intergrowths with either of the other two members of the triplet but reichenbachite and pseudomalachite should not form oriented intergrowths. Current knowledge concerning formation of the three polymorphs is considered.

Bis(1-phenyl-1-propyne) complexes of tungsten(II): crystal structures of [WI2(CO)(NCR)(η2-MeC2Ph)2] (R = Me, Et, or Ph)

2001 ◽  
Vol 79 (3) ◽  
pp. 263-271
Author(s):  
Paul K Baker ◽  
Michael GB Drew ◽  
Deborah S Evans
Keyword(s):  
Carbon Monoxide ◽  
Solid State ◽  
Crystal Structures ◽  
Octahedral Geometry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Alkyne Complexes ◽  
First Time

Reaction of [WI2(CO)3(NCMe)2] with two equivalents of 1-phenyl-1-propyne (MeC2Ph) in CH2Cl2, and in the absence of light, gave the bis(1-phenyl-1-propyne) complex [WI2(CO)(NCMe)(η2-MeC2Ph)2] (1) in 77% yield. Treatment of equimolar quantities of 1 and NCR (R = Et, i-Pr, t-Bu, Ph) in CH2Cl2 afforded the nitrile-exchanged products, [WI2(CO)(NCR)(η2-MeC2Ph)2] (2-5) (R = Et (2), i-Pr (3), t-Bu (4), Ph (5)). Complexes 1, 2, and 5 were structurally characterized by X-ray crystallography. All three structures have the same pseudo-octahedral geometry, with the equatorial sites being occupied by cis and parallel alkyne groups, which are trans to the cis-iodo groups. The trans carbon monoxide and acetonitrile ligands occupy the axial sites. In structures 1 and 2, the methyl and phenyl substituents of the 1-phenyl-1-propyne ligands are cis to each other, whereas for the bulkier NCPh complex (5), the methyl and phenyl groups are trans to one another. This is the first time that this arrangement has been observed in the solid state in bis(alkyne) complexes of this type.Key words: bis(1-phenyl-1-propyne), carbonyl, nitrile, diiodo, tungsten(II), crystal structures.

An Overview of the Interdiffusion Studies in Mo-Si and W-Si Systems

2014 ◽  
Vol 354 ◽  
pp. 79-83
Author(s):  
Soumitra Roy ◽  
Soma Prasad ◽  
Aloke Paul
Keyword(s):  
Crystal Structures ◽  
Atomic Number ◽  
Diffusion Coefficients ◽  
Relative Increase ◽  
The Other ◽  
Reactive Diffusion ◽  
Refractory Elements ◽  
Other Hand ◽  
Two Systems ◽  
Diffusion Rates

The growth of phases by reactive diffusion in Mo-Si and W-Si systems are compared. The crystal structures of MSi2 and M5Si3 phases (M = Mo, W) are similar in these two systems. However, the diffusion rates of the components change systematically with a change in the atomic number. Integrated diffusion coefficients in both phases increase with an increasing atomic number of refractory elements i.e. from Mo to W. On the other hand, the ratio of diffusivities of the components decreases. This indicates a relative increase in the diffusion rates of the metal components with increasing atomic number and a difference in defects concentrations in these two systems.

2,5-Bis(3,7-dichloroquinolin-8-yl)-1,3,4-oxadiazole

2006 ◽  
Vol 62 (7) ◽  
pp. o2594-o2595 ◽  
Author(s):  
E Ye ◽  
Yong-Wei Zhang ◽  
Hui Wang ◽  
Yun-Yin Niu ◽  
Seik Weng Ng
Keyword(s):  
Molecular Structure ◽  
Dihedral Angle ◽  
Triazole Ring ◽  
The Other ◽  
Central Ring ◽  
Steric Crowding

In the title molecular structure, C20H8Cl4N4O, the 1,3,4-triazole ring is twisted with an r.m.s. deviation of 0.0035 Å. One of the quinolinyl substituents makes a dihedral angle of 55.8 (1)° with respect to the central ring, while the other is rotated by 71.7 (1)°; these twists are necessary to relieve steric crowding.

A Systematic Study on Iron Carbides from First-Principles

2010 ◽  
Vol 654-656 ◽  
pp. 47-50 ◽  
Author(s):  
In Gee Kim ◽  
Gul Rahman ◽  
Jae Hoon Jang ◽  
You Young Song ◽  
Seung Woo Seo ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Systematic Study ◽  
First Principles ◽  
Formation Enthalpy ◽  
The Other ◽  
Iron Carbides ◽  
Ratio Dependence ◽  
Critical Concentrations

The formation enthalpy of a series of Fe-C carbides has been estimated using a first-principles approach. The Fe to C ratio dependence of the formation enthalpy is reasonable, but it is revealed that - and -carbides require an extraordinary environment to be able to form. Furthermore, an addition of substitutional solutes other than Fe and C should promote other carbides with different crystal structures. The analysis suggests further studies to discover the critical concentrations of alloying which stimulate the other carbides to become more stable.

Structural Studies on N-(2,4,6-Trimethylphenyl)-methyl/ chloro-acetamides, 2,4,6-(CH3)3C6H2NH-CO-CH3–yXy (X = CH3 or Cl and y = 0, 1, 2)

2006 ◽  
Vol 61 (10-11) ◽  
pp. 588-594 ◽  
Author(s):  
Basavalinganadoddy Thimme Gowda ◽  
Jozef Kožíšek ◽  
Hartmut Fuess
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Structural Data ◽  
The Other ◽  
Side Chain ◽  
Structural Studies ◽  
Asymmetric Unit ◽  
Lattice Constants ◽  
Peptide Linkage ◽  
The Mean

TMPAThe effect of substitutions in the ring and in the side chain on the crystal structure of N- (2,4,6-trimethylphenyl)-methyl/chloro-acetamides of the configuration 2,4,6-(CH3)3C6H2NH-COCH3− yXy (X = CH3 or Cl and y = 0,1, 2) has been studied by determining the crystal structures of N-(2,4,6-trimethylphenyl)-acetamide, 2,4,6-(CH3)3C6H2NH-CO-CH3 (); N-(2,4,6- trimethylphenyl)-2-methylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2-CH3 (TMPMA); N-(2,4,6- trimethylphenyl)-2,2-dimethylacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH(CH3)2 (TMPDMA) and N-(2,4,6-trimethylphenyl)-2,2-dichloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CHCl2 (TMPDCA). The crystallographic system, space group, formula units and lattice constants in Å are: TMPA: monoclinic, Pn, Z = 2, a = 8.142(3), b = 8.469(3), c = 8.223(3), β = 113.61(2)◦; TMPMA: monoclinic, P21/n, Z = 8, a = 9.103(1), b = 15.812(2), c = 16.4787(19), α = 89.974(10)◦, β = 96.951(10)◦, γ =89.967(10)◦; TMPDMA: monoclinic, P21/c, Z = 4, a =4.757(1), b= 24.644(4), c =10.785(2), β = 99.647(17)◦; TMPDCA: triclinic, P¯1, Z = 2, a = 4.652(1), b = 11.006(1), c = 12.369(1), α = 82.521(7)◦, β = 83.09(1)◦, γ = 79.84(1)◦. The results are analyzed along with the structural data of N-phenylacetamide, C6H5NH-CO-CH3; N-(2,4,6-trimethylphenyl)-2-chloroacetamide, 2,4,6-(CH3)3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)-acetamide, 2,4,6-Cl3C6H2NH-COCH3; N-(2,4,6-trichlorophenyl)-2-chloroacetamide, 2,4,6-Cl3C6H2NH-CO-CH2Cl; N-(2,4,6-trichlorophenyl)- 2,2-dichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CHCl2 and N-(2,4,6-trichlorophenyl)- 2,2,2-trichloroacetamide, 2,4,6-Cl3C6H2NH-CO-CCl3. TMPA, TMPMA and TMPDCA have one molecule each in their asymmetric units, while TMPDMA has two molecules in its asymmetric unit. Changes in the mean ring distances are smaller on substitution as the effect has to be transmitted through the peptide linkage. The comparison of the other bond parameters reveal that there are significant changes in them on substitution.

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