Computational Studies of cis– and trans–Isomer Preferences of Low-Spin d6 [M(DABF)2A2]+ and [M(CO)4A2]+ Complexes (M = Co, Rh, Ir; A = Anionic Ligand): Spectator Ligand π-Backbonding and DFT Exchange

2021 ◽  
pp. 113235
Author(s):  
Samantha M. Bacchi ◽  
Cara M. Waters ◽  
Oreoluwa A. Agunoye Jones ◽  
Greg Becker ◽  
Alexander P. Bryan ◽  
...  
Keyword(s):  
Trans Isomer ◽  
Computational Studies ◽  
Anionic Ligand ◽  
Cis And Trans

scholarly journals Reaction of cis- and trans-Dichlorotetra(Dimethylsulfoxide)Ruthenium(II) With the Antiviral Drug Acyclovir

2000 ◽  
Vol 7 (6) ◽  
pp. 325-334 ◽  
Author(s):  
Aglaia Koutsodimou ◽  
Giovanni Natile
Keyword(s):  
Trans Isomer ◽  
Early Stage ◽  
Antiviral Drug ◽  
Metallic Substrate ◽  
Purine Base ◽  
Coordination Environment ◽  
Molar Ratios ◽  
Discrete Amount ◽  
Cis And Trans ◽  
Cis Isomer

NMR was used to investigate the reaction of cis- and trans-[RuCl2(DMSO)4] with the antiviral drug acyclovir, a guanine derivative containing the acyclic (2-hydroxo) ethoxymethyl pendant linked to N(9). Studies were performed in aqueous solutions at ambient temperature and at 37 °C, and at various molar ratios. Both isomers yielded two compounds, a monoadduct and a bisadduct, the relative yields being dependent upon the metal to ligand concentration ratios. The products derived from the two Ru isomers displayed identical NMR spectra, suggesting that they have the same coordination environment, however the rate of formation of the monoadduct was higher in the case of the trans isomer than in the case of the cis isomer, while the rate of conversion of the monoadduct into the bisadduct appeared to be similar in both cases. As a consequence in the case of the trans isomer there is accumulation of monoadduct in the early stage of the reaction, whose concentration afterwards decreases with the progress of the reaction. As for platinum, also for ruthenium the preferred binding site is N(7) of the purine base, however, in the case of ruthenium a discrete amount of bisadduct is formed even in the presence of an excess of metallic substrate with respect to the acyclovir ligand; under similar conditions a platinum substrate would have given, nearly exclusively, the monoadduct.

Structure et réactivité. IV. Diastéréosélectivité de la réduction de cétones par le borohydrure de sodium. De l'influence de l'effet de champs de substituants polaires éloignés

1979 ◽  
Vol 57 (21) ◽  
pp. 2823-2826 ◽  
Author(s):  
Jean-Pierre Aycard ◽  
Ronald Lafrance ◽  
Bernard Boyer
Keyword(s):  
Trans Isomer ◽  
Cyano Group ◽  
Specific Effect ◽  
Group Effect ◽  
Stable Isomer ◽  
Free Enthalpy ◽  
Steric Strain ◽  
Experimental Values ◽  
Cis And Trans

The cyano group effect on diastereoselectivity is studied through the reduction of cis and trans 3-R 4-cyano cyclohexanones with NaBH4; the diastereoselectivity (zero for R = H) is 74 and 62% respectively (R = CH3) and 74 and 50% (R = (CH3)3C), the more stable isomer being always the major one. These stereoselectivities are rationalized from the experimental values of free enthalpy between conformers and from the diastereoselectivities of the 3-t-butyl (and 4-t-butyl) cyclohexanones, cis 3,5-dimethyl and 3,3,5-trimethyl cyclohexanones, without taking account of a cyano group specific effect. The decrease in diastereoselectivity for R = (CH3)3C (trans isomer) is associated with deformation induced by steric strain between the substituents.

[1H,15N] N.M.R. Kinetic Studies of Reactions of cis- and trans-[PtCl2(15NH3)(c-C6H1115NH2)] with Guanosine 5'-Monophosphate

1999 ◽  
Vol 52 (3) ◽  
pp. 173 ◽  
Author(s):  
Sarah J. Barton ◽  
Kevin J. Barnham ◽  
Abraha Habtemariam ◽  
Urban Frey ◽  
Rodney E. Sue ◽  
...  
Keyword(s):  
Trans Isomer ◽  
Active Metabolite ◽  
Kinetic Studies ◽  
Trans Influence ◽  
Trans Complex ◽  
Kinetics Of Reaction ◽  
Cis And Trans ◽  
Kinetics Of ◽  
Cis Isomer ◽  
Amine Ligand

cis-[PtCl2(15NH3)(c-C6H11NH2)] is an active metabolite of the oral platinum(IV) anticancer drug cis,trans,cis-[PtCl2(CH3CO2)2(NH2)(c-C6H11NH2)]. Since it is likely that guanine bases on DNA are targets for this drug, we have analysed the kinetics of reaction of this platinum(II) metabolite with guanosine 5′-monophosphate (5′-GMP) at 310 K, pH 7, using [1H, 15N] n.m.r. methods. Reactions of the trans isomer are reported for comparison. The reactions proceed via aquated intermediates, and, for the cis isomer, the rates of aquation and substitution of H2O by 5′-GMP are 2-5 times faster trans to the amine ligand (c-C6H11NH2) compared to trans to NH3 for both the first and second steps. For the trans complex, the first aquation step is c. 3 times faster than for the cis complex, as expected from the higher trans influence of Cl¯, whereas the rate of the second aquation step (trans to N7 of 5′-GMP) is comparable to that trans to NH3. These findings have implications for the courses of reactions with DNA.

Some investigations of the chemistry of tellurium chloride pentafluoride, its reaction with caesium fluoride, and the preparation of cis and trans methoxytellurium(VI) chloride tetrafluoride, (CH3O)TeClF4

1984 ◽  
Vol 62 (8) ◽  
pp. 1477-1482 ◽  
Author(s):  
Lawrence J. Lawlor ◽  
Jack Passmore
Keyword(s):  
Vibrational Spectrum ◽  
Trans Isomer ◽  
Room Temperature ◽  
Temperature Range ◽  
Cis And Trans

The reaction of TeClF5 with CH3OH, and CH3OSiMe3, leads to a mixture of cis- and trans-(CH3O)TeClF4 in a ratio of 1:6, as well as some unidentified Te(IV) product. The vibrational spectrum of the 1:6 mixture of cis- and trans-(CH3O)TeClF4 was accounted for on the basis of the predominant pseudo-C4vtrans isomer. TeClF5 is unreactive towards anhydrous HF, SbF5, AlCl3, SO2, F2, and ClF at room temperature. Over the temperature range 70–250 °C it thermally decomposes to TeF6, TeF4, and Cl2. It slowly reacts with CsF to form CsTeF5, TeF6, Cl2, and small amounts of ClF, and with HNMe2 it is also reduced to form TeF4•HNMe2.

Rotational spectra of 1-chloro-2-fluoroethylene. II. Equilibrium structures of the cis and trans isomer

2006 ◽  
Vol 125 (5) ◽  
pp. 054307 ◽  
Author(s):  
Cristina Puzzarini ◽  
Gabriele Cazzoli ◽  
Alberto Gambi ◽  
Jürgen Gauss
Keyword(s):  
Trans Isomer ◽  
Rotational Spectra ◽  
Equilibrium Structures ◽  
Cis And Trans

Sur la réduction de polyméthyldihydro-2,3 phénalènones-1 par l'hydrure de lithium et d'aluminium

1974 ◽  
Vol 52 (17) ◽  
pp. 3106-3112 ◽  
Author(s):  
E. Costakis ◽  
P. Canonne ◽  
R. St-Jean
Keyword(s):  
Trans Isomer ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Considerable Extent ◽  
Lithium Aluminum ◽  
Trans Isomers ◽  
Cis And Trans Isomers ◽  
Cis And Trans ◽  
Cis Isomer ◽  
Steric Constraints

The reduction of some polymethyl-2,3-dihydro phenalen-1-ones by lithium aluminum hydride yields a mixture of cis and trans isomers; the percentage of each isomer depends to a considerable extent on its structure. Indeed, for some, the trans isomer predominates while for others the cis isomer is obtained in up to 88% yields. Moreover, in the particular case in which the trans isomer is formed in low yields, its preferred conformation is trans diaxial.The steric constraints which render certain transition states unfavourable during the attack of the hydride are discussed with the aid of spectroscopic data on the alcohols obtained. [Journal translation]

Cooperation between Cis and Trans Influences incis-PtII(PPh3)2Complexes: Structural, Spectroscopic, and Computational Studies

2010 ◽  
Vol 49 (1) ◽  
pp. 123-135 ◽  
Author(s):  
Luca Rigamonti ◽  
Alessandra Forni ◽  
Mario Manassero ◽  
Carlo Manassero ◽  
Alessandro Pasini
Keyword(s):  
Computational Studies ◽  
Cis And Trans

SYNTHESES IN THE TERPENE SERIES: VIII. SYNTHESIS OF THE CIS- AND TRANS-ISOMERS OF 7,7,10-TRIMETHYLDECAL-1-ONE. A CONVENIENT MODIFICATION OF THE BROWN HYDRATION REACTION

1959 ◽  
Vol 37 (11) ◽  
pp. 1870-1880 ◽  
Author(s):  
Franz Sondheimer ◽  
Saul Wolfe
Keyword(s):  
Trans Isomer ◽  
Raney Nickel ◽  
Equilibrium Mixture ◽  
Hydration Reaction ◽  
Trans Isomers ◽  
Perbenzoic Acid ◽  
Cis And Trans Isomers ◽  
Cis And Trans

7,7,10-Trimethyl-Δ1(9)-octal-2-one (VII) was converted to the cycloethylenedithioketal (VIII), which on Raney nickel reduction yielded 7,7,10-trimethyl-Δ1(9)-octalin (IX). Oxidation with perbenzoic acid led to the corresponding oxide (X), which could be rearranged in low yield to an equilibrium mixture of 7,7,10-trimethyldecal-1-one consisting essentially of the trans-isomer (XI).A convenient modification of the Brown hydration reaction is described, whereby the necessity of generating diborane or of using diglyme is avoided. 7,7,10-Trimethyl-Δ1(9)-octalin (IX) on Brown hydration using this modification stereospecifically furnished 7,7,10β-tri-methyl-cis-decal-1β-ol (XII), which was oxidized to 7,7,10-trimethyl-cis-decal-1-one (XIII). Isomerization resulted in the above-described equilibrium mixture containing at least 90% of the trans-isomer (XI). Similarly, the previously described 10-methyl-Δ1(9)-octalin (XVI) yielded a mixture of the cis- and trans-isomers of 10-methyldecal-1-one (XIX). Syntheses of 2-methylene-7,7,10-trimethyl-Δ1(9)-octalin (XIV) and of 7,7,10-trimethyl-cis-decal-2,3-dione 3-dithiotrimethylene ketal (XXII) are also described.

Synthesis and study of Pt(II)–nitrile complexes. Multinuclear NMR spectra and crystal structures of compounds of the types [Pt(R-CN)Cl3]− and cis and trans-Pt(R-CN)2Cl2

1996 ◽  
Vol 74 (2) ◽  
pp. 144-152 ◽  
Author(s):  
Fernande D. Rochon ◽  
Robert Melanson ◽  
Eryk Thouin ◽  
Corinne Bensimon ◽  
André L. Beauchamp
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Trans Isomer ◽  
Nmr Spectra ◽  
Alkyl Chain ◽  
Coupling Constants ◽  
Trans Isomers ◽  
Multinuclear Nmr ◽  
Cis And Trans ◽  
Bond Trans

Complexes of the type [Pt(R-CN)Cl3]− were synthesized and studied by 1H, 13C, and 195Pt NMR spectroscopies. The 2J(195Pt-13C) coupling constants are about 240 Hz. The signals due to the cyano carbon atoms of the coordinated ligands were observed at higher fields than those of the free ligands. The shielding on the cyano carbon increases as the alkyl chain lengthens and also when the branching increases. The 195Pt signals of all the complexes were observed around −2000 ppm. The crystal structures of (NMe4)[Pt(C3H7-CN)Cl3] (1) and (NMe4)[Pt(p-HO-C6H4-CN)Cl3] (2) were determined. Compound 1 is monoclinic, P21/c, a = 8.384(5), b = 15.336(19), c = 11.759(9) Å, β = 99.52(6)°, Z = 4, R = 0.054, and wR = 0.051. Crystal 2 is tetragonal with a = 16.222(6), c = 12.052(5) Å, Z = 8, R = 0.059, and wR = 0.044. The Pt—CL bond trans to the nitrile ligand is shorter than normal (2.276(3) Å for 1 and 2.264(7) Å for 2) while the two other bonds are normal (2.293(4), 2.287(3) Å for 1 and 2.320(7), 2.275(8) Å for 2). The Pt—N bonds are 1.97(1) Å (1) and 1.92(2) Å (2) and the segments Pt-N≡C-C are linear. Disubstituted compounds were also synthesized and studied by multinuclear NMR. The 195Pt signals of the cis isomers were observed at lower fields than those of the trans isomers (Δ ≈ 65 ppm), while the 13C signals of the cyano carbons of the trans isomers were observed at lower fields than those of the cis compounds (Δ ≈ 0.6 ppm). The cis complexes isomerize to the trans compounds upon heating. The crystal structures of cis-(3) and trans-Pt(C2H5-CN)2Cl2 (4) and also of cis-Pt(p-HO-C6H4-CN)2Cl2 (5) were determined. Crystal 3 is monoclinic, P21/c, a = 7.506(5), b = 9.539(5), c = 14.823(7) Å, β = 92.31(4)°, Z = 4, R = 0.050, and wR = 0.042. The trans isomer 4 is monoclinic with the Pt atom on an inversion centre, P21/c, a = 5.149(4), b = 9.394(8), c = 10.944(10) Å, β = 97.84(7)°, Z = 4, R = 0.017 and wR = 0.020. Finally, compound 5 is triclinic, P-1, a = 7.464(3), b = 10.712(6), c = 12.291(5) Å, α = 75.63(4)°, β = 75.63(4)°, γ = 80.32(4)°, Z = 2, R = 0.045, and wR = 0.056. The Pt—Cl bond distances for the cis isomers are 2.269(5), 2.270(4) Å for 3 and 2.274(2), 2.279(3) Å for 5 while they are 2.289(3) Å for the trans isomer (4). The Pt—N bonds are 1.962(14), 1.988(11) Å (3), 1.972(7), 1.976(7) Å (5) and 1.969(5) Å for 4. Key words: platinum, nitrile, NMR, isomerization, crystal structure.

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