Polyhedral Oxaruthenaborane Chemistry. Characterisation of a [(η6-C6Me6)RuOB9H13] Species of arachno Eleven-Vertex Cluster Character and Other Aspects of Oxaborane Chemistry

2005 ◽  
Vol 70 (4) ◽  
pp. 410-429 ◽  
Author(s):  
Jonathan Bould ◽  
Mark Bown ◽  
John D. Kennedy
Keyword(s):  
Dft Calculations ◽  
Boron Atom ◽  
Nuclear Shielding ◽  
Cluster Geometry ◽  
Cluster Character

[(η6-C6Me6)RuOB9H13], obtained in trace yield from the reaction between [{RuCl2(η6-C6Me6)}2] and the [arachno-B6H11]- anion, has been shown by DFT calculations of structure and of boron-atom nuclear shielding to be of an arachno eleven-vertex cluster geometry that is derived by the removal of adjacent six-connected and five-connected vertices from a closed thirteen-vertex deltahedral 1:6:5:1 stack. The results lead to further considerations in oxaborane chemistry, which are explored and consolidated by calculation. Additional products from the reaction include [4-(η6-C6Me6)-n-arachno-4-RuB8H14], also substantiated by DFT calculations, and several four-, five-, six-, nine- and ten-vertex ruthenaboranes that are either known compounds or simple variants of known compounds.

The contrarotational fluxionality of [3,3-(PMe2Ph)2-closo-3,1,2-PtC2B9H11] and related species

2015 ◽  
Vol 44 (20) ◽  
pp. 9620-9629 ◽  
Author(s):  
Robert D. Kennedy ◽  
John D. Kennedy
Keyword(s):  
Dft Calculations ◽  
Related Species ◽  
Nuclear Shielding

DFT calculations allied with experimental crystallographic and NMR results elucidate the energetics and the geometrical and 11B nuclear shielding changes in the contrarotational fluxionality of [3,3-(PMe2Ph)2-closo-3,1,2-PtC2B9H11] and confirm the incidence and identities of two stable rotational conformers.

TDDFT study of the UV-vis spectra of subporphyrazines and subphthalocyanines

2011 ◽  
Vol 15 (11n12) ◽  
pp. 1220-1230 ◽  
Author(s):  
Al Mokhtar Lamsabhi ◽  
Manuel Yáñez ◽  
Otilia Mó ◽  
Cristina Trujillo ◽  
Fernando Blanco ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Absorption Spectra ◽  
Boron Atom ◽  
Energy Gap ◽  
Red Shift ◽  
Lumo Energy ◽  
Td Dft ◽  
Homo Lumo

The UV-vis spectra of a series of subporphyrazines, SubPz(A,R), and subphthalocyanines, SubPc(A,R) ( A = F, Cl; R = H, F, CH3, C3H7, SCH3, SC2H5 and SPh), where A is the substituent attached to the central boron atom and R is the substituent attached to the periphery of the molecule have been analyzed through the use of TD–DFT calculations in vacuum and using chloroform as a solvent. The absorption spectra depend on both, the characteristics of the substituent attached to the periphery of the molecule and the extension of the π-system on going from SubPz to the SubPc analog. These latter effects lead to a red-shift of both the Q-band and the B-band, although the effect is larger for the former, mainly due to the increase of HOMO–LUMO energy gap on going from the SubPz to the SubPc analog. The effect of the substituents R is more intricate, because the profile of the absorption spectra changes depending on whether both substituents are on the same side (uu or dd) or on opposite sides (ud) of the molecular cone. Since the three conformers are rather close in energy, the observed spectra correspond, very likely, to the sum of the spectra of all of them.

Methylaminodiphenylborane — Application of 11B, 13C, 14N, 15N NMR

1986 ◽  
Vol 41 (1) ◽  
pp. 59-62 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Boron Atom ◽  
Model Compound ◽  
Natural Abundance ◽  
15N Nmr ◽  
Hindered Rotation ◽  
Π Interactions ◽  
Nuclear Shielding ◽  
The Difference ◽  
Boron Nitrogen ◽  
C Nmr

11B, 13C, 14N, 15N NMR is used to study methylaminodiphenylborane (1). Compound 1 can be regarded as a model compound for studying BN(pp)π-. BC(pp)π interactions, for determining the barrier to rotation about the B-N bond and for the application of natural abundance 15N NMR to boron-nitrogen chemistry. The 13C NMR of 1 shows a large splitting of the 13C(para) resonances (in contrast to reports on similar compounds in the literature) as a consequence of hindered rotation about the BN bond. The difference in the 13C(para) nuclear shielding indicates different mesomeric interactions between the trigonal boron atom and the two phenyl groups.

Structure elucidation of a proton-deficient natural product using LR-HSQMBC supported by DFT calculations

Planta Medica ◽  
2015 ◽  
Vol 81 (11) ◽  
Author(s):  
J Saurí ◽  
STS Chan ◽  
AV Buevich ◽  
KR Gustafson ◽  
RT Williamson ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Natural Product ◽  
Structure Elucidation

Reactions of an Aluminium(I) Reagent with 1,2-, 1,3- and 1,5-Dienes: Dearomatisation, Reversibility, and a Pericyclic Mechanism

2019 ◽  
Author(s):  
Clare Bakewell ◽  
Martí Garçon ◽  
Richard Y Kong ◽  
Louisa O'Hare ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Pathways ◽  
Aromatic Rings ◽  
Aromatic Character ◽  
Pericyclic Reaction

The reactions of an aluminium(I) reagent with a series of 1,2-, 1,3- and 1,5-dienes are reported. In the case of 1,3-dienes the reaction occurs by a pericyclic reaction mechanism, specifically a cheletropic cycloaddition, to form aluminocyclopentene containing products. This mechanism has been interrogated by stereochemical experiments and DFT calculations. The stereochemical experiments show that the (4+1) cycloaddition follows a suprafacial topology, while calculations support a concerted albeit asynchronous pathway in which the transition state demonstrates aromatic character. Remarkably, the substrate scope of the (4+1) cycloaddition includes dienes that are either in part, or entirely, contained within aromatic rings. In these cases, reactions occur with dearomatisation of the substrate and can be reversible. In the case of 1,2- or 1,5-dienes complementary reactivity is observed; the orthogonal nature of the C=C π-bonds (1,2-diene) and the homoconjugated system (1,5-diene) both disfavour a (4+1) cycloaddition. Rather, reaction pathways are determined by an initial (2+1) cycloaddition to form an aluminocyclopropane intermediate which can in turn undergo insertion of a further C=C π-bond leading to complex organometallic products that incorporate fused hydrocarbon rings.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

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