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Title: Theoretical Study of the Rhenium-Alkane Interaction in TransitionMetal-Alkane sigma-Complexes

Abstract

No abstract prepared.

Authors:
; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
923285
Report Number(s):
LBNL-62065
R&D Project: 402101; BnR: KC0302010; TRN: US200804%%989
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the Academy of Sciences; Journal Volume: 104; Journal Issue: 17; Related Information: Journal Publication Date: 04/24/2007
Country of Publication:
United States
Language:
English
Subject:
37; RHENIUM COMPLEXES; ALKANES; INTERACTIONS; MATHEMATICAL MODELS

Citation Formats

Cobar, Erika A., Khaliullin, Rustam Z., Bergman, Robert G., and Head-Gordon, Martin. Theoretical Study of the Rhenium-Alkane Interaction in TransitionMetal-Alkane sigma-Complexes. United States: N. p., 2006. Web.
Cobar, Erika A., Khaliullin, Rustam Z., Bergman, Robert G., & Head-Gordon, Martin. Theoretical Study of the Rhenium-Alkane Interaction in TransitionMetal-Alkane sigma-Complexes. United States.
Cobar, Erika A., Khaliullin, Rustam Z., Bergman, Robert G., and Head-Gordon, Martin. Wed . "Theoretical Study of the Rhenium-Alkane Interaction in TransitionMetal-Alkane sigma-Complexes". United States. doi:.
@article{osti_923285,
title = {Theoretical Study of the Rhenium-Alkane Interaction in TransitionMetal-Alkane sigma-Complexes},
author = {Cobar, Erika A. and Khaliullin, Rustam Z. and Bergman, Robert G. and Head-Gordon, Martin},
abstractNote = {No abstract prepared.},
doi = {},
journal = {Proceedings of the Academy of Sciences},
number = 17,
volume = 104,
place = {United States},
year = {Wed Dec 27 00:00:00 EST 2006},
month = {Wed Dec 27 00:00:00 EST 2006}
}
  • No abstract prepared.
  • Reactions of [([eta][sup 5]-C[sub 5]H[sub 5])Re(NO)(PPh[sub 3])(ClCH[sub 2]Cl)][sup +]BF[sub 4][sup [minus]] and ArCHO (Ar = a, C[sub 6]F[sub 5]; b, 4-C[sub 6]H[sub 4]CF[sub 3]; c, 3-C[sub 6]H[sub 4]CF[sub 3]; d, 3-C[sub 6]H[sub 4]OCH[sub 3]; e, 2-C[sub 6]H[sub 4]OCH[sub 3]; f, 4-C[sub 6]H[sub 4]Cl; g, 4-C[sub 6]H[sub 4]F; h, 1-naphthyl; i, C[sub 6]H[sub 5]; j, 3,4,5-C[sub 6]H[sub 2](OCH[sub 3])[sub 3]; k, 4-C[sub 6]H[sub 4]C[sub 6]H[sub 5]; l, 4-C[sub 6]H[sub 4]CH[sub 3]; m, 2,4-C[sub 6]H[sub 3](OCH[sub 3])[sub 2]; n, 3,4-C[sub 6]H[sub 3](OCH[sub 3])[sub 2]; o, 4-C[sub 6]H[sub 4]OCH[sub 3]) give aromatic aldehyde complexes [([eta][sup 5]-C[sub 5]H[sub 5])Re(NO)(PPh[sub 3])(O[double bond]CHAr)][sup +]BF[sub 4][sup [minus]]more » (4a--o[sup +]BF[sub 4][sup [minus]], 80--97%). IR analyses (CH[sub 2]Cl[sub 2], 26[degrees]C) show 4a--o[sup +]BF[sub 4][sup [minus]] to be >96:<4 to 15:85 mixtures of [pi]/[sigma] isomers (v[sub NO] 1745--1733/1701--1692 cm[sup [minus]1]). Electron withdrawing substituents (which enhance aldehyde [pi] acidity and lower [sigma] basicity) favor the [pi] binding model. Electron donating substituents have an opposite effect. The [pi]/[sigma] ratios increase in more polar solvents and at lower temperatures. Van't Hoff plots give [Delta]H (4i,l,o[sup +]BF[sub 4][sup [minus]]; [pi] [yields] [sigma]) of 3.6, 2.8, and 1.8 kcal/mol and [Delta]S of 9.2, 9.5, and 9.1 eu. IR features unique to both binding modes, and visible absorptions characteristic of [sigma] isomers, are identified. Complex 4o[sup +]PF[sub 6][sup [minus]] crystallizes as a [sigma] isomer, with a conjugated Ar/C[double bond]O linkage, a lengthened C[double bond]O bond (1.271 (8) [angstrom]), and a 0[degrees] N-Re-O-C torsion angle. This Re-O conformation maximizes overlap of the d orbital HOMO of the rhenium fragment with C[double bond]O [pi]* orbital lobes on oxygen. 60 refs., 8 figs., 5 tabs.« less
  • The competition between long-range and short-range interactions among holes moving in an antiferromagnet (AF), is studied within a model derived from the spin density wave picture of layered transition metal oxides. A novel numerical approach is developed which allows one to solve the problem at finite hole densities in very large systems (of order hundreds of lattice spacings), albeit in a quasiclassical limit, and to correctly incorporate the long-range part of the Coulomb interaction. The focus is on the problem of charge ordering and the charge-phase diagram: at low temperatures four different phases are found, depending on the strength ofmore » the magnetic (dipolar) interaction generated by the spin-wave exchange, and the density of holes. The four phases are the Wigner crystal, diagonal shapes, a grid phase (horizontal-vertical stripe loops) and a glassy-clumped phase. In the presence of both in-plane and out-of-plane charged impurities the stripe ordering is suppressed, although finite stripe segments persist.At finite temperatures multiscale (intermittency) dynamics is found, reminiscent of that in glasses. The dynamics of stripe melting and its implications for experiments is discussed.« less
  • The activation of C-H and C-C bonds by different transition metal atoms has been studied using quantum chemical methods including electron correlation. The metals studied are iron, cobalt, nickel, rhodium, and palladium. A general result for all these metals is that the barrier for C-C insertion is found to be 14-20 kcal/mol higher than the barrier for C-H insertion. This can be explained by the difference in directionality between bonds to methyl groups and to hydrogen atoms. The size of the activation barrier is similar among transition metals in the same row but is considerably lower for the second-row metalsmore » than for the first-row metals studied here. This latter result follows from the more efficient sd-hybridization obtained for second-row metals, which in turn follows from the more similar size of the nd and (n + 1)s orbitals for these atoms. The differences in the atomic spectra between first- and second-row metals also play a part in making the barrier for second-row metals lower.« less