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Exo-bonded six-membered heterocycle in the crystal structures of RE7Co2Ge4 (RE = La-Nd)

Ponou, Siméon LU and Lidin, Sven LU (2016) In Dalton Transactions 45(46). p.18522-18531
Abstract

In this article four new ternary phases of RE7Co2Ge4 (RE = La-Nd) are reported. They were synthesized by a solid-state reaction of the elements at high temperature, and their crystal structures were investigated by single crystal X-ray diffraction data. The isostructural phases crystallize in a new monoclinic structure type, space group P21/c, Z = 4, Pearson code mP52, and Wyckoff sequence e13. They feature planar {Co4Ge6} clusters consisting of a benzene-like six-membered (Co4Ge2) metal heterocycle and four Co-Ge exo-bonds. Band structure calculations were carried out to investigate the electronic structures of... (More)

In this article four new ternary phases of RE7Co2Ge4 (RE = La-Nd) are reported. They were synthesized by a solid-state reaction of the elements at high temperature, and their crystal structures were investigated by single crystal X-ray diffraction data. The isostructural phases crystallize in a new monoclinic structure type, space group P21/c, Z = 4, Pearson code mP52, and Wyckoff sequence e13. They feature planar {Co4Ge6} clusters consisting of a benzene-like six-membered (Co4Ge2) metal heterocycle and four Co-Ge exo-bonds. Band structure calculations were carried out to investigate the electronic structures of La7Co2Ge4, in order to understand the nature of the chemical bonding, and the structure directing factors that determine the atomic ordering and the structure stability. These calculations indicate that the cobalt mid-transition metals are present as (formally) anionic species. They also reveal significant valence electron back-donation from the anionic {Co4Ge6} units to the La-d orbitals through multicenter bonding involving all atoms of the structure, which is key for the structure's stability with respect to incomplete charge transfer. The applicability of the 18 − n rule in rationalizing the Co-Co relative bond strength was also assessed and, the impact of these metal-metal interactions in stabilizing these clusters was described. Similar valence electron back-donation to stabilize further unusual cluster shapes is expected in other rare earth-transition metal-main group phases.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Dalton Transactions
volume
45
issue
46
pages
10 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:84999014692
  • wos:000388369000016
ISSN
1477-9226
DOI
10.1039/c6dt03302d
language
English
LU publication?
yes
id
559cbb00-58ac-4e63-84f9-fdbbb309c085
date added to LUP
2017-02-24 07:56:56
date last changed
2017-09-18 11:35:07
@article{559cbb00-58ac-4e63-84f9-fdbbb309c085,
  abstract     = {<p>In this article four new ternary phases of RE<sub>7</sub>Co<sub>2</sub>Ge<sub>4</sub> (RE = La-Nd) are reported. They were synthesized by a solid-state reaction of the elements at high temperature, and their crystal structures were investigated by single crystal X-ray diffraction data. The isostructural phases crystallize in a new monoclinic structure type, space group P2<sub>1</sub>/c, Z = 4, Pearson code mP52, and Wyckoff sequence e<sup>13</sup>. They feature planar {Co<sub>4</sub>Ge<sub>6</sub>} clusters consisting of a benzene-like six-membered (Co<sub>4</sub>Ge<sub>2</sub>) metal heterocycle and four Co-Ge exo-bonds. Band structure calculations were carried out to investigate the electronic structures of La<sub>7</sub>Co<sub>2</sub>Ge<sub>4</sub>, in order to understand the nature of the chemical bonding, and the structure directing factors that determine the atomic ordering and the structure stability. These calculations indicate that the cobalt mid-transition metals are present as (formally) anionic species. They also reveal significant valence electron back-donation from the anionic {Co<sub>4</sub>Ge<sub>6</sub>} units to the La-d orbitals through multicenter bonding involving all atoms of the structure, which is key for the structure's stability with respect to incomplete charge transfer. The applicability of the 18 − n rule in rationalizing the Co-Co relative bond strength was also assessed and, the impact of these metal-metal interactions in stabilizing these clusters was described. Similar valence electron back-donation to stabilize further unusual cluster shapes is expected in other rare earth-transition metal-main group phases.</p>},
  author       = {Ponou, Siméon and Lidin, Sven},
  issn         = {1477-9226},
  language     = {eng},
  number       = {46},
  pages        = {18522--18531},
  publisher    = {Royal Society of Chemistry},
  series       = {Dalton Transactions},
  title        = {Exo-bonded six-membered heterocycle in the crystal structures of RE<sub>7</sub>Co<sub>2</sub>Ge<sub>4</sub> (RE = La-Nd)},
  url          = {http://dx.doi.org/10.1039/c6dt03302d},
  volume       = {45},
  year         = {2016},
}