Variable-temperature X-ray crystallographic studies: a complementary tool for charge-density investigation of soft (organometallic) bonds

Macchi, Piero; Sironi, Angelo

doi:10.1107/s0108767304015582

Cited by 9 publications

(9 citation statements)

References 17 publications

(5 reference statements)

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“…Different data reduction and correction procedures always ended up with this feature. A similar residual in the same position was observed also after refining a model from a 90 K experiment (reported elsewhere) performed on another crystal, which reinforces the hypothesis that this feature is due to some atypical motion of the K atom (unavoidable even at 28 K). By including an anharmonic motion treatment for the K atom, an electron density model not significantly different was refined for the rest of the crystal, and the highest residual peak in the vicinity of K was reduced below 0.45 e/Å 3 .…”

Section: Methodssupporting

confidence: 86%

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

2005

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The accurate experimental electron density distribution of [Cr2(mu2-H)(CO)10]- has been determined through X-ray diffraction at T = 28 K and gas phase theoretical calculations. The nature of the Cr-H-Cr bond has been investigated by means of the quantum theory of atoms in molecules, including the analysis of the Fermi hole distribution and the delocalization indicators from the pair density distribution. We were able to clarify not only the delocalization mechanism inside the three-center system but also the unexpected role of the equatorial carbonyls. In addition, the comparative study of a few Cr-H-X three center interactions has provided more insight into the nature of the M-H-M bond itself and has shed light on its peculiar stereochemical flexibility.

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Section: Methodssupporting

confidence: 86%

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

2005

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“…For example, the trend in CoÀCo distance as a function of temperature ( Figure 6) is in agreement with the elongated Co À Co predicted in the gas phase. As discussed elsewhere, [20] it is not surprising that accurate ab initio gas-phase optimisations return geometries somewhat closer to those observed in the solid state at high temperatures. In fact, despite the loss of accuracy, at higher temperature the molecular geometries are less affected by the crystalline field (at least for materials with a positive expansion coefficient).…”

Section: Wwwchemeurjorgmentioning

confidence: 55%

Molecular Crystals Under High Pressure: Theoretical and Experimental Investigations of the Solid–Solid Phase Transitions in [Co₂(CO)₆(XPh₃)₂] (X=P, As)

Casati

Macchi

Sironi

2009

Chemistry A European J

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An accurate analysis of the solid-state structural transformations occurring in species of the general formula [Co(2)(CO)(6)(XPh(3))(2)] (X = P, As) by experimental X-ray diffraction under non-ambient conditions (on variation of pressure or temperature) and by ab initio theoretical modelling is presented. After a crystal-to-crystal phase transition, the conformation of carbonyl ligands about the Co-Co bond changes from staggered to (almost) eclipsed. The analysis of high-pressure and low-temperature structures sheds light on the peculiar behaviour of the metal-metal bond, the most flexible in the molecule, which is initially compressed, then elongated due to increased intra-carbonyl repulsion and eventually compressed again. Theoretical calculations in the solid state allow the thermodynamic quantities of the transformation to be computed and prediction of the distortions produced by the external stress. The change in molecular symmetry is induced by the increase in the high internal energy associated with the staggered carbonyl conformation, which does not allow efficient packing if the crystalline volume is reduced. The eclipsed conformer, though much less stable in isolation, guarantees better entanglement between molecules.

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“…Having found such large effects of anharmonic motion, we wondered why these have rarely been discussed in the literature − and are recently becoming more popular (for example, see refs − ). Therefore, we checked whether a resolution-dependent bias in the measured intensities could also cause similar features:…”

Section: Discussionmentioning

confidence: 99%

Anharmonic Motion in Experimental Charge Density Investigations

Herbst-Irmer,

Henn,

Holstein

et al. 2013

J. Phys. Chem. A

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In the charge density study of 9-diphenylthiophosphinoylanthracene the thermal motion of several atoms needed an anharmonic description via Gram-Charlier coefficients even for data collected at 15 K. As several data sets at different temperatures were measured, this anharmonic model could be proved to be superior to a disorder model. Refinements against theoretical data showed the resemblance of an anharmonic model and a disorder model with two positions very close to each other (~0.2 Å), whereas these two models could be clearly distinguished if the second position is 0.5 Å apart. The refined multipole parameters were distorted when the anharmonic motion was not properly refined. Therefore, this study reveals the importance of detecting and properly handling anharmonic motion. Unrefined anharmonic motion leads to typical shashlik-like residual density patterns. Therefore, careful analysis of the residual density and the derived probability density function after the refinement of the Gram-Charlier coefficients proved to be the most useful tools to indicate the presence of anharmonic motion.

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Variable-temperature X-ray crystallographic studies: a complementary tool for charge-density investigation of soft (organometallic) bonds

Cited by 9 publications

References 17 publications

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

Molecular Crystals Under High Pressure: Theoretical and Experimental Investigations of the Solid–Solid Phase Transitions in [Co₂(CO)₆(XPh₃)₂] (X=P, As)

Anharmonic Motion in Experimental Charge Density Investigations

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Variable-temperature X-ray crystallographic studies: a complementary tool for charge-density investigation of soft (organometallic) bonds

Cited by 9 publications

References 17 publications

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr2(μ2-H)(Co)10]-

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr2(μ2-H)(Co)10]-

Molecular Crystals Under High Pressure: Theoretical and Experimental Investigations of the Solid–Solid Phase Transitions in [Co2(CO)6(XPh3)2] (X=P, As)

Anharmonic Motion in Experimental Charge Density Investigations

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The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

The Electron Density of Bridging Hydrides Observed via Experimental and Theoretical Investigations on [Cr₂(μ₂-H)(Co)₁₀]^-

Molecular Crystals Under High Pressure: Theoretical and Experimental Investigations of the Solid–Solid Phase Transitions in [Co₂(CO)₆(XPh₃)₂] (X=P, As)