Ytterbium(III) chloride

Ytterbium(III) chloride

Names
IUPAC name Ytterbium(III) chloride
Identifiers
CAS Number	19423-81-1 N
3D model (Jmol)	Interactive image
ChemSpider	55430 Y
ECHA InfoCard	100.030.715
InChI InChI=1S/3ClH.Yb/h3*1H;/q;;;+3/p-3 Y Key: CKLHRQNQYIJFFX-UHFFFAOYSA-K Y InChI=1/3ClH.Yb/h3*1H;/q;;;+3/p-3 Key: CKLHRQNQYIJFFX-DFZHHIFOAT
SMILES Cl[Yb](Cl)Cl
Properties
Chemical formula	YbCl3
Molar mass	279.40 g/mol
Appearance	White powder
Density	4.06 g/cm3 (solid)
Melting point	854 °C (1,569 °F; 1,127 K)[1]
Boiling point	1,453 °C (2,647 °F; 1,726 K)[1]
Solubility in water	0.17 g/mL (25 °C)
Structure
Crystal structure	Monoclinic, mS16
Space group	C12/m1, No. 12
Related compounds
Other anions	Ytterbium(III) oxide
Other cations	Terbium(III) chloride, Lutetium(III) chloride
Supplementary data page
Structure and properties	Refractive index (n), Dielectric constant (εr), etc.
Thermodynamic data	Phase behaviour solid–liquid–gas
Spectral data	UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Ytterbium(III) chloride (YbCl₃) is an inorganic chemical compound. It reacts with NiCl₂ to form a very effective catalyst for the reductive dehalogenation of aryl halides.^[2] It is poisonous if injected, and mildly toxic by ingestion. It is an experimental teratogen, known to irritate the skin and eyes. When heated to decomposition it emits toxic fumes of Cl^-.^[3]

History

Ytterbium, a lanthanide series element, was discovered in 1878 by the Swiss chemist Jean-Charles Galissard de Marignac, who named the element after a town (Ytterby) in Sweden.^[4] The first synthesis of YbCl₃ in the literature was that of Jan Hoogschagen in 1946.^[5] YbCl₃ is now a commercially available source of Yb³⁺ ions and therefore of significant chemical interest.

Chemical properties

The valence electron configuration of Yb⁺³ (from YbCl₃) is 4f¹³5s²5p⁶, which has crucial implications for the chemical behaviour of Yb⁺³. Also, the size of Yb⁺³ governs its catalytic behaviour and biological applications. For example, while both Ce⁺³ and Yb⁺³ have a single unpaired f electron, Ce⁺³ is much larger than Yb⁺³ because lanthanides become much smaller with increasing effective nuclear charge as a consequence of the f electrons not being as well shielded as d electrons.^[4] This behavior is known as the lanthanide contraction. The small size of Yb⁺³ produces fast catalytic behavior and an atomic radius (0.99 Å) comparable to many biologically important ions.^[4]

The gas-phase thermodynamic properties of this chemical are difficult to determine because the chemical can disproportionate to form [YbCl₆]⁻³ or dimerize.^[6] The Yb₂Cl₆ species was detected by electron impact (EI) mass spectrometry as (Yb₂Cl₅⁺).^[6] Additional complications in obtaining experimental data arise from the myriad of low-lying f-d and f-f electronic transitions.^[7] Despite these issues, the thermodynamic properties of YbCl₃ have been obtained and the C_3V symmetry group has been assigned based upon the four active infrared vibrations.^[7]

Preparation

YbCl₃ is prepared from Yb₂O₃ with either high-temperature carbon tetrachloride gas,^[8] or hot hydrochloric acid followed by drying at high temperature.^[9]

2 Yb₂O₃ + 3 CCl_4(g) → 4 YbCl_3(s) + 3 CO_2(g)

Yb₂O₃ + 6 HCl_(g) → 2 YbCl_3(s) + 3 H₂O

In practice there are better ways to prepare YbCl₃ for lab use. The aqueous HCl/ammonium chloride route is unsophisticated but very effective. Alternatively hydrated YbCl₃ may be dehydrated using a variety of reagents, particularly trimethylsilyl chloride. Other methods have been published including reacting the finely powdered metal with mercuric chloride at high temperature in a sealed tube. A variety of routes to solvated YbCl₃ have been reported including reaction of the metal with various halocarbons in the present of a donor solvent such as THF, or dehydration of the hydrated chloride using trimethylsilyl or thionyl chloride, again in a solvent such as THF.

Uses

Catalysis

YbCl₃, with a single unpaired electron, acts as a Lewis acid in order to fill the 4f orbital. The Lewis acidic nature of YbCl₃ allows YbCl₃ to coordinate (usually as [YbCl₂]⁺) in transition states to catalyze alkylation reactions, such as the aldol reaction^[10] and the Pictet-Spengler reaction.^[11]

Aldol reaction

The aldol reaction is a versatile reaction in synthetic organic chemistry. YbCl₃ serves a Lewis acid catalyst which aids the Pd(0) catalyzed decarboxylative aldol reaction between a ketone enolate and an aldehyde. Transition states A and B show the coordination method of the ytterbium salt as a Lewis acid.^[10] For the depicted decarboxylative Aldol reaction with R = tert-butyl and R’ = -(CH₂)₂Ph, the reaction yields show YbCl₃ is an effective Lewis acid catalyst:

Pictet-Spengler reaction

The Pictet-Spengler reaction produces a valuable tetrahydro-β-carboline ring system which can be later used for synthetically prepared indole alkaloids.^[11] The Lewis acid catalyzed reaction with YbCl₃ gave excellent yields and reduced reaction times from four days to 24 hours.^[11]

Esterification

The small size of Yb³⁺ provides fast catalysis, but at the cost of selectivity. For example, the mono-acetylation ofmeso-1,2-diols is fastest (2 h) with YbCl₃, but chemoselectivity for the mono-acetylated product is low (50%) compared to CeCl₃ (23 h, 85%).^[12]

Acetalisation

Ytterbium(III) chloride is a powerful catalyst for the formation of acetals using trimethyl orthoformate.^[13] In comparison with cerium(III) chloride and erbium(III) chloride, the ytterbium salt was found to be the most effective. Excellent yields are obtained from a variety of aldehydes within a few minutes at room temperature, as in the example above involving an acid-sensitive aldehyde.

Biology

YbCl₃ is a NMR shift reagent that produces different resonances with nuclei in contact with the YbCl₃ versus those nuclei not in contact with the shift reagent.^[14] Generally paramagnetic species, such as a (lanthanide)⁺³ ion, are desirable shift reagents.^[14] Membrane biology has been greatly influenced by YbCl₃, where³⁹K⁺ and²³Na⁺ ion movement is critical in establishing electrochemical gradients.^[14] Nerve signaling is a fundamental aspect of life that may be probed with YbCl₃ using NMR techniques. YbCl₃ may also be used as a calcium ion probe, in a fashion similar to a sodium ion probe.^[15]

YbCl₃ is also used to track digestion in animals. Certain additives to swine feed, such as probiotics, may be added to either solid feed or drinking liquids. YbCl₃ travels with the solid food and therefore helps determine which food phase is ideal to incorporate the food additive.^[16] The YbCl₃ concentration is quantified by inductively coupled plasma mass spectrometry to within 0.0009 μg/mL.^[4] YbCl₃ concentration versus time yields the flow rate of solid particulates in the animal’s digestion. The animal is not harmed by the YbCl₃ since YbCl₃ is simply excreted in fecal matter and no change in body weight, organ weight, or hematocrit levels has been observed in mice.^[15]

The catalytic nature of YbCl₃ also has an application in DNA microarrays, or so called DNA “chips”.^[17] YbCl₃ led to a 50–80 fold increase in fluorescein incorporation into target DNA, which could revolutionize infectious disease detection (such as a rapid test for tuberculosis).^[17]

References