Ytterbium trichloride

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. 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−. 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. 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−. 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. The first synthesis of YbCl3 in the literature was that of Jan Hoogschagen in 1946. YbCl3 is now a commercially available source of Yb3+ ions and therefore of significant chemical interest. 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. 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. The gas-phase thermodynamic properties of this chemical are difficult to determine because the chemical can disproportionate to form −3 or dimerize. The Yb2Cl6 species was detected by electron impact (EI) mass spectrometry as (Yb2Cl5+). Additional complications in obtaining experimental data arise from the myriad of low-lying f-d and f-f electronic transitions. Despite these issues, the thermodynamic properties of YbCl3 have been obtained and the C3V symmetry group has been assigned based upon the four active infrared vibrations. YbCl3 is prepared from Yb2O3 with either high-temperature carbon tetrachloride gas, or hot hydrochloric acid followed by drying at high temperature. 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. YbCl3, with a single unpaired electron, acts as a Lewis acid inorder to fill the 4f orbital. The Lewis acidic nature of YbCl3 allows YbCl3 to coordinate (usuallyas +) in transition states to catalyze alkylation reactions, such as the aldol reaction and the Pictet-Spengler 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. 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: