Lutetium

{ syn. }

97.41 %

2.59%

{ syn. }

Risk

Powder

Lutetium is a chemical element with the element symbol Lu and atomic number 71 in the periodic table it is in the group of lanthanides and also making it one of the metals of the rare earths. As with the other lanthanides lutetium is a silvery heavy metal. Because of the lanthanide Lutetiumatome have the smallest atomic radius, also the element has the highest density and the highest melting point and boiling point of all lanthanides.

The element was almost simultaneously, but independently discovered in 1907 by Georges Urbain each other, Carl Auer von Welsbach and Charles James. Although in 1909 decided that Urbain entitled to the discovery and hence his proposed name lutetium has been set, proposed by Carl Auer von Welsbach name Cassiopeium (Cp ) was widespread long, especially in German-speaking countries.

Lutetium is one of the rarest of rare earth metals and is used economically only on a small scale it and as a result of the difficult separation from other rare earths. Among the most important applications of the element include the use of Lutetiumoxyorthosilicat for scintillation in positron emission tomography.

8.1 halides
8.2 Organometallic Compounds
8.3 Other compounds

History

Lutetium was 1907 as penultimate lanthanide ( only the radioactive and thus unstable promethium was later discovered ) almost simultaneously and independently discovered by three chemists. Both the Frenchman Georges Urbain, the Austrian Carl Auer von Welsbach and the American Charles James studied the ytterbium discovered in 1878 by Jean Charles de Galissard Marignac detail. Urbain reported on 4 November 1907 in the Paris Academy of Sciences that he had obtained by fractionation of Ytterbiumnitraten 800 times, which he had obtained from xenotime from the ytterbium Marignac two elements. This he called neo- ytterbium and lutecium the ancient name of Paris, Lutetia.

A short time later, on December 19, 1907, gave Carl Auer von Welsbach, as a result of research that he carried out since 1905, announced that he had from the radio spectra of various samples he had obtained by fractional crystallization of ytterbium - ammonium oxalate, closed that this must consist of two different elements. This he called Cassiopeium ( Cp, after the constellation Cassiopeia, corresponding lutetium ) and aldebaranium ( Ab, according to the star Aldebaran, corresponding ytterbium ). However, he could not win pure substances.

Charles James also worked on the separation of ytterbium using ytterbium - magnesium nitrate salts and received in 1907 large quantities of pure salts. After he had learned of the discovery Urbains, but he renounced any claims to the discovery of the new element.

In the following years there were between Urbain and Welsbach to some - by the political differences between France and Austria - Hungary intensified - struggles for recognition as the rightful discoverer of the new element, and thus for the right to define the name of the element. The international atomic weight Committee, consisting of Frank Wigglesworth Clarke, Wilhelm Ostwald, Thomas Edward Thorpe and Georges Urbain, 1909 finally opted for Urbain and his member name. However, the name was changed to neo- ytterbium ytterbium. Definitively the name lutetium has been set for the element in 1949 by the IUPAC. Until then, above all, many German chemists had stuck to the name Cassiopeium.

The exact atomic weight was determined in 1911 by Theodore William Richard based lutetium (III ) bromide, which has been cleaned in 15,000 fractional crystallizations. Metallic Lutetium was first produced in 1953.

Occurrence

Lutetium is a rare element on Earth, its abundance in the Earth's continental crust is about 0.8 ppm. It is the rarest lanthanide promethium and thulium after unstable, but more often than elements such as silver ( 0.079 ppm), mercury or bismuth.

There are no known Lutetiumminerale, the element always comes as an additive in other rare-earth minerals, especially those of yttrium and the heavier lanthanides, such as xenotime or gadolinite ago. So xenotime contains from Malaysia next yttrium, dysprosium, erbium and ytterbium and lutetium 0.4 %. Bastnäsit as a mineral of the lighter Ceriterden other hand, contains only traces of the element, monazite up to 0.1 %.

Important sources of lutetium are the Xenotimvorkommen in Malaysia ( there as an accessory mineral of cassiterite ), and lateritic clay minerals ionenadsorbierende in southern China's Jiangxi and Guangdong. Due to the difficult extraction it is produced and used only in small amounts and has a high price. Due to the low demand, the supply is not considered as critical with lutetium.

Production and representation

The extraction of lutetium is complicated and lengthy, especially through the difficult separation of the lanthanides. The output of minerals such as monazite or xenotime are first digested with acids or alkalis and brought into solution. The separation of lutetium from the other lanthanides is then possible by various methods, the separation by ion exchange is the most important industrial method for lutetium, as well as for other rare lanthanoids. The solution is applied with the rare earths to a suitable resin to which the individual lanthanide ions bind to different degrees. Then it is dissolved in a separation column with the aid of complexing agents such as EDTA, DTPA or HEDTA from the resin, through the different degrees of bonding to the resin thus obtained to the separation of individual lanthanides.

A recovery of Lutetiummetall is possible by reducing Lutetiumfluorid with calcium at 1500 to 1600 ° C.

Properties

Physical Properties

Lutetium is a soft, silvery heavy metal. The lanthanide contraction causes lutetium as the lanthanide with the highest atomic number of 175 pm has the smallest atomic radius. As a result, it also has 9.84 g/cm3 the highest density and the highest melting point (1652 ° C) and boiling point ( 3402 ° C) of all lanthanides.

Under standard conditions, crystallized lutetium in a hexagonal closest packing of spheres with lattice parameters a = 351.6 pm and c = 557.3 pm. In addition to this structure even more high-pressure modifications are known. From a pressure of 32 GPa crystallized lutetium in a structure of samarium- type, a complicated structure, the trigonal crystal structure with lattice parameters a = 317.6 pm and c = 2177 pm. During the phase transition, there is a loss in volume of 1.6%. Other phase transitions there is at a pressure of 45 GPa, from which a double - hexagonal closest structure is the most stable, and at 88 GPa with a transition to a distorted cubic closest structure ( HR24 ).

Less than 0.1 K, at a pressure of 18 GPa below 1.2 K, lutetium becomes superconducting.

Chemical Properties

Lutetium is a typical non-noble metal, especially at higher temperatures, will react with most non-metals. Reacts slowly with oxygen at standard conditions of dry air, faster in the presence of moisture. Metallic lutetium as other base metals, especially for large surface combustible. The reaction of hydrogen and lutetium is not complete, the hydrogen occurs instead in the octahedral interstices of the metal structure, and are formed of non-stoichiometric Hydridphasen, the exact composition of the temperature and the hydrogen pressure depends.

In water, Lutetium dissolves slowly in acids rapidly to form hydrogen. In solution are always trivalent, colorless Lutetiumionen.

Isotopes

There are a total of 34 known isotopes ( 150Lu to 184Lu ) and 35 Kernisomere of lutetium. Of these, only 175Lu is stable, and 176Lu with a half-life of 3.8 × 1010 years, the longest-lived. These two isotopes occur naturally, with 175Lu predominates, with a share of 97.41 % in the natural isotopic composition. Therefore, one gram of natural lutetium has a low intrinsic radiation of 51.8 Bq. All other isotopes have a short half-life, with a maximum of 3.31 years for 174Lu.

The slow decay of 176Lu to 176Hf can be used for determining the age of very old rocks. The different ratios of isotopes 176Hf and 177Hf are determined and compared with the known ratio in rocks age. With this method, the determination of age of the oldest known Martian meteorite ALH84001 managed to 4.091 billion years.

The radionuclide 177Lu is - complexed with ligands such as DOTA - as a short-range beta emitters in the therapy against neuroendocrine tumors or prostate cancer used.

Use

Metallic lutetium has no economic significance, it is only used in small quantities for research purposes. As alloy is the element like the other lanthanides ingredient in mixed metal.

In compounds of lutetium may be used as a catalyst for the cracking of petroleum and for polymerization reactions, as a scintillator material used in positron emission tomography, or as a dopant for the magnetic bubble memory of gadolinium gallium garnet.

Biological significance and toxicity

Lutetium has no biological significance and is included only in extremely small amounts in the human body. It has been found in experiments on rats that ingested lutetium mainly in the liver, in minor amounts is also stored in the bone and spleen.

About toxic effects of Lithium and its compounds on living organisms, little is known. In rats, acute toxicity was determined with an LD50 value of 315 mg / kg for intraperitoneal administration and 7100 mg / kg for oral administration over seven days for Lutetiumchlorid. A chronic toxicity could not be determined. Dissolved Lutetiumionen toxic to bacteria as Aliivibrio fischeri. Lu3 ions have a EC50 value of 1.57 uM and are therefore more toxic than zinc or cadmium ion, and comparable to copper ions in the bacterial toxicity.

Compounds

In compounds of lutetium always occurs in the 3 oxidation state.

Halides

The halogens fluorine, chlorine, bromine and iodine, in each case forms a lutetium halide having the empirical formula LUX3. These are typical salts with melting points between 892 ° C ( Lutetium (III) chloride), and 1184 ° C ( Lutetium (III ) fluoride ). Except Lutetiumfluorid which crystallizes in a terbium ( III) chloride - dimensional structure, which form an aluminum chloride Lutetiumhalogenide layer structure.

Organometallic Compounds

There are known a number of organometallic compounds. Compounds with a direct bond between lutetium and carbon are known only to a small extent, as it easily leads to secondary reactions such as β - Hydrideliminierungen in this as in many transition metals. They are, therefore, with bulky residues such as the tert- butyl group, or a larger number of smaller groups such as in a Hexamethyllutetat complex [ Lu ( CH3) 6] 3 stable. The main ligands of lutetium is cyclopentadienyl and derivatives thereof. However, a sandwich complex of the lutetium is not known, the most important classes are those of the formulas CpLuX2, Cp2LuX and Cp3Lu (X can halide, hydride, alkoxide or another ). In three cyclopentadienyl ligands, two ligands η5, η1 as a bridge to bind to another Lutetiumatom.