Lanthanides elements/metals, properties

The last of the lanthanides, this metal is also the hardest and the densest of them. It is a component of cerium mischmetal. Lutetium has some applications in optoelectronics. Shows great similarities to ytterbium. Its discoverer, Georges Urbain, carried out 15 000 fractional crystallizations to isolate pure lutetium (record ). The element has special catalytic properties (oil industry). 176Lu is generated artificially and is a good beta emitter (research purposes). 177Lu has a half-life of six days and is used in nuclear medicine. 

The lanthanide series is composed of metallic elements with similar physical properties, chemical characteristics, and unique structures. These elements are found in period 6, starting at group 3 of the periodic table. The lanthanide series may also be thought of as an extension of the transition elements, but the lanthanide elements are presented in a separate row of period 6 at the bottom of the periodic table. 

The sixth-period inner transition metals are called the lanthanides because they fall after lanthanum, La. Because of their similar physical and chemical properties, they tend to occur mixed together in the same locations in the earth. Also because of their similarities, lanthanides are unusually difficult to purify. Recently, the commercial use of lanthanides has increased. Several lanthanide elements, for example, are used in the fabrication of the light-emitting diodes (LEDs) of laptop computer monitors. 

Lanthanides are coextracted with actinides and then separated from actinides, which are forecasted to be sent to a repository. The lanthanide elements comprise a unique series of metals in the periodic table. These metals are distinctive in terms of size, valence orbitals, electrophilicity, and magnetic and electronic properties, such that some members of the series are currently the best metals for certain applications. Increased use of the lanthanides in the future is likely, because their unusual combination of physical properties can be exploited to accomplish new types of chemical transformations. These elements coextracted with actinides and then separated from the latter, could in the future be recovered and used (among the lanthanides, only 151Sm is a long-lived isotope (half-life 90 years)).4... 

When we classify the elements as metals and nonmetals we see that metals occupy very big part (about 80%) of the periodic table. The elements in B groups (transition elements, actinides and lanthanides) and the elements in the groups, 1 A, 2A and 3A (except hydrogen and boron) are metals. Only the eleven elements H, C, N, O, R S, Se, F, Cl, Br and I are nonmetals and the elements in group 8A are noble gases. However, among these elements, B, Si, Ge, As, Sb, Te, Po and At are metalloids and Sn, Pb and Bi and Be have metallic properties. 

The intrinsic properties of the lanthanide elements guarantee promising applications in the fields of catalysis and material science. How to cope with these features on a molecular level and under anaerobic conditions is discussed, including thermodynamic and kinetic considerations. Due to the importance of a prolific metal/ligand synergism, current developments in ligand design are emphasized. 

Of course, the fascinating steric features of lanthanide elements are most impressively expressed in the lanthanide contraction [76]. In textbooks, lanthanide contraction is often simply explained as being the phenomena responsible for similar chemical properties, in particular between the pairs of the d-transition metal homologues Zr/Hf, Nb/Ta and Mo/W. However, what does the contraction mean to the lanthanide elements (and compounds derived from them)... 

Crystal field theory is one of several chemical bonding models and one that is applicable solely to the transition metal and lanthanide elements. The theory, which utilizes thermodynamic data obtained from absorption bands in the visible and near-infrared regions of the electromagnetic spectrum, has met with widespread applications and successful interpretations of diverse physical and chemical properties of elements of the first transition series. These elements comprise scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper. The position of the first transition series in the periodic table is shown in fig. 1.1. Transition elements constitute almost forty weight per cent, or eighteen atom per cent, of the Earth (Appendix 1) and occur in most minerals in the Crust, Mantle and Core. As a result, there are many aspects of transition metal geochemistry that are amenable to interpretation by crystal field theory. 

Since the chemistry of organolanthanide complexes is rather invariant to the number of 4/ electrons, a metal of similar size and charge but with no/ electrons could have similar chemical properties. Such is the case for yttrium and it will be included in this article. Although yttrium is not formally a lanthanide element, it is congeneric with lanthanum. More importantly, the radial size of the trivalent yttrium ion is nearly identical with that of Er. As such, its chemistry, at least so far, has proven to be very similar to that of the late lanthanides. Since is diamagnetic (cf. Er, - 9.4-9.7 B.M.) with I = j, it provides NMR-accessible... 

The properties of the lanthanide elements and their organometallic complexes described in the previous section explain in part why organo-met lic chemists in the past found lanthanide chemistry much less interesting than transition metal chemistry. The highly ionic, trivalent organolanthanide complexes appeared to have little potential to interact with the small-molecule substrates that provide such a rich chemistry for the transition metals neutral unsaturated hydrocarbons, H2, CO, phosphines, etc. The two-electron oxidation reduction cycles so important in catalytic transition metal chemistry in 18 16 electron complexes seemed... 

Its 3d 4s2 structure gives element 21 properties similar to the lanthanides and to lanthanum (Sd s ) in particular. The covalent and ionic radii, 1.44 A and 0.68 A, respectively, are however much smaller than those of the lanthanides. In consequence the Sc ion has a greater polarising power and more readily forms complexes for instance crystalline KgScFg can be obtained. The ionisation potentials 1st, 6.56 eV 2nd, 12.9 cV 3rd, 21.8 cV are not much larger than those of the lanthanides so far as they are known, and the metal itself is almost as reactive. 

As a result of these intrinsic properties of the lanthanide elements and the specific metal/ligand interplay, ligand exchange and insertion reactions rule the mechanistic scenarios of lanthanide(III)-catalyzed transformations. 

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