Ytterbium-metal-carbon

The metal has very little commercial use. In elemental form it is a laser source, a portable x-ray source, and as a dopant in garnets. When added to stainless steel, it improves grain refinement, strength, and other properties. Some other applications, particularly in oxides mixed with other rare earths, are as carbon rods for industrial hghting, in titanate insulated capacitors, and as additives to glass. The radioactive isotope ytterbium-169 is used in portable devices to examine defects in thin steel and aluminum. The metal and its compounds are used in fundamental research. 

Roesky introduced bis(iminophosphorano)methanides to rare earth chemistry with a comprehensive study of trivalent rare earth bis(imino-phosphorano)methanide dichlorides by the synthesis of samarium (51), dysprosium (52), erbium (53), ytterbium (54), lutetium (55), and yttrium (56) derivatives.37 Complexes 51-56 were prepared from the corresponding anhydrous rare earth trichlorides and 7 in THF and 51 and 56 were further derivatised with two equivalents of potassium diphenylamide to produce 57 and 58, respectively.37 Additionally, treatment of 51, 53, and 56 with two equivalents of sodium cyclopentadienyl resulted in the formation of the bis(cyclopentadienly) derivatives 59-61.38 In 51-61 a metal-methanide bond was observed in the solid state, and for 56 this was shown to persist in solution by 13C NMR spectroscopy (8Ch 17.6 ppm, JYc = 3.6 2/py = 89.1 Hz). However, for 61 the NMR data suggested the yttrium-carbon bond was lost in solution. DFT calculations supported the presence of an yttrium-methanide contact in 56 with a calculated shared electron number (SEN) of 0.40 for the yttrium-carbon bond in a monomeric gas phase model of 56 for comparison, the yttrium-nitrogen bond SEN was calculated to be 0.41. 

This force field has also been used to explain the bent geometry of [M((CH3)5C5)2] complexes (M = calcium, strontium, barium, samarium, europium, or ytterbium). However, Hollis et al. set the ring carbon—dummy-dummy—ring carbon dihedral (as described by Doman et al.44) and dummy— metal-dummy bending force constants to zero. Thus, the force field is a points-on-a-sphere model. As one might expect, the calculated structures were... 

The reduction of a carbon-carbon multiple bond by the use of a dissolving metal was first accomplished by Campbell and Eby in 1941. The reduction of disubstituted alkynes to c/ s-alkenes by catalytic hydrogenation, for example by the use of Raney nickel, provided an excellent method for the preparation of isomerically pure c -alkenes. At the time, however, there were no practical synthetic methods for the preparation of pure trani-alkenes. All of the previously existing procedures for the formation of an alkene resulted in the formation of mixtures of the cis- and trans-alkenes, which were extremely difficult to separate with the techniques existing at that time (basically fractional distillation) into the pure components. Campbell and Eby discovered that dialkylacetylenes could be reduced to pure frani-alkenes with sodium in liquid ammonia in good yields and in remarkable states of isomeric purity. Since that time several metal/solvent systems have been found useful for the reduction of C=C and C C bonds in alkenes and alkynes, including lithium/alkylamine, ° calcium/alkylamine, so-dium/HMPA in the absence or presence of a proton donor,activated zinc in the presence of a proton donor (an alcohol), and ytterbium in liquid ammonia. Although most of these reductions involve the reduction of an alkyne to an alkene, several very synthetically useful reactions involve the reduction of a,3-unsaturated ketones to saturated ketones. ... 

The reduction of disubstituted acetylenes with ytterbium in liquid ammonia also produces trans-a -kenes in good yields. This reducing system does reduce some double bonds, such as the strained double bond in norbomadiene however, in general, carbon-carbon double bonds do not undergo reduction with this reducing system. The expense of powdered metallic ytterbium does not make this a very practical reducing agent for synthetic purposes. 

Here, the so-called heavy lanthanides include the elements from samarium to-lutetium, except for ytterbium and europium which behave like bivalent metals and have unique properties. For these heavy-lanthanide-carbon systems, no complete phase diagram was found, only some information about the formation and the crystal structure of the carbides is available. On the basis of these data the general characteristics of the phase diagrams of the heavy-rare-earth-carbon systems can be summarized. In this case the yttrium-carbon phase diagram may be regarded as the best prototype available for compounds of the heavy lanthanide systems with carbon. 

The solid solubility of a number of the non-rare earth metals (including europium and ytterbium in this group) are more extensive in the trivalent rare earths than vice versa, see fig. 14. This group includes the small size divalent metals (M = Mg, Zn, Cd and Hg), the interstitial elements (M = H, C and O), the two divalent barides (M = Eu and Yb), and the trivalent group III B metals (In and Tl, and probably Ga). Except for carbon, M is more soluble in the bcc phase than in the close-packed lower temperature polymorph. Indeed it is possible to retain the bcc phase at room temperature by modest quenching techniques in the R-Mg (Miller and Daane 1964, Herchenroeder et al. 1985) and R-Cd (Herchenroeder et al. 1985) alloys. 

Reactions with Transition Metals Forming Carbon-Carbon Bonds. The combination of certain lanthanides and TMS-Br has been found to produce lanthanum halides (LaX n = 2 or 3) that are very active reducing reagents (eq 19). So far, the only metals to be used in these reactions are samarium (Sm) and ytterbium (Yb). In addition to TMS-Br, these reactions have been accomplished using Sm/TMS-Cl/Nal under similar conditions with corr5>arable yields. 

A large variety of rare earth derivatives have been used to initiate ROP of cyclic carbonates. Their usually high reactivity must be emphasized, as exemplified by the polymerization of TMC with Ln(OAr)3 (Ln = Lanthanide = f-block elements) under mild conditions, in contrast to the long reaction time and high temperature required when tin-based or aluminum-based catalysts were used. As rare earth metals La (lanthanum), Ce (cerium), Nd (neodymium), Sm (samarium), Gd (gadolinium), Dy (dysprosium), Er (erbium), Yb (ytterbium). Sc (scandium), and Y (yttrium) are most often applied. ... 

An interesting reaction was observed when Yb(C5Me5)2(OEt2) was opposed to various carbonyl complexes (Tilley et al., 1982). Mixed complexes were obtained with bridged carbon monoxide, the oxygen and carbon being bound to ytterbium and to the transition metal, respectively. The following reactions were studied ... 

---