Ytterbium iodide

P. Girard, J. L. Namy, and H. B. Kagan, Divalent lanthanide derivatives in organic synthesis. 1. Mild preparation of samarium iodide and ytterbium iodide and their use as reducing or coupling agents,. /. Am. Chem. Soc., 102 (1980) 2693-2698. 

X = Me, CH=CH2, Ph, OMe), synthesized from RI and Yb. The alkyl ytterbium iodides have iodo-bridged dimeric structures, containing four-coordinate ytterbium when X = Me, but five-coordinate for X = OMe, due to chelation. When R = CH=CH2, Ph, OMe (but not Me), the equilibrium can be displaced to the right on heating... 

The same complex has been obtained also by the treatment of ytterbium iodide with the mixture formed in the reaction of CjoHgK with CP2V. 

In the presence of In powder 2-cycIohexen-l-one is converted by allyl iodide and Me3SiCI 14, in 63% yield, into the 1,4-addition product 2179 [84], which is also obtained in 73% yield by Sakurai 1,4-addition ofallyltrimethylsilane 82 to 2-cyclohexene-l-one in the presence of excess Me3SiCl 14 and catalytic amounts of InCl3 [85] (Scheme 13.25). Ytterbium] 111) triflate-catalyzed imino-ene reactions of N-tosylaldimines with a-methylstyrene are dramatically accelerated on addition of Me3SiCl 14 [85 a]. 

Organoytterbium chemistry has been developed in the last 20 years, although the development rate is much slower than the other lanthanides like samarium or cerium. Dianionic complexes that are produced from the reaction of ytterbium with diaryl ketones react with various kinds of electrophiles including carbon-heteroatom unsaturated bonds.35 Phenylytterbium iodide, a Grignard-type reagent, is known to have reactivity toward carbon dioxide,36 aldehydes, ketones,37,37 and carboxylic acid derivatives38,3811 to form the corresponding adducts respectively. 

Solutions of alkali metals in ammonia have been the best studied, but other metals and other solvents give similar results. The alkaline earth metals except- beryllium form similar solutions readily, but upon evaporation a solid ammoniste. M(NHJ)jr, is formed. Lanthanide elements with stable +2 oxidation states (europium, ytterbium) also form solutions. Cathodic reduction of solutions of aluminum iodide, beryllium chloride, and teUraalkybmmonium halides yields blue solutions, presumably containing AP+, 3e Be2, 2e and R4N, e respectively. Other solvents such as various amines, ethers, and hexameihytphosphoramide have been investigated and show some propensity to form this type of solution. Although none does so as readily as ammonia, stabilization of the cation by complexation results in typical blue solutions... 

Both samarium iodide and ytterbium triisopropoxide catalyse the ring opening45 of epoxides by TMS-azide in the latter case, due to an acidic work-up, the products are isolated as vicinal azido alcohols. 

Barbier cyclization (cf. 11, 307-308).- Sml, is effective for intramolecular cycli-zation of ot-(co-iodoalkyl)cycloalkanones to bicyclic alcohols. Yields can be improved by addition of Fe(IIl) catalysts such as tris(dibenzoylmethane)iron (6, 259). Cyclizations induced with ytterbium(ll) iodide are also stereoselective. 

Organoytterbium(II) halides are most conveniently prepared by oxidative metalation of organic iodides with ytterbium metal (equation 84). Since an induction period is often noticed in such reactions, activation of the metal with a trace amount of CH2I2 can be utilized to facilitate this process. ... 

Hou, Z., Zhang, Y., Wakatsuki, Y. Molecular structures of HMPA-coordinated samarium(ll) and ytterbium(ll) iodide complexes. A structural basis for the HMPA effects in Sml2-promoted reactions. Bull. Chem. Soc. Jpn. 1997, 70, 149-153. 

In the presence of methyl iodide, metallic ytterbium can easily react with allylbromide in anhydrous THF to form allylytterbium bromide, which reacts readily with imines to give the corresponding bromoallylamines in satisfactory yields under mild and neutral conditions (Scheme 303).1091... 

The most fundamental precursors to organometallic complexes of group 3 elements are the trichlorides, MCI3. The commercially available trichlorides are hydrated, and even for those claimed dehydrated it is advisable to take the appropriate steps necessary to dry them further before use. The divalent iodide complexes Ml2 are available for certain group 3 elements such as samarium and ytterbium, and they serve as conve-... 

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