Group IIIB and Lanthanides

The first compound of this series, CeSI, was reported by Carter (68) in 1961, and later discussed by Dagron (93). It was obtained by the reaction of iodine with cerium sulfide at 430°C, or by direct synthesis from the elements at 500°C. This was the start of a detailed investigation of this group of compounds mainly by Dagron and co-workers. The present situation is presented in Table VII. No scandium compounds are known thus far, and the same is true for selenium and tellurium halides of these elements. 

The best way of preparation seems to be the successive reaction of the respective elements (94), as described in detail for the sulfide bro- 

Chalcogenide Halides of Group IIIB and Lanthanides Bibliography 

For single crystals, the same method is applied, using an excess of metal and of halogen. After reaction, the mixture of the sulfide halide and the halide is heated to a temperature slightly above the melting point of the respective halide. Perfect, small crystals for X-ray determination are formed. The excess of the trihalide is removed by treatment with anhydrous alcohol 92, 93, 96). CeSI may also be prepared from the sulfides 68, 93) CeSCl is formed by reaction 4 92). 

Besides a few colorless compounds, such as YSBr, most of these compounds are slightly colored, e.g., yellow (YbSBr), green (PrSI), rose (ErSI), and orange (YbSI). They are very sensitive to humidity, and must be kept under vacuum or dry nitrogen. 

---

Methylenecycloalkanes. Strained cycloalkanes with exo-methylene groups have been homopolymerized as well as copolymerized with ethylene by catalysts such as [(C5(CH3)5)2Zr(CH3)]+[(CH3)B(C6F5)3] and analogous Group IIIB and lanthanide metallocenes via the C—C bond migration mechanism shown in equation 30 (216). 

The f block elements Lanthanide and actinide elements. These two series often appear with a or in Group IIIB (3), but these elements do not belong to that family. (Note that the transition metals do not belong to group IIA (2), which they follow.) The most common oxidation state for the lanthanides and some of the actinides is +3, hence the popularity of the IIIB (3) position. Because of their remarkable electronic and chemical properties they should be set apart, but most periodic tables give no special numerical appellations to these elements. 

The rare earth elements here referred to include the group IIIB metals (Sc, Y and La) and the lanthanide elements (Ce to Lu) and are sometimes loosely referred to as lanthanide elements, as the main characteristics and reactivity of these elements are similar in many cases. 

R ligands which may effectively prevent solvent molecules from entering the yttrium coordination sphere. It is relevant to mention here the compounds CpJTiR (R = H, CH ) which don t show benzene metallation not even when solutions of CpJTiR are heated for prolonged periods in at 90 C (vide supra). This clearly demonstrates the difference between Ti on one side and Group IIIB metals and lanthanides on the other. 

Group NIB and f-BIOCk Metallocenes. The need for expensive cocatalysts has always hampered the development of metallocene catalysts for olefin polymerization. It was recognized early on that substitution of the Group IVB metal with a lanthanide or Group IIIB element in the -1-3, state would represent a cocatalyst-free analogue of the Kaminsky system. Active catalysts are indeed obtained from bis-Cp lanthanocenes and yttrium- and scandium-based congeners. The lutetium dimer 29 has an activity of >7 kg/mmol(Lu)/h/atm for ethylene polymerization in cyclohexane (95). (This remarkable compound can also break the C—H bonds of alkanes.)... 

Period 5 (group 3 [IIIB] to group 12 [IIB]) is located in the second row of the transition elements and represents 10 of the transition metals to nonmetals found in the periodical table of chemical elements. This period is also known to include some of the so-called rare-earth elements. Most of the rare-earths are found in the lanthanide series, which follows barium (period 6, group 3). (Check the periodic table to locate the major rare-earth elements in the lanthanide series. These are addressed in a later section of the book.)... 

---