Group 3 Scandium Yttrium

There are some vertical chemical similarities between the elements to justify the numbering of the groups within the d-block in the periodic table. For example, in group 3, scandium, yttrium and lutetium all have a common oxidation state of +3. In most cases the three elements in each vertical column have the same outer electron configuration, for example, scandium 3dHs, yttrium 4d 5s and lutetium 5s 6s. ... 

To avoid this confusion, and because many of the elements are actually far from rare, the terms lanthanide , lanthanon and lanthanoid have been introduced. Even now, however, there is no general agreement about the position of La, i.e, whether the group is made up of the elements La to Lu or Ce to Lu. Throughout this chapter the term lanthanide and the general symbol, Ln, will be used to refer to the fourteen elements cerium to lutetium inclusive, the Group 3 elements, scandium, yttrium and lanthanum having already been dealt with in Chapter 20. 

Group IIIA (3). Scandium, Yttrium, Lanthanoids, Actinoids... 

The 3rd group of the Periodic Table (the 1st column within the block of the transition elements) contains the metals scandium, yttrium, lanthanum, and actinium. Lanthanum (atomic number 57) may be considered the earliest member of the family of metals, called lanthanides (general symbol Ln), forming, inside the principal transition series, an inner transition series (up to atomic number 71). Scandium and yttrium together with the lanthanides are also called rare earth metals (general symbol R). 

Hydrogen reacts at elevated temperatures with many transition metals and their alloys to form hydrides. The electropositive elements are the most reactive, that is, scandium, yttrium, the lanthanides, the actinides and members of the titanium and vanadium groups (Figure 5.20). 

Recently, rare-earth metal complexes have attracted considerable attention as initiators for the preparation of PLA via ROP of lactides, and promising results were reported in most cases [94—100]. Group 3 members (e.g. scandium, yttrium) and lanthanides such as lutetium, ytterbium, and samarium have been frequently used to develop catalysts for the ROP of lactide. The principal objectives of applying rare-earth complexes as initiators for the preparation of PLAs were to investigate (1) how the spectator ligands would affect the polymerization dynamics (i.e., reaction kinetics, polymer composition, etc.), and (2) the relative catalytic efficiency of lanthanide(II) and (III) towards ROPs. 

Group 3 of the Periodic Table consists of the elements scandium, yttrium and either lanthanum or lutetium, depending upon the preferred arrangement of the Table. Group 3 elements have the outer electronic configuration ns2 p, and invariably their solution chemistry is that of the + 3 state. In this text, treatment of both La and Lu is carried out in Chapter 8, which deals with the f-block elements. Lanthanum and lutetium represent the first and last members of the lanthanide series. 

To date no triazole complexes appear to have been reported for the scandium, yttrium, and lanthanum group of metals. 

Synthetic strategies to alkoxide complexes have been covered in full by previous reviews [14]. The silylamide route proved to be an advantageous method of preparation, especially in the case of homoleptic derivatives [15]. The group (IIIA) elements - scandium, yttrium and lanthanum - are considered as lanthanides on the basis of their general chemical similarity to the true lanthanides. 

Rare Earth Sulfides. In Group Ilia of the periodic classification, there are scandium, yttrium, and the rare earths. We have not yet studied the scandium sulfides, but we have studied the yttrium sulfides and the rare earth sulfides for the last six years (4,9, 10,20). We now turn to the research on these last sulfides done in our laboratory (6,7, 8). 

The Group 3 elements are scandium, yttrium, and lanthanum. Strictly speaking actinium should also be included, but it is the general practice to associate it with the elements that follow it (the actinides) and treat them all separately, as we do in this book in Chapter 20. 

Scandium, yttrium, and lanthanum, in group Ilia of the periodic table, usually occur in nature with the fourteen rare-earth elements, cerium (atomic number 58) to lutetium (atomic number 71). All of these elements except promethium (which is n ade artificially) occur in nature in very small quantities, the principal source being the mineial monazite, a mixture of rare-earth phosphates containing also some thoriurn phosphate. 

Chapter 2 is concerned with the chemistry of scandium, yttrium, and the lanthanides and is discussed according to the nature of the ligand in which the donor is from Groups 14-17. Divalent and tetravalent lanthanide chemistry is also described. 

Yttrium is a transition metal. Transition metals are those elements in Groups 3 through 12 of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. The element above yttrium in the periodic table is scandium. The space below yttrium is taken up by a group of elements known as the rare earth elements. Scandium, yttrium, and the rare earth elements are often found together in nature. 

The chemistries of scandium and yttrium are often reported together (although yttrium is also often grouped with the lanthanides) so in this section they will be discussed together. Reference, where appropriate, will be made to the first volume in this series, Comprehensive Coordination Chemistry The Synthesis, Reactions, Properties and Applications of Coordination Compounds (CCC, 1987). Volume 3 of CCC (1987) contained a chapter entitled Scandium, Yttrium and the Lanthanides and this chapter is designed to follow part of that chapter. The articles reviewed will cover the period 1982-2001 although earlier work may be cited. Volume 2 of CCC (1987), devoted to ligands, will also be referred to in this chapter. 

Phosphorus, arsenic, antimony, and bismuth ligands have been discussed in CCC (1987).153 Complexes containing bonds between scandium, yttrium, and phosphorus or arsenic have been reviewed,154 as have complexes with neutral phosphorus ligands.155 Many of the complexes described in these reviews contain organic substituents such as cyclopentadienyl or alkyl groups. 

Metal-metal bonded dinuclear complexes are absent for the group 3 metals scandium, yttrium, and lanthanum while dititanium chemistry is truly in its infancy. 

The scandium, yttrium, or lanthanide atoms in these compounds evidently form such bridges to make better use of their valence shell electrons and orbitals. (C5H5)2MR monomers would contain only 14 valence shell electrons (five from each cyclopentadienyl ligand, one from the alkyl group in addition to the three metal electrons), well short of the 16 or preferably 18 valence shell electrons normally present in stable organotransition metal compounds " dimerization to (C5H5)2M(p-R)2M(C5H5)2 raises the valence shell electron count to 16 and uses a metal orbital that would be vacant in the monomer. 

If we consider the vertical columns instead of the horizontal rows, we find elements with similar chemical properties listed one below the other. Group I, for example, includes hydrogen and the alkali metals like lithium and sodium. Group III includes scandium, yttrium and all the lanthanide and actinide elements. 

In this chapter we look at /-block metals and their compounds. There are two series of metals the lanthanoids (the 14 elements that follow lanthanum in the periodic table) and the actinoids (the 14 elements following actinium). The lanthanoids and actinoids (Table 24.1) are collectively known as the inner transition metals, while scandium, yttrium, lanthanum and the lanthanoids are together called the rare earth metals. Although La and Ac are strictly group 3 metals, the chemical similarity of La to the elements... 

We have found tantalum to be especially suitable for synthetic reactions and equilibrations involving elements and their reduced halides which lie to the left of group V in the periodic table, namely the alkali metals and alkaline earth metals scandium, yttrium, and the lanthanides titanium, zirconium, hafnium, thorium, and uranium. Tantalum and niobium are also uniquely suitable containers for the syntheses of their own lowest halides, for example, Ta6Br14 3 and CsNb6In.4 Tantalum containers have been extensively employed for the synthesis of halides, but reduced compounds of some other nonmetals, some oxides, for example, perhaps can be handled as well. 

These complexes can involve all combinations of main group, transition metal (both early and late), and lanthanide see Scandium, Yttrium the Lanthanides Organometallic Chemistijj and actinide see Actinides Organometallic Chemistry) complexes (equations 40-42). 

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