Scandium organometallic compounds

Organometallic compounds of lanthanide metals other than Sm, Eu, and Yb are very rare until now. But the development of this chemistry became possible after the synthesis of divalent precursors of Tm, Dy, and Nd in the late 1990s, namely of their diiodides (see Scandium, Yttrium the Lanthanides Inorganic Coordination Chemistry) and by using hgands such as phospholyl or arsolyl, which stabilize divalent lanthanide ions. 

It should be noted that there are organometallic compounds involving polyhapto ligands that contain linkages such as Sc— Te that are not found in coordination compounds. In addition, a number of recent reviews on the organometallic chemistry of the lanthanides include reference to scandium compounds. ... 

In this article the term organometallic compound includes alkyl and aryl derivatives of the rare earths—the transition metals of group III, scandium, yttrium, lanthanum and the lanthanides cerium to liitetium with covalent metal-to-carbon a-bonds, as well as the so-called 77-complexes with more than monohapto metal-to-carbon bonds, for example cyclopentadienyl and olefin complexes, metal acetylides, but not carbonyls, cyanides and isocyanide complexes. Derivatives of scandium, yttrium and lanthanum are included and discussed together with the compounds of the lanthanides, because of many similarities in the synthesis and the chemistry of these organometallic derivatives of the rare earths. 

The organometallic chemistry of scandium is generally similar to that of the later lanthanides. It thus forms a cyclopentadienyl ScCps that has mixed mono- and pentahapto-coordination like LuCps. An anionic methyl [Li(tmed)]3[M(CH3)6] is formed by scandium, as by the lanthanides. However, there are often subtle differences that should be borne in mind. The pentamethylcyclopentadienyl compound [ScCp 2Me] is a monomer but the lutetium compound is an asymmetric dimer [Cp 2Lu(/u.-Me)LuCp 2Me]. Similarly, whilst triphenylscandium is obtained as a bis(thf) adduct, [ScPh3(thf)2], which has a TBPY structure with axial thf molecules, the later lanthanides form octahedral [LnPh3(thf)3]. Triphenylscandium and the phenyls of the later lanthanides are made by different routes. 

The discovery of ferrocene and of the other sandwich complexes initiated a new field of organometallic chemistry, the chemistry of the w-complexes. Wilkinson and Birmingham (1954) prepared the first organometallic w-complexes of the rare earths, the tricyclopentadienyl complexes of Sc, Y, La, Ce, Pr, Nd, Sm and Gd. It was not until 14 years later with the synthesis of triphenyl scandium (Hart and Saran, 1968) that the first a-bonded aryl-rare-earth compound was made. 

Scandium chemistry is reviewed while other reviews concern organolanthanides in catalysis, the organometallic chemistry of the rare earths organolanthanide chemistry , and compounds of the type U(=CHPR3)Cp3. 

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