Organolanthanide chemistry is the field of
chemistry that studies compounds with a
lanthanide-to-
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
bond. Organolanthanide compounds are different from their
organotransition metal analogues in the following ways:
*They are far more air- and water-sensitive and are often
pyrophoric
A substance is pyrophoric (from grc-gre, πυροφόρος, , 'fire-bearing') if it ignites spontaneously in air at or below (for gases) or within 5 minutes after coming into contact with air (for liquids and solids). Examples are organolit ...
.
*Chemistry in the 0
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
is far more limited. In fact, their electropositive nature makes their organometallic compounds more likely to be ionic.
*They form no stable
carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
s at room temperature; organolanthanide carbonyl compounds have been observed only in
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...
matrices, and decompose when heated to 40
K.
σ-Bonded complexes
Metal-carbon σ bonds are found in alkyls of the lanthanide elements such as
nMe6sup>3− and Ln
H(SiMe3)2sub>3.
Methyllithium
Methyllithium is the simplest organolithium reagent with the empirical formula CH3Li. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used in so ...
dissolved in
THF
Tetrahydrofuran (THF), or oxolane, is an organic compound with the formula (CH2)4O. The compound is classified as heterocyclic compound, specifically a cyclic ether. It is a colorless, water- miscible organic liquid with low viscosity. It is ...
reacts in stoichiometric ratio with LnCl
3 (Ln =
Y,
La) to yield Ln(CH
3)
3 probably contaminated with
LiCl.
If a chelating agent (L-L), such as
tetramethylethylenediamine
Tetramethylethylenediamine (TMEDA or TEMED) is a chemical compound with the formula (CH3)2NCH2CH2N(CH3)2. This species is derived from ethylenediamine by replacement of the four amine hydrogens with four methyl groups. It is a colorless liquid, ...
(tmed or tmeda) or
1,2-dimethoxyethane
Dimethoxyethane, also known as glyme, monoglyme, dimethyl glycol, ethylene glycol dimethyl ether, dimethyl cellosolve, and DME, is a colorless, aprotic, and liquid ether that is used as a solvent, especially in batteries. Dimethoxyethane is misc ...
(dme) is mixed with MCl
3 and CH
3Li in THF, this forms
i(tmed)sub>3
(CH3)6and
i(dme)sub>3
(CH3)6
Certain powdered lanthanides react with
diphenylmercury
Diphenylmercury is the organomercury compound with the formula Hg(C6H5)2. It is a white solid. The compound is of historic interest as a particularly stable organometallic compound but it finds few uses because of its high toxicity.
Preparation
...
in THF to yield octahedral complexes:
::2 Ln + 3 Ph
2Hg + 6 THF → 2 LnPh
3(THF)
3 + Hg (Ln =
Ho,
Er,
Tm,
Lu).
π-Bonded complexes
Cyclopentadienyl complex
A cyclopentadienyl complex is a coordination complex of a metal and cyclopentadienyl groups (, abbreviated as Cp−). Cyclopentadienyl ligands almost invariably bind to metals as a pentahapto (''η''5-) bonding mode. The metal–cyclopentadien ...
es, including several
lanthanocenes, are known for all lanthanides. All, barring tris(cyclopentadienyl)promethium(III) (Pm(Cp)
3), can be produced by the following reaction scheme:
:3 Na
p+ MCl
3 → M
psub>3 + 3 NaCl
Pm(Cp)
3 can be produced by the following reaction:
:2 PmCl
3 + 3 Be
psub>2 → 3 BeCl
2 + 2 Pm
psub>3
These compounds are of limited use and academic interest.
References
{{Branches of chemistry