User:Dr.MeowMeow/Organolanthanide chemistry

Organolanthanide chemistry is the field of chemistry that studies compounds with a lanthanide-to-carbon bond. Organolanthanide chemistry is a subdivision of organometallic chemistry. Lanthanides are f-block elements. They are referred to as inner transition metals and are considered transition metals. Despite the similarities between organolanthanide and organotransition metal analogues they differ in the following ways,

• They are far more air- and water-sensitive and are often pyrophoric.
• Chemistry in the 0 oxidation state is far more limited. In fact, their electropositive nature makes their organometallic compounds more likely to be ionic.
• They form no stable carbonyls at room temperature; organolanthanide carbonyl compounds have been observed only in argon matrices, and decompose when heated to 40 K.

Lanthanides in the periodic table

σ-Bonded complexes

Metal-carbon σ bonds are found in alkyls of the lanthanide elements such as [LnMe₆]³⁻ and Ln[CH(SiMe₃)₂]₃ (Me represents a methyl group). Methyllithium dissolved in THF reacts in stoichiometric ratio with LnCl₃ (Ln = Y, La) to yield Ln(CH₃)₃ probably contaminated with LiCl.

If a chelating agent (L-L), such as tetramethylethylenediamine (TMED or TMEDA) or 1,2-dimethoxyethane (DME) is mixed with MCl₃ and CH₃Li in THF, this forms [Li(TMED]₃[M(CH₃)₆] and [Li(DME)]₃[M(CH₃)₆].

Certain powdered lanthanides react with diphenylmercury in THF to yield octahedral complexes:

2 Ln + 3 Ph₂Hg + 6 THF → 2 LnPh₃(THF)₃ + Hg (Ln = Ho, Er, Tm, Lu).

π-Bonded complexes

Cyclopentadienyl complexes, 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[Cp] + MCl₃ → M[Cp]₃ + 3 NaCl

Pm(Cp)₃ can be produced by the following reaction:

2 PmCl₃ + 3 Be[Cp]₂ → 3 BeCl₂ + 2 Pm[Cp]₃

These compounds are of limited use and academic interest.

Electronic Structure of Organolanthanides

The electronic structure of organolanthanides is very unique. Since they are the only elements with 4f electrons they have their own unique properties when they bond to organic elements. The way the 4f ions are structured give them their own distinct properties when they form their coordination complexes. The 4f electrons are electronically shielded by the 5s and 5p orbitals. This gives organolanthanides the effect that any surrounding ligands will effect the interelectron repulsion and spin orbit coupling far less.

Synthesis of Oranolanthanide molecules

There is a wide range of organolanthanide molecules that can be synthesized but thee will be two specific examples of organolanthanide molecules that have been synthesized.

Since there has been a growing interest in lanthanide indium perovskites LnInO₃ their synthesis has been improved over the years. Ternary lanthanide indium oxides (Ln=La,Pr,Nd,Sm) have been synthesized by using high temperature solid state reactions such as the ceramic method. This involves reacting highly pure In₂O₃ with either La₂O₃,Pr₆O₁₁,Nd₂O₃, or Sm₂O₃ with In₂O₃ at very high temperatures. The reagents are ground together to powders in stochiometric amounts then pressed into pellets. The pellets are placed into an alumina boat and heated to 1200 degrees Celsius for 48 hours then slowly cooled to an annealing temperature of 600 degrees Celsius over 24 hours. The length of this reaction is to limit the impurities of the product. The product is then characterized using XPS (X-ray photoelectron spectroscopy).

Applications of Organolanthanide chemistry

Organolanthinides are used today primarily in catalysis and in organic synthesis. The unique reactivity of organolanthanides come from the electronic structure of the f-block elements. The lanthanides can easily react and form compounds while being in the (II) and (III) oxidation states. Due to their stability against forming carbonyls at room temperature they are used very often in OLED's (organic light emitting diodes). Incorporating organolanthanide molecules into OLED's have been found to improve color saturation for visible OLEDS. They also increase the internal efficiency of conventional OLED's de to their radiation being combined by their singlet excitons.

Orgnaolanthanides have been used as single component catalysts in the polymerization of acrylonitrile. In the past polyacetonitrile was obtained by using BeR₂ or MgR₂ as initiators but their reactivity was very low. Ind₂LnN(i-Pr)₂ (Ln=Y,Yb) were reported to exhibit relatively high catalytic activity in the polymerization of acetonitrile.