Organolanthanide chemistry is the field of chemistry that studies compounds with a lanthanide-to-carbon 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.
• 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.

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. 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.^[1]