Organoantimony chemistry

Organoantimony chemistry is the chemistry of compounds containing a carbon to antimony (Sb) chemical bond. Relevant oxidation states are Sb(V) and Sb(III). The toxicity of antimony limits practical application in organic chemistry.

Organoantimony(V) chemistry

Antimony compounds of the type R₅Sb (stiboranes) can be synthesised from trivalent Sb precursors:

Ph₃Sb + Cl₂ → Ph₃SbCl₂

Ph₃SbCl₂ + 2 PhLi → Ph₅Sb

Asymmetric compounds can also be obtained through the stibonium ion:

R₅Sb + X₂ → [R₄Sb]⁺[X]

[R₄Sb]⁺[X] + R'MgX → R₄R'Sb

Just as in the related organobismuth compounds (same group 15), organoantimony(V) compounds form onium compounds and ate complexes.

Pentaphenylantimony decomposes at 200 °C to triphenylstibine and biphenyl. It forms a trigonal bipyramidal molecular geometry. In the related Me₅Sb all methyl protons are equivalent at -100 °C in proton NMR. Compounds of the type R₄SbX tend to form dimers.

Organoantimony(III) chemistry

Compounds of the type R₃Sb (stibines) can be accessed by reaction of antimony trichloride with organolithium compounds or Grignards.

SbCl₃ + 3 RLi (or RMgCl) → R₃Sb

Typical reactions are:

R₃Sb + Br₂ → R₃SbBr₂

R₃Sb + O₂ → R₃SbO

R₃Sb + Na + NH₃ → R₂SbNa

R₃Sb + B₂H₆ → R₃Sb·BH₃

Stibanes are weak Lewis acids and therefore ate complexes are not encountered. On the other hand, they have good donor properties and are therefore widely used in coordination chemistry. R₃Sb compounds are more air-sensitive than the R₅Sb counterparts.

Antimony Metallocenes are known as well:

14SbI₃ + 3 (Cp*Al)₄ → [2Cp*Sb]⁺[AlI₄]⁻ + 8Sb + 6 AlI₃

The Cp*-Sb-Cp* angle is 154°.

The cyclic compound stibole, a structural analog of pyrrole, has not been isolated, but substituted derivatives known as stiboles are known.

Organoantimony(II) chemistry

Distibines have a Sb-Sb single bond and are of some interest as thermochromic materials. For example, tetramethyldistibine is a colorless as a gas, yellow as a liquid, red as solid just below the melting point of 18.5 °C and again yellow well below the melting point.

See also

• Chemical bonds of carbon with other elements in the periodic table:

CH He CLi CBe CB CC CN CO CF Ne CNa CMg CAl CSi CP CS CCl CAr CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn Fr CRa Rf Db CSg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo ↓ CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr Chemical bonds to carbon Core organic chemistry Many uses in chemistry Academic research, but no widespread use Bond unknown