Organotitanium compound

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Organotitanium compounds

Organotitanium compounds in organometallic chemistry contain carbon to titanium chemical bonds. Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis and reactions. They are reagents in organic chemistry[1][2]

Contents

[edit] Brief history

Although the first attempt at an organotitanium compound dates back to 1861, it took until 1953 for the first such compound to arrive. In that year titanium phenyl-tri(isopropoxide) was prepared by Herman and Nelson from titanium isopropoxide, phenyllithium and titanium(IV) chloride. Titanocene dichloride was invented in 1954 and the first methyltitanium compounds were introduced in 1959. Ziegler-Natta catalysts as a major commercial application soon followed for which the Nobel Prize in Chemistry of 1963 was awarded.

[edit] Properties

The titanium electron configuration ([Ar]3d24s2) resembles that of carbon and like carbon the +4 oxidation state dominates and like carbon compounds, those of titanium have a tetrahedral molecular geometry. Their bond lengths are much longer than that of C-C bond, with a recorded 210 picometer for the Ti-C bond in tetrabenzyltitanium. Simple tetraalkyltitanium compounds are monomers in solutions and in the gas-phase while their tetra-alkoxy counterparts can be tetrameric.

Due to its low electronegativity, Ti-C bonds are very polarized towards carbon and in many titanium compounds the carbon atom behaves as a carbanion. Organotitanium compounds are lewis acids with vacant coordination sites which can be occupied by forming octahedral complexes with bidentate ligands such as bipy.

[edit] Chemistry

Organotitanium compounds are important reagents in organic chemistry.

  • Another methylenation reagent combination is the carbenoid Lombardo's reagent or Dibromomethane-Zinc-Titanium(IV) Chloride (1982),[4] for example applied in a conversion of a ketene into an allene:[5]
Lombardo reagent reaction
Petasis Reagent
  • Tebbe's reagent reacts with simple alkenes to titanocyclobutanes which can be regarded as stable olefin metathesis intermediates.[6] These compounds are reagents in itself such as 1,1-bis(cyclopentadienyl)-3,3-dimethyltitanocyclobutane, the adduct of Tebbe's reagent with isobutene catalysed with 4-dimethylaminopyridine.
  • The Kulinkovich reaction is a cyclopropanation method starting from a Grignard reagent and an ester. The first step is transmetallation forming a dialkyltitanium intermediate.

[edit] See also

CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl Ar
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr Kr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI Xe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Uub Uut Uuq Uup Uuh Uus Uuo
↓
La CCe Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Ac Th Pa CU Np Pu Am Cm Bk Cf Es Fm Md No Lr


Chemical bonds to carbon
Core organic chemistry many uses in chemistry.
Academic research, but no widespread use Bond unknown / not assessed.

[edit] References

  1. ^ Encyclopedia of Reagents for Organic Synthesis, L.A. Paquette, Ed.: J. Wiley and Sons: Sussex, England, 1996
  2. ^ Organotitanium Reagents in Organic Synthesis (Reactivity and Structure Concepts in Organic Chemistry, Vol 24) Manfred T. Reetz 1986 ISBN 0-387-15784-0
  3. ^ Organic Syntheses, Coll. Vol. 8, p.495 (1993); Vol. 67, p.180 (1989) Link.
  4. ^ Organic Syntheses, Coll. Vol. 8, p.386 (1993); Vol. 65, p.81 (1987) Link.
  5. ^ Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes Stephen P Marsden and Pascal C Ducept Beilstein Journal of Organic Chemistry 2005, 1:5 doi:10.1186/1860-5397-1-5
  6. ^ Titanium metallacarbene-metallacyclobutane reactions: stepwise metathesis T. R. Howard, J. B. Lee, and R. H. Grubbs J. Am. Chem. Soc.; 1980; 102(22) pp 6876 - 6878; doi:10.1021/ja00542a050