My watch list
my.chemeurope.com  
Login  

Organozirconium chemistry



  Organozirconium compounds are organometallic compounds containing a carbon to zirconium chemical bond. Organozirconium chemistry is the corresponding science exploring properties, structure and reactivity of these compounds [1]. In general organozirconium compounds are stable and non-toxic. They are used organic chemistry as an intermediate in the synthesis of chemical compounds and share characteristics with organotitanium compounds also a Group 4 element.

The first ever organozirconium compound discovered (1954), zirconocene dichloride [2], belongs to the metallocene family. It was prepared in a reaction of the sodium salt of cyclopentadiene with Zirconium(IV) chloride. Zirconocenes are used as polymerization catalysts such as Kaminsky catalysts, partly replacing organotitanium compounds.

The so-called Schwartz's reagent (1974) is a zirconocene hydrochloride and a reagent in hydrometalation reactions (called hydrozirconation) with wide use in organic chemistry.

Additional recommended knowledge

Contents

Hydrozirconation

Substrates for hydrozirconation are alkenes and alkynes. With terminal alkynes the terminal vinyl zirconium product is predominantly formed. Secondary reactions are nucleophilic additions, transmetalations [3], conjugate additions [4], coupling reactions, carbonylation and halogenation.

History

The development of zirconium hydrides obviously preceded that of hydrozirconation. The first such hydride,Cp2ZrH2, was developed in 1966 by M.G.H. Wallbridge in a reaction of (Cp)2Zr(BH4)2 with triethylamine in benzene as an uneventful insoluble solid [5]. In 1970 H. Weigold and P.C. Wailes prepared the hydrochloride from the dichloride (Cp2Cl2) and Lithium aluminium hydride (or the related LiAlH(t-BuO)3) [6]. They went on to investigate the reaction of these novel hydrides with carboxylic acids [7] (for example to compounds like CpZr(OCOR)3) and in 1971 then arrived at their reactions with alkynes. [8].

For example, with one equivalent of Cp2ZrClH they obtained from diphenylacetylene the corresponding alkenylzirconium as a mixture of cis and trans isomer. With two equivalents of hydride the endproduct was a mixture of erythro and threo zircono alkanes:

In 1974 Donald W. Hart and Jeffrey Schwartz realized how these compounds could be used in organic synthesis by reacting the organozirconium intermediates with electrophiles such as hydrochloric acid, bromine and acid chlorides to the corresponding alkane, bromoalkanes and ketones [9]:

The corresponding organoboron and organoaluminum compounds were already known but these are air-sensitive and/or pyrophoric whereas organozirconium compounds are not.

Scope

In one study the usual regioselectivity of an alkyne hydrozirconation is reversed with the addition of zinc chloride [10] [11]

One example of a one-pot hydrozirconation - carbonylation - coupling is depicted below [12] [13]:

With certain allyl alcohols, the alcohol group is replaced by nucleophilic carbon forming a cyclopropane ring[14]

See also

  • Other chemistries 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 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 Ce 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.


References

  1. ^ ORGANOZIRCONIUM CHEMISTRY ARRIVES A. MAUREEN ROUHI Chemical & Engineering News April 19, 2004 Volume 82, Number 16 pp. 36-39 Article
  2. ^ Bis-cyclopentadienyl Compounds of Ti, Zr, V, Nb and Ta G. Wilkinson and J. M. Birmingham J. Am. Chem. Soc. pp 4281 - 4284; 1954doi:10.1021/ja01646a008
  3. ^ Organic Syntheses, Coll. Vol. 9, p.143 (1998); Vol. 74, p.205 (1997).Abstract
  4. ^ Organic Syntheses, Coll. Vol. 9, p.640 (1998); Vol. 71, p.83 (1993). Article
  5. ^ Reactions of Lewis bases with tetrahydroborate derivatives of the Group IVa elements. Preparation of new zirconium hydride species Bruce D. James, R. K. Nanda, Malcolm G. H. Walbridge Inorg. Chem.; 1967; 6(11); 1979-1983. doi:10.1021/ic50057a009
  6. ^ Hydrido complexes of zirconium I. Preparation Journal of Organometallic Chemistry, Volume 24, Issue 2, September 1970, Pages 405-411 P. C. Wailes and H. Weigold doi:10.1016/S0022-328X(00)80281-8
  7. ^ Hydrido complexes of zirconium II. Reactions of dicyclopentadienylzirconium dihydride with carboxylic acids Journal of Organometallic Chemistry, Volume 24, Issue 2, September 1970, Pages 413-417 P. C. Wailes and H. Weigold doi:10.1016/S0022-328X(00)80282-X
  8. ^ Hydrido complexes of zirconium: III. Reactions with acetylenes to give alkenylzirconium derivatives Journal of Organometallic Chemistry, Volume 27, Issue 3, 16 March 1971, Pages 373-378 P.C. Wailes, H. Weigold and A.P. Bell doi:10.1016/S0022-328X(00)82168-3
  9. ^ Hydrozirconation. Organic synthesis via organozirconium intermediates. Synthesis and rearrangement of alkylzirconium(IV) complexes and their reaction with electrophiles Donald W. Hart, Jeffrey Schwartz J. Am. Chem. Soc.; 1974; 96(26); 8115-8116. doi:10.1021/ja00833a047
  10. ^ Directed Hydrozirconation of Propargylic Alcohols Donghui Zhang and Joseph M. Ready J. Am. Chem. Soc., 129 (40), 12088 -12089, 2007. doi:10.1021/ja075215o
  11. ^ The electrophile in this reaction is iodine. The additive is believed to promote kinetic reaction control.
  12. ^ Palladium-catalyzed coupling reaction of acylzirconocene chlorides with hypervalent iodonium salts: synthesis of aryl-substituted ketones Suk-Ku Kang and Seok-Keun Yoon J. Chem. Soc., Perkin Trans. 1, 2002, 459 - 461, doi:10.1039/b110983a
  13. ^ Reagents: phenylacetylene, Schwartz's reagent, tetraphenylpalladium and the periodinane diphenyliodoniumtetrafluoroborate (phenyl group donor)
  14. ^ A one-pot access to cyclopropanes from allylic ethers via hydrozirconation–deoxygenative ring formation Vincent Gandon, Jan Szymoniak, Chem. Commun., 2002, (12),1308-1309 doi:10.1039/b203762a 10.1039/b203762a
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Organozirconium_chemistry". A list of authors is available in Wikipedia.
Your browser is not current. Microsoft Internet Explorer 6.0 does not support some functions on Chemie.DE