Organopalladium

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Organopalladium chemistry is a branch of organometallic chemistry that deals with organic palladium compounds and their reactions. Palladium is often used as a catalyst in the reduction of alkenes and alkynes with hydrogen. This process involves the formation of a palladium-carbon covalent bond. Palladium is also prominent in carbon-carbon coupling reactions, as demonstrated in tandem reactions [1].

Organopalladium chemistry timeline.

Overview

In contrast to its next-door neighbors the group 11 elements, the element palladium in organic chemistry does not involve preparation of organopalladium compounds itself but rather organopalladium reactive intermediates [3]. On top of that in many reactions only catalytical amounts of the metal are used.

Pd Alkene complexes

Palladium reacts with alkenes to form a pi complex which can react with a multitude of nucleophiles akin a oxymercuration reaction. The C-Pd bond is then removed by a reduction or an elimination. In the industrially important Wacker process, ethylene is converted to acetaldehyde with palladium chloride.


Pd Allyl complexes

Allyl compunds with suitable leaving groups react with palladium(II) salts to pi-allyl complexes having hapticity 3 such as the Allylpalladium chloride dimer. These intermediates too react with nucleophiles for example carbanions derived from malonates [4]


Allylpalladium intermediates also feature in the Trost asymmetric allylic alkylation and the Carroll rearrangement and an oxo variation in the Saegusa oxidation.

Pd insertion compounds

Zerovalent Pd(0) compounds such as tris(dibenzylideneacetone)dipalladium(0) and tetrakis(triphenylphosphine)palladium(0) react with halocarbon R-X in oxidative addition to R-Pd-X intermediates with covalent Pd-C bonds. This chemistry forms the basis of a large class of organic reactions called coupling reactions. Palladium(II) trifluoroacetate has been demonstrated to be effective in aromatic decarboxylation [5]:

Aromatic decarboxylation by Palladium(II) trifluoroacetate

In the proposed reaction mechanism Pd(II) replaces the carboxylic acid proton while losing a TFA group, carbon dioxide is lost in a first order reaction and TFA destroys the formed Ar-Pd-TFA complex without Pd changing its oxidation state.

See also

  • Compounds 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. Handbook of Organopalladium Chemistry for Organic Synthesis Ei-Negishi John Wiley (2002) ISBN 0471315060
  2. Phillips, F. C.; Am. Chem. J. 1894, 16, 255.
  3. F.A. Carey R.J. Sundberg Advanced Organic Chemistry 2nd Ed. ISBN 0306411997
  4. Organic Syntheses, Coll. Vol. 8, p.5 (1993); Vol. 69, p.38 (1990). Link
  5. Development of a Catalytic Aromatic Decarboxylation Reaction Joshua S. Dickstein, Carol A. Mulrooney, Erin M. O'Brien, Barbara J. Morgan, and Marisa C. Kozlowski Org. Lett.; 2007; 9(13) pp 2441 - 2444; (Letter) doi:10.1021/ol070749f



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