Format

Send to

Choose Destination
See comment in PubMed Commons below
J Am Chem Soc. 2010 Sep 29;132(38):13443-52. doi: 10.1021/ja105239t.

Functionalization of metallabenzenes through nucleophilic aromatic substitution of hydrogen.

Author information

  • 1Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand.

Abstract

The cationic metallabenzenes [Ir(C(5)H(4){SMe-1})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (1) and [Os(C(5)H(4){SMe-1})(CO)(2)(PPh(3))(2)][CF(3)SO(3)] (2) undergo regioselective nucleophilic aromatic substitution of hydrogen at the metallabenzene ring position γ to the metal in a two-step process that first involves treatment with appropriate nucleophiles and then oxidation. Thus, reaction between compound 1 and NaBH(4), MeLi, or NaOEt gives the corresponding neutral iridacyclohexa-1,4-diene complexes Ir(C(5)H(3){SMe-1}{H-3}{Nu-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2) (Nu = H (3), Me (4), OEt (5)). Similarly, reaction between 2 and NaBH(4) or MeLi gives the corresponding osmacyclohexa-1,4-diene complexes Os(C(5)H(3){SMe-1}{H-3}{Nu-3})(CO)(2)(PPh(3))(2) (Nu = H (8), Me (9)). The metallacyclohexa-1,4-diene rings in all these compounds are rearomatized on treatment with the oxidizing agent O(2), CuCl(2), or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Accordingly, the cationic metallabenzene 1 or 2 is returned after reaction between 3 and DDQ/NEt(4)PF(6) or between 8 and DDQ/NaO(3)SCF(3), respectively. The substituted cationic iridabenzene [Ir(C(5)H(3){SMe-1}{Me-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (6) or [Ir(C(5)H(4){SMe-1}{OEt-3})(κ(2)-S(2)CNEt(2))(PPh(3))(2)]PF(6) (7) is produced in a similar manner through reaction between 4 or 5, respectively, and DDQ/NEt(4)PF(6), and the substituted cationic osmabenzene [Os(C(5)H(3){SMe-1}{Me-3})(CO)(2)(PPh(3))(2)]Cl (10) is formed in good yield on treatment of 9 with CuCl(2). The starting cationic iridabenzene 1 is conveniently prepared by treatment of the neutral iridabenzene Ir(C(5)H(4){SMe-1})Cl(2)(PPh(3))(2) with NaS(2)CNEt(2) and NEt(4)PF(6), and the related starting cationic osmabenzene 2 is obtained by treatment of Os(C(5)H(4){S-1})(CO)(PPh(3))(2) with CF(3)SO(3)CH(3) and CO. The stepwise transformations of 1 into 6 or 7 as well as 2 into 10 provide the first examples in metallabenzene chemistry of regioselective nucleophilic aromatic substitutions of hydrogen by external nucleophiles. DFT calculations have been used to rationalize the preferred sites for nucleophilic attack at the metallabenzene rings of 1 and 2. The crystal structures of 1, 3, 6, and 7 have been obtained.

[PubMed]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for American Chemical Society
    Loading ...
    Write to the Help Desk