Anhydrous Monomeric Glyoxal: Pyrolytic Generation and Stabilization by the Chiral Rhenium Fragment [(.eta.5-C5H5)Re(NO)(PPh3)]+ Academic Article uri icon

abstract

  • Reaction of [η5-C5H5)Re(NO)(PPh3)(ClCH2Cl)]+BF4− (5+BF4−) and a CH3OH/H2O glyoxal solution gives the π complex [(η5-C5H5)Re(NO)(PPh3)(η2-O=CHCH=O)]+BF4− (1+BF4−) in 17 % yield as a 95:5 mixture of RS,SR/RR,SS diastereomers. The trimeric dihydrate of glyoxal and P2O5 are pyrolyzed under vacuum at 160 °C. Pure anhydrous monomeric glyoxal can be trapped at −80 °C, as assayed by 1H and 13C NMR. Subsequent reaction with 5+BF4− gives 1+BF4− (33%; 95:5 RS,SR/RR,SS). The NMR and IR properties of 1+BF4− are studied in detail, especially with regard to the free and bound O=CH moieties. A 1H NOE experiment suggests that an s-cis O=C‒C=O conformer dominates in solution. The crystal structure of (RS,SR) 1+BF4− also shows an s-cis conformer, with free/bound O=C bond lengths of 1.206(7)/1.331(5) Å. Reaction of 1+BF4− and NaI in CH3CN gives 1+I− (75%), which when placed in CH3OH gives (η5-C5H5)Re(NO)(PPh3)(I) (69%). Reaction of 1+BF4− and CD3CN at 80 °C gives [(η5-C5H5)Re(NO)(PPh3)(NCCD3)]+BF4−. However, in none of these substitutions is free glyoxal detected. Well-defined additions to the glyoxal ligand could not be effected. © 1994, American Chemical Society. All rights reserved.

author list (cited authors)

  • Wang, Y., Arif, A. M., & Gladysz, J. A.

citation count

  • 5

publication date

  • June 1994