Reactions of Diazo Compounds and Chiral Rhenium Alkylidene Complexes of the Formula [(η5‐C5H5)Re(NO)(PPh3)(CHR)]+ PF −6 A Versatile and Highly Stereoselective Route to Alkene Complexes Academic Article uri icon

abstract

  • The methylidene complex [(η5‐C5H5)Re(NO)(PPh3)(CH2)]+ PF −6 or the ReCD2 analog react with diazo compounds N2CHR [R  H, Si(CH3)3, COPh, CO2C2H5] in CH2Cl2 at −80°C to give alkene complexes [(η5‐C5H5)Re(NO)(PPh3)(η2‐H2CCHR)]+ PF −6 or D2CCHR analogs. The two ReC geometric isomers of benzylidene complex [(η5‐C5H5)Re‐(NO)(PPh3)(CHPh)]+ PF −6 and CH2N2 react to give opposite configurational diastereomers of styrene complex [(η5‐C5H5)Re(NO)(PPh3)(η2‐H2CCHPh)]+ PF −6. Stereochemical features of these reactions are analyzed in detail, and are interpreted in terms of models involving (a) attack of the diazo compound upon the ReC face opposite to the bulky PPh3 ligand, (b) an antiperiplanar disposition of the ReC and CN2 bonds in the transition state, utilizing the diazo carbon face that minimizes interactions of the substitutent (R) and cyclopentadienyl ligand, and (c) N2 loss from the resulting intermediate [(η5‐C5H5)Re(NO)(PPh3)(CHR′CHRN2)]+ PF −6 via a conformer with antiperiplanar PReCHR′C and ReCHR′CHRN linkages, with anchimeric assistance of the rhenium fragment d orbital HOMO from the backside. Copyright © 1995 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim

author list (cited authors)

  • Wang, V., & Gladysz, J. A.

citation count

  • 10

publication date

  • March 1995

publisher