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Reactions of Diazo Compounds and Chiral Rhenium Alkylidene Complexes of the Formula [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(CHR)] + PF − 6 A Versatile and Highly Stereoselective Route to Alkene Complexes
Author(s) -
Wang Van,
Gladysz John A.
Publication year - 1995
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19951280303
Subject(s) - chemistry , diastereomer , rhenium , stereochemistry , ligand (biochemistry) , diazo , conformational isomerism , alkane stereochemistry , osmium , walden inversion , cyclopentadienyl complex , medicinal chemistry , molecule , crystal structure , crystallography , ruthenium , catalysis , biochemistry , receptor , organic chemistry , inorganic chemistry
The methylidene complex [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(CH 2 )] + PF − 6or the ReCD 2 analog react with diazo compounds N 2 CHR [R H, Si(CH 3 ) 3 , COPh, CO 2 C 2 H 5 ] in CH 2 Cl 2 at −80°C to give alkene complexes [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(η 2 ‐H 2 CCHR)] + PF − 6or D 2 CCHR analogs. The two ReC geometric isomers of benzylidene complex [(η 5 ‐C 5 H 5 )Re‐(NO)(PPh 3 )(CHPh)] + PF − 6and CH 2 N 2 react to give opposite configurational diastereomers of styrene complex [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(η 2 ‐H 2 CCHPh)] + 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 ReC face opposite to the bulky PPh 3 ligand, (b) an antiperiplanar disposition of the ReC and CN 2 bonds in the transition state, utilizing the diazo carbon face that minimizes interactions of the substitutent (R) and cyclopentadienyl ligand, and (c) N 2 loss from the resulting intermediate [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(CHR′CHRN 2 )] + PF − 6via a conformer with antiperiplanar PReCHR′C and ReCHR′CHRN linkages, with anchimeric assistance of the rhenium fragment d orbital HOMO from the backside.