Synthesis, structure, and reactivity of chiral rhenium imine and methyleneamido complexes of the formulas [(.eta.5-C5H5)Re(NO)(PPh3)(.eta.1-NR'':CRR')]+ TfO- and (.eta.5-C5H5)Re(NO)(PPh3)(N:CRR') Academic Article uri icon

abstract

  • Three syntheses of σ-imine complexes [(η5-C5H5)Re(NO)(PPh3)(η1-N(R″)C(R)R′)]+TfO− (2) have been developed. Reactions of (η5-C5H5)Re(NO)(PPh3)(OTf) (1) and R′(R)CNR″ (R/R′/R″ = Ph/Ph/H (a), Me/Ph/H (b), H/Ph/Me (c); 25–110 °C) give2a−c (79–88%). Reactions of [(η5-C5H5)Re(NO)(PPh3)(NH3)]+TfO− with n-BuLi and then R′(R)CO give 2d−h (R/R′/R″ = Me/Me/H (d), Me/Et/H (e), (−CH2−)5/H (f), H/Ph/H (g), H/CHCHMe/H (h; after TfOH addition); 56–87%). Reactions of [(η5-C5H5)Re(NO)(PPh3)(NCR′)]+TfO− with R− and then TfOH give 2b,i,j (R/R′/R″ = p-tol/p-tol/H (i), H/Me/H (j); 78–98%). Reaction of (+)-(S)-l (98% ee) and c gives (+)-(S)-2c (98% ee; retention). Complexes 2b,c,e,g,h,j are obtained as (90–81):(10–19), 95:5, 68:32, >99:<1, >99:<1, and >99:<1 mixtures of E/Z NC geometric isomers, which do not readily interconvert. Crystallization gives pure (E)-2b,c. Crystal structures of 2a and (E)-2c show identical NC bond lengths (1.272(5)−1.275(5) Å) but opposite ReN conformations. Methyleneamido complexes (η5-C5H5)Re(NO)(PPh3)(N̈C(R)R′) are isolated from reactions of 2a,b and t-BuO−K+ (R/R′ = Ph/Ph, Me/Ph; 76–77%) or [(η5-C6H5)Re(NO)(PPh3)(NCR′)]+TfC− and R− (R/R′ = Me/Ph, p-tol/p-tol (8); 55–61%). These undergo facile exchange of E/Z N̈C substituents (8, ΔG‡(181.4 K) = 8.9 kcal/mol) and N-methylation. © 1993, American Chemical Society. All rights reserved.

author list (cited authors)

  • Knight, D. A., Dewey, M. A., Stark, G. A., Bennett, B. K., Arif, A. M., & Gladysz, J. A.

citation count

  • 27

publication date

  • November 1993