SYNTHESIS, STRUCTURE, AND REACTIVITY OF CHIRAL RHENIUM IMINE AND METHYLENEAMIDO COMPLEXES OF THE FORMULAS [(ETA-5-C5H5)RE(NO)(PPH3)(ETA-1-N(R'')=C(R)R']+TFO- AND (ETA-5-C5H5)RE(NO)(PPH3)(N=C(R)R')
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Three syntheses of -imine complexes [(5-C5H5)Re(NO)(PPh3)(1-N(R)C(R)R)]+TfO (2) have been developed. Reactions of (5-C5H5)Re(NO)(PPh3)(OTf) (1) and R(R)CNR (R/R/R = Ph/Ph/H (a), Me/Ph/H (b), H/Ph/Me (c); 25110 C) give2ac (7988%). Reactions of [(5-C5H5)Re(NO)(PPh3)(NH3)]+TfO with n-BuLi and then R(R)CO give 2dh (R/R/R = Me/Me/H (d), Me/Et/H (e), (CH2)5/H (f), H/Ph/H (g), H/CHCHMe/H (h; after TfOH addition); 5687%). Reactions of [(5-C5H5)Re(NO)(PPh3)(NCR)]+TfO with R and then TfOH give 2b,i,j (R/R/R = p-tol/p-tol/H (i), H/Me/H (j); 7898%). Reaction of (+)-(S)-l (98% ee) and c gives (+)-(S)-2c (98% ee; retention). Complexes 2b,c,e,g,h,j are obtained as (9081):(1019), 95:5, 68:32, >99:<1, >99:<1, and >99:<1 mixtures of E/Z NC geometric isomers, which do not readily interconvert. Crystallization gives pure (E)-2b,c. Crystal structures of 2a and (E)-2c show identical NC bond lengths (1.272(5)1.275(5) ) but opposite ReN conformations. Methyleneamido complexes (5-C5H5)Re(NO)(PPh3)(NC(R)R) are isolated from reactions of 2a,b and t-BuOK+ (R/R = Ph/Ph, Me/Ph; 7677%) or [(5-C6H5)Re(NO)(PPh3)(NCR)]+TfC and R (R/R = Me/Ph, p-tol/p-tol (8); 5561%). These undergo facile exchange of E/Z NC substituents (8, G(181.4 K) = 8.9 kcal/mol) and N-methylation. 1993, American Chemical Society. All rights reserved.
