SYNTHESES OF CYCLIC IMINE COMPLEXES OF THE CHIRAL RHENIUM LEWIS-ACID [(ETA(5)-C5H5)RE(NO)(PPH3)]+ BY HYDRIDE ION ABSTRACTION FROM AMIDO COMPLEXES

Reactions of.(eta5-C5H5)Re(NO)(PPh3)(OTf) and the cyclic amines HHCH2C H2CH2(CH2)n-4 give adducts [(eta5-C5H5)Re(NO)(PPh3)(HNCH2CH2Ch2(CH2)n- 4)]+ TfO- (3a-e + TfO-; n = a, 3; b, 4; c, 5; d, 6; e, 7) in 98-88% yi elds. Reactions of 3a-e+ TfO- and (t)BuO- K+ give the labile amido com plexes (eta5-C5H5)Re(NO)(PPh3) (NCH2CH2CH2(CH2)n-4) (4a-e), which are characterized in situ at -20-degrees-C. Subsequent reactions of 4b-e w ith Ph3C+ PF6-, and metatheses with NH4+ PF6-, give the cyclic imine c omplexes (eta5-C5H5)Re(NO)(PPh3)(eta1-N=CHCH2CH2(CH2)n-4)]+ PF6- (5b-e + PF6-). However, 5d,e+ PF6- are difficult or impossible to separate f rom byproducts (up to 30%). In order to circumvent these and other com plications, 3a-e+ TfO- and NH4+ PF6- are first allowed to react to giv e 3a-e' PF6- (94-76%). Additions of (t)BuO- K+ and then Ph3C+ PF6- giv e, under carefully optimized conditions, 5b-e+ PF6- of > 98% purities. All attempts to prepare the three-membered cyclic imine complex 5a+ P F6-, and phenyl-substituted analogs, are unsuccessful. The IR and NMR properties of the preceding compounds are analyzed in detail.