OPTICALLY-ACTIVE TRANSITION-METAL COMPLEXES .4. RHENIUM COMPLEXES WITH THE ENANTIOPURE CYCLOPENTADIENYL LIGAND PCP - X-RAY STRUCTURE OF THE EXO ISOMER OF S-RE-(PCP)RE(NO)(PPH(3))(CH3)

Treatment of a 1:1 mixture of the diastereomers S-Re- and R(Re)-exo-[(eta(5)-PCp)Re(NO)-(PPh(3))(CO)](BF4-)-B-+ (1a,b) (PCp = ''pinene-fused cyclopentadienyl') with sodium methoxide in methanol affords the derivative 'esters' S-Re- and RRe-exo-(eta(5)-PCp)Re(NO)(PPh(3))(COOMe) (2a,b) (S-Re:R(Re) = 1:1). Reation of 2a,b with (+)-(R)-(1-naphthylethyl)amine gives the ''amides'' S-Re - and RRe-exo-(eta(5)-PCp)Re(NO)(PPH3)[CONHCH(CH3)C10H7] (3a,b) S-Re:R(Re)=1:1). 3a,b are separated by recrystallization. 3a is treated with CF3CO2 and NaBF4 to give S-RE-(1a). 1a is theb converted to S-Re-exo-(eta(5)-PCp)Re9NO)PPh(3))(CH3) (4a). Protonolysis of 4a with HBF4/Et(2)O in CD2Cl2 at -78 degrees C results in solvent-stabilized S-Re-exo-[(eta(5)-PCp)Re(NO)(PPh(3))(ClCD2Cl)](BF4-)-B-+ (5a); the thermal and configurational stability of 5a is investigated at various tempertures. An X-ray crystal structure of 4a establishes the absolute configurations of 1a, 3a, and 4a.