Synthesis and Reactivity of Chiral Rhenium Alcohol Complexes of the Formula [(η⁵‐C₅H₅)Re(NO)(PPh₃)(ROH)]⊕BF₄⊖

Reactions of dichloromethane complex [(η 5 ‐C 5 H 5 )Re(NO)‐(PPh 3 )(ClCH 2 Cl)]⊕ BF 4 ⊖ ( 2 ⊕ BF 4 ⊖ and alcohols ROH give the title compounds [(η 5 ‐C 5 H 5 )Re(NO)‐(PPh 3 )(ROH)]⊕ BF 4 ⊖; ( 3 ⊕ BF 4 ⊖; a : R = Me, b : Et, c : CH 2 Ph, d : t ‐Bu) in 91–95% yields as air‐stable powders after workup. Reactions of 3a – c ⊕ BF 4 ⊖ and Et 3 N produce alkoxide complexes (η 5 ‐C 5 H 5 )Re(NO)‐(PPh 3 )(OR) ( 4a – c , 80–90%), which in turn react with HBF 4 – OEt 2 to give 3a – c ⊕ BF 4 ⊖. Reactions of 3a – c ⊕ BF 4 ⊖ and Ph 3 PX⊕ Br⊖ give the bromide complex (η 5 ‐C 5 H 5 )Re(NO)‐(PPh 3 )(Br) (85‐98%) and alcohols ROH. 3b,c ⊕ BF 4 ⊖ and aldehydes react to give π complexes [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(η 2 ‐OCHR′)]⊕ BF 4 ⊖ (>94%). Reaction of 3b ⊕ BF 4 ⊖ and HSi(OEt) 3 generates the hydride complex (η 5 ‐C 5 H 5 )Re(O)(PPh 3 )(H) ( 5 , 77%). Reaction of 5 with Ph 3 C⊕ PF 6 ⊖ and then ROH gives 3 ⊕ PF 6 ⊖ (88–91%). NMR experiments establish the order OCHR > ROH > ROR for ligand binding energies to the rhenium fragment [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )]⊕.