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

Abstract

AbstractReactions of dichloromethane complex [(η5‐C5H5)Re(NO)‐(PPh3)(ClCH2Cl)]⊕ BF4⊖ (2⊕ BF4⊖ and alcohols ROH give the title compounds [(η5‐C5H5)Re(NO)‐(PPh3)(ROH)]⊕ BF4⊖; (3⊕ BF4⊖; a: R = Me, b: Et, c: CH2Ph, d: t‐Bu) in 91–95% yields as air‐stable powders after workup. Reactions of 3a–c⊕ BF4⊖ and Et3N produce alkoxide complexes (η5‐C5H5)Re(NO)‐(PPh3)(OR) (4a–c, 80–90%), which in turn react with HBF4– OEt2 to give 3a–c⊕ BF4⊖. Reactions of 3a–c⊕ BF4⊖ and Ph3PX⊕ Br⊖ give the bromide complex (η5‐C5H5)Re(NO)‐(PPh3)(Br) (85‐98%) and alcohols ROH. 3b,c⊕ BF4⊖ and aldehydes react to give π complexes [(η5‐C5H5)Re(NO)(PPh3)(η2‐OCHR′)]⊕ BF4⊖ (>94%). Reaction of 3b⊕ BF4⊖ and HSi(OEt)3 generates the hydride complex (η5‐C5H5)Re(O)(PPh3)(H) (5, 77%). Reaction of 5 with Ph3C⊕ PF6⊖ and then ROH gives 3⊕ PF6⊖ (88–91%). NMR experiments establish the order OCHR > ROH > ROR for ligand binding energies to the rhenium fragment [(η5‐C5H5)Re(NO)(PPh3)]⊕.