Syntheses and structural analyses of chiral rhenium containing amines of the formula (η5-C5H5)Re(NO)(PPh3)((CH2)nNRR′) (n = 0, 1)

The reaction of the racemic chiral methyl complex (η5-C5H5)Re(NO)(PPh3)(CH3) (1) with CF3SO3H and then NH2CH2C6H5 gives [(η5-C5H5)Re(NO)(PPh3)(NH2CH2C6H5)]+ CF 3 SO 3 - ([4a-H]+ CF 3 SO 3 - ; 73%), and deprotonation with t-BuOK affords the amido complex (η5-C5H5)Re(NO)(PPh3)(NHCH2C6H5) (76%). Reactions of 1 with Ph3C+ X− and then primary or secondary amines give [(η5-C5H5)Re(NO)(PPh3)(CH2NHRR′)]+ X− ([6-H]+ X−; R/R′/X = a, H/NH2CH2C6H5/BF4; a′, H/NH2CH2C6H5/PF6; b, H/NH2CH2(CH2)2CH3/PF6; c, H/(S)-NH2CH(CH3)C6H5/BF4); d, CH2CH3/CH2CH3/PF6; e, CH2(CH2)2CH3/CH2(CH2)2CH3/PF6; f, CH2C6H5/CH2C6H5/PF6; g, -CH2(CH2)2CH2-/PF6; h, –CH2(CH2)3CH2–/PF6; i, CH3/CH2CH2OH/PF6 (62–99%). Deprotonations with t-BuOK afford the amines (η5-C5H5)Re(NO)(PPh3)(CH2NRR′) (6a–i; 99–40%), which are more stable and isolated in analytically pure form when R ≠ H. Enantiopure 1 is used to prepare (RReSC)-[6c-H]+ BF 4 - , (RReSC)-6c, (S)-[6g-H]+ PF 6 - , and (S)-6g. The crystal structures of [4a-H]+ CF 3 SO 3 - , a previously prepared NH2CH2Si(CH3)3 analog, [6a′,d,f,h-H]+ PF 6 - , (RReSC)-6c, and 6f are determined and analyzed in detail, particularly with respect to cation/anion hydrogen bonding and conformation. In contrast to analogous rhenium containing phosphines, 6a–i show poor activities in reactions that are catalyzed by organic amines.