Syntheses and structural analyses of chiral rhenium containing amines of the formula (η 5-C 5H 5)Re(NO)(PPh 3)((CH 2) nNRR′) ( n = 0, 1)

Abstract

The reaction of the racemic chiral methyl complex (η 5-C 5H 5)Re(NO)(PPh 3)(CH 3) ( 1) with CF 3SO 3H and then NH 2CH 2C 6H 5 gives [(η 5-C 5H 5)Re(NO)(PPh 3)(NH 2CH 2C 6H 5)] + CF 3 SO 3 - ([ 4a-H] + CF 3 SO 3 - ; 73%), and deprotonation with t-BuOK affords the amido complex (η 5-C 5H 5)Re(NO)(PPh 3)(NHCH 2C 6H 5) (76%). Reactions of 1 with Ph 3C + X − and then primary or secondary amines give [(η 5-C 5H 5)Re(NO)(PPh 3)(CH 2NHRR′)] + X − ([ 6-H] + X −; R/R′/X = a, H/NH 2CH 2C 6H 5/BF 4; a′, H/NH 2CH 2C 6H 5/PF 6; b, H/NH 2CH 2(CH 2) 2CH 3/PF 6; c, H/( S)-NH 2CH(CH 3)C 6H 5/BF 4); d, CH 2CH 3/CH 2CH 3/PF 6; e, CH 2(CH 2) 2CH 3/CH 2(CH 2) 2CH 3/PF 6; f, CH 2C 6H 5/CH 2C 6H 5/PF 6; g, -CH 2(CH 2) 2CH 2-/PF 6; h, –CH 2(CH 2) 3CH 2–/PF 6; i, CH 3/CH 2CH 2OH/PF 6 (62–99%). Deprotonations with t-BuOK afford the amines (η 5-C 5H 5)Re(NO)(PPh 3)(CH 2NRR′) ( 6a– i; 99–40%), which are more stable and isolated in analytically pure form when R ≠ H. Enantiopure 1 is used to prepare ( R Re S C)-[ 6c-H] + BF 4 - , ( R Re S C)- 6c, ( S)-[ 6g-H] + PF 6 - , and ( S)- 6g. The crystal structures of [ 4a-H] + CF 3 SO 3 - , a previously prepared NH 2CH 2Si(CH 3) 3 analog, [ 6a′, d, f, h-H] + PF 6 - , ( R Re S C)- 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.