摘要:
Reactions of a mixture of doubly bonded and double-bridged trans/anti and translsyn-(eta(5)-RC5H4)(2)M-2(CO)(2)(mu-SePh)(2) isomers with elemental selenium afford a series of novel doubly bonded and quadruply bridged isomers, trans/anti- (eta(5)-RC5H4)(2)M-2(mu-Se)(2)(mu-SePh)(2) (1a, M=Mo, R=H; 2a, M=Mo, R=MeO2C; 3a, M=Mo, R=EtO2C; 4a, M=W, R=MeO2C; 5a, M=W, R=EtO2C) and trans/syn-(eta(5)- RC5H4)(2)M-2(mu-Se)(2)(mu-SePh)(2) (1b, M=Mo, R=H; 2b, M=Mo, R=MeO2C; 3b, M=Mo, R=EtO2C; 4b, M=W, R=MeO2C; 5b, M=W, R=EtO2C). Such reactions were found to involve configuration inversions of the phenyl groups bonded to selenium atoms from syn to anti or vice versa. Thus, the reaction of single isomer trans/syn-(eta(5)-C5H5)(2)Mo-2(CO)(2)(mu-SePh)(2) with elemental selenium in tetrahydrofuran (THF) or toluene at reflux gave single trans/anti isomer 1a, whereas trans/anti-(eta(5)-EtO2CC5H4)(2)Mo-2(CO)(2)(mu-SePh)(2) reacted with selenium powder under similar conditions gave single trans/syn isomer 3b. Except for isomer 1b (previously prepared by another route), all of the above quadruply bridged isomers have been characterized by elemental analysis, MS, IR and H-1 NMR spectroscopies, as well as partly by C-13 NMR and Se-77 NMR spectroscopies. (C) 1999 Elsevier Science Ltd. All rights reserved.