Syntheses and Reactivity of Functionalized (η⁵-Tetramethylcyclopentadienyl) Rhenium Complexes:  Molecular Structures of (η⁵:η²-C₅Me₄CH₂CH₂CHCH₂)Re(CO)₂and (η⁵-C₅Me₄CH₂-2-C₄H₃S)Re(CO)₂(PMe₃)

Abstract

The fulvene complexes (η 6 -C 5 Me 4 CH 2 )Re(CO) 2 R ( 1, R = C 6 F 5; 2, R = I) react at the exocyclic methylene carbon with allylmagnesium chloride or 2-thienyllithium to yield the anionic species [(η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 R] - (L = −CH 2 CH CH 2, −2-C 4 H 3 S). Further reaction with CH 3 I at room temperature affords the methyl complexes (η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (R)(Me) ( 3, R = C 6 F 5; 4, R = I). Protonation of the anionic species with HCl at low temperature gives the hydride complexes trans- (η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (R)(H) ( 5, R = C 6 F 5; 6, R = I). Thermolysis of hexane solutions of 6, under CO atmosphere, produces the tricarbonyl complexes (η 5 -C 5 Me 4 CH 2 L)Re(CO) 3 ( 7 ) in moderate yields; if the reaction is carried out in the presence of PMe 3, the analogous dicarbonyl phosphine derivatives (η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (PMe 3 ) ( 9 ) are obtained, but no coordination of the lateral functionality is observed. In clear contrast, thermolysis of hexane solutions of the pentafluorophenyl hydride complexes trans- (η 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (C 6 F 5 )(H), even under CO atmosphere, yields the chelated complexes (η 5:η x -C 5 Me 4 CH 2 L)Re(CO) 2 ( 8a, L = −CH 2 CH CH 2, x = 2; 8b, L = −2-C 4 H 3 S, x = 1). However, prolonged thermal treatment of 8b under a CO atmosphere affords the corresponding tricarbonyl complex 7b . The molecular structures of 8a and 9b have been determined. Both molecules exhibit formal three-legged piano-stool structures, with three terminal ligands in 9b (two CO and one PMe 3 ), but in the case of 8a, in addition to the two CO's, the third position corresponds to the η 2 -coordination of the butenyl substituent of the η 5 -C 5 Me 4 ring. Attempts to displace the coordinated sidearm in complex 8a have been investigated, as well as the photochemical reactions of tricarbonyl complexes 7 .