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). 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-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) 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.

Synthesis and reactivity of η5-tetramethylcyclopentadienyl-propenyl rhenium complexes: Molecular structure of [(η5:η2-C5Me4CH2CHCH2)Re(CO)2]

“…The IR data was identical to those reported for this compound by Schmidt et al [17]. Complex 3, showed two CO absorption bands at 2014 and 1924 cm À1 , almost identical to those reported for the related pentamethyl and tetramethylcyclopentadienyl functionalized tricarbonyl complexes [11]. The 1 H NMR spectrum of 3 shows two singlets at about 2 ppm, attributed to methyl groups of the cyclopentadienyl ligand, and a signal at d 3.17 assigned to the methylenic protons.…”

“…These anionic species were not isolated due to their extreme air sensitivity, and they were characterized only by IR spectroscopy. Two absorption m(CO) bands were observed at 1875 and 1728 cm À1 , comparable to those reported for analogous rhenium anions [11,15]. Further reaction of [(g 5 -C 5 Me 4 CH 2 CH@CH 2 )Re(CO) 2 (R)] À with HCl at 0°C gave the hydride complexes [trans-(g 5 -C 5 Me 4 CH 2 CH@CH 2 )Re(CO) 2 (R)(H)] (2a-b) (Scheme 1).…”

“…Both IR and NMR parameters are similar to those found in the analogous iodo and fluoroaryl rhenium complexes [trans-(g 5 -C 5 Me 4 CH 2 L)Re(CO) 2 (R)(H)] (L@CH 2 CH@CH 2 , PPh 2 ; R@I, C 6 F 5 ) [11,12].…”

“…The 13 C NMR showed, in addition to the carbons of the C 5 Me 4 fragment, two singlets at d: 116.0 and 137.0 attributed to alkenyl group, and a singlet for the CO groups at d 198.2. Identical values were found for [(g 5 -C 5 Me 4 CH 2 CH 2 CH@CH 2 )Re(CO) 3 ] [11]. The mass spectrum of 3 exhibits a typical fragmentation pattern for rhenium complexes: 432…”

“…We also have reported that, the fulvene complexes [(g 6 -C 5 Me 4-CH 2 )Re(CO) 2 (R)] (R@I, C 6 F 5 ) react with allylmagnesium chloride, 2-thienyllithium and potassium diphenylphosphide to yield the anionic species [(g 5 -C 5 Me 4 CH 2 L)Re(R)(CO) 2 ] À (L@CH 2 CH@CH 2 ; 2-C 4 H 3 S; PPh 2 ). Protonation with HCl afforded the trans hydride complexes, which under thermolysis conditions (hexane solution under an N 2 atmosphere at 40°C) yielded the compounds [(g 5 :g x -C 5 Me 4 CH 2 L)Re(CO) 2 ] (x = 2 and 1, respectively) [11,12].…”