Synthesis and reactions of the rhenium fulvene complexes [Re(η6-C5Me4CH2)(CO)2(C6F4R)] (R = F or CF3): products derived from initial C–F activation

Abstract

The UV irradiation of [Re(η 5 -C 5 Me 5 )(CO) 3 ] in the presence of C 6 F 6 effected intermolecular C᎐F and intramolecular C-H activation generating [Re(η 6 -C 5 Me 4 CH 2 )(CO) 2 (C 6 F 5 )] 1a in two isomeric forms. In the major isomer the CH 2 group lies trans to the C 6 F 5 group both in solution and in the crystal. In the minor isomer the CH 2 lies cis to the C 6 F 5 group. A similar reaction with C 6 F 5 CF 3 generates [Re(η 6 -C 5 Me 4 CH 2 )(CO) 2 (C 6 F 4 CF 3 )] 1b in four isomeric forms. In the major form the CF 3 group is in the 4 position and the CH 2 group lies trans to the C 6 F 4 CF 3 group. The other three isomers are formed by rotation of the η 6 -C 5 Me 4 CH 2 ligand as above, by placing the CF 3 at the 3 position, and by a combination of the two. Complex 1a reacted with PMe 3 to form the zwitterionic complex [Re(η 5 -C 5 Me 4 CH 2 PMe 3 )(CO) 2 (C 6 F 5 )] and with MeO Ϫ to form the anion [Re(η 5 -C 5 Me 4 CH 2 OMe)(CO) 2 (C 6 F 5 )] Ϫ , isolable as the NEt 4 ϩ salt. The reaction of 1a with HX (X = Cl or Br) generated cis-[Re(η 5 -C 5 Me 5 )(CO) 2 (C 6 F 5 )X] initially. More prolonged reaction led to the trans isomers. On reaction with HI, only the trans isomer was formed. Reaction of 1a with HBF 4 in Et 2 O in the presence of MeCN led to formation of the salt [Re(ηThe halogens Cl 2 , Br 2 and I 2 reacted to form (halogenomethyl)tetramethylcyclopentadienyl complexes trans-[Re(η 5 -C 5 Me 4 CH 2 X)(CO) 2 (C 6 F 5 )X] (X = Cl, Br or I). The bromo complex has been characterized crystallographically.

Photochemical CCl bond activation of trichloroarenes by the rhenium complex (η5-C5Me5)Re(CO)3. X-ray structure of trans-(η5-C5Me5)Re(CO)2(2-methoxy-4,5-dichlorophenyl)chloride

“…1) confirms the geometry of the isomer and adds to the list of determined structures of related cyclopentadienyl complexes containing the aryl-Re-halogen moiety. These include trans -(h 5 -C 5 Me 5 )Re(CO) 2 (2,3,4,5-C 6 HCl 5 )Cl [3], trans -(h 5 -C 5 Me 5 )Re(CO) 2 (C 6 H 5 )I [15], trans -(h 5 -C 5 Me 4 CH 2 Br)Re(CO) 2 (C 6 F 5 )Br [16] and trans -(h 5 -C 5 H 5 )Re(CO) 2 (C 6 HF 4 )Br [17]. Selected bond lengths and angles are presented in Table 1.…”

Zwitterionic Organometallates

“…[24] The γ-charge separation in allyl-type configurations is not greatly stabilized, as has previously been emphasized for the η 2 -allylphosphonium ferrate complexes 19, [30] but many related complexes have been isolated (Scheme 5). Scheme 5 The principle of the above reaction (cleavage of a metal-CH 2 bond by a phosphane) can be applied to the preparation of zwitterionic phosphonium rhenate complexes, [31] e.g. 20 (Scheme 6), where the link between the charges contains a cyclopentadienyl ligand as in [ -Cr(CO) 3 {η 5 -C 5 H 4 (CH 2 P ϩ Et 3 )}] [32] or in the bimetallic complex [Fe{η 5 -…”

Conversion of Carbon–Fluorine Bonds α to Transition Metal Centers to Carbon–Hydrogen, Carbon–Carbon, and Carbon–Heteroatom Bonds

“…B-F, Si-F, or H-F bonds, [21,93] bonds between early transition metals or actinides and fluorine, [94] or ionic metal fluorides. [8,[95][96] Aromatics can be readily activated by oxidative addition of the C-F bond via an η 2 -arene intermediate [8,47,[49][50][51][52][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111] or by addition/elimination using metal nucleophiles. [8,51,[112][113] Likewise, some fluorinated alkenes have yielded to C-F bond activation.…”