Photochemical reactions of [Re(?5-C5R5)(CO)3] (R = H or Me) with partially fluorinated benzenes: C-H and C-F activation

Godoy, F; Klahn A.H.; Oelckers, B; Higgitt C.L.; Perutz R.N.; Parsons, S


UV Irradiation of [Re(?5-C5R5)(CO)3] (R = Me or H) in the presence of C6F5H or 1,2,4,5-C6F4H2 effected intramolecular C-H activation, generating the hydrido complexes trans-[Re(?5-C5R5)(CO)2(Ar) FH] [(Ar)F = C6F5 or 2,3,5,6-C6F4H] as the principal photochemical products. The identities of the hydrido complexes were confirmed by independent thermal syntheses. The photoreaction of [Re(?5-C5Me5)(CO)3] with C6F5H also generated the fulvene complex [Re(?6-C5Me4CH2)(CO) 2(C6F5)] 2a and two bis(aryl) derivatives: cis-[Re(?5-C5Me5)(CO)2(C 6F5)2] 3a and [Re(?5-C5Me5)(CO)2(C 6F5)(2,3,5,6-C6F4H)] 4a in low yield. Complex 2a results from an intramolecular C-H activation, while 3a and 4a derive from a C-H and a C-F activation of a second molecule of pentafluorobenzene, respectively. The origin of the minor products was elucidated by showing that UV irradiation of [Re(?5-C5Me5)(CO)2-(C 6F5)H] in C6F5H produces 2a, 3a and 4a, while photolysis of 2a produces only 3a. The reaction of [Re(?5-C5Me5)-(CO)3] with 1,2,4,5-C6F4H2 gave analogues 2b and 4b as minor products. The photoreaction of [Re(?5-C5H5)(CO)3] in C6F5H or 1,2,4,5-C6F4H2 generated bis(aryl) compounds and the unusual binuclear complexes [Re2(?5-C5H5)(?-? 1:?5-C5H4)(CO) 4(Ar)F] as the minor products. The binuclear complex with (Ar)F = 2,3,5,6-C6F4H has been characterized by X-ray crystallography. The Re-Re bond [3.0258(7) Å] is close to collinear with the Re-C (aryl) bond. One {Re(CO)2} unit is twisted by about 73.0° with respect to the other.

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Título de la Revista: Journal of the Chemical Society - Dalton Transactions
Número: 12
Editorial: Society of Laparoendoscopic Surgeons
Fecha de publicación: 1999
Página de inicio: 2039
Página final: 2047