π-Olefin—iridium-komplexe XXIV photoreaktionen von [CpM(C 2H 4) 2](M = Rh, Ir) mit Alkinen — Fundgrube für neue π-Komplexe

Abstract

UV irradiation of [CpRh(C 2H 4) 2] in pentane in the presence of alkynes C 2R 2 [R = Me ( a); Et ( b)] gives a variety of products, and several compounds have been isolated by chromatography. The η 4-benzene complexes [CpRhC 6R 6] ( 2a,b) and the rhodacyclopentadienyl species [Cp 2Rh 2C 4R 4] ( 3a,b) were obtained as main products. The isolable but highly reactive complexes [CpRh(C 2H 4)(C 2R 2)] ( 1a,b) act as precursors for 3 and for hexaalkylbenzene, and by hydrolysis during chromatography also give the 1-rhoda-2-oxa-cyclohexa-3,5-diene compounds [Cp 2Rh 2C 4R 4O]( 6a,b). Further isolated products are the bis( μ-vinyl) compound [Cp 2Rh 2(C 2H 3)(C 2HMe 2)] ( 4a) as well as the η 4-butadiene species [CpRh{C 4HR 4-C 5H 4Rh(C 2H 4) 2}] ( 5a) the formation of which involves the unusual C-H activation of a Cp moiety. From the reaction mixture formed by UV irradiation of [CpIr(C 2H 4) 2] in hexane only the μ-vinyl species [Cp 2Ir 2(C 2H 3) 2] ( 7) was isolated, while irradiation in the presence of butyne-2 yielded the η 4-hexamethylbenzene complex [CpIrC 6Me 6] ( 8). The compounds 2b, 3b, 5a, and 8 were characterised by X-ray crystal analysis.