The addition of small molecules to (η-C 5H 5) 2Rh 2(CO)(CF 3C 2CF 3)—IX. CH bond activation in the reactions with dienes, polyenes and arenes; the crystal and molecular structure of [(η-C 5H 5) 2Rh 2{C(CF 3)C(CF 3)H}] 2(C 6H 4)

Abstract

The sunlight assisted reactions of (η-C 5H 5) 2Rh 2(CO)(CF 3C 2CF 3) with acyclic dienes (1,3-butadiene, allene and 1-methyl-1,2-butadiene) and cyclic polyenes (1,5-cyclooctadiene, norbornadiene, 1,4- and 1,3-cyclohexadiene, cyclopentadiene, methylcyclopentadiene, cycloheptatriene and cyclooctatetraene) result in facile CH bond activation and the formation of (η-C 5H 5) 2Rh 2{C(CF 3)C(CF 3)H}(polyene-H). Often, two or more structural isomers of the product are identified. In some instances, a subsequent reaction with more (η-C 5H 5) 2Rh 2(CO)(CF 3C 2CF 3) gives [(η-C 5H 5) 2Rh 2{C(CF 3) C(CF 3)H}] 2(polyene-2H). With arenes (benzene, chlorobenzene, toluene and dichlorobenzenes), the activation of two CH bonds occurs simultaneously to give [(η-C 5H 5]2 Rh 2{C(CF 3)C(CF 3)H}] 2(arene-2H). The structure of [(η-C 5H 5) 2Rh 2{C(CF 3)C(CF 3)H}] 2 (C 6H 4), which is derived from the reaction with benzene, was confirmed by single crystal X-ray diffraction studies. It is monoclinic, space group P2 1/ c with a = 16.958(6), b = 9.119(5), c = 24.74(1) Å and β = 118.57(4)°. The structure was solved by direct methods and refined by least-squares to the R value of 0.037 for 3870 observed reflections. The σ-bonded rhodium atoms adopt meta positions and are coplanar with the ring carbons. One π-bonded rhodium is above and the other below the plane of the ring. The π-electron density in the ring is essentially localized.