PHOTOCHEMICAL-REACTIONS OF CYCLOPENTADIEN YLBIS(ETHENE)RHODIUM WITH PHENANTHRENE, ACENAPHTHYLENE, AND TRIPHENYLENE, AND UNUSUAL H EXCHANGE BETWEEN ETA(2)-COORDINATED PHENANTHRENE OR ACENAPHTHYLENE AND ETA(5)-CYCLOPENTADIENYL LIGANDS

During UV irradiation of [CpRh(C2H4)(2)] (Cp = eta(5)-C5H5) in hexane/ ether in the presence of phenanthrene one ethene ligand is displaced b y coordination of the 9,10 double bond of phenanthrene, and l)(eta(2)- ethene)(eta(2)-9,10-phenanthrene)rhodium (1) is formed. The analogous reaction in hexane in the presence of acenaphthylene occurs with forma tion of the complexes ne)(eta(5)-cyclopentadienyl)(eta(2)-ethene)rhodi um 2 and ,2-acenaphthylene)(eta(5)-cyclopentadienyl)rhodium 3 in which one and two ethene molecules of [CpRh(C2H4)(2)], respectively, are su bstituted by eta(2)-1,2-acenaphthylene. The irradiation of [CpRh(C2H4) (2)] with triphenylene in hexane yields the compounds [CpRh(eta(4)-1,2 ,3,4-triphenylene)] (4), [(CpRh)(2)(mu-eta(3):eta(3)-triphenylene)](5) , and CpRh)(3)(mu(3)-eta(2):eta(2):eta(2)-triphenylene)] (6). Despite the partially very low yields the new complexes could be unequivocally characterized spectroscopically and in the case of 1 and 3 by X-ray s tructural analysis. The compounds 1 and 2 in solution reveal a novel d ynamic behaviour; via an intramolecular C-H activation, exchange occur s between the protons of the eta(2)-coordinated arene and the Cp ligan d. The complex 4 in solution is fluxional, too.