ABSORPTION-SPECTROSCOPY OF (IND)NI(PPH(3))X (IND EQUALS INDENYL, 1-ME-INDENYL X=CL, BR, ME) AND M(IND)(2) (M=NI, RU IND EQUALS INDENYL)

The electronic structures of two types of transition metal indenyl com plexes have been studied. The first type, a series of (Ind)Ni(PPh(3))X compounds (Ind = indenyl, 1-Me-indenyl; X = Ci, Br, Me) was investiga ted by absorption spectroscopy and Extended Huckel Molecular Orbital c alculations. The energy differences between calculated levels are in g ood agrement with experimental band positions. For example, the lowest energy singlet-singlet band maximum for (Ind)Ni(PPh(3))Cl is at 19 50 0 cm(-1) and the calculated HOMO-LUMO difference is 19 817 cm(-1). For X = Me, the calculated energy difference increases to 21 930 cm(-1) a nd the corresponding absorption band is at 22 500 cm(-1). The influenc e of the metal-ligand interactions on the molecular orbitals is discus sed. The second category of indenyls, the bis(indenyl) compounds of Ni and Ru, show absorption spectra that are markedly different from thos e of nickelocene and ruthenocene. For example, in comparison to nickel ocene, the first absorption band of Ni(Ind)(2) is 5700 cm(-1) higher i n energy and is more intense by two orders of magnitude; in contrast, the first absorption maximum of Ru(Ind)(2) is 6600 cm(-1) lower in ene rgy than observed for ruthenocene. The characteristics and relaxation dynamics of the lowest energy excited states are discussed.