Photodissociation of lanthanide metal cation complexes with cyclooctatetraene

Abstract

Lanthanide metal (Sm, Dy, Nd) cation complexes with 1,3,5,7-cyclooctatetraene (COT) are produced by laser vaporization in a pulsed nozzle cluster source. The clusters are mass-selected and photodissociated using the third harmonic of a Nd:YAG laser (355 nm). Samarium–COT complexes prefer to form [Sm n (COT) n ] + stoichiometries and fragment extensively when more than one metal atom is present in the cluster. However, the fragmentation patterns indicate the possible presence of multiple decker sandwich structures. Dysprosium–COT and neodymium–COT complexes prefer [M n (COT) n+1 ] + ratios, probably due to their preference for the +3 oxidation state. This stoichiometry pattern indicates that these clusters produce sandwich and multiple decker sandwich structures. Throughout the spectra for Dy and Nd complexes, a commonly occurring fragment is [M(C 5H 5)] +. Fragmentation of the COT ligand occurs either because of a strong interaction with the metal or because of photochemical decomposition. Presuming that C 5H 5 exists as the cyclopentadienyl anion, the Dy and Nd metals in these fragments exist in an unusual +2 oxidation state.