SYNTHESES OF ORGANOLANTHANUM AND ORGANOCERIUM CATIONS AND LABILE PRECURSORS

The lanthanide-iodide compounds Cp”2Ln(I)(NCMe)2 (Ln = La, Ce; Cp” = 1,3-C5H3(SiMe3)2) serve as useful precursors for complexes containing the early-lanthanide fragments [Cpʺ2LnIII]+. This moiety has been incorporated into compounds in which it binds either neutral or anionic ligands. Among these is the heterobimetallic compound [Cp”2Ce(µ-η2-OC)W(CO)(Cp)(µ-η2-CO)]2 (3), which is unusual in that the cerium(III) center is wholly nonemissive. This observation is explained on the basis of cerium-to-tungsten excited-state energy transfer, since dissolution in polar solvent (acetonitrile) leads to symmetrically solvated ions, loss of close Ce-W contact, and cerium(III) luminescence. Also, the cationic organolanthanide fragments have been seen to bind tetrafluoroborate anion, exhibiting an interesting trend in ligand lability; thus, in Cp”2Ln(NCMe)2(FBF3) (4), the nitrile ligands are more labile in THF solution than is the tetrafluoroborate ligand. Finally, the ionic compounds [Cp”2Ln(NCMe)(DME)][BPh4]·0.5DME (5) have been prepared and the lanthanum analogue (5b) has been structurally characterized. © 1990, American Chemical Society. All rights reserved.