Synthesis and properties of sigma-bonded organolanthanide and organoactinide compounds

New organolanthanide and organoactinide complexes containing sigma bonds have been synthesized and characterized. The actinide complexes consist of two uranium derivatives, mono- and bis[tris(pentahaptocyclopentadienyl)uranium]ferrocene (I and II). II is the first example of a complex containing two Cp₃U-moieties sigma-bonded to the same ligand (ferrocene here). Also, I and II are the only examples of organoactinide or organolanthanide compounds that are sigma-bonded to a ligand which is an organometallic moiety. Infrared data of I and II are consistent with their formulation as compounds containing sigma bonds. Other spectroscopic data for these compounds indicate that there is a noticeable degree of covalency in the sigma bond. Magnetic data indicate that there are increased intramolecular interactions which are absent when the uranium is sigma-bonded to an R group which is an organic moiety. New organolanthanide complexes of the type Cp₂Ln-R (Cp = pentahaptocyclopentadienyl) have been prepared. The erbium, holmium and gadolinium derivatives represent the first examples of metal-carbon sigma bonds for these elements. The R group is either methyl (Ln = Gd, Er, Yb), phenyl (Ln = Gd, Er, Yb), phenylacetylide (Ln = Gd, Ho, Er, Yb), or allyl (Ln = Sm, Ho, Er). A bis alkynyl derivative, CpHo-(C[triple bar]CPh)₂ was also prepared. Infrared data reported for these compounds are consistent with the assignment of the R group as being sigma-bonded for all cases except one. Visible spectroscopy and magnetic studies indicate that there is at least some degree of covalent interaction in the sigma bond. The allyl complexes were found to be pi-bonded rather than sigma-bonded, indicating that the other complexes are coordinatively unsaturated. That this is so is further indicated by evidence that the allyl complexes will form adducts with THF in solution