Synthesis and Studies on the Reactivities of Dicyclopentadienylytterbium Derivatives Containing Carbazolate and Pyrazolate Ligands

Two ytterbocene derivatives containing aromatic nitrogen ligands, (C 5 H 5 ) 2 YbCbz(THF) ( 1 ) and (C 5 H 5 ) 2 YbPzMe 2 (THF) ( 4 ), were synthesized, and their reactivities toward N, N ‘-diisopropylcarbodiimide, phenyl isothiocyanate, and phenyl isocyanate were studied. Abstraction of cyclopentadienyl from (C 5 H 5 ) 3 Yb with 1 equiv of carbazole (HCbz) in THF at room temperature gives 1 . Reaction of 1 with N, N ‘-diisopropylcarbodiimide ( i PrN C N i Pr) results in monoinsertion of i PrN C N i Pr into the Yb−N(Carbazolate) bond, yielding the ytterbocene guanidinate (C 5 H 5 ) 2 Yb[ i PrN C(Cbz) N i Pr] ( 2 ), while treatment of 1 with 1 equiv of phenyl isothiocyanate (PhNCS) gives the unexpected monocyclopentadienylytterbium complex (C 5 H 5 )Yb[S C(Cbz) NPh] 2 (THF) ( 3 ) and (C 5 H 5 ) 3 Yb(THF), which may be rationalized by the ligand rearrangement of the monoinsertion product (C 5 H 5 ) 2 Yb[S C(Cbz) NPh]. (C 5 H 5 ) 3 Yb reacts with 3,5-dimethylpyrazole (HPzMe 2 ) in a 1:1 ratio at ambient temperature to form complex 4 . Reaction of 4 with PhNCO gives the insertion product (C 5 H 5 ) 2 Yb[OC( NPh)PzMe 2 ](THF) ( 5 ). In contrast to 1, however, complex 4 does not react with i PrNCN i Pr under the same conditions. All these complexes were characterized by elemental analysis and spectroscopic properties. The structures of complexes 2 − 5 were also determined by X-ray single-crystal diffraction analyses. These reactions present the first example of 1,3-heterocumulene insertions into the Ln−N(aromatic ring) bond and provide a new strategy for introducing a substituent at the nitrogen atom of organic heterocycle compounds.