Yttrium Complexes of a Phenanthrene-Fused Cyclopentadienyl: Synthetic, Structural, and Reactivity Studies

The tris-alkyl complex Y(CH2SiMe3)3(THF)2 reacts with 1,2,3-trimethyl-1H-cyclopenta[l]phenanthrene (PCp*H) to give (PCp*)Y(CH2SiMe3)2(THF) (1), characterized structurally by X-ray crystallography. VT NMR spectra of 1 reveal a dynamic equilibrium between the THF-free and mono(THF) solvate in solution. Complex 1 undergoes substitution of THF by 2,2′-bipyridine (bipy) to give (PCp*)Y(CH2SiMe3)2(bipy) (2); the latter complex does not undergo ligand exchange in solution. Insertion reactions of 1 with CO2, Me3SiNCO, and Me2CHNCNCHMe2 afford (PCp*)Y[κ2-(O,O)-O2C(CH2SiMe3)]2 (3), (PCp*)Y[κ2-(N,O)-(Me3Si)NC(CH2SiMe3)O]2 (4), and (PCp*)Y[κ2-(N,N)-(Me2CH)NC(CH2SiMe3)N(CHMe2)]2 (5). Reaction of 1 with 2 equiv of Me3SiCCH affords a terminal bis(acetylide) (PCp*)Y(CCSiMe3)2(THF) (6) in solution; however, X-ray analysis of crystals obtained from a solution of 6 shows that it dimerizes to {[(PCp*)Y(CCSiMe3)(THF)]2(μ-CCSiMe3)2} (7). A toluene solution of complex 1 and 1 equiv of [Ph3C]+[B(C6F5)4]− shows modest catalytic activity for the polymerization of ethylene at room temperature (20 kg mol−1 h−1bar−1).