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Abstract:
Alkane elimination between Y(CH2SiMe3)3(THF)2 and the diprotio ligands [(3,6-tBu2C13H7)SiR2NHtBu] (R = Me, 1a; R = Ph, 1b) gave [η3:η1-((3,6-tBu2C13H6)SiR2NtBu)Y(CH2SiMe3)(THF)2] (R = Me, 2a; R = Ph, 2b). 2a is thermally stable in toluene solution and shows a dynamic behavior connected to THF dissociation, while 2b is thermally unstable. Reaction of 2a with H2 or PhSiH3 led to the putative hydrido complex “[(3,6-tBu2Flu)SiMe2NtBu)YH(THF)]n” (3). Deprotonation of 1a with 1 and 2 equiv of nBuLi gave [(3,6-tBu2C13H6)SiMe2NHtBu]Li (5) and [(3,6-tBu2C13H6)SiMe2NtBu]Li2 (4), respectively, both of which were characterized crystallographically. Salt elimination reactions between LnCl3(THF)n precursors (Ln = Y, La, Nd) and 1 equiv of 4 gave mixtures of complexes, from which ionic complexes that contain two chelated ligands per lanthanide center, [{η3:η1-(3,6-tBu2C13H6)SiMe2NtBu}2Ln]-[Li(solvent)n]+ (Ln = Y, solvent = THF, n = 4, 6; Ln = La, solvent = THF, n = 4, 7; Ln = La, solvent = Et2O, n = 2, 8; Ln = Nd, solvent = THF, n = 4, 9), were isolated. The neutral dimeric chloro complex [η5:η1-((3,6-tBu2C13H6)SiMe2NtBu)Nd(μ-Cl)(THF)]2 (10) was also crystallized from the crude metathesis product. The solid-state structures of 2a, 8, 9, and 10 show versatile coordination modes of the fluorenyl ligands, either η3 or η5 symmetric, involving carbon atoms of the central Cp ring (8 and 10), or unusual η3 dissymmetric, involving carbon atoms of the central Cp and one adjacent phenyl rings (2a and 9). Some of the complexes obtained were explored as catalysts for ethylene and MMA polymerization.
