Supersize Cp! Tetrabenzo[a,c,g,i]fluorenyl complexes of yttrium

Abstract

The synthesis of tetrabenzo[a,c,g,i]fluorenyl (Tbf) yttrium dialkyl complexes, (Tbf)Y(CH2SiMe3)2(L) (L = tetrahydrofuran (THF), 1; L = bipy, 2), by direct protonolysis of the tris(alkyl) complex, Y(CH2SiMe3)3(THF)2, are reported. The X-ray crystal structures of 1 and 2 display the helical twisting typically observed for the Tbf ligand. Dynamic nuclear magnetic resonance (NMR) studies on 1 show a barrier to Tbf helical inversion (epimerization or “wagging”) of 38.1 ± 0.5 kJ mol−1. The reaction of 1 with acidic hydrocarbons such as 1,3-bis(trimethylsilyl)cyclopentadiene or trimethylsilylacetylene results in protonolysis to form the mixed Cp derivative [(Tbf){C5H3(SiMe3)2}Y(CH2SiMe3)(THF)] (3) or [(Tbf)Y(CCSiMe3)2(THF)]n (4), respectively. In the case of 4, a small amount of the trinuclear cluster (Tbf)Y3(μ3-CCSiMe3)2(μ2-CCSiMe3)3(CCSiMe3)3(THF)2 (5) was isolated and characterized by X-ray crystallography. Dialkyl 1 undergoes smooth insertion of trimethylsilyl isocyanate to afford [(Tbf)Y{κ2-(N,O)-Me3SiN(Me3SiCH2)CO}2(THF)] (6) but it does not react with alkenes. Treating 1 with [Ph3C]+[B(C6F5)4]− in bromobenzene generates a moderately active ethylene polymerization catalyst (36 kg mol−1 h−1 bar−1).

Experimental methods in chemical engineering: Preface

“…Most of the subjects are related to hydrodynamic modellingprocess simulation, computational fluid dynamics (CFD), finite elements-but it also has fluid bed reactors and bioreactors, which are closely related to the other two clusters. [24][25][26] Fluidized bed reactors (red cluster) have a heavier modelling component compared to fixed bed reactors (blue cluster). These two experimental techniques are close in proximity in the bibliometric map, which confirms that they are related.…”

Cerium Fluorenyl Complexes Including CC Coupling Reactions

“…Our recent studies on fluorenyl-supported tetramethylaluminate complexes also emphasized the particular stability of half-sandwich complexes of the larger rare-earth metals . On the other hand, sterically demanding fluorenyl ligands also stabilize half-sandwich derivatives of the smaller rare-earth metals as shown for, for example, (Flu R )­Ln­(CH 2 SiMe 3 ) 2 (THF) (Ln = Sc, Y, and Lu) and (Tbf)­Y­(CH 2 SiMe 3 ) 2 (THF) (Tbf = tetrabenzo­[a,c,g,i]­fluorenyl) …”

“…7 On the other hand, sterically demanding fluorenyl ligands also stabilize half-sandwich derivatives of the smaller rare-earth metals as shown for, for example, (Flu R )Ln-(CH 2 SiMe 3 ) 2 (THF) (Ln = Sc, Y, and Lu) 8 and (Tbf)Y-(CH 2 SiMe 3 ) 2 (THF) (Tbf = tetrabenzo[a,c,g,i]fluorenyl). 9 To this day, neither tris(fluorenyl) rare-earth metal complexes nor any cerium-fluorenyl derivatives have been fully characterized. Since cerium provides ready access to the oxidation state +IV, we were tempted to investigate into the redox chemistry of cerium-fluorenyl complexes.…”

Benz[e]indenyl and benz[f]indenyl molybdenum compounds: evidence of the η3-coordination mode

“…34 A similar behavior was observed for yttrium complexes. 35 Contributions of Thiel et al on various dibenzo[c,g]fluorenyl compounds have proven a partial loss of aromaticity in the angularly annulated fluorenyl ligands that finally led to revision of the concept of aromaticity in metallocene compounds with extended psystems. [36][37][38][39] The aim of this study is to synthesize new benz[e]indenyl (e-Bind) and benz[f]indenyl (f-Bind) compounds capable of Z 5 -Z 3 rearrangement.…”