A New Heteroatom Coordination Promoted Homolysis of the Yb−N Bond. Synthesis and Structural Characterization of a New Class of Ytterbium(II) and Ytterbium(III) Complexes with Amido and Indenyl Ligands and Catalytic Activities of Ytterbium(II) Complexes

Reaction of Me 2 Si(Me 2 NCH 2 CH 2 C 9 H 6 )Cl with 1 equiv of t -BuNHLi yielded Me 2 Si(Me 2 NCH 2 CH 2 C 9 H 6 )( t -BuNH) ( 1 ). Treatment of Me 2 NCH 2 CH 2 C 9 H 7 with 1 equiv of n -BuLi, followed by reaction with an excess of Me 3 SiCl, produced Me 2 NCH 2 CH 2 C 9 H 6 SiMe 3 ( 2 ) in 79% yield. Interaction of YbCl 3 with 3 equiv of (Me 3 Si) 2 NLi in THF, after workup, produced the tetracoordinate ytterbium(III) amide [(Me 3 Si) 2 N] 3 Yb III ( μ -Cl)Li(THF) 3 ( 3 ) in 85% yield. Treatment of 3 with 2 equiv of 1 gave the ytterbium(II) complex [ η 5: η 1 -Me 2 Si(Me 2 NCH 2 CH 2 C 9 H 5 )( t -BuNH)] 2 Yb II ( 4 ) in 58% yield via a reductive reaction. To get some insight into the reaction, several reactions were initiated to study the effects of the t -BuNH group, silyl group, and N, N -dimethylaminoethyl group of the indene compounds, effects of coordinate ClLi(THF) 3 in 3, and temperature effect on the reductive reaction. Treatment of 3 with 2 equiv of 2 afforded ( η 5: η 1 -Me 2 NCH 2 CH 2 C 9 H 5 SiMe 3 ) 2 Yb II ( 5 ) in 52% yield. Interaction of 3 with 2 equiv of Me 2 NCH 2 CH 2 C 9 H 7 produced a ytterbium(II) complex ( η 5: η 1 -Me 2 NCH 2 CH 2 C 9 H 6 ) 2 Yb II ( 6 ) in 63% yield. Treatment of the ytterbium(III) complex [(Me 3 Si) 2 N] 3 Yb III with 2 equiv of Me 2 NCH 2 CH 2 C 9 H 7 also afforded the ytterbium(II) complex ( η 5: η 1 -Me 2 NCH 2 CH 2 C 9 H 6 ) 2 Yb II ( 6 ) in 62% yield, which provides an alternate method for the preparation of 6 . Treatment of 3 with 2 equiv of indene(C 9 H 8 ) produced the ytterbium(III) complex ( η 5 -C 9 H 7 ) 2 Yb III N(SiMe 3 ) 2 ( 7 ). Treatment of 3 with 1 equiv of 1,2-bis(indenyl)ethane also produced the ytterbium(III) complex meso -[ethylenebis( η 5 -indenyl)ytterbium III bis(trimethylsily)amide ((EBI)Yb III N(SiMe 3 ) 2 ) ( 8 ). All the compounds were fully characterized by spectroscopic methods and elemental analyses. Complexes 3, 4, 5, 6, and 8 were additionally characterized by a single-crystal X-ray diffraction study. The formation pathway for the ytterbium(II) complexes is proposed. The study showed that ytterbuim(II) complexes 4, 5, and 6 can function as single-component MMA polymerization catalysts with good activity.