C–H Bond Activation and Isoprene Polymerization by Rare-Earth-Metal Tetramethylaluminate Complexes Bearing Formamidinato N‑Ancillary Ligands
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https://figshare.com/articles/dataset/C_H_Bond_Activation_and_Isoprene_Polymerization_by_Rare_Earth_Metal_Tetramethylaluminate_Complexes_Bearing_Formamidinato_N_Ancillary_Ligands/2436292
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The bimetallic formamidinate complexes Ln(Form)(AlMe4)2 (Ln = Y, Form (ArNCHNAr) = EtForm (Ar = 2,6-Et2C6H3), MesForm (Ar = 2,4,6-Me3C6H2), DippForm (Ar = 2,6-iPr2C6H3), tBuForm
(Ar = 2-tBuC6H4); Ln = La,
Form = DippForm, tBuForm) were obtained in high yield
by protonolysis reactions between formamidines (FormH) and homoleptic
rare-earth-metal tetramethylaluminates Ln(AlMe4)3. Y(Form)(AlMe4)2 (Form = EtForm, DippForm)
were also prepared by treatment of Y(Form)[N(SiHMe2)2]2(thf) with trimethylaluminum after the former
were prepared by the protonolysis of Y[N(SiHMe2)2]3(thf)2 complexes with EtFormH or DippFormH.
The monomeric six-coordinate complexes Ln(Form)(AlMe4)2 (Ln = Y, Form = EtForm, MesForm, DippForm, tBuForm; Ln = La, Form = DippForm, tBuForm) show
similar molecular structures with distorted-octahedral geometry and
bidentate (N,N′) Form and AlMe4 ligands. The complex
[La(EtFormAlMe3)(AlMe4)2](C7H8)1.5 from a protonolysis reaction between
La(AlMe4)3 and EtFormH has the EtForm ligand
adopting a configuration in which one nitrogen and one aryl substituent
are coordinated to the eight-coordinate lanthanum center in an η1(N):η6(arene) manner. From the reaction of
La(AlMe4)3 with MesFormH, C–H bond activation
of an o-methyl group of the mesityl moiety occurred,
yielding [La{η1(N):η6(Ar)-Me2CH2FormAlMe3}(AlMe3)(AlMe4)][La(Me2CH2FormAlMe3)(AlMe3)(AlMe4)](C6H14)1.5 (Me2CH2Form = MesForm-H(o-Me)), in which two linkage isomers
of Me2CH2Form were observed. Investigations
were carried out on the compounds [Ln(Form)(AlMe4)2] (Ln = Y, La; Form = EtForm, DippForm) as precatalysts activated
by [Ph3C][B(C6F5)4] or
[PhNMe2H][B(C6F5)4] in
isoprene polymerization. While the lanthanum complexes showed narrower
molecular weight distributions (PDI < 1.2), a stereodirecting role
was evidenced for the cocatalysts (trityl borate, maximum 87% trans-1,4-selectivity;
anilinium borate, maximum 82% cis-1,4-selectivity).
创建时间：
2016-02-19
