The C-H polyaddition of dimethoxyarenes such as 1,4-dimethoxybenzene and 4,4'-dimethoxybiphenyl to unconjugated dienes such as norbornadiene and 1,4-divinylbenzene has been achieved for the first time by using cationic half-sandwich rare earth alkyl catalysts. This protocol afforded novel polymer materials consisting of dimethoxyarene moieties and nonpolar hydrocarbon structure motifs (cyclic, linear, and aromatic) in perfectly alternating sequences that are otherwise difficult to make. The reaction proceeded via C═C double bond insertion into a C-H bond ortho to each of the two methoxy groups in a step-growth polymerization fashion.
A convenient synthetic route has
been developed for preparing the
novel rigid 4,5-(PR2)2–2,7,9,9-tetramethylacridane-based
pincer ligands (acri‑RPNP; R =
i
Pr and Ph), and the first rare-earth (Ln = Y, Lu) alkyl complexes
bearing the acri‑RPNP ligands were synthesized by
a salt metathesis reaction (for the isopropyl-substituent acri‑iPrPNP complexes, 1-Ln) or direct alkylation
(for the phenyl-substituent acri‑PhPNP complexes, 2-Ln). For both 1-Ln and 2-Ln, the
NMR spectroscopy and X-ray diffraction study confirmed the successful
coordination of the acri‑RPNP ligand to the central
metal ion in a tridentate manner via the two phosphine and the nitrogen
donors. In contrast to 1-Ln that are solvent-free complexes,
the metal centers in 2-Ln are each coordinated with one
tetrahydrofuran molecule. Upon activation by [Ph3C][B(C6F5)4], 1-Y and 2-Lu could catalyze the living polymerization of isoprene and β-myrcene
with high catalytic activity and high cis-1,4-selectivity
(up to 92.3% for isoprene and 98.5% for β-myrcene). Moreover,
the 1-Y/[Ph3C][B(C6F5)4] catalytic system also could promote the polymerization
of butadiene and its copolymerization with isoprene to produce copolymers
with high cis-1,4-selectivity and narrow polydispersity.
In situ two-dimensional NMR and fluorescence emission spectroscopy were employed to investigate the cooperative structure-direction effect of organic amine such as morpholine in the synthesis of aluminophosphate molecular sieves in ionic liquids. In situ rotating frame nuclear Overhauser effect spectra (ROESY) together with fluorescence measurements demonstrate that the aggregates between imidazolium cations and morpholines through intermolecular hydrogen bonds can be formed in the gel during the crystallization of molecular sieves. Combining with the characterizations of the solid products by solid-state NMR, it is verified that different aggregates of organic amines with imidazolium cations, which is similar to self-assembled supramolecular analogues, could act as the structure-directing agents for selective tuning of the framework topologies such as AEL, AFI and LTA in the final solid products.
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