Ein Katalysator für die Tandem-Ringöffnungsmetathesepolymerisation/Vinylinsertionspolymerisation

Tandem vinyl insertion-/ring-opening metathesis copolymerization with ansa-6-[2-(dimesitylboryl)-phenyl]pyrid-2-ylamido zirconium complexes: role of trialkylaluminum and MAO

Activation of Zr-bisalkyl complexes containing the η⁵-tetramethylcyclopentadienyl-6-[2-(dimesitylboryl)phenyl]pyrid-2-ylamido motif with MAO offers access to poly(ethylene)-co-poly(norbornene) with ROMP-derived sequences.

Group 4 metal complexes bearing the aminoborane motif: origin of tandem ring-opening metathesis/vinyl-insertion polymerization

The origin of tandem ring-opening metathesis/vinyl-insertion polymerization using tailored group 4 metal complexes is outlined.

Access to Ultra-High-Molecular Weight Poly(ethylene) and Activity Boost in the Presence of Cyclopentene With Group 4 Bis-Amido Complexes

Zr^IV complexes of the type [Me₂ Si{(NR)(6-{2-(diethylboryl)phenyl}pyridyl-2-yl-N)}ZrCl₂ ⋅thf] (R=tBu (4), adamantyl (7 a); thf=tetrahydrofuran), [Me₂ Si{(NAd)(6-{2-(diphenylboryl)phenyl}pyridyl-2-yl-N)}ZrCl₂ ] (Ad=adamantyl (7 b)), the nonbridged half-titanocene complexes of the type [(N-{6-(2-diethylborylphenyl)pyrid-2-yl}-NR)Cp'TiCl₂ ] (R=Me, Cp'=C₅ H₅ (12), Cp'=C₅ Me₅ (13)), and the titanium(IV)-based metallocene-type complex [bis{N-(6-{2-(diethylboryl)phenyl}pyrid-2-yl)NMe}TiCl₂ ] (14) have been synthesized. The structures of complexes 7 b, 12, and 13 were determined by single-crystal X-ray diffraction analysis. In solution, complex 4 slowly rearranges to [Me₂ Si{(N-tBu)(6-{2-(diethylboryl)phenyl}pyridyl-2-yl-N)}₂ Zr] (4 a), the structure of which was unambiguously confirmed by single-crystal X-ray crystallography. Similarly, reaction of HfCl₄ with Me₂ Si({RNLi}{6-[2-(diethylboryl)phenyl]pyridyl-2-ylNLi}) yielded the corresponding Hf^IV complexes [Me₂ Si{(NR)(6-{2-(diethylboryl)phenyl}pyridyl-2-ylN)}₂ Hf] (R=tBu (8) and Ad (9)). Upon activation of these complexes with methylalumoxane (MAO), complexes 4, 7 a, 7 b, and 12-14 showed activities up to 750 kg of polyethylene (PE)/mol_cat.  bar h in the homopolymerization of ethylene (E), producing mainly linear PE (high-density PE, HDPE) with molecular weights in the range of 1 800 000<M_n <4×10⁶  g mol^-1 . In the copolymerization of E with cyclopentene (CPE), the polymerization activities of complexes 4, 7 a, and 7 b can be enhanced by a factor of 140 up to 7500 kg PE/mol_cat.  bar h, which produced PE-co-poly(CPE) containing 3.5 mol % of CPE. This dramatic increase in polymerization activity for E in the presence of CPE can be attributed to an involvement of CPE in the polymerization process rather than to solvent polarity.

Group 4 dimethylsilylenebisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif: synthesis and use in tandem ring-opening metathesis/vinyl-insertion copolymerization of cyclic olefins with ethylene

Two novel Zr(IV)- and Hf(IV)-based bisamido complexes bearing the 6-[2-(diethylboryl)phenyl]pyrid-2-yl motif, that is, [ZrCl(2){Me(2)Si(DbppN)(2)}(thf)] (9) and [HfCl(2){Me(2)Si(DbppN)(2)}(thf)(2)] (10) (DbppN=6-[2-(diethylboryl)phenyl]pyridine-2-amido) have been prepared. Their reactivities have been compared with that of a model precatalyst that does not bear the aminoborane motif. Upon activation with methylalumoxane, precatalysts 9 and 10 are active in the homopolymerization of ethylene (E) yielding high-density polyethylene (HDPE). In the copolymerization of E with cyclopentene (CPE), for example by the action of 9, the presence of CPE resulted in a dramatic increase in the polymerization activity of E, while CPE incorporation remained close to or at zero. In the vinyl-insertion copolymerization of norborn-2-ene (NBE) with E by the action of 9, statistical cyclic olefin copolymers of these two monomers were obtained. At higher NBE concentrations, however, 9 gave rise to reversible ring-opening metathesis (ROMP)/vinyl-insertion polymerization (VIP) of NBE with E, resulting in the formation of multi-block copolymers of the general formula poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E). This particular feature of precatalyst 9, that is, the ability to induce a reversible α-H elimination/α-H addition reaction, is attributed to the unique role of the 6-[2-(diethylboryl)phenyl]pyrid-2-yl ligand. Accordingly, a model precatalyst lacking this ligand does not have the ability to induce α-H elimination/α-H addition reactions. The different (11)B NMR shifts of various diethylborylphenylpyrid-2-ylamines and -amides permit a ranking of the strengths of the B-N bonds in these compounds. This strength of the B-N bond is correlated with the propensity of 9/MAO to produce poly(NBE)(ROMP)-co-poly(NBE)(VIP)-co-poly(E) at different temperatures.