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We report here the preparation and characterization of new well‐defined silica‐supported Ti imido complexes that present an L‐ligand variation in a structure of currently the most active oxo/imido heterometathesis catalyst (≡SiO)Ti(=NtBu)(Me2Pyr)(py)2 (1s), where py is replaced with stronger electron‐donating 4‐(N,N‐dimethylamino)pyridine (2s) or bidentate 2,2′‐bipyridine (3s). The materials were characterized with elemental and mass balance analyses and IR and solid‐state NMR that confirmed the selective formation of surface Ti species with terminal imido ligand. Evaluation of the catalytic oxo/imido heterometathesis activity of the obtained materials demonstrated that L‐ligands have a pronounced influence on the catalytic performance. In particular, the replacement of pyridine with stronger donating ligands resulted in a significant drop of activity. The catalytic results are discussed in view of the reaction mechanism and implications for further catalyst development. [ABSTRACT FROM AUTHOR]

Continuing our investigation of catalytic oxo/imido heterometathesis as novel water‐free method for C=N bond construction, we report here the application of classical transition metal oxides dispersed on silica (MOx/SiO2, M=V, Mo, W) as cheap, robust and readily available alternative to the catalysts prepared via Surface Organometallic Chemistry (SOMC). The oxide materials demonstrated activity in heterometathetical imidation of ketones, WO3/SiO2 being the most efficient. We also describe a new well‐defined supported W imido complex (≡SiO)W(=NMes)2(Me2Pyr) (Mes=2,4,6‐Me3C6H2, Me2Pyr=2,5‐dimethylpyrrolyl) and characterize it with SOMC protocols, which allowed us to identify the position of W on the oxo/imido heterometathesis activity scale (Mo

We investigate Ti(NEt2)4 supported on silica dehydroxylated at 700 °C as an easily accessible pre-catalyst for oxo/imido heterometathesis reactions. Being activated with TolNH2, the supported Ti amide (≡SiO)Ti(NEt2)3 (1) demonstrates catalytic activity in the imidation of ketones with N-sulfinylamines comparable with the most active previously described well-defined imido catalyst (≡SiO)Ti(＝NtBu)(Me2Pyr)(py)2 (2) (Me2Pyr = 2,5-dimethylpyrrolyl), which implies the in situ formation of surface imido species in this system. The materials obtained via treatment of 1 with anilines (TolNH2 (1a) and p-MeOC6H415NH2 (1b)) were studied with IR, EA and 1H, 13C, 15N and 2D solid-state NMR, although the proposed imido intermediate has not been detected, pointing towards tris-amides (≡SiO)Ti(NHC6H4X)3 (X = Me, OMe) being the major surface species in the isolated materials 1a and 1b. The system 1/TolNH2 was tested in a range of imidation reactions and demonstrated excellent performance for express high-yielding preparation of ketimines, formamidines, lactone imidates and sulfurdiimines, making it a convenient alternative to the well-defined supported Ti imido catalysts. [ABSTRACT FROM AUTHOR]

Binuclear and hexanuclear titanium complexes stabilized by tetradentate [OOOO]4--type ligand were active in ethylene polymerization in the presence of Et2AlCl/Bu2Mg binary co-catalyst, giving high molecular weight polyethylene. The binuclear complex showed significantly higher catalytic activity and thermal stability in comparison to mononuclear analogue. Ultra high molecular weight polyethylene (UHMWPE) samples were processed by a solid-state uniaxial deformation into high-strength (up to 2.5 GPa) and highmodulus (over 100 GPa) oriented film tapes, which indirectly indicates a low degree of entanglements between the macromolecular chains. [ABSTRACT FROM AUTHOR]

Combining Surface Organometallic Chemistry with rigorous olefin purification protocol allows evaluating and comparing the intrinsic activities of Mo and W olefin metathesis catalysts towards different types of olefin substrates. While well‐defined silica‐supported Mo and W imido‐alkylidenes show very similar activities in metathesis of internal olefins, Mo catalysts systematically outperform their W analogs in metathesis of terminal olefins, consistent with the formation of stable unsubstituted W metallacyclobutanes in the presence of ethylene. However, Mo catalysts are more prone to induce olefin isomerization, in particular when ethylene is present, probably because of their propensity to undergo more easily reduction processes. [ABSTRACT FROM AUTHOR]

5‐Coordinated methoxybenzylidene complexes M(=NAr)(=CH−C6H4−o‐OMe)(OtBuF3)2 (Ar=2,6‐iPr2C6H3; tBuF3=CMe2(CF3)) of Mo (1mMo) and W (1mW) were synthesized by cross‐metathesis from the corresponding neophylidene/neopentylidene precursors and o‐methoxystyrene. 1mMo and 1mW were grafted onto the surface of silica partially dehydroxylated at 700 °C to give well‐defined silica‐supported alkylidenes (≡SiO)M(=NAr)(=CH−C6H4−o‐OMe)(OtBuF3) (M=Mo (1Mo), W (1W)). Supported methoxybenzylidene complexes were tested in metathesis of cis‐4‐nonene, 1‐nonene, and ethyl oleate, and compared to their molecular precursors and supported classical analogs (≡SiO)M(=NAr)(=CHCMe2R)(OtBuF3) (M=Mo, R=Ph (2Mo), M=W, R=Me (2W)). Both grafted complexes 1Mo and 1W show significantly better performance as compared to their molecular precursors 1mMo and 1mW but are less efficient than the classical 4‐coordinated alkylidenes 2Mo and 2W. Noteworthy, both 1Mo and 1W can reach equilibrium conversion in metathesis of cis‐4‐nonene at catalyst loadings as low as 50 ppm. [ABSTRACT FROM AUTHOR]

[Display omitted] Well-defined silica-supported Ti imido complex (SiO)Ti(NBut)(Me 2 Pyr)(Py) 2 (Me 2 Pyr = 2,5-dimethyl- pyrrolyl) catalyzes condensation of N -sulfinylanilines into sulfurdiimines via the oxo/imido heterometathesis providing a convenient synthetic route to functionalized sulfurdiimines. [ABSTRACT FROM AUTHOR]