The hydrosilylation of CO with different silanes such as HSiEt , HSiMe Ph, HSiMePh , HSiMe(OSiMe ) , and HSi(OSiMe ) in the presence of catalytic ammounts of the iridium(III) complex [Ir(H)(CF CO )(NSiN*)(coe)] (1; NSiN*=fac-bis-(4-methylpyridine-2-yloxy); coe=cis-cyclooctene) has been comparatively studied. The activity of the hydrosilylation catalytic system based on 1 depends on the nature of the reducing agent, where HSiMe(OSiMe ) has proven to be the most active. The aforementioned reactions were found to be highly selective toward the formation of the corresponding silylformate. It has been found that using 1 as catalyst precursor above 328 K decreases the activity through a thermally competitive mechanistic pathway. Indeed, the reduction of the ancillary trifluoroacetate ligand to give the corresponding silylether CF CH OSiR has been observed. Moreover, mechanistic studies for the 1-catalyzed CO -hydrosilylation reaction based on experimental and theoretical studies suggest that 1 prefers an inner-sphere mechanism for the CO reduction, whereas the closely related [Ir(H)(CF SO )(NSiN)(coe)] catalyst, bearing a triflate instead of trifluoroacetate ligand, follows an outer-sphere mechanism.
A wide range of diaryl ethers and alkyl aryl ethers are synthesized through intermolecular C(aryl)-O bond formation from the corresponding aryl iodides/aryl bromides and phenols/alcohols through Ullmann-type coupling reaction in the presence of a catalytic amount of easily available (+/-)-diol L3-CuI complex under very mild reaction conditions. Less reactive aryl bromides can also be used for O-arylation of phenols under the same reaction conditions without increasing the reaction temperature, catalyst loading, and time. The catalytic system not only is capable of coupling hindered substrate but also tolerates a broad range of a series of functional groups.
The complex [Ir(H)(CF3SO3)(NSiN)(coe)] (NSiN=bis(pyridine‐2‐yloxy)methylsilyl fac‐coordinated) (1) is an effective catalyst precursor for the solvent‐free synthesis of silyl carbamates from reaction of aliphatic secondary amines with CO2 and HSiMe(OSiMe3)2. The preferential formation of the silyl carbamate instead of the expected formamide or methylamine has proven to be consequence of an iridium‐catalyzed dehydrogenative Si−N coupling between the silane and the amine to afford the corresponding silyl amine, which under the reaction conditions reacts with CO2 to give the corresponding silyl carbamate.
Toward gaining insight into the behavior of bimetallic catalysts for olefin polymerization, a series of structurally related binuclear zirconium catalysts with bisamine bisphenolate and pyridine bisphenolate ligands connected by rigid teraryl units were synthesized. Anthracene-9,10-diyl and 2,3,5,6-tetramethylbenzene-1,4-diyl were employed as linkers. Bulky Si i Pr 3 and SiPh 3 substituents were used in the position ortho to the phenolate oxygen. Pseudo-C s and C 2 symmetric isomers are observed for the binuclear complexes of bisamine bisphenolate ligands. In general, binuclear catalysts show higher isotacticity compared to the monozirconium analogues, with some differences between isomers. Amine bisphenolate-supported dizirconium complexes were found to be moderately active (up to 1.5 kg mmol Zr −1 h −1 ) for the polymerization of 1-hexene to isotactically enriched poly-1-hexene (up to 45% mmmm) in the presence of stoichiometric trityl or anilinium borate activators. Moderate activity was observed for the production of isotactically enriched polypropylene (up to 2.8 kg mmol Zr −1 h −1 and up to 25.4% mmmm). The previously proposed model for tacticity control based on distal steric effects from the second metal site is consistent with the observed behavior. Both bisamine bisphenolate and pyridine bisphenolate supported complexes are active for the production of polyethylene in the presence of MAO with activities in the range of 1.1−1.6 kg mmol Zr −1 h −1 and copolymerize ethylene with αolefins. Little difference in the level of α-olefin incorporation is observed between mono-and dinuclear catalysts supported with the pyridine bisphenolate catalysts. In contrast, the size of the olefin affects the level of incorporation differently between monometallic and bimetallic catalysts for the bisamine bisphenolate system. The ratio of the incorporation levels with dinuclear vs mononuclear catalysts decreases with increasing comonomer size. This effect is attributed to steric pressure provided by the distal metal center on the larger olefin in dinuclear catalysts.
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