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.

Catalyst design for iridium-catalyzed CO2 hydrosilylation processes: improvement of the selectivity and reduction of the reaction time.

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.

The Ir(i) complexes [Ir(cod)(κP,C,P'-NHO(PPh2))]PF6 and [IrCl(cod)(κC-NHO(OMe))] (cod = 1,5-cyclooctadiene, NHO(PPh2) = 1,3-bis(2-(diphenylphosphanyl)ethyl)-2-methyleneimidazoline) and NHO(OMe) = 1,3-bis(2-(methoxyethyl)-2-methyleneimidazoline), both featuring an N-heterocyclic olefin ligand (NHO), have been tested in the transfer hydrogenation reaction; this representing the first example of the use of NHOs as ancillary ligands in catalysis. The pre-catalyst [Ir(cod)(κP,C,P'-NHO(PPh2))]PF6 has shown excellent activities in the transfer hydrogenation of aldehydes, ketones and imines using (i)PrOH as a hydrogen source, while [IrCl(cod)(κC-NHO(OMe))] decomposes throughout the reaction to give low yields of the hydrogenated product. Addition of one or two equivalents of a phosphine ligand to the latter avoids catalyst decomposition and significantly improves the reaction yields. The reaction mechanism has been investigated by means of stoichiometric studies and theoretical calculations. The formation of the active species ([Ir(κP,C,P'-NHO(PPh2))((i)PrO)]) has been proposed to occur via isopropoxide coordination and concomitant COD dissociation. Moreover, throughout the catalytic cycle the NHO moiety behaves as a hemilabile ligand, thus allowing the catalyst to adopt stable square planar geometries in the transition states, which reduces the energetic barrier of the process.

Tetramerization of ethylene by chromium catalysts stabilized with functionalized N -aryl phosphineamine ligands C 6 H 4 ( m -CF 3 )N(PPh 2 ) 2 ( 1 ), C 6 H 4 ( p -CF 3 )N(PPh 2 ) 2 ( 2 ), C 6 H 4 ( o -CF 3 )N=PPh 2 -PPh 2 ( 3 ), and C 6 H 3 (3,5-bis(CF 3 ))N(PPh 2 ) 2 ( 4 ) was evaluated. The parameter optimization includes temperature, co-catalyst, and solvent. Upon activation with MMAO-3A, the new catalyst system especially with m -functional PNP ligand ( 1 ) exhibited high 1-octene selectivity and productivity while giving minimum undesirable polyethylene and C 10 + olefin by-products. Using PhCl as a solvent at 75 °C led to a remarkable α-olefin (1-C 6 + 1-C 8 ) selectivity (>90 wt %) at a reaction rate of 2000 kg·g Cr –1 ·h –1 . Under identical conditions, analogous PNP ligands bearing −CH 3 , −Et, and −Cl functional moieties at the meta position of the N -phenyl ring displayed significantly lower reactivity. The catalyst with p -functional ligand ( 2 ) exhibited lower activity and comparable selectivities, while the Cr/PPN (with ligand 3 ) system gave no noticeable reactivity. The molecular structure of the precatalyst ( 1 -Cr), exhibiting a monomeric structural feature, was elucidated with the aid of single-crystal X-ray diffraction study.

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