Bis(imino)pyridine Complexes of the First-Row Transition Metals: Alternative Methods of Activation

Abstract

The use of AlEt 3 (TEA) in combination with [Ph 3 C][Al(O t Bu F ) 4 ] (TA) for the activation of a range of bis(imino)pyridine complexes of vanadium, chromium, iron, and cobalt is reported. It is shown that this activator combination successfully replaces MMAO, in some cases showing improvements in terms of activity and productivity. Furthermore, when activities and productivities are considered in terms of the aluminum center (MMAO vs TEA), the true cost driver in the commercialization of most catalyst systems, then in nearly all cases a significant improvement is seen.

Synthesis of Ruthenium(II) Complexes Containing Tridentate Triamine (′N ͡N ͡N′) and Bidentate Diamine Ligands (N ͡N′): as Catalysts for Transfer Hydrogenation of Ketones

“…The axial positions in the octahedron are occupied by one chlorine ligand (Cl1) and one nitrogen atom of the bidentate ligand (N7). As can be seen from the trans angles, which vary from 156.6(4) to 178.4(5)°for 9 and from 155.88 (11) to 179.33(12)°for 10, and the cis angles, which vary from 77.1(4) to 104.2(4)°for 9 and from 77.93 (12) to 102.73 (12)°f or 10, the coordination octahedron around the Ru(II) ions is rather deformed, the major distortion arising via the N3À Ru1ÀN5 angle. This angle is considerably smaller than the ideal angle of 180°.…”

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…[129] Furthermore,the [Al(OR F ) 4 ] À anion demonstrated excellent stability towards Brønsted acids,itisstable up to the level of protonated mesitylene [6,130] as well as against highly electrophilic cations such as [CX 3 ] + (where X = Cl, Br,o r I) [131] or the bulkier silylium ion [Si(C 6 Me 5 ) 3 ] + . [137,138] In contrast to the highly fluorinated aluminates described above,aseries of halogen-free and "lipophilic" aluminate anions based on as ubstituted biphenol moiety have recently been developed by Straub and co-workers. [133] As ar esult of the aforementioned stability and the commercially available synthetic precursors the [Al(OR F ) 4 ] À anion represents at rue alternative to the more traditional borate-based anions,particularly in the field of homogeneous catalysis,w here very weak interactions between the cation and anion are beneficial.…”

Extremely Active Ethylene Tetramerization Catalyst Avoiding the Use of Methylaluminoxane: [iPrN{P(C6H4‐p‐SiR3)2}2CrCl2]+[B(C6F5)4]−

“…Even though the reported activity of the typical Sasol system calculated based on Cr was extremely high (1200 kg/g‐Cr), the productivity calculated based on the feed amount of MMAO was unsatisfactory (∼2.0 kg/g‐MMAO) . Consequently, attempts have been made to replace expensive MMAO with inexpensive iBu 3 Al or Et 3 Al in combination with a stoichiometric amount of discrete non‐coordinating anions (e. g., [Ph 3 C] + [B(C 6 F 5 ) 4 ] − or [PhN(H)Me 2 ] + [B(C 6 F 5 ) 4 ] − ) . However, most of these attempts, especially with commonly used [Ph 3 C] + [B(C 6 F 5 ) 4 ] − and [PhN(H)Me 2 ] + [B(C 6 F 5 ) 4 ] − , have been unsuccessful .…”

“…[16,17] Consequently, attempts have been made to replace expensive MMAO with inexpensive iBu 3 Al or Et 3 Al in combination with a stoichiometric amount of discrete non-coordinating anions (e. g., [Ph 3 C] + [B(C 6 F 5 ) 4 ] À or [PhN(H)Me 2 ] + [B(C 6 F 5 ) 4 ] À ). [15,[18][19][20][21][22][23] However, most of these attempts, especially with commonly used [Ph 3 C] + [B(C 6 F 5 ) 4 ] À and [PhN(H)Me 2 ] + [B(C 6 F 5 ) 4 ] À , have been unsuccessful. [24,25] The low working temperature (~60°C) is also an issue.…”