Numerous efforts have been made to achieve “on-purpose” 1-octene production since Sasol discovered a Cr-based selective ethylene tetramerization catalyst in the early 2000s. By preparing a series of bis(phosphine) ligands iPrN(PAr2)2 where the Ar contains a bulky –SiR3 substituent (Ar = −C6H4-p-Si(nBu)3 (1), −C6H4-p-Si(1-hexyl)3 (2), −C6H4-p-Si(1-octyl)3 (3), −C6H4-p-Si(2-ethylhexyl)3 (4), −C6H4-p-Si(3,7-dimethyloctyl)3 (5)), we obtained an extremely active catalyst that meets the criteria for commercial utilization. The Cr complexes [iPrN(PAr2)2−CrCl2]+[B(C6F5)4]–, obtained by reacting ligands 1–5 with [(CH3CN)4CrCl2]+[B(C6F5)4]–, showed high activity exceeding 6000 kg/g-Cr/h, when combined with the inexpensive iBu3Al, thus avoiding the use of expensive modified methylaluminoxane (MMAO). The bulky –SiR3 substituents played a key role in the success of catalysis by blocking the formation of inactive species (Cr complexes coordinated by two iPrN(PAr2)2 ligands, that is, [(iPrN(PAr2)2)2−CrCl2]+[B(C6F5)4]–). Among the complexes prepared, [3−CrCl2]+[B(C6F5)4]– exhibited the highest activity (11,100 kg/g-Cr/h, 100 kg/g-catalyst) with high 1-octene selectivity (75 wt%) and, moreover, mitigated the generation of undesired > C10 fractions (10.7 wt%). A 10-g-scale synthesis of 3 was developed, as well as a facile and low-cost synthetic method for [(CH3CN)4CrCl2]+[B(C6F5)4]–.

α-Olefin trimers are used at a bulk scale as top-tier lubricant base oils, with putative future applications as diesel fuels obtainable from renewable ethylene. α-Olefin trimers are conventionally obtained in the cationic oligomerization process, during which a range of n-mers are simultaneously generated alongside severe skeleton rearrangement. In this context, catalysts that can selectively convert α-olefin to its trimers are valuable. However, few examples have been reported. Herein, we report selective α-olefin trimerization catalysts constructed via the modification of the Chevron–Phillips ethylene trimerization catalytic system and avoiding the use of expensive activators, such as methylaluminoxane (MAO), B­(C6F5)3, and [B­(C6F5)4]− salt, despite the typical Chevron–Phillips system being inactive for α-olefin. A catalytic system Cr­(acac)3/[2,5-Me2C4H2N–Al­(iBu)3]−Na+/(iBu)3Al demonstrating high turnover numbers exceeding 10,000 (31 kg/g-Cr for 1-decene), generating trimers selectively without other higher or lower fractions, was developed, confirmed by simulated distillation gas chromatography analysis. The hypothesized η5-pyrrolide chromium active species was partially confirmed by the structure elucidation of [η5-Me2C4H2N–AlMe3]­Cr­(Me)­[CH2C6H4(ortho-NMe2)-κ2 C,N]. The prepared 1-decene trimers (after hydrogenation) exhibited an advantageously higher viscosity index than the commercial product PAO-4.0 (128 vs 123). Fluids demonstrating similar lubricant characteristics to either the 1-decene trimers or PAO-4.0 were obtained by using a 1-octene/1-dodecene blend.

Grignard reagents featuring carbanion characteristics are mostly unreactive toward alkyl halides and require a catalyst for the coupling reaction. With the need to prepare p-(CH2CH)C6H4CH2CH2CH2Cl on a large scale, the coupling reaction of p-(CH2CH)C6H4MgCl with BrCH2CH2CH2Cl was attempted to screen the catalysts, and CuCN was determined to be the best catalyst affording the desired compound in 80% yield with no formation of Wurtz coupling side product CH2CHC6H4–C6H4CHCH2. The p-(CH2CH)C6H4Cu(CN)MgCl species was proposed as an intermediate based on the X-ray structure of PhCu(CN)Mg(THF)4Cl. p-ClC6H4MgCl did not react with sterically encumbered R3SiCl (R = n-Bu or n-octyl). However, the reaction took place with the addition of 3 mol % CuCN catalyst, affording the desired compound p-ClC6H4SiR3. The structures of p-(CH2CH)C6H4CH2CH2CH2MgCl and p-ClC6H4MgCl were also elucidated, which existed as an aggregate with MgCl2, suggesting that some portion of the Grignard reagents were possibly lost in the coupling reaction due to coprecipitation with the byproduct MgCl2. R3SiCl (R = n-Bu or n-octyl) was also prepared easily and economically with no formation of R4Si when SiCl4 was reacted with 4 equiv of RMgCl. Using the developed syntheses, [p-(CH2CH)C6H4CH2CH2CH2]2Zn and iPrN[P(C6H4-p-SiR3)2]2, which are potentially useful compounds for the production of PS-block-PO-block-PS and 1-octene, respectively, were efficiently synthesized with substantial cost reductions.