A competetive way to low-viscosity PAO base stocks via heterocene-catalyzed oligomerization of dec-1-ene

• Synthesis and study of –CH 2 CH 2 – bridged indeno[2,1- b ]indole Zr (IV) ansa -complexes. • Study of dec-1-ene oligomerization using MMAO-12 and [PhNMe 2 H][B(C 6 F 5 ) 4 ] activators. • Formation and X-ray diffraction analysis of [ L6 -Zr(μ-Cl) 2 Al i Bu 2 ][B(C 6 F 5 ) 4 ]. • Oligomerization of dec-1-ene without double bond shift and skeletal rearrangements. • Hydrogenated lightweight oligomers of dec-1-ene are high-quality PAO base stocks. Hydrogenated oligomers of higher α-olefins (primarily, dec-1-ene) represent base stocks for high-quality polyolefin oils (PAOs), transmission fluids, lubricants and greases. Competitive advantages of zirconocene catalysts in oligomerization of α-olefins have been already demonstrated and industrially implemented for higher oligomers. However, the problem of the selective synthesis of α-olefin oligomers that have degree of polymerization ( DP n ) 3 and 4, remains unresolved. A series of –CH 2 CH 2 – bridged ansa -zirconocenes derived from 5,10-dihydroindeno[1,2- b ]indole, 'heterocenes' Zr4 – Zr6 , were synthesized and characterized by NMR spectroscopy and X-ray diffraction (XRD) analysis. New complexes Zr4 – Zr6 and known –SiMe 2 – bridged ansa -heterocenes Zr1 – Zr3 were investigated in oligomerization of dec-1-ene using MMAO-12 or [PhNMe 2 H][B(C 6 F 5 ) 4 ] activators. In the atmosphere of molecular hydrogen, at [dec-1-ene]/[Zr] ratios up to 4·10 5 , rac -forms Zr4r – Zr6r provided more than 85% yields of dec-1-ene oligomers without skeletal rearrangements. In some experiments, at least 50% yields of lightweight oligomers ( DP n =3–4) were achieved. After activation of Zr6r by TIBA and [PhNMe 2 H][B(C 6 F 5 ) 4 ] and completion of dec-1-ene oligomerization, we isolated new cationic complex Zr6r-Al containing Zr-(μ-Cl) 2 -Al fragment, as confirmed by XRD. Zr6r-Al alone was inactive against dec-1-ene, but after addition of TIBA oligomerization started. Due to uniform molecular structure of oligomers, complete catalytic hydrogenation of oligo(dec-1-ene)s was conducted using Ni/Al 2 O 3 catalyst under mild conditions (150°C, 3 h, 20 bar). Hydrogenated dec-1-ene oligomers turned out to be high-quality PAO base stocks far exceeding industrial dec-1-ene PAOs in terms of viscosity characteristics.