Trinuclear tris(ansa-metallocene) complexes of zirconium and hafnium for olefin polymerization

New platforms for trinuclear complexes, 1,3,5-tris(fluoren-2-yl-R)benzene (Ph{2-FluRH}3; R = H (2a), 6-tBu (2b), 7-tBu (2c), Tet (2d) (Tet = 2,2,5,5-tetramethyl-tetrahydrobenzofluorene), were synthesized via an acid-catalyzed cyclotrimerization of the corresponding substituted 2-acetylfluorenes. Subsequent nucleophilic addition of the [Ph{2-FluR}3]3− trianions onto 6,6,-dimethylfulvene afforded the corresponding isopropylidene-bridged pro-ligands Ph{Me2C(2-FluRH)(C5H5)}3 (3a-d). Discrete trinuclear tris(dichloro-ansa-zirconocene and hafnocene), Ph[{Me2C(2-FluR)(C5H4)}MX2]3 (X = Cl: 4b-d-Zr, 4c,d-Hf) were prepared by salt metathesis reactions. Some zirconium complexes were further alkylated towards the corresponding tris(dialkyls) (X = Me: 5c,d-Zr; X = CH2SiMe3: 6c-Zr). The structures of these metal complexes were determined by elemental analyses, and by 1D, inverse 2D heteronuclear correlation, and DOSY NMR spectroscopy, as well as by theoretical computations. Those studies revealed the existence of two isomers, of C3 and C1 symmetry respectively, originating from the mutual orientation of the three ansa-metallocene fragments. Preliminary studies on the catalytic performances of the dichloro complexes, upon activation with MAO, in ethylene and propylene homopolymerization and ethylene/1-hexene copolymerization were carried out and compared to those of the monometallic analogues under identical conditions. Trinuclear group 4 tris(ansa-metallocene) complexes based on an original 1,3,5-phenylene-tris(isopropylidene-bridged cyclopentadienyl/fluorenyl) platform were synthesized and used as precatalysts in polymerization of ethylene and propylene and ethylene/1-hexene copolymerization. [Display omitted] •Design of an original 1,3,5-phenylene-tris(isopropylidene-bridged cyclopentadienyl/fluorenyl) platform.•Synthesis of trinuclear group 4 tris(ansa-metallocene) complexes.•Polymerization catalysis of ethylene and propylene and ethylene/1-hexene.