Tailored RuNi heterobimetallic complexes as dual catalysts for ROMP of norbornene and ethylene oligomerization

A series of four novel Ru L -Ni L heterobimetallic complexes was synthesized via the in-situ condensation of primary amine Ru precursors with salicylaldehyde or 3- tert -butylsalicylaldehyde, generating an N, O-chelated iminic bridge that links the two metal centers. The reaction between (Ph) Ni (PPh 3) 2 Cl, RuCl 2 (p -cymene) (4- (aminomethyl) pyridine) or RuCl 2 (p -cymene) (4- (aminomethyl) piperidine), and the aldehydes in a 1: 1: 1 M ratio afforded the complexes Ph (PPh 3) Ni (μ -N, O-Schiff) Ru (p -cymene) pip (Ru pip -Ni H), Ph (PPh 3) Ni (μ -N, O- tert -butyl-Schiff) -Ru (p -cymene) pip (Ru pip -Ni t Bu), Ph (PPh 3) Ni (μ -N, O-Schiff) Ru (p -cymene) pyridine (Ru py -Ni H), and Ph (PPh 3) Ni (μ -N, O- tert -butyl-Schiff) Ru (p -cymene) pyridine (Ru py -Ni t Bu). The complexes were fully characterized by FTIR, UV–vis, 1 H and 31 P 1 H NMR spectroscopy, cyclic voltammetry, and DFT calculations. Structurally, the Schiff-base fragment functions as a rigid μ- (N, O) iminic bridge, coordinating the Ni II center while preserving the “piano-stool” Ru II geometry, thereby enforcing a well-defined Ru L -Ni L arrangement supported by DFT-optimized geometries. Electrochemical studies revealed two oxidation processes at ~1. 05 V (Ni II/III, irreversible) and ~1. 21 V (Ru II/III, quasi-reversible). The catalytic performance of the complexes was assessed in two benchmark transformations. In ROMP of norbornene using ethyldiazoacetate as carbene source, the complexes produced polyNBE in yields of 40–76% (1 h, 50 °C), with Ru pip -Ni t Bu showing superior activity. In ethylene oligomerization (EASC cocatalyst, 25 °C, 15 bar), all complexes displayed high turnover frequencies of ~150 s −1 and strong preference for C 4 oligomers (79–90%), with tert-butyl-containing systems offering enhanced α-C 4 selectivity.