Catalyst Deactivation by β‐Hydride Elimination: Olefin and Alkyne Insertion into Arenido–Nickel(II) Bonds

Abstract

Square planar arenido-(triphenylphosphane)nickel(II) complexes (3) containing a N,O-chelate ligand are catalysts for the carbon monoxide/ethene copolymerisation reaction. Pathways for catalyst deactivation have been elucidated by investigating the reactions of such complexes with aliphatic unsaturated compounds like olefins and alkynes. We have shown that the double or triple bond, respectively, inserts into the nickel-carbon bond followed by β-hydride elimination resulting in aryl-substituted olefins and allenes, which

Square-planar mesitylenido(triphenylphosphane)nickel(II) complexes containing bidendate N,O-ligands: Changes in catalytic efficiency upon small alterations in the ligand backbone

“…We introduced the mesitylenido group mostly for stability reasons as the mesitylenido nickel(II) complexes turned out to be significantly more stable in benzene or dichloromethane solution in air than their 2-toluenido analogues. No decomposition that would be noticeable in the 31 P{ 1 H} NMR spectrum takes place in a benzene solution for weeks even under aerobic conditions, whereas the corresponding 2-toluenido nickel(II) complexes decompose to paramagnetic nickel(II) compounds, triphenylphosphane and triphenylphosphane oxide within days [15]. Decomposition is even faster in analogous complexes comprising a benzenido ligand.…”

“…We added ca. 70 bar ethene and stirred at room temperature for 72 h. During that time, all of the ethene was consumed and reacted to polyethylene [15]. The same reaction procedure was applied to the other catalysts, K 1 , K 2 and K 2 0 .…”

“…Complex K 1 0 is an active catalyst for the polymerisation of ethene yielding polyethylene [15]. In a standard 100 mL autoclave setup we used the respective complex in a ca.…”

“…The stability and reactivity of the complexes were investigated using the previously described reaction with 2-hexyne [15]. 2-Hexyne inserts into the nickelecarbon bond and the resulting insertion product reacts under b-hydride elimination [15].…”

“…The stability and reactivity of the complexes were investigated using the previously described reaction with 2-hexyne [15]. 2-Hexyne inserts into the nickelecarbon bond and the resulting insertion product reacts under b-hydride elimination [15]. The four complexes K 1 , K 1 0 , K 1 00 and K 1 000 can be ranked qualitatively in the following order of decreasing reactivity: K 1 0 > K 1 00 > K 1 000 > K 1 , obviously due to the inductive effects of the methyl groups, not merely steric effects.…”