Force-Modulated C–C Reductive Elimination from Nickel Bis(polyfluorophenyl) Complexes

• Published in: Organometallics 2023-08, Vol.42 (15), p.1918-1926
• Main Authors: Duan, Chenghao, Zheng, Xujun, Craig, Stephen L., Widenhoefer, Ross A.
• Format: Article
• Language: English
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Ligands; Macrocycles; Nickel; Platinum; Reductive elimination
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.3c00168

We have analyzed the rate of C­(sp2)–C­(sp2) reductive elimination from nickel­(II) bis­(2,4,6-trifluorophenyl) complexes (P–P)­Ni­(2,4,6-C6H2F3)2 containing either MeOBiPhep (3a) or a macrocyclic bisphosphine ligand (3b–3e) as a function of force applied to the biaryl backbone of these ligands through intramolecular tension generated by a molecular force probe. Nickel complexes 3 were isolated in 22–60% yield from the reaction of bisphosphine with the bis­(tetrahydrofuranyl) complex (THF)2Ni­(2,4,6-C6H2F3)2 followed by chromatography. Thermolysis of complexes 3 in C6D6 at 68 °C leads to first-order decay through >3 half-lives to the form 2,2′,4,4′,6,6′-hexafluoro­biphenyl as the exclusive fluorine-containing product in ≥93% yield. Whereas compressive forces up to −65 pN have no significant effect on the rate of reductive elimination, extension forces increase the rate of reductive elimination by a factor of 3 over an ∼230 pN range of restoring forces relative to the strain-free MeOBiphep complex. The rate response of reductive elimination from nickel­(II) bis­(trifluorophenyl) complexes as a function of extension force is similar to the previously reported 2.8-fold increase in the rate of reductive elimination from platinum diaryl complexes (P–P)­Pt­(4-C6H4NMe2)2 over the same range of forces.