Premium
Pyridine(diimine) Iron Diene Complexes Relevant to Catalytic [2+2]‐Cycloaddition Reactions
Author(s) -
Kennedy C. Rose,
Zhong Hongyu,
Joannou Matthew V.,
Chirik Paul J.
Publication year - 2020
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201901289
Subject(s) - chemistry , diene , cycloaddition , diimine , isoprene , ethylene , catalysis , pyridine , medicinal chemistry , ligand (biochemistry) , pincer ligand , cyclooctadiene , photochemistry , stereochemistry , organic chemistry , copolymer , pincer movement , natural rubber , biochemistry , polymer , receptor
The synthesis, characterization, and catalytic activity of pyridine(diimine) iron piperylene and isoprene complexes are described. These diene complexes are competent precatalysts for (i) the selective cross‐[2+2]‐cycloaddition of butadiene or (E) ‐piperylene with ethylene and α‐olefins and (ii) the 1,4‐hydrovinylation of isoprene with ethylene. In the former case, kinetic analysis implicated the diamagnetic η 4 ‐piperylene complex as the resting state prior to rate‐determining oxidative cyclization. Variable temperature 1 H NMR and EXSY experiments established that diene exchange from the diamagnetic, 18e – complexes occurred rapidly in solution at ambient temperature through a dissociative mechanism. The solid‐state structure of( Me ( Et ) PDI ) Fe(η 4 ‐piperylene) ( Me (Et)PDI=2,6‐(2,6‐Me 2 ‐C 6 H 3 N=CEt) 2 C 5 H 3 N) was determined by single‐crystal X‐ray diffraction and confirmed the s‐ trans coordination of the monosubstituted 1,3‐diene. Possible relationships between ligand‐controlled diene coordination geometry, metallacycle denticity, and chemoselectivity of iron‐mediated cycloaddition reactions are discussed.