Synthesis and Reactivity of Pyridine(diimine) Molybdenum Olefin Complexes: Ethylene Dimerization and Alkene Dehydrogenation

Matthew V. Joannou, Máté J. Bezdek, Khalid Al-Bahily, Ilia Korobkov, Paul J. Chirik

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Reduced pyridine(diimine) molybdenum olefin complexes have been synthesized and structurally characterized. Examples with 1,5-cyclooctadiene, (PDI)Mo(η22-1,5-COD) (COD = 1,5-cyclooctadiene) adopt a distorted-trigonal-bipyramidal geometry and are best described as low-spin Mo(II) compounds arising from significant π back-donation to the ligand from a reduced molybdenum center. With the 2,6-diisopropyl N-aryl-substituted variant of the pyridine(diimine) ligand, a molybdenum bis(ethylene) complex was obtained. Reducing the size of the N-aryl substituents to 2,4,6-trimethyl resulted in isolation of (MesPDI)Mo(η4-butadiene)(η2-ethylene) following sodium amalgam reduction of the corresponding molybdenum(III) trichloride complex in the presence of excess ethylene. Analysis of the byproducts of the reaction and olefin addition experiments demonstrate that butadiene formation is consistent with a pathway involving ethylene coupling to form 1-butene followed by allylic dehydrogenation to produce butadiene. Excess ethylene serves as the hydrogen acceptor. The dehydrogenation reaction was also compatible with α-olefins, as reduction of either (iPrPDI)MoCl3 or (MesPDI)MoCl3 in the presence of 1-hexene resulted in isolation of (PDI)Mo(η4-1,3-hexadiene)(η2-1-hexene) complexes. An α,ω-diene complex, (iPrPDI)Mo(η22-1,6-heptadiene), was also synthesized and importantly displayed no cycloaddition chemistry, suggesting that first-row metal pyridine(diimine) complexes are thus far unique in promoting cyclobutane synthesis.

Original languageEnglish (US)
Pages (from-to)4215-4223
Number of pages9
JournalOrganometallics
Volume36
Issue number21
DOIs
StatePublished - Nov 13 2017

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Fingerprint Dive into the research topics of 'Synthesis and Reactivity of Pyridine(diimine) Molybdenum Olefin Complexes: Ethylene Dimerization and Alkene Dehydrogenation'. Together they form a unique fingerprint.

Cite this