Exceptionally large "through-space" nuclear spin coupling in a 2,4,6-tri(phosphanyl)-1,3,5-triphosphabenzene

Area of Science:

• Organometallic Chemistry
• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Computational Chemistry

Background:

• 1,3,5-triphosphabenzene derivatives are explored for unique electronic properties.
• Spin-spin coupling (SSC) provides insights into molecular structure and bonding.
• Understanding transmission pathways of SSC is crucial for chemical applications.

Purpose of the Study:

• To synthesize a novel phosphanyl-functionalized 1,3,5-triphosphabenzene.
• To investigate the unusually large indirect spin-spin coupling (SSC) between phosphorus-31 nuclei.
• To computationally elucidate the mechanisms governing this spin-spin coupling.

Main Methods:

• Synthesis of phosphanyl-functionalized 1,3,5-triphosphabenzene.
• Nuclear Magnetic Resonance (NMR) spectroscopy for spin-spin coupling measurement.
• Density Functional Theory (DFT) calculations to analyze transmission pathways.

Main Results:

• A phosphanyl-functionalized 1,3,5-triphosphabenzene with a 432 Hz indirect spin-spin coupling (SSC) was synthesized.
• DFT calculations revealed significant s-orbital character contributing to effective orbital overlap.
• Chemical oxidation of phosphanyl groups disrupted the 'through-space' SSC pathway, yielding 'through-bond' coupling.

Conclusions:

• The study demonstrates a novel phosphabenzene with significant phosphorus-31 spin-spin coupling.
• Computational analysis successfully deconvoluted 'through-space' and 'through-bond' SSC mechanisms.
• Chemical modification provides a method to tune and control spin-spin coupling interactions.