Electrostatic vs. inductive effects in phosphine ligand donor properties and reactivity

Area of Science:

• Organometallic Chemistry
• Computational Chemistry
• Catalysis

Background:

• Enzyme activity is influenced by electric fields in active sites.
• Leveraging electrostatics with charged groups is a promising strategy for tuning molecular reactivity.
• Distinguishing through-space and through-bond effects of charged groups remains challenging.

Purpose of the Study:

• To develop a method for quantifying the electrostatic contribution of charged moieties to donor strength.
• To investigate the impact of covalently bound charged functionalities on chemical reactivity.
• To validate theoretical predictions regarding electrostatic effects in chemical reactions.

Main Methods:

• Synthesis of novel anionic phosphine selenides, including PPh2CH2BF3K.
• Quantification of electrostatic contributions using phosphorus selenium coupling values (J P-Se) and Coulomb's law.
• Investigation of reactivity enhancement in C-F oxidative addition and catalytic fluoroarene C-F borylation reactions.

Main Results:

• The J P-Se method quantified up to an 80% electrostatic contribution to donor strength in anionic phosphine selenides.
• Controls excluded ion pairing effects, confirming the electrostatic influence of the borate moiety.
• The novel phosphine ligand accelerated C-F oxidative addition by an order of magnitude and improved catalytic borylation yields.

Conclusions:

• Covalently bound charged functionalities exert significant electrostatic influence under solution conditions.
• The developed J P-Se method provides a reliable way to measure electrostatic contributions in molecular systems.
• This work experimentally validates theoretical predictions and opens new avenues for designing reactive molecular systems.