Strain Control: Reversible H2 Activation and H2/D2 Exchange in Pt Complexes.

Area of Science:

• * Inorganic Chemistry
• * Catalysis
• * Computational Chemistry

Background:

• * Efficient hydrogen activation is crucial for various chemical processes.
• * Platinum-tin (Pt-Sn) complexes have shown promise in catalyzing H2 activation.
• * The role of ligand bulk and complex strain in H2 activation mechanisms remains an active area of research.

Purpose of the Study:

• * To elucidate the mechanisms of reversible H2 activation catalyzed by a specific Pt-Sn complex, Pt(Sn(t)Bu3)2(CN(t)Bu)2 (1a).
• * To investigate the influence of steric bulk and strain on the catalytic activity of Pt-Sn complexes in H2 activation and H2/D2 exchange.
• * To compare the performance of Pt-Sn catalysts with their Pt-Ge and Pt-Si analogues.

Main Methods:

• * Synthesis and characterization of Pt-Sn complexes.
• * Experimental studies on H2 activation and H2/D2 exchange reactions.
• * Computational modeling, including direct dynamics calculations, to determine reaction mechanisms, activation energies, and kinetic isotope effects.

Main Results:

• * Only the strained Pt-Sn complex 1a demonstrated efficient reversible H2 activation, requiring minimal distortion energy and entropy of activation.
• * Computational studies predicted that strained Pt-Ge complexes could also efficiently activate H2 reversibly.
• * Direct dynamics calculations revealed significant contributions of H/D atom tunneling to the reductive elimination of H2, HD, and D2, leading to enhanced kinetic isotope effects.

Conclusions:

• * Steric bulk and strain are critical factors for designing efficient Pt-Sn catalysts for reversible H2 activation.
• * Strain control is proposed as a viable design strategy for developing novel H2 activation catalysts.
• * Understanding the mechanistic details, including tunneling effects, is essential for optimizing catalytic performance.