Molecular
main-group hydride catalysts are attractive as cheap
and Earth-abundant alternatives to transition-metal analogues. In
the case of the latter, specific steric and electronic tuning of the
metal center through ligand choice has enabled the iterative and rational
development of superior catalysts. Analogously, a deeper understanding
of electronic structure–activity relationships for molecular
main-group hydrides should facilitate the development of superior
main-group hydride catalysts. Herein, we report a modular Sn–Ni
bimetallic system in which we systematically vary the ancillary ligand
on Ni, which, in turn, tunes the Sn center. This tuning is probed
using Sn L1 XAS as a measure of electron density at the
Sn center. We demonstrate that increased electron density at Sn centers
accelerates the rate of σ-bond metathesis, and we employ this
understanding to develop a highly active Sn-based catalyst for the
hydroboration of CO2 using pinacolborane. Additionally,
we demonstrate that engineering London dispersion interactions within
the secondary coordination sphere of Sn allows for further rate acceleration.
These results show that the electronics of main-group catalysts can
be controlled without the competing effects of geometry perturbations
and that this manifests in substantial reactivity differences.