# Controlling Reductive Elimination Pathways in Ti(IV) Pincer Complexes: Concerted versus Radical Mechanisms via Ligand Design

## TL;DR

The paper explores how ligand design can control chemical reactions in titanium complexes, enabling selective bond formation.

## Contribution

The study demonstrates a rare, selective, and quantitative concerted reductive elimination in titanium(IV) complexes through ligand design.

## Key findings

- Selective alkyl radical expulsion was achieved in titanium complexes depending on ligand and oxidant.
- Concerted reductive elimination was observed in a titanium(IV) complex using tridentate, redox-active ligands.
- Quantum calculations and experiments revealed how ligand design suppresses one-electron pathways.

## Abstract

Oxidatively induced
reductive elimination (OIRE) is a powerful
strategy for the formation of carbon–carbon bonds and has been
widely employed in late transition metal catalysis. In contrast, early
transition metals, especially titanium, have remained largely unexplored
in this context. Here, we report two classes of pyridine-based titanium
complexes that are structurally similar yet electronically distinct
and investigate their oxidation chemistry. Depending on the ligand,
the organyl bound to titanium, and the oxidant, selective alkyl radical
expulsion is demonstrated, and most notably, a rare, highly selective,
and quantitative concerted reductive elimination from a titanium­(IV)
complex was established. A combination of quantum chemical calculations,
electrochemical measurements, and crossover experiments provided valuable
insights into the reaction mechanism. These results demonstrate that
appropriate ligand design, particularly the use of tridentate, redox-active
ligands, can effectively suppress competing one-electron pathways
and allow for selective concerted reactivity. In this way, control
over this traditionally elusive elementary step in titanium chemistry
was achieved, marking an advance in the development of OIRE processes
for early transition metals.