# Oxidant-Dependent Switch of a Molybdenum(VI) Tetrazolate Complex from a Homogeneous to a Self-Separating Catalyst for Olefin Epoxidation

## TL;DR

A molybdenum-based catalyst can switch from a homogeneous to a self-separating form depending on the oxidant used, enabling efficient and reusable epoxidation of various substrates.

## Contribution

A self-separating molybdenum(VI) tetrazolate catalyst is developed, combining homogeneous activity with heterogeneous recovery using hydrogen peroxide.

## Key findings

- High epoxide selectivities (96–100%) and conversions (88–100%) were achieved under mild conditions for various substrates.
- The catalyst remains homogeneous with tert-butyl hydroperoxide but becomes self-separating with hydrogen peroxide.
- The system is effective for epoxidizing biobased substrates like dl-limonene and fatty acid methyl esters.

## Abstract

Although several decades have passed since the introduction
of
homogeneous molybdenum catalysts for the bulk industrial production
of epoxides from light olefins, the development of recyclable catalytic
systems to produce more complex epoxides remains a challenge. In this
work, we present a strategy for preparing a self-separating catalyst
by exploiting reaction-induced precipitation, starting from the molybdenum­(VI)
tetrazolate complex [MoO­(O2)­(pto)2] (Hpto =
5-(2-pyridyl-1-oxide)­tetrazole), which was synthesized via a one-pot
approach and crystallographically characterized. High epoxide selectivities
(96–100%) were achieved at high conversions (88–100%)
under mild conditions (70 °C) in all the studied reactions, from
that of the model substrate cis-cyclooctene to the
epoxidation of biobased dl-limonene and fatty acid methyl esters.
The catalytic reaction is homogeneous using tert-butyl
hydroperoxide as the oxidant, whereas with hydrogen peroxide, a transformation
to a self-separating catalyst takes place, which combines the high
catalytic activity of a homogeneous catalyst with the easy recovery
and reuse of a heterogeneous catalyst.