# Ultrashort Mn-Mn Bonds in Organometallic Complexes

## TL;DR

This study uses density functional theory to reveal ultrashort Mn-Mn bonds in organometallic complexes, showing that benzene and similar molecules can cage Mn atoms to form Mn-Mn triple bonds with potential for synthesis.

## Contribution

The paper demonstrates the existence of ultrashort Mn-Mn bonds in organometallic complexes and explores their stability and formation mechanisms through computational methods.

## Key findings

- Mn-Mn bond length of 1.8 Å indicating a triple bond
- Benzene cages facilitate ultrashort Mn-Mn bonds
- Multiple spin states with energy barriers affect synthesis

## Abstract

Manganese metallocenes larger than the experimentally produced sandwiched MnBz$_2$ compound are studied using several density functional theory methods. First, we show that the lowest energy structures have Mn clusters surrounded by benzene molecules, in so-called rice-ball structures. We then find a strikingly short bond length of 1.8 {\AA} between pairs of Mn atoms, accompanied by magnetism depletion. The ultrashort bond lengths are related to Bz molecules caging a pair of Mn atoms, leading to a Mn-Mn triple bond. This effect is also found when replacing benzenes by other molecules such as borazine or cyclopentadiene. The stability of the Mn-Mn bond for Mn$_2$Bz$_2$ is further investigated using dissociation energy curves. For each spin configuration, the energy versus distance plot shows different spin minima with barriers, which must be overcome to synthesize larger Mn-Bz complexes.