# Dihapto-Coordinated Conjugated Carbocycles (η2‑C n H n n = 5–8): Blurring the Line Between Aromatic and Antiaromatic Hydrocarbons

## TL;DR

This paper explores how a tungsten fragment can disrupt the stability of aromatic and antiaromatic hydrocarbons, enabling chemical modifications.

## Contribution

The study extends dihapto-coordination to various carbocycles, revealing new reactivity patterns.

## Key findings

- Dihapto-coordinated complexes of tropylium, cyclopentadienyl cation, and cyclooctatetraene were synthesized and characterized.
- These complexes show fluxional behavior and undergo electrophilic/nucleophilic additions like protonation and methylation.
- The tungsten fragment effectively dearomatizes hydrocarbons, enabling further chemical transformations.

## Abstract

The tungsten fragment {WTp­(NO)­(PMe3)} (Tp
= trispyrazolylborate)
is an effective dearomatization agent for benzene and its derivatives.
The dihapto-coordination of this system to an arene disrupts its aromatic
stability, thereby promoting facile electrophilic additions to the
hydrocarbon, which can then be followed by the addition of nucleophiles.
This preliminary study endeavors to extend this conceptual approach
to other aromatic and antiaromatic carbocycles. Dihapto-coordinated
complexes of η2-tropylium, η2-cyclopentadienyl
cation, and η2-cyclooctatetraene have been synthesized
and characterized using SC-XRD, DFT, CV, and 1H, 31P, and 13C NMR (including COSY, NOESY, HSQC, HMBC). Their
fluxional behavior and reactivity toward electrophilic/nucleophilic
additions, such as protonation and methylation, are also demonstrated.