# Reactivity of [{Cp'Fe(μ‐I)}2] toward 3‐phospha‐ and 3‐arsaethynolate

## TL;DR

This paper reports a new method to synthesize iron complexes with phosphorus and arsenic under mild conditions and explores their reactivity.

## Contribution

A new mild synthetic method for [(Cp'Fe)2(μ-η2:η2-E2)(μ-CO)] complexes and insights into their reactivity under UV light and heat.

## Key findings

- Complexes [(Cp'Fe)2(μ-η2:η2-P2)(μ-CO)] and [(Cp'Fe)2(μ-η2:η2-As2)(μ-CO)] are synthesized at ambient temperature.
- UV-light induces CO release to form [(Cp'Fe)2(μ-η2:η2-E2)] with byproducts identified.
- Thermal CO elimination from arsenic complex yields Fe3As6-cluster [(Cp'Fe)3(As3)2] in low yield.

## Abstract

[{Cp'Fe(μ‐I)}2] (I; Cp’ = η5–1,2,4‐(Me3C)3C5H2) reacts with [Na(OCP)(1,4‐dioxane)x] and K(OCAs) to yield [(Cp'Fe)2(μ‐η2:η2‐P2)(μ‐CO)] (1) and [(Cp'Fe)2(μ‐η2:η2‐As2)(μ‐CO)] (3), respectively. While complex 1 was previously accessed by Scherer and co‐workers using rather harsh reaction conditions, the new synthetic method already proceeds at ambient temperature. UV‐light irradiation of 1 and 3 induces CO release forming complexes [(Cp'Fe)2(μ‐η2:η2‐E2)] (E = P (2) and As (4)), respectively. However, both reactions also yielded several byproducts which were spectroscopically identified. Furthermore, upon thermally triggered CO elimination from 3 the Fe3As6‐cluster [(Cp'Fe)3(As3)2] (5) is isolated in low yield. In addition, zero‐field 57Fe Mössbauer spectra were recorded on complexes 1–4 and computational studies complement the experimental findings and provide additional insights into the bonding in these complexes and the reaction pathways resulting in the formation of complexes 1–4.

[(Cp'Fe)2(μ‐η2:η2‐E2)(μ‐CO)] (E = P, As) can be isolated from the reaction of [{Cp'Fe(μ‐I)}2] (Cp’ = η5‐1,2,4‐(Me3C)3C5H2) with [Na(OCP)(1,4‐dioxane)x] and K(OCAs), respectively. UV‐light induced CO elimination yields [(Cp'Fe)2(μ‐η2:η2‐E2)] (E = P and As). 57Fe Mössbauer spectra as well as computational studies were performed.