# A Mixed-Valent and High-Spin Vanadium Phosphide

## TL;DR

This paper reports the synthesis of a high-spin and mixed-valent vanadium phosphide complex with unique structural and electronic properties.

## Contribution

The study introduces a novel high-spin, mixed-valent vanadium phosphide complex with an S=3/2 ground state.

## Key findings

- A VII complex [(pyrNdipp)2V(L)2] is formed via reductive elimination of the PCO– moiety.
- Photolysis leads to a high-spin and mixed-valent vanadium phosphide [(pyrNdipp)2V=P=V(pyrNdipp)2].
- Theoretical analysis shows the complex avoids spin-pairing due to weak ligand-field splitting.

## Abstract

Accessing high-spin
configurations of transition metal
phosphides
defines a dividing line that prevents common properties of solid-state
materials from being replicated within multiple-bonded molecular analogs.
Here, we report the synthesis of a VIII phosphaethynolate
complex, [(pyrNdipp)2V­(PCO)] (2) in a halide
metathesis with Na­(OCP). Exposure of 2 to Lewis-basic
ligands induces a one-electron reductive elimination of the PCO– moiety, generating VII complexes [(pyrNdipp)2V­(L)2] (L = THF, DMAP; 3

THF
, 3

DMAP
). When 2 is instead photolyzed, a cascade of reduction, decarbonylation,
and multiple-bond formation steps affords a high-spin and mixed-valent
vanadium phosphide, [(pyrNdipp)2VPV­(pyrNdipp)2] (4) comprising formal [V2
III, IV] nodes. Structural characterization coupled with vibrational, UV–visible,
and X-ray spectroscopic studies reveals an S
4 symmetrical [VPV] centered architecture conforming
to a fully delocalized, mixed-valency description. Theoretical studies
demonstrate that 4 evades spin-pairing by leveraging
the weak ligand-field splitting at the vanadium nodes, leading to
a high-spin, S
T = 3/2 ground state of
this multiple-bonded, weakly Jahn–Teller distorted system.