# A facile route to ‘naked’ Ag+ ions enabling the coordination of the weak Lewis base Ni(CO)4

## TL;DR

This paper presents a simple method to create highly electrophilic silver ions with a weak counteranion, enabling the first structural study of a nickel tetracarbonyl complex as a Lewis base.

## Contribution

The paper introduces a new method to generate Ag+ ions with a weakly coordinating anion, enabling the first structural characterization of Ni(CO)4 as a ligand.

## Key findings

- A straightforward synthesis of Ag+ salts with the [µ-(CN)(BCF)2]− anion was developed.
- The first structurally characterized complex with Ni(CO)4 acting as a ligand was synthesized.
- The extremely low basicity of the [µ-(CN)(BCF)2]− anion was confirmed.

## Abstract

The reaction of AgCN with two equivalents of tris(pentafluorophenyl)borane (BCF) in CH2Cl2 or ortho-difluorobenzene (oDFB) provides a straightforward access to (solvated) Ag+ salts of the weakly coordinating cyanide-bridged anion [µ-(CN)(BCF)2]− (suggested abbreviation [BCNB]). Reacting Ag[BCNB] with Ni(CO)4 yields the first structurally characterized complex in which Ni(CO)4 acts as a ligand towards a transition metal ion proving the extremely low basicity of the anion.

We report an easy method to generate highly electrophilic Ag+ ions in combination with a very weakly-coordinating counteranion. This allowed the first structural characterization of a metal complex featuring Ni(CO)4 as a Lewis base.