Flash Communication: Pd2Zn2 Clusters from the Reduction of Palladium(II) Dichloride Precursors with Metallic Zinc

TL;DR

Scientists created new Pd2Zn2 clusters using zinc to reduce palladium precursors, and found these clusters can effectively couple aryl bromides.

Contribution

The synthesis and characterization of novel Pd2Zn2 clusters with unique Zn oxidation states and potential for catalytic homocoupling.

Findings

Pd2Zn2 clusters with a Pd2Zn2Cl3 core and chelating phosphine ligands were synthesized and structurally characterized.

Zinc in these clusters is in a formal +1.5 oxidation state with limited Zn-Zn bonding.

One cluster acts as an effective precursor for the homocoupling of aryl bromides.

Abstract

We report the synthesis and solid-state characterization
of two
unusual Pd2Zn2 clusters formed from the partial
reduction of [PdL2Cl2] precursors (L2 = dcpe or dppe) with metallic zinc. The new clusters have been characterized
by single crystal X-ray diffraction and contain a Pd2Zn2Cl3 core capped by two chelating phosphine ligands
with Zn in the formal +1.5 oxidation state. While they possess a near
tetrahedral arrangement of metal ions, calculations and bonding analysis
(NBO, AIM) suggest that there is limited Zn- - -Zn bonding
in these species. Characterization in the solution state is suggestive
of dynamic behavior on dissolution, with both diamagnetic and paramagnetic
species observed by NMR and EPR spectroscopy. One of these Pd2Zn2 clusters was shown to be an effective precursor
for the homocoupling of an aryl bromide.

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