Construction of heterometallic clusters with multiple uranium–metal bonds by using dianionic nitrogen–phosphorus ligands

Abstract

Compared with the prevalent metal–metal bond in transition metals, examples of the actinide–metal bond in heterometallic clusters are rare. Herein, a series of heterometallic clusters with multiple uranium–metal bonds has been prepared based on two newly synthesized nitrogen–phosphorus ligands L1 {O[(CH₂)₂NHP(ⁱPr)₂]₂} and L2 {[CH₂O(CH₂)₂NHP(ⁱPr)₂]₂}. Different P–P distances, 6.069 and 4.464 Å, are observed in the corresponding uranium complexes 1 {O[(CH₂)₂NP(ⁱPr)₂]₂UCl₂} and 2 {[CH₂O(CH₂)₂NP(ⁱPr)₂]₂UCl₂}, respectively, and lead to the different coordination modes with transition metals. The reactions of zero-valent group 10 metal compounds with complex 1 generate heterometallic clusters (3-U₂Ni₂ and 4-U₂Pd₂) featuring four uranium–metal bonds; whereas reactions with 2 afford one-dimensional metal-chain 5-(UNi)_n, bimetallic species 6-UPd, and a tri-platinum bridged diuranium molecular cluster 7-U₂Pt₃. Complex 5-(UNi)_n represents the first infinite chain containing the U–M bond and 7-U₂Pt₃ is the first species with multiple U–Pt bonds. This study further highlights the important role of ligands in the construction of multiple uranium–metal bonds and may allow the synthesis of novel d–f heterometallic clusters and the investigation of their applications in catalysis and small-molecule activation.