First Isolable Molecular Thorium Nitride Complex

First Isolable Molecular Thorium Nitride Complex


Studying uranium nitride complexes, actinide chemists have gained important insights into 5f covalency and discovered novel modes of reactivity. However, isolable molecular thorium nitride complexes have remained unknown.

Guang Wu and Trevor Hayton, University of California, Santa Barbara, USA, Jochen Autschbach, University of Buffalo, State University of New York, USA, and colleagues have synthesized the first isolable molecular thorium nitride complex, [Na(18-crown-6)(Et2O)][(R2N)3Th(m-N)Th(NR2)3] (R = SiMe3) or in short [Na][1]. The team synthesized this bridged thorium nitride complex by reacting the thorium metallacycle [Th{N(R)(SiMe2)CH2}(NR2)2] (R = SiMe3) with NaNH2 in THF, in the presence of 18-crown-6. In a first reaction step, [Th{N(R)(SiMe2)CH2}(NR2)2] is deprotonated by NaNH2. The thorium bis(metallacycle) complex, [Na(THF)x][Th{N(R)(SiMe2CH2)}2(NR2)], and NH3 is formed. NH3 reacts with unreacted [Th{N(R)(SiMe2)CH2}(NR2)2], forming [Th(NR2)3(NH2)]. This protonates [Na(THF)x][Th{N(R)(SiMe2CH2)}2(NR2)] to give [Na][1].

[Na][1] was isolated in 66 % yield after work-up. The complex is thermally stable. The team characterized the thorium nitride complex by 15N NMR spectroscopy and DFT calculations. This has allowed them to evaluate the degree of 5f covalency within the Th=N=Th unit. The degree of covalency in this compound is greater than in a related oxo compound.

According to the researchers, this work further strengthens the use of NMR spectroscopy as an important tool for probing the electronic structure of the actinides.


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