Homoleptic U(iii) and U(iv) amidate complexes

Abstract

The syntheses of the first homoleptic U(iii) and U(iv) amidate complexes are described. These can be interconverted by chemical reduction/oxidation, showing an unusual change in coordination number from four in the U(iii) complex to eight in the U(iv) complex in the solid state structures.

Chemical Vapor Deposition of Phase‐Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors

“…Deprotonation of 1 and 2 with KN(SiMe 3 ) 2 in THF generated the corresponding potassium amidates K-(ITA) (3)and K(TTA) (4)inhigh yield. As we have observed previously in related systems, [25] using these potassium amidates directly for the metalation of uranium led to the formation of undesirable -ate complexes,r esulting in poor yields of the anticipated products.T his was overcome by adding 18-crown-6 to 3 and 4 to give the crowned potassium amidates K(ITA)(18c6) (5)a nd K(ITA)(18c6) (6)i nn earquantitative yield (Scheme 1);t hese ligand salts performed much more favorably for the metalation of uranium.…”

“…[14,[16][17][18][19][20][21][22] In contrast to the myriad quantity of CVD precursors that have been described for these metals,o nly as mall handful of uranium oxide CVD precursors have ever been reported. [24] We sought to develop aclass of volatile,non-fluorinated precursors with an easily-accessible thermal decomposition pathway to UO 2 , thereby minimizing the heat required to form phase-pure UO 2 films.B ased on previous research in our group [25] and promising results from related transition-metal systems, [26][27][28] we turned to uranium amidate complexes to meet these requirements.A midate ligand substituents can be readily varied to cover aw ide range of steric and electronic properties,e nabling control over the geometry,t hermal stability, volatility,a nd decomposition mechanisms of the resulting metal complexes.U sing new U IV amidate precursors with aw ell-defined decomposition mechanism, we synthesized crystalline,phase-pure UO 2 films via CVD. [23] In am ore recent single-source process,f ilms containing am ixture of uranium oxides were synthesized via thermal CVD from fluorinated uranium heteroarylalkenolate precursors.…”

“…[23] In am ore recent single-source process,f ilms containing am ixture of uranium oxides were synthesized via thermal CVD from fluorinated uranium heteroarylalkenolate precursors. [24] We sought to develop aclass of volatile,non-fluorinated precursors with an easily-accessible thermal decomposition pathway to UO 2 , thereby minimizing the heat required to form phase-pure UO 2 films.B ased on previous research in our group [25] and promising results from related transition-metal systems, [26][27][28] we turned to uranium amidate complexes to meet these requirements.A midate ligand substituents can be readily varied to cover aw ide range of steric and electronic properties,e nabling control over the geometry,t hermal stability, volatility,a nd decomposition mechanisms of the resulting metal complexes.U sing new U IV amidate precursors with aw ell-defined decomposition mechanism, we synthesized crystalline,phase-pure UO 2 films via CVD.Thea mide proligands N-tert-butylisobutyramide (H-(ITA)) (1)a nd N-tert-butylpivalamide (H(TTA)) (2)w ere synthesized according to literature methods [29] and purified by sublimation. Deprotonation of 1 and 2 with KN(SiMe 3 ) 2 in THF generated the corresponding potassium amidates K-(ITA) (3)and K(TTA) (4)inhigh yield.…”

Chemical Vapor Deposition of Phase‐Pure Uranium Dioxide Thin Films from Uranium(IV) Amidate Precursors

“…Deprotonation of 1 and 2 with KN(SiMe 3 ) 2 in THF generated the corresponding potassium amidates K(ITA) ( 3 ) and K(TTA) ( 4 ) in high yield. As we have observed previously in related systems, using these potassium amidates directly for the metalation of uranium led to the formation of undesirable ‐ate complexes, resulting in poor yields of the anticipated products. This was overcome by adding 18‐crown‐6 to 3 and 4 to give the crowned potassium amidates K(ITA)(18c6) ( 5 ) and K(ITA)(18c6) ( 6 ) in near‐quantitative yield (Scheme ); these ligand salts performed much more favorably for the metalation of uranium.…”

“…We sought to develop a class of volatile, non‐fluorinated precursors with an easily‐accessible thermal decomposition pathway to UO 2 , thereby minimizing the heat required to form phase‐pure UO 2 films. Based on previous research in our group and promising results from related transition‐metal systems, we turned to uranium amidate complexes to meet these requirements. Amidate ligand substituents can be readily varied to cover a wide range of steric and electronic properties, enabling control over the geometry, thermal stability, volatility, and decomposition mechanisms of the resulting metal complexes.…”