Journal
CHEMICAL SCIENCE
Volume 10, Issue 26, Pages 6431-6436Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/c9sc01960j
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Funding
- U.S. Department of Energy, Office of Basic Energy Sciences, Chemical Sciences, Biosciences, and Geosciences Division [DE-SC0001861]
- U.S. Department of Energy, Office of Basic Energy Sciences, Heavy Element Chemistry program [DE-SC0001136]
- U.S. Department of Energy (DOE) [DE-SC0001861] Funding Source: U.S. Department of Energy (DOE)
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Reaction of the thorium metallacycle, [Th{N(R)(SiMe2)CH2}(NR2)(2)] (R = SiMe3) with 1 equiv. of NaNH2 in THF, in the presence of 18-crown-6, results in formation of the bridged thorium nitride complex, [Na(18-crown-6)(Et2O)][(R2N)(3)Th(mu-N)(Th(NR2)(3)] ([Na][1]), which can be isolated in 66% yield after work-up. Complex [Na] [1] is the first isolable molecular thorium nitride complex. Mechanistic studies suggest that the first step of the reaction is deprotonation of [Th{N(R)(SiMe2)CH2}(NR2)(2)] by NaNH2, which results in formation of the thorium bis(metallacycle) complex, [Na(THF)(x)][Th{N(R)(SiMe2CH2)}(2)(NR2)], and NH3. NH3 then reacts with unreacted [Th{N(R)(SiMe2)CH2}(NR2)(2)], forming [Th(NR2)(3)(NH2)] (2), which protonates [Na(THF)(x)][Th{N(R)(SiMe2CH2)}(2)(NR2)] to give [Na][1]. Consistent with hypothesis, addition of excess NH3 to a THF solution of [Th{N(R)(SiMe2)CH2}(NR2)(2)] results in formation of [Th(NR2)(3)(NH2)] (2), which can be isolated in 51% yield after work-up. Furthermore, reaction of [K(DME)][Th{N(R)(SiMe2CH2)}(2)(NR2)] with 2, in THF-d(8), results in clean formation of [K][1], according to H-1 NMR spectroscopy. The electronic structures of [1](-) and 2 were investigated by N-15 NMR spectroscopy and DFT calculations. This analysis reveals that the Th-Nnitride bond in [1](-) features more covalency and a greater degree of bond multiplicity than the Th-NH2 bond in 2. Similarly, our analysis indicates a greater degree of covalency in [1](-) vs. comparable thorium imido and oxo complexes.
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