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Synthesis and characterization of an f-block terminal parent imido [U═NH] complex: a masked uranium(IV) nitride.

King DM, McMaster J, Tuna F, McInnes EJ, Lewis W, Blake AJ, Liddle ST - J. Am. Chem. Soc. (2014)

Bottom Line: Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(Tren(TIPS))(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride.The uranium-imido linkage was found to be essentially linear, and theoretical calculations suggested σ(2)π(4) polarized U-N multiple bonding.Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(Tren(TIPS))(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium-nitride complex [U(Tren(TIPS))(N)] (5); this reaction is a new way to prepare the terminal uranium-nitride linkage and was calculated to be exothermic by -3.25 kcal mol(-1).

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Nottingham , University Park, Nottingham NG7 2RD, U.K.

ABSTRACT
Deprotonation of [U(Tren(TIPS))(NH2)] (1) [Tren(TIPS) = N(CH2CH2NSiPr(i)3)3] with organoalkali metal reagents MR (M = Li, R = Bu(t); M = Na-Cs, R = CH2C6H5) afforded the imido-bridged dimers [{U(Tren(TIPS))(μ-N[H]M)}2] [M = Li-Cs (2a-e)]. Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(Tren(TIPS))(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride. The uranium-imido linkage was found to be essentially linear, and theoretical calculations suggested σ(2)π(4) polarized U-N multiple bonding. Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(Tren(TIPS))(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium-nitride complex [U(Tren(TIPS))(N)] (5); this reaction is a new way to prepare the terminal uranium-nitride linkage and was calculated to be exothermic by -3.25 kcal mol(-1).

No MeSH data available.


Structure of 2c (40% displacement ellipsoids; non-imidoH atoms and agostic-type M···HC interactions omittedfor clarity). Complexes 2a, 2b, 2d, and 2e are essentially isostructural.
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fig1: Structure of 2c (40% displacement ellipsoids; non-imidoH atoms and agostic-type M···HC interactions omittedfor clarity). Complexes 2a, 2b, 2d, and 2e are essentially isostructural.

Mentions: To confirm the molecular structures of 2a–e, we determined their structures byX-ray crystallographyand found that the whole series adopts an essentially isostructuraldimeric formulation constructed around centrosymmetric M2N2 rings; the structure of the representative potassiumcomplex 2c is illustrated in Figure 1.9 In 2a–e the imido centers adopt distorted tetrahedral geometries,and other than the expected expansion of the M2N2 ring size as the group-1 metal becomes larger, the basic structuralunit varies little over the entire size range of the group-1 metals.The imido H atoms could be located in the Fourier transform differencemaps but were then restrained during refinement of these heavy-atomstructures. The U1–N5 bond lengths in 2a–e span the range 2.042(3) to 2.135(3) Å, with the longerU–Nimido bond lengths observed in the lighter alkalimetal complexes. This can be rationalized on the basis that lithiumand sodium are more polarizing than the heavier alkali metals. Thus,the former polarize and lessen the electron density in the U–Nimido linkage more than the latter, resulting in the observedtrend. Notably, however, the U–Nimido bond lengthsin 2a–e are significantly shorterthan the U–NH2 bond length of 2.228(4) Å in 1,6b reflecting the imido characterof 2a–e compared with the amide characterof 1. The U–Namide, U–Namine, and M–N bond lengths in 2a–e are unexceptional.11


Synthesis and characterization of an f-block terminal parent imido [U═NH] complex: a masked uranium(IV) nitride.

King DM, McMaster J, Tuna F, McInnes EJ, Lewis W, Blake AJ, Liddle ST - J. Am. Chem. Soc. (2014)

Structure of 2c (40% displacement ellipsoids; non-imidoH atoms and agostic-type M···HC interactions omittedfor clarity). Complexes 2a, 2b, 2d, and 2e are essentially isostructural.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4353020&req=5

fig1: Structure of 2c (40% displacement ellipsoids; non-imidoH atoms and agostic-type M···HC interactions omittedfor clarity). Complexes 2a, 2b, 2d, and 2e are essentially isostructural.
Mentions: To confirm the molecular structures of 2a–e, we determined their structures byX-ray crystallographyand found that the whole series adopts an essentially isostructuraldimeric formulation constructed around centrosymmetric M2N2 rings; the structure of the representative potassiumcomplex 2c is illustrated in Figure 1.9 In 2a–e the imido centers adopt distorted tetrahedral geometries,and other than the expected expansion of the M2N2 ring size as the group-1 metal becomes larger, the basic structuralunit varies little over the entire size range of the group-1 metals.The imido H atoms could be located in the Fourier transform differencemaps but were then restrained during refinement of these heavy-atomstructures. The U1–N5 bond lengths in 2a–e span the range 2.042(3) to 2.135(3) Å, with the longerU–Nimido bond lengths observed in the lighter alkalimetal complexes. This can be rationalized on the basis that lithiumand sodium are more polarizing than the heavier alkali metals. Thus,the former polarize and lessen the electron density in the U–Nimido linkage more than the latter, resulting in the observedtrend. Notably, however, the U–Nimido bond lengthsin 2a–e are significantly shorterthan the U–NH2 bond length of 2.228(4) Å in 1,6b reflecting the imido characterof 2a–e compared with the amide characterof 1. The U–Namide, U–Namine, and M–N bond lengths in 2a–e are unexceptional.11

Bottom Line: Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(Tren(TIPS))(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride.The uranium-imido linkage was found to be essentially linear, and theoretical calculations suggested σ(2)π(4) polarized U-N multiple bonding.Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(Tren(TIPS))(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium-nitride complex [U(Tren(TIPS))(N)] (5); this reaction is a new way to prepare the terminal uranium-nitride linkage and was calculated to be exothermic by -3.25 kcal mol(-1).

View Article: PubMed Central - PubMed

Affiliation: School of Chemistry, University of Nottingham , University Park, Nottingham NG7 2RD, U.K.

ABSTRACT
Deprotonation of [U(Tren(TIPS))(NH2)] (1) [Tren(TIPS) = N(CH2CH2NSiPr(i)3)3] with organoalkali metal reagents MR (M = Li, R = Bu(t); M = Na-Cs, R = CH2C6H5) afforded the imido-bridged dimers [{U(Tren(TIPS))(μ-N[H]M)}2] [M = Li-Cs (2a-e)]. Treatment of 2c (M = K) with 2 equiv of 15-crown-5 ether (15C5) afforded the uranium terminal parent imido complex [U(Tren(TIPS))(NH)][K(15C5)2] (3c), which can also be viewed as a masked uranium(IV) nitride. The uranium-imido linkage was found to be essentially linear, and theoretical calculations suggested σ(2)π(4) polarized U-N multiple bonding. Attempts to oxidize 3c to afford the neutral uranium terminal parent imido complex [U(Tren(TIPS))(NH)] (4) resulted in spontaneous disproportionation to give 1 and the uranium-nitride complex [U(Tren(TIPS))(N)] (5); this reaction is a new way to prepare the terminal uranium-nitride linkage and was calculated to be exothermic by -3.25 kcal mol(-1).

No MeSH data available.