U(SMes*)_n, (n = 3, 4) and Ln(SMes*)₃ (Ln = La, Ce, Pr, Nd):  Lanthanide(III)/Actinide(III) Differentiation in Agostic Interactions and an Unprecedented η³ Ligation Mode of the Arylthiolate Ligand, from X-ray Diffraction and DFT Analysis

Abstract

Reaction of U(NEt(2))(4) with HS-2,4,6-(t)Bu(3)C(6)H(2) (HSMes) gave U(SMes)(3)(NEt(2))(py) (1), whereas similar treatment of U[N(SiMe(3))SiMe(2)CH(2)][N(SiMe(3))(2)](2) afforded U(SMes)[N(SiMe(3))(2)](3) (2) and U(SMes)(3)[N(SiMe(3))(2)]. The first neutral homoleptic uranium(IV) thiolate to have been crystallographically characterized, U(SMes)(4) (4), was isolated from the reaction of U(BH(4))(4) and KSMes. The first homoleptic thiolate complex of uranium(III), U(SMes)(3) (5), was synthesized by protonolysis of U[N(SiMe(3))(2)](3) with HSMes in cyclohexane. The crystal structure of 5 exhibits the novel eta(3) ligation mode for the arylthiolate ligand. Comparison of the crystal structure of 5 with those of the isomorphous lanthanide congeners Ln(SMes)(3) (Ln = La, Ce, Pr, and Nd) indicates that the U-S, U-C(ipso)(), and U-C(ortho)() bond lengths are shorter than the corresponding ones in the 4f-element analogues, when taking into account the variation in the ionic radii of the metals. The distance between the uranium and the carbon atoms involved in the U...H-C epsilon agostic interaction of each thiolate ligand is shorter, by approximately 0.05 A, than that expected from a purely ionic bonding model. The lanthanide(III)/actinide(III) differentiation was analyzed by density functional theory (DFT). The nature of the M-S bond is shown to be ionic strongly polarized at the sulfur for M = U and iono-covalent (i.e. strongly ionic with low orbital interaction), for M = Ln. The strength of the U...H-C epsilon agostic interaction is proposed to be controlled by the maximization of the interaction between U(+) and S(-) under steric constraints. The eta(3) ligation mode of the arylthiolate ligand is also obtained from DFT.

Synthesis of Terminal Uranium(IV) Disulfido and Diselenido Compounds by Activation of Elemental Sulfur and Selenium

“…28 The US distances of 2.628(2) and 2.6214(19) Å are the same within error, and within the range of U IV thiolates (2.588 to 2.736 Å), supporting anionic interactions between sulfur and uranium 10. 29, 30 The US bonds in 2 are also similar to U VI terminal disulfido compounds,31–33 including [( n ‐C 3 H 7 ) 2 NH 2 ] 2 [(UO 2 )(( n ‐C 3 H 7 ) 2 NCOS) 2 (η 2 ‐S 2 )], which has distances of 2.711(3) and 2.873(2) Å, and the uranyl persulfido, Na 4 [(UO 2 )(η 2 ‐S 2 ) 3 (CH 3 OH) 8 ,34 with distances ranging from 2.751(1) to 2.796(1) Å. The SS bond of 2.075(3) Å in 2 is within error of that reported for [( n ‐C 3 H 7 ) 2 NH 2 ] 2 [(UO 2 )(( n ‐C 3 H 7 ) 2 NCOS) 2 (η 2 ‐S 2 )] (2.05(1) Å) and similar to those for Na 4 [(UO 2 )(η 2 ‐S 2 ) 3 ](CH 3 OH) 8 (2.077(2) to 2.082(2) Å) as well as other terminal disulfido complexes for uranium (2.077(2) to 2.09(1) Å)31–33 and transition metals (2.010 to 2.072 Å),35–39 supporting the formation of the S 2 2− moiety.…”

“…[21,28] The U À S distances of 2.628(2) and 2.6214 (19) are the same within error, and within the range of U IV thiolates (2.588 to 2.736 ), supporting anionic interactions between sulfur and uranium. [10,29,30] The U À S bonds in 2 are also similar to U VI terminal disulfido compounds, [31][32][33] including…”

DFT modeling of the relative affinity of nitrogen ligands for trivalent f elements: an energetic point of view

“…Theoretical calculations can indeed help in interpreting experimental findings by providing tools for a detailed description of the metal-ligand bond. [26][27][28][29][30][31][32][33][34][35][36][37][38] However, they should not be analyzed without a direct comparison with experiments whereas experimental data are rather scarce, especially for heavy trivalent actinides. To date, theoretical studies dedicated to trivalent rare earth complexes have thus been mainly applied to structural data, with very satisfying agreements, but other computational analyses, and notably energetic analyses, have seldom been validated.…”

New UIII and UIV silylamides and an improved synthesis of NaN(SiMe2R)2 (R = Me, Ph)

“…Å) are typical of U(IV) amides[6,48], Agostic-type interactions between the uranium atom and four SieH bonds are suggested by the bent nature of the ligand as evidenced by the UeNeSi angles (Si(…”