Uranium(iv) amide and halide derivatives of two tripodal tris(N-arylamido-dimethylsilyl)methanes

Abstract

Reaction of three equivalents of ArNH(2) (Ar = 3,5-Me(2)C(6)H(3)) with HC(SiMe(2)Br)(3) in the presence of the auxiliary base NEt(3) afforded the tripodal tris(N-arylamine-dimethylsilyl)methane HC{SiMe(2)N(H)Ar}(3) (1) in 83% yield. Three-fold deprotonation of 1 with n-butyllithium afforded the corresponding tri-lithium tris(N-arylamido-dimethylsilyl)methane etherate [HC{SiMe(2)N(Li)Ar}(3)(OEt(2))] (2) in 92% yield. Salt elimination reactions between 2 or the known complex [HC{SiMe(2)N(Li)Ar'}(3)(OEt(2))(2)] (3) (Ar' = 4-MeC(6)H(4)) with one equivalent of uranium(IV) tetrachloride afforded the corresponding tris(N-arylamido-dimethylsilyl)methane uranium(IV) chloride complexes as monomeric [U(Cl){HC(SiMe(2)NAr)(3)}(THF)] (4) and dinuclear [{HC(SiMe(2)NAr')(3)}U(Cl)(mu-Cl)U(THF)(2){(Ar'NSiMe(2))(3)CH}] (5) species in 70 and 90% crystalline yields, respectively. Treatment of 4 and 5 with one equivalent of trimethylsilyl iodide resulted in halide exchange and formation of [U(I){HC(SiMe(2)NAr)(3)}(THF)(2)] (6) and [U(I){HC(SiMe(2)NAr')(3)}(THF)] (7) in 85 and 90% yields, respectively. The heteroleptic amide [U(NCy(2)){HC(SiMe(2)NAr)(3)}(THF)] (8) was prepared from the reaction between 4 and one equivalent of lithium dicyclohexylamide and was isolated in 78% yield. Analogous attempts to prepare [U(NCy(2)){HC(SiMe(2)NAr')(3)}(THF)] (9) from 5 consistently resulted in intractable mixtures of products. Complexes 1-8 have been characterised by X-ray crystallography, NMR spectroscopy, FTIR spectroscopy, room temperature Evans method solution magnetic moments, and CHN micro-analyses.

The Nature of Unsupported Uranium–Ruthenium Bonds: A Combined Experimental and Theoretical Study

“…The methine resonance of the HCSi 3 groups in the spectra of 11 (d = À81.6 ppm) and 12 (d = À76.5 ppm) are particularly diagnostic of product formation, and compare to 1 H NMR chemical shifts of d = À49.1 and À65.3 ppm for 3 and 4, respectively. [22] The 1 H NMR spectra of 9-12 are consistent with equivalent groups and effective threefold symmetry of the tripodal uranium-ligand groups on the NMR timescale and show no nonequivalence that might be anticipated from the asymmetric coordination spheres at uranium and/or ruthenium. We monitored the 1 H NMR spectra of 9-12 over the temperature range 218-298 K and found no evidence for decoalescence.…”

“…Deuterated benzene was distilled from potassium, degassed by three freeze-pump-thaw cycles, and stored under nitrogen. The compounds 1-4 [20,21,22] …”

“…[22] Some of these precursors have been successfully used to prepare the U-Ga complex [(Tren TMS )A C H T U N G T R E N N U N G (THF)UGa-A C H T U N G T R E N N U N G (NAr'CH) 2 ] [5, Ar' = 2,6-iPr 2 C 6 H 3 ], [23] and the U-Re com-…”

“…Since those initial reports, a number of supported dative actinide-metal interactions have been reported, [14,15] and unsupported uranium-metal bonds have been reported in the p-block derivatives [{(Ar)A C H T U N G T R E N N U N G (tBu)N} 3 USi-A C H T U N G T R E N N U N G (SiMe 3 ) 3 ] (Ar= 3,5-Me 2 C 6 H 3 ), [16] [(h 5 -C 5 H 5 ) 3 USnPh 3 ], [17] and [(h 5 -C 5 H 4 SiMe 3 ) 3 UEA C H T U N G T R E N N U N G (h 5 -C 5 Me 5 )] (E = Al, Ga). [18] In the past three years we have been investigating the chemistry of uranium-metal bonds using tripodal triamido uranium groups [19] derived from the precursors [ (Tren TMS ) [21] [(Ts 3 ], [22] and [(Ts…”

Uranium halide complexes stabilized by a new sterically demanding tripodal tris(N-adamantylamidodimethylsilyl)methane ligand

“…[19,20] Multidentate, sterically-demanding tripodal ligands have proven to be effective supports for low-valent uranium, exemplified by the isolation of unstable yet significant main group fragments including multiply bonded mono-and polychalcogenides and -pnictides [42,43] when coordinated to a uranium centre can impart sufficient kinetic and thermodynamic control to access a range of novel chemistry including uranium-metal bond formation, isolation of remarkable 10π-electron arene tetra-anions sandwiched between two uranium(V) centres, reductive assembly of cyclobutadienyl and diphosphacyclobutadienyl inverted sandwiches, and Zintl-cluster formation chemistry. [44][45][46][47] However, Ts p-Tol and Ts Xy are not particularly sterically demanding, and inspection of space filling diagrams from crystal structure data show that these ligands occupy at best a hemisphere of the coordination sphere at uranium.…”