Denise Baudry

Tetramethylphospholyluranium complexes and their pentamethylcyclopentadienyl analogues

Abstract The mono- and bis-(tetramethylphospholyl)uranium complexes [U(tmp)(Cl) 3 (L) 2 ] (tmp = C 4 Me 4 P, L = tetrahydrofuran or L 2 = dimethoxyet

Arene uranium borohydrides: synthesis and crystal structure of (η-C6Me6)U(BH4)3

Thermal decomposition of U(BH4)4 (I) in mesitylene afforded red crystals of (η-mesitylene)U(BH4)3 (II); displacement of the arene ligand of II by hexamethylbenzene gave (C6Me6)U(BH4)3 (III). The crystal structure of III revealed tetrahedral coordination, with the BH4 ligands eclipsed by three methyl substituents of the aromatic ring. The cyclopentadienyl complexes CpU(BH4)3, Cp2U(BH4)2Na, Cp3U(BH4)Na, and Cp3U(THF) were prepared from II.

The activation of C–H bonds in cyclopentane by bis(phosphine)rhenium heptahydrides

In the presence of 3,3-dimethylbut-1-ene, the complexes L2ReH7(L = PPh3 or PEt2Ph) dehydrogenate cyclopentane, giving the dihydrido-cyclopentadienyl compounds L2(η5-C5H5)ReH2.

Influence of electronic factors on the structure and stability of uranium compounds. Tri-tert-butyl methoxide uranium(IV) complexes

Abstract The complexes (tritox)UCI3(THF)x (I) and (tritox)2UCI2(THF)2 (II) (tritox = tBu3CO, THF = tetrahydrofuran) have been prepared by treating UCI4 with (tritox)Li. Compund II was a precursor for a series of (tritox)2UX2 compounds (X = BH4, CH3COCHCOCH3, η-C3H5, CH2Ph). The uranium borohydride derivative (tritox)U(BH4)3(THF) (IX) was isolated from the reaction of U(BH4)4(THF)2 with (tritox)H and was successively transformed into (tritox)2U(BH4)2 (IV) and (tritox)3U(BH4) (XI) by treatment with (tritox)Li. The crystal structures of the trigonal bipyramidal compound IX and the pseudo tetrahedral complex XI provide clear evidence of the strong Oπ→U contribution to the metaloxygen bonds. The structure and stability of these tritox compounds are quite different from those of the isosteric cyclopentadienyl analogues, and reveal the determining role of the electronic factors.

Monocyclooctatetraenyluranium(IV) borohydrides. Crystal structure of (η-C8H8)U(BH4)2(OPPh3)

U(BH4)4 has been shown to react with (COT)2U (COT = η-C8H8) or cyclooctatetraene to give the monocyclooctatetraenyl complex (COT)U(BH4)2 (III), which has been converted into the Lewis base adducts (COT)U(BH4)2L (L = PPh3, V; THF, VI; OPPh3, VII) and the mixed ring derivatives (COT(Cp)U(BH4)L (Cp = η-C5H5; L = THF; OPPh3. VIII). The crystal structure of VII shows it to have a three-legged piano stool configuration.

Metalloligands containing samarium(III). Access to binuclear f-metal (samarium)-d-metal (rhodium) complexes

The synthesis of the new dimethylphosphinotetramethylcyclopentadiene HC5Me4PMe2 and of its potassium salt KC5Me4PMe2 are reported. Reactions of this potassium salt (as well as of the known LiC5H4PPh2 and KC5Me4PPh2) with [(COT)SMCl(THF)2]2 gave a series of metalloligands (COT)Sm(C5R4PR′2(THF)n (R = H or Me; R′ = Me or Ph; n = 0 or 2; COT = η8-cyclooctatetraenyl; THF = tetrahydrofuran). The X-ray crystal structure of (COT)Sm(C5H4PPh2(THF)2 is described. These metallophosphines reacted quantitatively with (C5H5)Rh(CO)2 to give phosphido-bridged bimetallic samarium(III)-rhodium(I) complexes (COT)Sm(μ-C5R4PR′2)Rh(C5H5)(CO) (R = H or Me; R′= Me or Ph). Crystal data: C33H38O2PSm, triclinic, P1 a = 8.606(2), b = 11.458(3), c = 14.632(2) A, α = 87.09(2), β = 86.93(2), γ = 87.18(2)°, V = 1437.3 A3, Z = 2, Dx = 1.497 g cm−3, m = 21.305 cm−1, λ (Mo-Kα) = 0.71073 A, R = 0.036.

Lanthanide bis(trifluoromethanesulfonyl)amides, synthesis, characterization and catalytic activity

Abstract The synthesis of lanthanum, neodymium and ytterbium bis(trifluoromethanesulfonyl)amides, named triflimidates, from acetates, carbonates and oxides is investigated. When the synthesis is performed in water, all the salts contain one molecule of water and the lanthanum and neodymium salts synthesized from the acetates also contain one molecule of acetic acid. After removal of the water and acetic acid in refluxing ethanol, the salts are obtained anhydrous but associated for lanthanum and neodymium, whereas the ytterbium salt is monomeric and volatile. When the synthesis is performed directly in ethanol, the neodymium salt contains two molecules of coordinated ethanol. In non-hazardous solvents, these triflimidates are better catalysts than the analogous triflates toward either Friedel–Crafts acylations, or Fries transpositions or Baeyer–Villiger oxidations. Unexpectedly, the cerium(IV) triflimidate catalyzes the oxidation of aromatic ketones to give the corresponding acids.

Unsolved dimeric organometallic samarium hydride versus solvated trisalkylborane supported monomeric hydride

The dimeric hydride [Cp′2SmH]2 and the monomeric trisalkylborohydride Cp′2SmHBEt3(THF)n (Cp′  C5H4tBu) are obtained from the starting dimeric chloride [Cp′2SmCl]2 by reaction with a hydridic reagent: NaHBEt3. By hydrogenolysis of Cp′2SmR (R  CH2SiMe3 or CH(SiMe3)2) in the presence of an ancillary ligand as PMe3, a monomeric hydride: Cp′2SmH(PMe3)2 is formed. The trisalkylborohydride is fairly stable in solution when other new hydrides are only moderately stable: upon standing at room temperature, an irreversible transformation into Cp′3Sm is observed. All hydrideds react with propanone to give the corresponding alkoxide: [Cp′2SmOCHMe2]2. The new alkyl complex [Cp′2SmMe]2 is isolated and characterized by NMR and elemental analysis. After hydrogenolysis of this dimer or by reaction of one equivalent of NaHBEt3 with the dimer [Cp′2SmCl]2, mixed bridged hydrides of the general formula Cp′2Sm(μ−H)(μ−X)SmCp′2 (X  Me or Cl) are formed. A mixed bridged chloroalkoxy complex Cp′2Sm(μ-OCHR2)(μ-Cl)SmCp′2 is also obtained.

Pentadienyluranium borohydride complexes and their cyclopentadienyl analogues; crystal structures of (η-2,4-Me2C5H5)U(BH4)3 and (η-C5H5)U(BH4)3

Abstract Treatment of U(BH 4 ) 4 (I) with the potassium salt of the 2,4-dimethylpentadienyl anion (dmpd) afforded the pentadienyl complex (dmpd)U(BH 4 ) 3 (II), whereas the reaction of (dmpd) 3 U (VI) with TIBH 4 gave (dmpd) 2 U(BH 4 ) (IV). Complex VI reacted with KBH 4 in the presence of 18-crown-6-ether to give the anionic uranium(III) compound [(dmpd) 2 ][K(18-crown-6)] (VII), and the corresponding cyclopentadienyl derivative [Cp 2 U(BH 4 ) 2 ][Na(18-crown-6)] (VIII) was obtained from the Na/Hg reduction of Cp 2 U(BH 4 ) 2 (V). The open pentadienyl ligand of these complexes was found to be less strongly bound to the metal centre than its cyclic counterpart in the corresponding cyclopentadienyl derivatives. The crystal structures of the pseudo-tetrahedral II and CpU(BH 4 ) 3 (III) complexes show that the UC-(pentadienyl) bonds are longer than UC (cyclopentadienyl bonds, and that there is a large degree of ionic character in the metal-pentadienyl bonding.

Synthesis of a hydride-rich uranium-rhenium dimer: [(p-F-C6H4)3P]2ReH6U(η-C5H5)3

Abstract Reaction of L 2 ReH 6 K with Cp 3 UCl gives the complexes L 2 ReH 6 UCp 3 (L = Ph 3 P or ( p -F-C 6 H 4 ) 3 P).