Angela Domingos

SYNTHESIS OF LANTHANIDE COMPLEXES COORDINATED BY AN ASYMMETRIC CYCLOPENTADIENYL LIGAND

Abstract The synthesis and characterization of bis- and monocyclopentadienyl lanthanide [(S)-Cp′]2Lnl (Ln  Sm, 3; Ln  La, 4) and (S)-Cp′Lnl2(THF)R, (Ln  Sm, n = 3, 5; Ln  La, n = 2, 6) coordinated by an asymmetric cyclopentadienyl ligand (Cp′ = C5H2CH2CH(CH3)OCH2Ph) have been carried out. Variable-temperature NMR study of compounds 3 and 4 reveals a fluxional process in solution. The X-ray crystal structure analysis of 3 shows a bent metallocene structure with intramolecular coordination to the oxygen atoms of the side chains of both cyclopentadienyl ligands. For monocyclopentadienyl complexes, intramolecular coordination is observed only for the lanthanum complex 6. All compounds exhibit activity for the catalysis of Diels-Alder reactions.

Molecular structure of trans-bis[1,2-bis(diphenylphosphino)ethane]chloro(t-butylisocyanide)rhenium(I)-tetrahydrofuran solvate, trans-{ReCl[CN(t-C4H9)]-(Ph2PCH2CH2PPh2)2}•C4H8O

Abstract Crystals of trans -{ReCl[CN(t-C 4 H 9 )](Ph 2 PCH 2 CH 2 PPh 2 ) 2 } · C 4 H 8 O solvate are monoclinic, space group P 2 1 / n , a 24.098(7), b 16.558(5), c 13.402(4) A, β 90.97(3)°, V 5346.82 A 3 at 25°C. F (000)= 2392, Z = 4, λ(Cu-K α 1.5418 A, μ(Cu-K α ) 57.99 cm −1 D c 1.46 g cm −3 . The structure was solved by Patterson and difference Fourier electron density syntheses and refined to R ( F )= 0.048 and R w ( F )= 0.067 for 4763 observed reflections. The Re atom is in a distorted octahedral coordination with the chloride and the isocyanide as axial ligands and the two dppe groups as equatorial ligands. The ReC bond length is 1.926(9) A and the ClReC bond angle is 175.5(2)°. The CNBu t ligand is nearly linear with a 174.0(9)° angle at the N and a CN bond length of 1.154(10) A. The t-Bu group and the solvate molecules are disordered.

Iodo bis bistrimethylsilylamido lanthanides

Abstract Reactions of lanthanide triiodides with potassium bistrimethylsilyl amide have been investigated. For lanthanum, recrystallisation from THF–toluene led to monocrystals of the dimeric bisamide [La(μ-I){N(TMS) 2 } 2 (THF)] 2 . We have shown that samarium diiodide and lanthanide triiodides are efficient for lanthanum and samarium reactions, a mixture of tris amides and iodo bisamides is obtained, while only the latter compound is obtained for ytterbium.

Synthesis and characterization of polynuclear lanthanide aryloxides

The reactions of europium and ytterbium in liquid ammonia with a solution of 1-naphthol in tetrahydrofuran provide a convenient route to lanthanide aryloxides. The polymetallic lanthanide complexes [Eu 4 (μ-OC 10 H 7 ) 6 (OC 10 H 7 ) 2 (THF) 10 ].2THF 1 and [Yb(μ-OC 10 H 7 )-(OC 10 H 7 ) 2 (THF)(MeCN)] 2 .2MeCN 2 were synthesized and characterized by X-ray diffraction studies.

(R)-Binaphthoxy diiodide lanthanides

Abstract The synthesis and characterization of novel enantiopure binaphthoxy-diiodo lanthanides [(R)-2-(1-naphthol)-1′-naphthoxide)LnI2(THF)3] (Ln=Sm (4a), Yb (4b), La (4c)) are described. These complexes have been prepared by reacting the mono potassium salt of (R)-binaphthol with the corresponding lanthanide triiodides and were characterized by elemental analysis, IR and NMR spectroscopies. Recrystallization of 4c from THF–hexane led to monocrystals of [(R)-2-(1-naphthol)-1′-naphthoxide)]-diiodolanthane-tetrakistetrahydrofurane] (4c*). Complex 4c* crystallizes in the orthorhombic space group, P212121 with cell parameters a=13.086(1) A, b=15.496(1) A, c=18.854(1) A, V=3823.2(6) A3, and Z=4.

Chloro-lanthanide, and plutonium complexes containing the hydrotris (3,5-dimethylpyrazol-1-yl)borate ligand: the crystal and molecular structures of [PrCl (μ-Cl)TpMe2 (3,5-Me2pzH)]2 and YbCl2TpMe2 (THF)

Abstract Reactions of PuCl3 and LnCl3 (Ln=Pr, Nd ) with the stoichiometric amount of KTpMe2 (TpMe2=HB (3,5-Me2pz)3) yielded the dimeric [MCl (μ-Cl)TpMe2 (Me2pzH)]2 compounds (M=Pu (1), Pr (2), Nd (3)). The analogous reaction with YbCl3 afforded the monomeric YbCl2TpMe2 (THF) complex (4). The crystal and molecular structures of 2 and 4 have been assessed by means of single crystal X-ray diffraction analysis. In 2 each Pr atom is seven-coordinate and is linked to the adjacent metal centre by two bridging chlorine ligands. In 4 the Yb atom is six-coordinate and displays octahedral geometry. 4 undergoes intermolecular rearrangement reactions to yield [YbCl2TPMe2 (Me2pzH)]·THF (6) and [YbCl3TpMe2]− [ (Me2pzH2)]+ (7). The molecular structures of 6 and 7 were determined by X-ray diffraction. In 6 the tridentate ligand, the two chlorine atoms and the nitrogen atom of the neutral dimethylpyrazole describe a distorted octahedron. 7 consist of discrete [YbCl3TpMe2]− and [ (Me2pzH2)]+ ions, with the ytterbium atom of the cation coordinated to three pyrazolyl nitrogens and three chlorine atoms.

Disruption of Unprecedented B‐H…M Agostic Interactions: An Alternative Approach for Labeling Bioactive Molecules

The agostic B‐H…Re bond in complexes [Re{κ3‐R(μ‐H)B(timMe)2}(CO)3] (R=H (1), Ph (2), timMe = 2‐mercapto‐1‐methylimidazolyl) is readily cleaved by t‐butylisonitrile or cyclohexylisonitrile leading to the mixed‐ligand complexes [Re{κ2‐Ph(μ‐H)B(timMe)2}(C≡NtBu)(CO)3] (3) and [Re{κ2‐H(μ‐H)B(timMe)2}(C≡N‐cyclohexyl)(CO)3] (4), respectively. Bearing in mind the so‐called [2 + 1] mixed ligand approach for the development of target‐pecific radiopharmaceuticals, reactions of 1 with isonitriles carrying the (2‐methoxyphenyl)piperazine pharmacophore (part of WAY 100635) were also studied and the complexes [Re{κ2‐H(μ‐H)B(timMe)2}(C≡N‐R′‐WAY)(CO)3] (R′ = butylene (5), pentylene (6) or hexylene (7)) isolated. The novel mixed Re(I) tricarbonyl complexes (3–7) have been characterized by the usual analytical techniques, which included X‐ray diffraction analysis in the cases of 3, 4 and 5. The affinity of the complexes 5–7 toward the 5‐HT1A receptors was tested in competitive receptor binding assays and the IC50 values found were in the 21.9–66.5 nM range. Complex 7, with the longest spacer length between the isonitrile function and the pharmacophore, has shown an improved selectivity towards the 5‐HT1A subtype of receptors when compared with 5 and 6. This work has been partially supported by the FCT (POCTI/QUI/42939/2001) and by COST B12. Raquel Garcia would like to thank Fundação para a Ciência e Tecnologia for a PhD research grant.

Actinide poly(pyrazol-1-yl)borate complexes: Synthesis and characterization of hydrotris(3,5-dimethylpyrazol-1-yl) borate actinide(IV) aryloxides

Abstract Reactions of MCl3[HB(3,5-Me2Pz)3](thf) [M  Th(IV), U(IV)] with NaOAr (Ar  C6H5, C6H2-2,3,5-Me3) in thf yielded the complexes MCl3 − x(OAr)x[HB(3,5-Me2Pz)3](thf)y (x = 1–3; y = 0, 1) which were characterized by IR, near-IR-visible, and 1H-NMR spectroscopies. The single crystal X-ray structure of UCl(OC6H5)2 [HB(3,5-Me2Pz)3](thf) was determined. The uranium centre is seven-coordinate and displays capped octahedral geometry. This structure is compared with the previously reported structure of UCl3[HB(3,5-Me2Pz)3](thf).

Stereochemistry of two dicyclopentadienylmolybdenum complexes. Molecular structure of DI-η5-cyclopentadienyl-N-(α,α′-dimethylmethoxy)pyrazolatomolybdenum(IV) hexafluorophosphate and DI-η5-cyclopentadienylbispyrazolatomolybdenum(IV)

Abstract Crystals of di-η 5 -cyclopentadienyl- N -(α,α′-dimethylmethoxy)pyrazolatomolybdenum(IV) hexafluorophosphate, [Mo(η 5 -C 5 H 5 ) 2 (N 2 C 3 H 3 C(CH 3 ) 2 O)](PF 6 ), 1 , are monoclinic space group P 2 1 / n with a 12.943(2) A, b 10.895(2) A, c 13.623(2) A, β 105.22(1)° and Z = 4. Crystals of di-η 5 -cyclopentadienylbispyrazolatomolybdenum(IV), [Mo(η 5 -C 5 H 5 ) 2 (N 2 C 3 H 3 ) 2 ], 2 , are monoclinic space group P 2 1 / n with a 8.510(1) A, b 9.631(1) A, c 18.264(3) A, β 102.73(1)° and Z = 4. The structures were solved by Patterson and difference electron density syntheses and refined by least-squares to R 1 of 0.046 for 3791 reflexions for 1 and R 1 of 0.029 for 2109 reflexions for 2 . The structure of compound 1 consists of discrete cations with an approximate C 2υ symmetry at the molybdenum atom and PF 6 − anions. The molybdenum atom is at an average distance of 1.995 A from the cyclopentadienyl rings, and the angle between these normals is 128.8°. The MoO and MoN bond lengths are 2.026(2) and 2.123(3) A, and the OMoN bond angle is 75.4(1)°. The structure of compound 2 consists of discrete molecules with an approximate C s symmetry at the molybdenum. The molybdenum atom lies at an average distance of 1.982 A from the cyclopentadienyl rings and the angle between the ring normals is 133.2°. The MoN bond lengths are 2.166(3) and 2.157(3) A and the NMoN bond angle is 83.3(1)°.

Alkoxide and aryloxide derivatives of UCl2(HBPz3)2

Abstract Complexes of the type UCl 2 − x (OR) x (HBPz 3 ) 2 ( Pz ≡ pyrazolyl ; x = 1 or 2; R ≡ CH 3 , C 2 H 5 , C 6 H 5 , C 6 H 2 -2,3,5- Me 3 ) were prepared and characterized. The room temperature 1 H-NMR spectra of these complexes indicated that they have equivalent pyrazolyl rings, thus showing fluxional behaviour. The dynamic process can be slowed at low temperatures but the activation energy for the rearrangement is smaller than for the related complexes UCl 2 − x (X) x (HBPz 3 ) 2 ( x = 1: X = NEt 2 , NPh 2 , 3,5- Me 2 Pz ; x = 2: X ≡ SPr 1 , SBu t ; x = 1, 2: X = OBu t , OPr i , OC 6 H 2 -2,4,6- Me 3 ). The structures of theeight-coordinate complexes UCl(OC 6 H 5 )(HBPz 3 ) 2 and of the previously reported UCl(OBu t )(HBPz 3 ) 2 were determined by single crystal X-ray diffraction and are discussed.