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Various 2-aryloxazoline ligands, especially o-hydroxyaryl-substituted ones, are prepared via conversion of arylaldehydes to the corresponding nitriles following by ZnCl2-catalyzed reaction with 2-amino alcohols.

Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.

Ytterbium triflate has been found to be an excellent Lewis acid catalyst for the reaction of aldehydes with allyltributylstannane.

15-crown-5 greatly facilitates Williamson ether synthesis when sodium hydride base is used in THF solvent. This mild yet versatile procedure has been employed in the synthesis of new homochiral polyether ligands and bis-allylic ethers which are inaccessible by conventional methods.

Ytterbium triflate, Yb(OTf) 3 , catalyzes the intermolecular reductive homocouplings of imines, aldehydes, and ketones at loadings of 5 mol % in the presence of Mg and Me 3 SiCl to give isolated yields of up to 95%. Diastereoselectivity of up to 4/96 ( dl / meso ) is achieved for aromatic aldehydes, up to 100% dl for aliphatic aldehydes, and 100% dl for an intramolecular imine coupling.

Lanthanum triflate–benzoic acid catalyses the in situ formation and allylation of various imines from aldehydes and an aromatic amine.

The four coordinate complexes [LnL3(Ph2CO)] [Ln = La, Eu, Tb, Yb or Y; L = N(SiMe3)2] have been prepared by reaction of [LnL3]with one equivalent of Ph2 CO. The crystal and molecular structure of [TbLn3 (Ph2CO)] have been determined by X-ray diffraction [monoclinic P21/n; a = 11.738(4), b = 31.425(4), c = 12.729(2) A; β = 110.16(3)°; Z = 4; R = 0.0437 for 5276 unique reflections]. The complex has a distorted tetrahedral arrangement of ligand atoms around terbium, and Ph2CO is coordinated through oxygen. Spectroscopic (1H NMR, 13 C NMR, IR and UV-vis) and analytical data are consistent with this structure for Ln = La, Eu, Yb or Y. Variable temperature 1H NMR studies of [EuL3(Ph2CO)] show that rotation about the EuN bonds is frozen out at 203 K, but there is still rapid rotation about the EuO bond at 180 K.

Anhydrous lithium lanthanide binaphtholates have been prepared by reaction of lanthanide tris(silylamides) with 3 equiv of LiHbinol. Li3[Y(R-binol)3]·6THF has been characterized by single-crystal X-ray diffraction, and Li3[La(S-binol)3]·6THF has been shown to be an effective reagent for the enantioselective addition of MeLi to a range of aldehydes.

Thin films of metal oxides are finding an ever increasing application in the fields of microelectronics and telecommunications, such as next-generation computer memories, microprocessors, infrared detectors, optical wave-guides and electro-optic storage1(Table 8.1).

Thin films of lanthanum zirconium oxide, LaxZr1–xO2–δ (x = 0.09 – 0.77) are deposited by liquid injection metal-organic (MO)CVD and atomic layer deposition (ALD) using toluene solutions of the precursors [(iPrCp)3La] and [(MeCp)2ZrMe(OMe)]. Auger electron spectroscopy (AES) shows that LaxZr1–xO2–δ films grown by ALD at 300 °C contain carbon at levels of 3.2 – 5.4 at.- %, whilst films grown by MOCVD at 400 °C contain carbon levels of 2.4 – 10.5 at.- %. Analysis by X-ray diffraction (XRD) shows that films with lower La contents (x) of 0.09 and 0.22 crystallize into cubic lanthanum-stabilized zirconia phase on annealing at 700 °C, whereas films of higher La content (x = 0.35, 0.63) remain amorphous. In general, the onset of crystallization of these films increases with the lanthanum fraction. For x = 0.35, crystallization to the cubic phase of ZrO2 is observed between 800 and 900 °C. LaxZr1–xO2–δ films grown by ALD show good dielectric properties with low hysteresis voltages, negligible flatband voltage shifts, and k values ranging from 11 to 14. LaxZr1–xO2–δ films grown by ALD have leakage current densities of 2.6 × 10–6 – 5.3 × 10–7 A cm–2, while films grown by MOCVD have leakage current densities of between 1.1 × 10–6 A cm–2 and 8.3 × 10–7 A cm–2.

Lanthanide complexes with the simple tert-butyl thiolate ligand are polymeric, and mostly insoluble, even in coordinating solvents; molecular complexes of the later lanthanides with this ligand are, however, stabilized by coordination of 2,2‘-bipyridyl.

A number of high-permittivity (κ) dielectric oxides are currently being investigated as alternatives to SiO 2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metal-organic (MO)CVD and atomic layer deposition (ALD) are promising techniques for the deposition of these high-K dielectric oxides. In this paper it is shown how the use of "designed" metal alkoxide precursors, containing bidentate donor-functionalized alkoxide ligands, in MOCVD leads to a marked improvement in the physical properties of the MOCVD precursors and process parameters. However, the use of such ligands is not as beneficial in the ALD process, highlighting the very different requirements of MOCVD and ALD precursors.

A complex of samarium diiodide (SmI2) with tetraglyme catalyzes the intermolecular pinacol coupling of aromatic or aliphatic aldehydes at loadings of 10 mol % in the presence of Me2SiCl2 and Mg. Diastereoselectivity of up to 95/5 (±/meso) has been achieved for aliphatic aldehydes and up to 19/81 (±/meso) for aromatic aldehydes. De values of up to 99% have been achieved in intramolecular pinacol coupling reactions using the SmI2/tetraglyme/Mg/Me2SiCl2 catalytic system.

Thin films of praseodymium oxide have been deposited by liquid injection MOCVD using the volatile praseodymium alkoxide, [Pr(mmp) 3 ] (mmp = 1-methoxy-2-methyl-2-propanolate, OCMe 2 CH 2 OMe). The films were grown over a wide range of substrate temperatures (250-600°C) and were found to consist predominantly of the Pr 6 O 11 phase. Praseodymium silicate films containing ∼16-22 at.-% Si were deposited over the temperature range 350-550°C using [Pr{N(SiMe 3 ) 2 } 3 ] in the absence of any additional Si source.

Thin films of gadolinium oxide, GdOx, have been deposited by liquid injection MOCVD using the volatile gadolinium alkoxide precursor, [Gd(mmp)3] (mmp = 1-methoxy-2-methyl-2-propanolate, OCMe2CH2OMe). Carbon-free GdOx films were grown over a wide range of substrate temperatures (300–600 °C) on both Si(100) and GaAs(100) substrates. X-ray diffraction (XRD) data indicated that GdOx films grown on Si(100) were amorphous at low deposition temperatures, and crystalline with a C-type structure at growth temperatures of 450 °C and above. GdOx films grown on GaAs at 450 °C showed a strong preferred orientation, dominated by the (222) reflection.

Lithium bis(o-anisyl)phosphide (1)may be prepared by reaction of n-BuLi with bis(o-anisyl)phosphine in THF or toluene; sodium bis(o-anisyl)phosphide (2) is prepared by reaction of sodium with tris(o-anisyl)phosphine in liquid ammonia/THF; both compounds are isolated as unsolvated solids. 1 decomposes quantitatively in THF to give tetrakis(o-anisyl)diphosphine (4); 2 decomposes in THF to give a mixture containing 4 and bis(o-anisyl)phosphine. Addition of diglyme to 2 gives [Na{mgr;-P(C(6)H(4)OMe-o)(2)}(MeO(CH(2)CH(2)O)(2)Me)](2) (2a), which has been characterized by single-crystal X-ray diffraction. Each Na atom in 2a is 6-coordinate, being bonded to two P atoms, three diglyme O atoms, and one O atom from an o-anisyl group. Crystal data: monoclinic, P2(1)/n, a = 14.549(4) Å, b = 18.555(6) Å, c = 15.846(4) Å, beta = 91.07(2) degrees, Z = 4, final R = 0.041, R(w) = 0.053.

The effect of cerium doping on the dielectric properties of hafnium dioxide is reported. Thin films of cerium-doped hafnium oxide Cex–Hf1−xO2 (x=0.10,0.17,0.34) have been grown by liquid injection atomic layer deposition. After annealing at 900 °C, all films were transformed from an amorphous state into a stabilized cubic or tetragonal phase. As-deposited films of Ce0.1–Hf0.9O2 showed low hysteresis voltages and negligible flat band voltage shifts. After annealing to form the crystalline cubic or tetragonal phase, the relative permittivity (κ) increased from 25 to 32 at 100 kHz with leakage current densities at ±1 MV cm−1 of ∼1.58×10−5 A cm−2.

Thin films of ZrO2 and HfO2 have been deposited by liquid injection metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) using a range of ansa-metallocene precursors [(Cp2CMe2)ZrMe2] (1), [(Cp2CMe2)ZrMe(OMe)] (2) [(Cp2CMe2)HfMe2] (3), and [(Cp2CMe2)HfMe(OMe)] (4) with O2 (MOCVD) or ozone (ALD) as oxygen source. The crystal structures of the new complexes 2 and 3 have been determined and they are shown to be mononuclear and isostructural to complex 1, containing a chelating [Cp2CMe2] ligand leading to a pseudo-four-coordinate distorted tetrahedral geometry around the central Zr or Hf atom, in agreement with structures from Density Functional Theory (DFT). The ZrO2 and HfO2 films were deposited by MOCVD over the temperature range 400–650 °C and by ALD over the temperature range 175–350 °C. X-Ray diffraction analysis showed that the HfO2 films deposited by MOCVD were amorphous, whereas the ZrO2 films deposited by MOCVD were in the tetragonal phase. Auger electron spectroscopy showed that residual carbon was present in all the films and that the films grown by MOCVD contained more carbon (2.4–17.0 at.%) than the films grown by ALD (1.8–2.8 at.%). The dielectric properties of ZrO2 and HfO2 films deposited by ALD were evaluated using [Al/MO2/n-Si] metal oxide semiconductor capacitor (MOSC) structures which showed that the films had low current leakage densities of less than 6 × 10−7 A cm−2 at ±2 MV cm−1.

Thin films of lanthanum zirconium oxide, LaxZr1−xO2−δ (x=0.22,0.35,0.63), have been grown by liquid injection atomic layer deposition using [(PriCp)3La] and [(MeCp)2ZrMe(OMe)] precursors. At lower La atomic fractions (x=0.22) films were stabilized in the cubic phase after annealing at 700°C in air. At higher La atomic fractions (x>0.35), the films remained amorphous after annealing. The films deposited showed good dielectric properties with low hysteresis voltages and negligible flatband voltage shifts. The relative permittivity (κ) ranged from 11 to 14 with leakage current densities at 1MVcm−1 in the range of 2.6×10−6–5.3×10−7Acm−2.

Lanthanum aluminate has been deposited for the first time by liquid injection atomic layer deposition (ALD) using a bimetallic alkoxide precursor, [LaAl(OiPr)6(iPrOH)]2 with H2O as oxygen source. The ALD growth rate was constant in the temperature range 160–300 °C, but ALD growth was not fully self-limiting. Comparisons are made with film growth by liquid injection MOCVD. Auger electron spectroscopy (AES) showed that the films contained no detectable C contamination (detection limit ∼0.5%) and XRD showed that films remained amorphous at temperatures below 850 °C. Films grown by ALD were all La deficient with La : Al ratios of 0.50–0.61; films grown by MOCVD at 300 and 450 °C have La : Al ratios of 1.24 and 0.84, respectively. C–V and leakage current data for films grown by ALD and MOCVD are presented and a LaAlOx film (La : Al = 0.54) film had a permittivity (k) of ∼13.

The new bimetallic alkoxide complex [LaAl(OPri)6(PriOH)]2 has been synthesised from the reaction between LaCl3, KAl(OPri)4 and KOPri in PriOH/toluene. The complex is volatile and has been used as a “single-source” precursor for the deposition of LaAlO3 by liquid injection MOCVD. The crystal structure of [LaAl(OPri)6(PriOH)]2 has also been determined.

Thin films of ZrO2 and HfO2 have been deposited by liquid injection MOCVD using the new alkoxide precursors [Zr(OBut)2(dmop)2] (1) and [Hf(OBut)2(dmop)2] (2) [dmop = 2-(4,4-dimethyloxazolinyl)-propanolate]. The crystal structures of 1 and 2 have been determined, and they are shown to be six-coordinate monomeric complexes. They are volatile, and are significantly less reactive to air and moisture than existing Zr and Hf alkoxide precursors such as [Zr(OBut)4] and [Hf(OBut)4]. The ZrO2 and HfO2 thin films were deposited over substrate temperatures ranging from 350–550 °C. Analysis by X-ray diffraction shows that the films were deposited in the thermodynamically stable α- or monoclinic phase, and Auger electron spectroscopy shows that the ZrO2 and HfO2 films are non-stoichiometric and that carbon (1.9–8 at%) was present in the oxide films.

Azatrane complexes with the [N(CH2CH2NSiMe3)]3- ligand are known for main group, transition, and actinide metals but, until now, not for the rare earths. Here we report the reaction of Li3[N(CH2CH2NSiMe3)3] with YCl3 to give a remarkable Y2Li3 cluster containing not only a [N(CH2CH2NSiMe3)3]3- ligand but also fragments arising from a facile cleavage of THF solvent.

Ytterbium triflate has been found to be an excellent Lewis acid catalyst for the reaction of aldehydes with allyltributylstannane.

Template condensation of 2,6-diacetylpyridine with 1,3-diamino-2-hydroxypropane in refluxing methanol in the presence of Ln(NO3)3·xH2O (Ln = La, Pr, Eu or Gd) gives [Ln3L3(OH)2(NO3)4]·nH2O (n= 4–7), where L3 is a trianionic Schiff-base macrocyclic ligand formed from three diketone and three diamine units. Analogous reactions with Ln(NCS)3·xH2O (Ln = La, Pr, Eu or Gd) as template give [Ln3L3(OH)(NCS)5]·7H2O, while Ca(NO3)2·xH2O gives [CaL2(NO3)2], where L2 is a ring-contracted 2′+ 2′ Schiff-base macrocycle. The crystal structure of [La3L3(OH)2(NO3)4]·7H2O has been determined [orthorhombic, space group Pbca(no. 61), a= 22.74(2), b= 21.130(5), c= 23.245(6)AR= 0.081, R′= 0.061]. An approximately equilateral triangle of La atoms (La ⋯ La ≈ 4 A) is bridged by a µ3-OH– ligand and encapsulated by the (3 + 3) macrocycle.

Reaction of a solution of [LaL3(Ph3PO)][L = N(SiMe3)2] with Ph2PH followed by Ph3PO yields [LaL2(PPh2)(Ph3PO)2], which has been isolated as highly air-sensitive orange crystals and characterised by solution NMR spectroscopy (31P and 1H) and X-ray crystallography. The structure was refined to a final R value of 0.056 and shows the complex to have a terminal PPh2– ligand with planar co-ordination at P. Variable-temperature 31P NMR spectroscopy indicates rapid exchange between free and co-ordinated Ph3PO at room temperature but at 193 K is consistent with the solid-state structure with two Ph3PO ligands.

The single crystal ESR spectrum of Gd 3+ doped into La(bipy) 2 (NO 3 ) 3 has been recorded at 290 K for many orientations of the crystal axes with respect to the magnetic field. A good fit of the spin Hamiltonian parameters to the experimental data has been achieved with a more efficient algorithm than previously used in this context, a significant saving being the computation of the eigenvalues only. It has been shown that previously reported spin Hamiltonian parameters for the title compound are not sufficient to describe the spectra recorded for arbitrary orientations of the single crystal and that low symmetry Gd 3+ complexes require all possible parameters to be included.

Reaction of LnCl3 with 2 equivalents of LiL [L = N(SiMe3)2] in tetrahydrofuran (thf) at –5 °C yields [{LnL2Cl(thf)}2] for Ln = Eu, Gd, or Yb or [YL2Cl(thf)2] for Ln = Y. X-Ray crystal structure analysis of the compounds of Gd and Yb confirms the formation of halide-bridged dimers. In the M2Cl2 bridging unit the M–Cl bond lengths differ slightly and the angle at the metal (ca. 74°) is much smaller than at chlorine (ca. 106°). The metal co-ordination geometries are irregular but can be best described as distorted trigonal bipyramidal with the bridging chlorines spanning one axial and one equatorial site. The bond lengths M–Cl and M–N indicate a Gd–Yb radius difference of ca. 0.07 A, but the M–O distances differ by 0.093 A. Variable-temperature n.m.r. studies of [{EuL2Cl(thf)}2] and [{YbL2Cl(thf)}2] show that there is free rotation about Ln–N and Ln–O bonds at room temperature. These rotations are frozen out at low temperatures to give a solution structure having higher symmetry (C2h) than that found in the crystal.

Decarbonylation of [Mn2HBr(CO)5(dppm)2](dppm = Ph2PCH2PPh2) using Me3No and treatment of the resultant tetracarbonyl derivative in tetrahydrofuran with LiAlH4 gives deep purple crystals of the formally unsaturated compound [Mn2H2(CO)4(dppm)2]which inserts MeCHO or MeNC to give µ-EtO or µ-MeNCH complexes and reacts with certain orher ligands such as CO or P(OMe)3 with displacement of H2.

Addition of protic acids with weakly co-ordinating anions (HBF4 or HSO3F) to dichloromethane solutions of [Mn2(CO)5(dppm)2](dppm = Ph2PCH2PPh2) containing a µ-σ,η2-CO ligand leads to the cationic complexes [Mn2H(CO)6(dppm)2][Y](Y = BF4 or SO3F·nH2O). The extra CO must have come from destruction of a manganese carbonyl intermediate compound, but under an atmosphere of CO one molecule of CO is absorbed and better yields are obtained. Addition of HCl to [Mn2(CO)5(dppm)2] gives the neutral adduct [Mn2H(Cl)(CO)5(dppm)2]. Trifluoroacetic acid shows both types of behaviour normally giving [Mn2H(CO)6(dppm)2][(CF3CO2)2H], but if the reaction solution is flushed with N2 or is kept under reduced pressure then an analogue of the chloro-compound, [Mn2H(CF3CO2)(CO)5(dppm)2], with monodentate trifluoroacetate is obtained. All protonated compounds give 1H n.m.r. quintets at high field consistent with bridging hydride ligands. The products were further characterised by their 31P-{1H} n.m.r. spectra.

Reaction of [Mn2(CO)5(dppm)2](dppm = Ph2PCH2PPh2) with HBF4·Et2O in the presence of acetonitrile gives the complex [Mn2H(CO)5(NCMe)(dppm)2][BF4] which reacts with cyanide ion to give [Mn2H(CN)(CO)5(dppm)2], shown by 1H, and 13C (90% enriched 13CN) n.m.r. to contain a terminal cyanide ligand. Decarbonylation with Me3NO·2H2O gives [Mn2H(CN)(CO)4(dppm)2], n.m.r. spectra of which at –90 °C are consistent with an asymmetrically bridging CN, probably C-bonded at one Mn atom and η2-bonded at the other. The 13C n.m.r. signal with coupling to 31P changes from a 1 : 4 : 6 : 4 : 1 quintet (J= 10.8 Hz) at 25 °C to a 1 : 2 : 1 triplet (J= 22.1 Hz) at –90 °C because the CN group is oscillating between the two metal atoms.