Diphenyllead(IV) thiosemicarbazonates and pyrazolonates: Synthesis and characterization

Cyclization of thiosemicarbazones derived from β-keto esters and β-keto amides (HTSC) in the presence of diphenyllead(IV) acetate was explored in methanol solution at room temperature and under reflux. All β-keto ester TSCs underwent cyclization to give the corresponding pyrazolone (HL), which, except in one case, deprotonated and coordinated the PbPh₂²⁺ moiety to form homoleptic [PbPh₂(L)₂] or heteroleptic [PbPh₂(OAc)(L)] derivatives. Cyclization did not occur with β-keto amide TSCs and only [PbPh₂(TSC)₂] or [PbPh₂(OAc)(TSC)] thiosemicarbazonates were isolated. The complexes were characterized by IR spectroscopy in the solid state and by ¹H, ¹³C and ²⁰⁷Pb NMR spectroscopy in DMSO–d₆ solution, in which they evolve and decompose with time. Additionally, crystals of p-acetoacetanisidide thiosemicarbazone (HTSC¹⁰), [PbPh₂(OAc)(L⁵)] · MeOH (HL⁵ = 2,5-dihydro-3,4-dimethyl-5-oxo-1H-pyrazolone-1-carbothioamide), [PbPh₂Cl(L²)] (HL² = 2,5-dihydro-5-oxo-3-phenyl-1H-pyrazolone-1-carbothioamide), [PbPh₂(OAc)(TSC⁸)] · 2MeOH (HTSC⁸ = acetoacetanilide thiosemicarbazone), [PbPh₂(OAc)(TSC¹⁰)] · H₂O and [PbPh₂(OAc)(TSC¹¹)] · 0.75MeOH (HTSC¹¹ = o-acetoacetotoluidide) were studied by X-ray crystallography. The complexes, monomers or dimers with almost linear C–Pb–C moieties, are compared with the corresponding derivatives of Pb(II).     

Surfactant induced softening in gelatin hydrogels

Effect of binding of three surfactants, alpha olefin sulfonate (AOS, anionic), Triton-X100 (TX-100, non-ionic) and cetyl trimethyl ammonium bromide (CTAB, cationic) to the hydrogels of gelatin was studied at room temperature (25 °C) by dynamic light scattering and oscillatory rheology with surfactant concentrations (20-100 mM) much larger than the critical micellar concentrations (cmc) of these surfactants. The measured intensity auto-correlation function of light scattered from gels revealed the presence of finite heterodyne contribution ≈0.11 ± 0.01 that increased to ≈0.25 ± 0.02 after transition to the soft gel state indicating a softening process for surfactant concentrations exceeding 50 mM. The dynamic structure factor S(q, t) of micelle bound gelatin gels revealed two clearly identifiable relaxation modes namely; the fast mode, S(q, t) ∼ exp · (−D_fq²t) for t ? 1 ms and a stretched exponential mode, S(q, t) ∼ exp · −(t/τ_c)^β for 1 ms ? t ? 1 s. This behaviour was universal with β ≈ 0.85 ± 0.04 independent of the surfactant type. The low frequency (1.5 rad/s) storage modulus G′, loss modulus G″ and tan δ behaviour revealed a gradual softening of the gel independent of the surfactant type. The exponent (β) fast mode diffusivity (D_f) and stretched exponential mode relaxation time were found to be less sensitive to this softening transition.     

Three new dinuclear manganese(II) complexes with bis(μ-phosphinato)-bridges

A new series of dinuclear phosphinato-bridged manganese(II) complexes [Mn(μ-bmp)(bpy)(NO₃)]₂ (1), [Mn(μ-bmp)(phen)(NO₃)]₂·4CH₂Cl₂ (2) and [Mn₂(μ-bmp)₂(5-dmbpy)₂(NO₃)]₂ (3) where Hbmp is bis(4-methoxyphenyl)phosphinic acid, bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline and 5-dmbpy = 5,5′-dimethyl-2,2′-dipyridyl, have been synthesized and structurally characterized by X-ray crystallography. In this series, the structures consist in bis(4-methoxyphenyl)phosphinato anions (bmp) bridging the two Mn(II) centers in a syn-syn coordination mode. The coordination geometry around the Mn(II) ions in 1-3 is six-coordinate with distorted octahedral environment. The magnetic behavior of these complexes is reported. The complexes show weak antiferromagnetic coupling with |J| in the range 0.1-0.6 cm⁻¹. The magnetic properties are discussed in relation to the structural data.     

X-ray, Raman and FTIRS studies of the microstructural evolution of zirconia particles caused by the thermal treatment

Genesis of the structure of zirconia particles prepared by precipitation of amorphous hydrated zirconia by ammonia from the ZrO(NO₃)₂ solution followed by a mild hydrothermal treatment (HTT) of precipitate, washing and calcination under air up to 1000 °C has been studied by X-ray diffraction (XRD), Raman and FTIRS. As revealed by FTIRS of lattice modes, the local structure of amorphous zirconia subjected to HTT is close to that in m-ZrO₂. This helps to obtain nearly single-phase monoclinic nanozirconia (particle size 5-15 nm) already after a mild calcination at 500 °C. Stability of this phase with nanoparticles sizes below the critical value determined by thermodynamic constraints is due to its excessive hydroxylation demonstrated by FTIRS. Dehydroxilation and sintering of these nanoparticles at higher (600-650 °C) temperatures of calcination leads to reappearance of the (111) “cubic” reflection in XRD patterns. Modeling of XRD patterns revealed that this phenomenon could be explained by polysynthetic (001) twinning earlier observed by HRTEM.     

Infinite chains constructed from flexible bis(benzimidazole)-based ligands

Two neutral ligands, L¹ · 2H₂O and L² · H₂O, and seven complexes, [Cu(pmb)₂(L¹)] (1), [Cu(pmb)₂(L²)] (2), [Cu(Ac)₂(L²)] · 4H₂O (3), [Cu(4-aba)₂(L²)] (4), [Ag(4-ts)(L¹)(H₂O)] (5), [Ag₂(epes)₂(L¹)] · 2H₂O (6), [Ag(1,5-nds)_0.5(L²)] · 0.5C₂H₅OH · H₂O (7) [where L¹ = 1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole); L² = 1,1′-(1,4-butanediyl)bis(2-ethylbenzimidazole), pmb = p-methoxybenzoate anion; Ac = acetate anion; 4-aba = 4-aminobenzoate anion; 4-ts = p-toluenesulfonate anion; epes = N-(2-hydroxyethyl)piperazine-N′-(2-ethanesulfonate) anion; 1,5-nds = 1,5-naphthalenedisulfonate anion], have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The L¹ and L² ligands in compounds 1–7 act as bridging ligands, linking metal ions into chain structures. The chains in compounds 3, 4 and 6 interlace with each other by hydrogen bonds to generate 3D supramolecular structures. In compound 5, π–π interactions between adjacent L¹ ligands hold the chains to a supramolecular layer. In compound 7, the sulfonate anions act as counterions in the framework. The thermal stabilities of 3, 6 and 7, and the luminescent properties for 5–7 in the solid states are also discussed.     

Magnetic coupling in EE and EO azido-bridged binuclear copper complexes: Synthesis,structure and magnetic studies

Four azide bridged dinuclear copper(II) complexes, [Cu₂(L^X)₂(N₃)₂](ClO₄)₂, with L^X = substituted N,N-bis[(3,5-dimethylpyrazole-1-yl)-methyl]benzylamine, [X = H (1), OMe (2), Me (3) and Cl (4)] have been synthesized, out of which complexes 1 and 2 have been characterized structurally. In Complex 1 the two bridging azide ligands have connected the two metal centers in an end-on (EO) fashion with aSP (asymmetric Square Pyramidal) geometry and showed an weak antiferromagnetic interaction (J = −3.34 cm⁻¹). On the contrary, in complex 2, the two metal centers have been connected in end-to-end (EE) fashion exhibiting moderately strong ferromagnetic interaction (J = +19.7 cm⁻¹). Cyclic voltammetric studies performed on all the four complexes show a reasonably good correlations when E_1/2 for Cu^IICu^II → Cu^IICu^III and Cu^IICu^III → Cu^IIICu^III oxidations are plotted against σ (substituent constants) with ρ = −0.182 (R² = 0.92) and −0.684 (R² = 0.99) respectively.     

Activation of the Si-H bond of Et2SiH2 in photochemical reaction with W(CO)6: Spectroscopic characterization of intermediate W-Si compounds and the revisited crystal structure of the bis{(μ-η-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η-H-SiEt2)(CO)4}2]

The photochemical reaction of W(CO)₆ with diethylsilane has been used to generate new tungsten-silicon compounds varying in stability. The initially formed η²-silane intermediate complex [W(CO)₅(η²-H-SiHEt₂)], characterized by two equal-intensity doublets with ²J_H-H = 10 Hz at δ = 5.10 (¹J_Si-H = 217 Hz) and δ = −8.05 (¹J_W-H = 38 Hz, ¹J_Si-H = 93 Hz), was detected by the ¹H NMR spectroscopy (methylcyclohexane-d₁₄, −10 °C). The η²-silane complex was converted in the dark to give more stable species. One of them was characterized by two equal-intensity proton signals observed as doublets with ²J_H-H = 5.2 Hz at δ = −8.25 and −10.39 ppm. The singlet proton resonance at δ = −9.31 flanked by ²⁹Si and ¹⁸³W satellites (¹J_Si-H = 43 Hz, ²J_Si-H = 34 Hz, ¹J_W-H = 40 Hz) was assigned to the agostic proton of the W(η²-H-SiEt₂) group in the most stable compound isolated from the photochemical reaction products in crystalline form. The molecular structure of the bis{(μ-η²-hydridodiethylsilyl)tetracarbonyltungsten(I)} complex [{W(μ-η²-H-SiEt₂)(CO)₄}₂] was established by single-crystal X-ray diffraction studies. The tungsten hydride observed in the ¹H NMR spectrum at δ = −9.31 was located in the structure at a chemically reasonable position between the W and Si atoms of the W-Si bond of the bridging silyl ligand. The reactivity of photochemically generated W-Si compounds towards norbornene, cyclopentene, diphenylacetylene, acetone, and water was studied. As was observed by IR and NMR spectroscopy, the η²-silane ligand in the complex [W(CO)₅(η²-H-SiHEt₂)] is very easily replaced by an η²-olefin or η²-alkyne ligand.     

Anomalous charge transport in CeB6

The comprehensive study of conductivity σ, Hall coefficient R_H and Seebeck coefficient S has been carried out on high-quality single crystals of CeB₆ in a wide range of temperatures 1.8-300 K. An anomalous behavior of all transport characteristics (σ, R_H, S) was found for the first time in the vicinity of T^*≈80 K. The strong decrease of conductivity σ as well as the unusual asymptotic behavior of Seebeck coefficient S(T)∼−ln T observed below T^* allowed us to conclude in favor of crossover between different regimes of charge transport in CeB₆. The pronounced change of Hall mobility μ_H, which diminishes from the maximum value of 20 cm²/(V s) at T^* to the values of ∼6 cm²/(V s) at T∼10 K, seems to be attributed to the strong enhancement of charge carriers scattering due to fast spin fluctuations on Ce-sites. The low-temperature anomalies of the charge transport characteristics are compared with the predictions of the Kondo-lattice model.     

A new [Ni4] distorted cubane assembly on four solvent derived μ3-OMe corners: Solvent dependent formation and cleavage of exogenous bridges

A new Ni₄ distorted cubane complex [Ni₄(μ₃-OMe)₄Q₄(MeOH)₄] (1) (where Q⁻ is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)₂ · 4H₂O in refluxing MeOH via solvent derived μ₃-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni₄(OMe)₄] cubane is covered by four Q⁻ and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH₂(CH₂)₂OH), an amine substituted ethanol, producing monomeric [NiQ₂(Hgl)₂] · 2H₂O (2 · 2H₂O) instead and is able to cleave 1 to yield 2 · 2H₂O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J₁ = −1.8(1) cm⁻¹, J₂ = 3.9(1) cm⁻¹ and g = 2.24.     

Synthesis,characterization and structures of copper(II) complexes with amide-based ligands: Unusual formation of a linear trimer and a zig-zag chain and their contrast magnetic behaviour

The present work illustrates the versatile coordination modes of the amide-based ligands towards copper(II) ion. The reaction of the deprotonated form of the ligand, [L¹]²⁻ with CuCl₂ affords a linear trinuclear complex, [Cu₃(L¹)₂(Cl)₂(H₂O)] (1) which has been characterized thoroughly including single crystal structure analysis. The structure of 1 shows that one of the arm of the flexible ligand flips to coordinate second copper(II) centre, resulting in the formation of a trinuclear complex. On the other hand, ligand H₂L² in its deprotonated form reacts with Cu(II) ion to give complex 2 with general formula, [Cu(L²)]_n (2). The crystal structure of the complex 2 shows that each copper is square-pyramidal with 5th coordination coming from the O-atom of the amide group from a neighbouring complex. This results in the generation of an one-dimensional zig-zag chain. The variable temperature magnetic measurements of the complexes, 1 and 2 show that while Cu ions in the former are antiferromagnetically coupled (J = −110.34 cm⁻¹), a weak ferromagnetic interaction (J = +3.08 cm⁻¹) exists in the later. A rationale, based on the orbital overlap from the copper ions and associated ligands, is provided for the observed magnetic coupling between the copper ions.     

Wave packet and quasiclassical trajectory calculations for the N(D) + H2 reaction and its isotopic variants

The N(²D) + H₂(v = 0, j = 0) reaction and its HD and D₂ isotopic variants have been studied by means of quantum mechanical real wave packet and wave packet with split operator and quasiclassical trajectory methodologies on the potential energy surface of Ho et al. [J. Chem. Phys. 119 (2003) 6]. Total initial state-selected and final state-resolved reaction probabilities and product rotational distributions have been calculated for total angular momentum J = 0 in a broad range of collision energies. The real wave packet results are in very good agreement with the corresponding split operator wave packet calculations. A reasonable overall good agreement has been found between the wave packet and quasiclassical trajectory results. Integral cross-sections and thermal rate constants have been calculated from the wave packet reaction probabilities by means of standard J-shifting, refined J-shifting and uniform J-shifting methods in combination with the centrifugal sudden approximation for J > 0. Comparisons with available exact wave packet, quasiclassical trajectory and experimental results are made and discussed.     

Synthesis of arene ruthenium triazolato complexes by cycloaddition of the corresponding arene ruthenium azido complexes with activated alkynes or with fumaronitrile

The neutral arene ruthenium azido complexes [(η⁶-p-cymene)Ru(LL)(N₃)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η⁶-p-cymene)Ru(LL){N₃C₂(CO₂R)₂}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η⁶-p-cymene)Ru(LL)(N₃C₂HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η⁶-p-cymene)Ru(dppe)(N₃)]⁺ and [(η⁶-p-cymene)Ru(dppm)(N₃)]⁺ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction.     

Two novel rhenium complexes derived from [ReO(OMe)Cl2(dpphen)] - Synthesis, crystal structure, spectroscopic and magnetic properties

The reaction of [ReO(OMe)Cl₂(dpphen)] (dpphen = 4,7-diphenyl-1,10-phenanthroline) with triphenylphosphine has been examined and two novel rhenium complexes - [Re^IIICl₃(dpphen)(PPh₃)]·Me₂CO (1) and [Re^IVCl₄(dpphen)]·CHCl₃ (2) - have been obtained. The compounds have been characterised by elemental analysis, IR, UV-Vis spectroscopy, magnetic measurements and X-ray crystallography. The electronic structures of [ReCl₃(dpphen)(PPh₃)] and [ReCl₄(dpphen)] have been studied by DFT/B3LYP level calculations, and TD-DFT calculations have been employed for discussion of the electronic spectra in more detail. The magnetic behaviour of 1 is characteristic of mononuclear complexes with d⁴ low-spin octahedral Re(III) complexes (³T_1g ground state) and arise because of the large spin-orbit coupling (ζ = 2500 cm⁻¹), which gives diamagnetic ground state. For complex 2 the results of calculations revealed value of zero-field splitting parameter D = 10.8 cm⁻¹, g_|| = 2.49 and g_⊥ = 1.51.     

Novel oxorhenium complexes with 2-(2′-hydroxyphenyl)-2-benzothiazolinato ligand: X-ray studies,spectroscopic characterization and DFT calculations

The [ReOX₂(hbt)(EPh₃)] (X = Cl, Br; E = As, P) chelates have been prepared in the reactions of [ReOX₃(EPh₃)₂] complexes (X = Cl, Br; E = P, As) with 2-(2′-hydroxyphenyl)-2-benzothiazole (hbtH) in acetone. From the reactions of [ReOX₃(PPh₃)₂] with hbtH two kind of crystals [ReOX₂(hbt)(PPh₃)] · MeCN and [ReOX₂(hbt)(PPh₃)] with different arrangement of halide ions (cis and trans) were isolated, whereas the [ReOX₃(AsPh₃)₂] oxocompounds react with hbtH to give only cis-halide isomers. The complexes were structurally and spectroscopically characterised. The electronic structures of both [ReOBr₂(hbt)(PPh₃)] isomers have been calculated with the density functional theory (DFT) method. The TDDFT/PCM calculations have been employed to produce a hundred of singlet excited-states starting from the ground-state geometry optimized in the gas phase of cis- and trans-halide isomers of [ReOBr₂(hbt)(PPh₃)] and the UV–Vis spectra of these complexes have been discussed on this basis.     

Neutral and cationic cyclometallated Ir(III) complexes of anthra[1,2-d]imidazole-6,11-dione-derived ligands: Syntheses, structures and spectroscopic characterisation

The syntheses of two new ligands and five new heteroleptic cyclometallated Ir(III) complexes are reported. The ligands are based upon a functionalised anthra[1,2-d]imidazole-6,11-dione core giving LH¹⁻³ incorporating a pendant pyridine, quinoline or thiophene unit respectively. Neutrally charged, octahedral complexes [Ir(ppy)₂(L¹⁻³)] are chelated by two cyclometallated phenylpyridine (ppy) ligands and a third, ancillary deprotonated ligand L¹⁻³, whilst cationic analogues could only be isolated for [Ir(ppy)₂(LH¹⁻²)][PF₆]. X-ray crystal structures for [Ir(ppy)₂(L¹)], [Ir(ppy)₂(LH¹)][PF₆] and [Ir(ppy)₂(L²)] showed the complexes adopt a distorted octahedral coordination geometry, with the anthra[1,2-d]imidazole-6,11-dione ligands coordinating in a bidentate fashion. Preliminary DFT calculations revealed that for the complexes of LH¹ and LH² the LUMO is exclusively localized on the ancillary ligand, whereas the nature of the HOMO depends on the protonation state of the ancillary ligand, often being composed of both Ir(III) and phenylpyridine character. UV-vis. and luminescence data showed that the ligands absorb into the visible region ca. 400 nm and emit ca. 560 nm, both of which are attributed to an intra-ligand CT transition within the anthra[1,2-d]imidazole-6,11-dione core. The complexes display absorption bands attributed to overlapping ligand-centred and ¹MLCT-type electronic transitions, whilst only [Ir(ppy)₂(L²)] appeared to possess typical ³MLCT behaviour (λ_em = 616 nm; τ = 96 ns in aerated MeCN). The remaining complexes were generally visibly emissive (λ_em ≈ 560-570 nm; τ < 10 ns in aerated MeCN) with very oxygen-sensitive lifetimes more indicative of ligand-centred processes.     

Quantum chemical study of the bond orders in the ruthenium,diruthenium and dirhodium nitrosyl complexes

Density functional calculations with the B3LYP functional were carried out for the [Ru(NO)Cl₅]²⁻, [Ru(NO)(NH₃)₅]³⁺, [Ru(NO)(CN)₅]²⁻, [Ru(NO)(CN)₅]³⁻, [Ru(NO)(hedta)]^q (hedta = N-(hydroxyethyl)ethylenediaminetriacetate triple-charged anion; q = 0, −1, −2), Rh₂(O₂CR)₄, Rh₂(O₂CR)₄(NO)₂, Ru₂(O₂CR)₄, Ru₂(O₂CR)₄(NO)₂, Ru₂(dpf)₄, and Ru₂(dpf)₄(NO)₂ (dpf = N,N′-diphenylformamidinate ion; R = H, CH₃, CF₃) complexes. The electronic structure was analyzed in terms of Mayer and Wiberg bond order indices. The technique of bond order indices decomposition into σ-, π-, and δ-contributions was proposed.     

Iodomethane oxidative addition to β-diketonatobis(triphenylphosphite)rhodium(I) complexes: A synthetic, kinetic and computational study

New rhodium(I)- and rhodium(III)-β-diketonato complexes of the type [Rh(FcCOCHCOR)(P(OPh)₃)₂] and [Rh(FcCOCHCOR)(P(OPh)₃)₂(CH₃)(I)], with Fc = ferrocenyl and R = Fc, CH₃ and CF₃, have been synthesized. The reactivity of complexes of the type [Rh(β-diketonato)(P(OPh)₃)₂] increase in the order: β-diketonato = (CF₃COCHCOCF₃)⁻ < (CF₃COCHCOPh)⁻ < (CF₃COCHCOCH₃)⁻ < (PhCOCHCOPh)⁻ < (CF₃COCHCOFc)⁻ < (CH₃COCHCOPh)⁻ < (CH₃COCHCOCH₃)⁻ < (CH₃COCHCOFc)⁻ < (FcCOCHCOFc)⁻, giving linear relationships between the kinetic parameter ln k₂ and the parameters that are related to the electron density on the rhodium centre; the sum of the group electronegativities of the β-diketonato side groups (χ_R + χ_R′) and the pK_a of the uncoordinated β-diketone RCOCH₂COR′. The large negative values of the volume and entropy of activation indicated a mechanism which occurs via a polar transition state. A density functional theory study, at the PW91/TZP level of theory, indicates that oxidative addition of iodo methane to [Rh(FcCOCHCOCF₃)(P(OCH₃)₃)₂] occurs via a two-step mechanism. This mechanism involves a nucleophilic attack by the metal on the methyl carbon to displace iodide to form a metal-carbon bond and the coordination of iodide to the five-coordinated intermediate to give a six-coordinated trans alkyl product.     

Mononuclear ruthenium complexes containing chiral aminooxazolines: Syntheses, X-ray studies and catalytic activity

The synthesis and characterisation of three novel mononuclear ruthenium(II) complexes containing one of the following chiral auxiliary ligands: 2-amino-(4R)-phenyl-2-oxazoline (amphox), indanyl-2-amino-(4R,5S)-2-oxazoline (aminox) or indanyl-(2′-anilinyl)-(4R,5S)-2-oxazoline (aninox) is described using [Ru₂Cl₄(η⁶-p-cym)₂] (p-cym = 1-isopropyl-4-methylbenzene) as the Ru starting material. The new complexes have been identified as the neutral derivatives [RuCl₂(η⁶-p-cym)(amphox-κ¹N_ox)] (1), [RuCl₂(η⁶-p-cym)(aminox-κ¹N_ox)] (2) and the salt [RuCl(η⁶-p-cym)(aninox-κ²N,N′)]Cl (3). These materials have been fully characterised (elemental analysis, NMR, IR, conductance, MS, etc.) and, in the case of 2 and 3, structurally elucidated in the solid-state using single crystal X-ray diffraction methods. All three complexes show good catalytic activity (max. conversion >99%, TOF = 424 h⁻¹) but only modest enantio-selectivity (max. ee = 40%) for the transfer hydrogenation reaction of acetophenone with isopropyl alcohol. The complexes were also tested in an asymmetric Diels-Alder reaction involving cyclopentadiene and acrolein (max. conversion >99%, TOF = 42 h⁻¹). In this case, the diastereo-selectivity was good to moderate (max. de = 84%), but the ee values were poor (max. ee = 12%).