Tris Adducts Research Articles

Coordinatively Unsaturated Metal Centers as Building Blocks for High Coordination Number Metallomesogens

A monotropic smectic A phase is exhibited by adducts of tris(β-diketonato)lanthanide(III) complexes with a non-mesomorphic salicylaldimine Schiff base as Lewis base. Only four terminal alkyl chains were necessary in the Schiff base to induce mesomorphism in [La(dbm)3] (see formula). Hdbm = 1,3-diphenyl-1,3-propanedione (dibenzoylmethane).

Coordinatively Unsaturated Metal Centers as Building Blocks for High Coordination Number Metallomesogens.

A monotropic smectic A phase is exhibited by adducts of tris(β-diketonato)lanthanide(III) complexes with a non-mesomorphic salicylaldimine Schiff base as Lewis base. Only four terminal alkyl chains were necessary in the Schiff base to induce mesomorphism in [La(dbm)3] (see formula). Hdbm = 1,3-diphenyl-1,3-propanedione (dibenzoylmethane).

Organophosphoryl adducts of tris(pentafluorophenyl)borane; crystal and molecular structure of B(C6F5)3·Ph3PO

A series of 1 ∶ 1 adducts of B(C6F5)3 with the organophosphoryl ligands Et3PO, Ph3PO, Prn3PO, Octn3PO, (MeO)3PO, (EtO)3PO, (PhO)3PO, (EtO)2(H)PO, (BunO)2(H)PO, (PhO)2(H)PO, (MeO)2MePO, (EtO)2MePO, (EtO)2PhPO, and (EtO)Me2PO have been synthesized and characterised by elemental analysis, mp, and spectroscopic (1H, 13C, 11B, 19F, 31P NMR and IR) methods. B(C6F5)3·Ph3PO was further characterised in the solid state by a single-crystal X-ray diffraction study. 31P NMR chemical shifts and ν(PO) IR stretching frequencies are discussed in relation to substituent at phosphorus.

Dehydration from tris[β-diketonato]lanthanoids(III) on the 1,10-phenanthroline adduct formation across lanthanoid series

The residual hydration number of the metal ion in the 1,10-phenanthroline adducts of tris[1,1,1-trifluoro-5,5′-dimethyl-2,4-hexanedionato]lanthanoids in chloroform has been determined by coulometric Karl–Fischer titration and also by the luminescence lifetime of europium(III) in the complex. The residual hydration number was essentially zero for all lanthanoids across the series. This data and the hydration number of the lanthanoids(III) complexed with the β-diketone can be used to explain the trend of the variation of the formation constants of the adducts across the lanthanoid series.

Aqua, Alcohol, and Acetonitrile Adducts of Tris(perfluorophenyl)borane: Evaluation of Brønsted Acidity and Ligand Lability with Experimental and Computational Methods

Equilibrium studies have been performed to determine the Brønsted acidity of [(C6F5)3B(OH2)]·H2O, the aqua species that exists in acetonitrile solutions of B(C6F5)3 in the presence of water. NMR spectroscopic analysis of the deprotonation of [(C6F5)3B(OH2)]·H2O with 2,6-But2C5H3N in acetonitrile allows a pK value of 8.6 to be determined for the equilibrium [(C6F5)3B(OH2)]·H2O ⇄ [(C6F5)3B(OH)]- + [H3O]+. On the basis of a calculated value for the hydrogen bond interaction in [(C6F5)3B(OH2)]·H2O, the pKa for (C6F5)3B(OH2) is estimated to be 8.4 in acetonitrile. Such a value indicates that (C6F5)3B(OH2) must be regarded as a strong acid, with a strength comparable to that of HCl in acetonitrile. Dynamic NMR spectroscopic studies indicate that the aqua and acetonitrile ligands in (C6F5)3B(OH2) and (C6F5)3B(NCMe) are labile, with dissociation of H2O being substantially more facile than that of MeCN, by a factor of ca. 200 in rate constant at 300 K. Ab initio calculations were performed in the gas phase and with a dielectric solvent model to determine the strength of B−L bonds (L = H2O, ROH, MeCN) and hydrogen bonds involving B−OH2 and B−O(H)R derivatives.

Structures of the 1,10-phenanthroline and 2,2′-dipyridyl adducts of tris(2,6-dimethylheptane-3,5-dionato)europium(III)

The title compounds, conveniently abbreviated Eu(DMH) 3·o-phen and Eu(DMH) 3·dipy, have been prepared and characterized by means of their luminescence spectra and by complete structure determination by X-ray diffraction. The spectral results indicated the existence of two europium sites in the dipy compound but only one in the o-phen complex. The X-ray results show that the o-phen complex has a single geometry, the coordination polyhedron of which is best approximated as a square antiprism, whereas there are two geometries in the dipy complex, both of which are also square antiprisms but are more distorted. In all cases the chelate rings span the s edges of the square antiprism and the bond distances are typical for this type of complex.

Lewis Acid Properties of Tris(pentafluorophenyl)borane. Structure and Bonding in L−B(C6F5)3 Complexes

A variety of donor adducts of tris(pentafluorophenyl)borane were experimentally generated by reaction of a Lewis base with an excess of B(C6F5)3 in pentane. In this way, nitrile complexes (C6F5)3B·NCR (R = CH3 1a, p-CH3−C6H4 1b, p-NO2−C6H4 1c), isonitrile complexes (C6F5)3B·CNR (R = C(CH3)3 3a, C(CH3)2CH2C(CH3)3 3b, 2,6-(CH3)2−C6H3 3c), and the phosphine adduct (C6F5)3B·P(C6H5)3 (6) could be prepared. The compounds were characterized by IR and NMR spectroscopy and by X-ray structure analyses (1a, 1c, 3a, 3b, and 6). Coordination of the nitriles as well as the isonitriles to the neutral Lewis acid leads to a substantial increase in the C⋮N bond strength. This is evident from a marked shift of the ν̃C⋮N IR band to higher wavenumbers, and this interpretation is supported by the small but experimentally significant decrease of the C⋮N bond length observed by X-ray diffraction. The experimental work is complemented by a density functional study on the model complexes (C6F5)3B·L, L = CNCH3, NCCH3, PH3, CO. A detailed analysis revealed that the bonding in (C6F5)3B·L complexes is mainly dominated by electrostatic interaction, which in turn is responsible for the observed structural and spectroscopic changes. In the context of this work, the bonding of the neutral B(C6F5)3 Lewis acid is compared to the positively charged organometallic d0-Cp3M+ system (M = Zr, Hf). It was found that electrostatic effects are more pronounced for B(C6F5)3 than for the transition metal fragments. The question as to the existence of a nonclassical main group carbonyl complex, (C6F5)3B·CO, is addressed.

Complexation of tris(β-diketonato)lanthanoids with monodentate and bidentate Lewis bases in chloroform

The enthalpy change and the equilibrium constants for the formation of adducts of tris(1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)lanthanoids (LnA3) with triphenylphosphine oxide (TPPO) and 1,10-phenanthroline (phen) in chloroform across the lanthanoid series have been determined by calorimetric titration and solvent extraction techniques. The formation constants with phen increase from the light to the middle lanthanoids, and the constants do not change from the middle to the heavy lanthanoids, while the constants of the second adducts with TPPO (LnA3/TPPO=1:2) decrease with increasing atomic number, although those of the first (1:1) adducts do not change much. The enthalpy change in adduct formation with phen changes remarkably from endothermic to exothermic from light to heavy lanthanoids, while the enthalpy changes with TPPO do not vary much across the series. This suggests that, in adduct formation with phen, the match between the N–N distance in phen and the size of the lanthanoids(III), as well as dehydration from LnA3, is a significant factor in determining the stability order of the adducts, while the degree of dehydration is significant for adduct formation with TPPO.

A Fullerene derivative as an electron beam resist for nanolithography

We have explored the application of chemical derivatives of C60 as high-resolution electron beam resists. Facile spin coating was used to produce ∼100-nm-thick films of a C60 tris adduct (three functional groups) on Si surfaces. We find that these films function as high-resolution negative resists for electron beam lithography using monochlorobenzene as a developer. The film has a sensitivity of ∼1 mC/cm2 for 20 keV electrons, an order of magnitude higher than that of C60 itself, and the dry-etch durability is much better than that of conventional novolac based electron beam resists. Features with widths of 20 nm were produced.

Reversible adduct formation between phosphines and triarylboron compounds

The acceptor strength of a number of Lewis-acidic fluorinated triarylboron compounds has been established and shown to depend on the amount and position of fluorine substitution. The donor strength of tert-butyl-phosphine has been found to be greater than phosphine towards these acceptor compounds; two series of adducts have been characterised and reversible adduct formation has been demonstrated for some adducts. Crystal structures of the phosphine adducts of tris(pentafluorophenyl)boron and tris(2,6-difluorophenyl)boron have been compared with those of the tert-butylphosphine adducts of tris(pentafluorophenyl)boron and tris(3,4,5-trifluorophenyl)boron to show a correlation between the length and the strength of the adduct bond. Mixing aryl groups in the acceptor compounds has not produced new adducts. The strong acceptor compounds have been found to form unstable adducts with water which act as drying agents ultimately producing arylboric acids; the crystal structure of (2,6-difluoropheny)dihydroxyborane has been determined.

Structure and Equilibration Studies of Bis- and Tris(spirodienone) Derivatives of Medium-Sized Calixarenes

The isomerism of the tris(spirodienone) derivatives of p-tert-butylcalix[6]arene and bis(spirodienone) derivatives of p-tert-butylcalix[5]arene is analyzed. Oxidation of p-tert-butylcalix[6]arene with phenyltrimethylammonium tribromide/base afforded two chiral tris(spirodienone) calix[6]arene derivatives (3 and 4) which react with excess benzyne yielding the corresponding all-exo tris adducts 5 and 6. The structural characterization of the tris(spirodienone) derivatives was achieved by 2D NMR methods and in the case of 3, by X-ray crystallography. The main product 3 possess an alternant disposition of the ether and carbonyl functional groups and three spiro stereocenters of dissimilar configurations (RRS/SSR), while the disposition of the functional groups in 4 is nonalternant. Equilibration studies in toluene at 85 °C indicate that 3 is the thermodynamically most stable isomer. The tris adduct 5 exists in two nearly equally populated conformations which interconvert with a barrier of 12.1 ± 0.2 kcal mol-...

THE RELATIVE STABILITY OF TRIS (2-THENOYLTRI-FLUOROACETONATO)LANTHANOID(III) ADDUCTS WITH CARBOXYLIC ACIDSHAVING NAPHTHALENERING

ABSTRACT The formation constants of the adducts of tris(l-(2-thienyl) -4,4,4-trifluoro-l,3-butanedionato) lantha-noids(III) with 1- and 2-naphthalenecarboxylic or 1-and 2-naphthaleneacetic acids have been determined by the solvent extraction method at 298K. It has been found that the adducts with naphthalenecarboxylic acid are a little more stable than those with naphthalene-acetic acid irrespective of lanthanoid as similar as the formation of more stable adducts with benzoic acid than with phenylacetic acid reported before. The formation constants of the adducts of several lanthanoid chelates with these four carboxylic acids decreased from lanthanum to samarium and from terbium to lutetium with increasing atomic number, while the constants did not change much in the middle of the series. Such trend has been discussed in the relation to the difference of the coordination number between the lighter and the heavier lanthanoids(III).

Spectroscopically distinct geometrical isomers in a single crystal. Characterization of the eight-coordinate adducts of tris(dipivaloylmethanato)lanthanide(III) with 2,9-dimethyl-1,10-phenanthroline

Tris(dipivaloylmethanato)(2,9-dimethyl-1,10-phenanthroline)lanthanide(III), [Ln(DPM)[sub 3][center dot]DMOP], complexes (Ln = La, Eu, Tb, Ho) were synthesized from [Ln(DPM)[sub 3]] and 2,9-dimethyl-1,10-phenanthroline in carbon tetrachloride. The Eu[sup 3+] and Tb[sup 3+] complexes were characterized spectroscopically by infrared and luminescence techniques. The luminescence spectra of the Eu[sup 3+] and Tb[sup 3+] adducts were recorded at 77 K. For Eu[sup 3+], two transitions in the [sup 5]D[sub 0] [yields] [sup 7]Fo region are observed which are separated by an unprecedented 35 cm[sup [minus]1]. The [sup 5]D[sub 0] [yields] [sup 7]F[sub 1] and [sup 5]D[sub 0] [yields] [sup 7]F[sub 2] spectral regions contain six and eight bands, respectively, indicating two distinct Eu[sup 3+] environments. The Eu[sup 3+] luminescence spectrum indicates that both Eu[sup 3+] environments have local site symmetry C[sub 1]. The crystal structure of [Eu(DPM)[sub 3][center dot]DMOP] was solved by single-crystal X-ray diffraction methods. Two geometrical isomers were found to exist in the unit cell with the ligating atoms forming an eight-coordinate distorted square antiprism. The two isomers differ only in the way the chelate rings span the lateral (1) and square (s) edges of a square antiprism with occupancy factors of 59 and 41%. X-ray crystallographic occupancy factors were determined for [La(DPM)[sub 3][center dot]DMOP], [Tb(DPM)[submore » 3][center dot]DMOP], and [Ho(DPM)[sub 3][center dot]DMOP], and each complex was found to crystallize in the monoclinic space group P2[sub 1]/n. Each of these adducts contain isomers which exist in 57 to 43%, 58 to 42%, and 55 to 45% ratios for La[sup 3+], Tb[sup 3+], and Ho[sup 3+], respectively. The isomer found more often in each case has all four chelate rings spanning the l edges of a square antiprism while the remaining isomer has two [beta]-diketonate rings spanning s edges and a [beta]-diketonate and a DMOP chelate ring spanning l edges.« less

ChemInform Abstract: Diphenylphosphine Adducts of Tris(neopentyl) and Tris(trimethylsilylmethyl)gallium and ‐indium Including the Crystal and Molecular Structure of (Me3CCH2)3Ga·P(H)Ph2.

AbstractThe phosphine‐Ga(III) adducts (III) ((IIIa): space group P1, Z=2) are isolated as crystalline solids at room temp. and characterized by cryoscopic mol.

The chemistry of diphenylphosphine adducts of tris(neopentyl) and tris(trimethylsilyl-methyl)gallium and -indium including the crystal and molecular structure of (Me 3CCH 2) 3Ga·P(H)Ph 2

The adducts (Me 3CCH 2) 3Ga·P(H)Ph 2 and (Me 3SiCH 2) 3Ga·P(H)Ph 2 have been prepared as crystalline solids at room temperature and characterized by cryoscopic molecular weight measurements in benzene solution and 1H NMR, 31P NMR and IR spectroscopic data. The molecular weight studies demonstrate that both adducts are extensively dissociated in solution and that Ga(CH 2CMe 3) 3 is a stronger Lewis acid than Ga(CH 2SiMe 3) 3. An X-ray structural study defined the nature of (Me 3CCH 2) 3Ga·P(H)Ph 2 in the solid state. The colourless crystal contains two discrete molecules in each unit cell. The compound crystallizes in the triclinic space group P 1 with unit cell dimensions of a = 9.564(8), b = 12.208(5), c = 12.946(9) Å, α = 100.00(5), β = 100.41(8), γ = 102.97(7)° and D calc = 1.10 g cm −3. The adduct has a relatively long GaP distance of 2.683(5) Å and the α-carbon atoms of the substituents on gallium and phosphorus are essentially but not perfectly eclipsed. The syntheses of (Me 3CCH 2) 3In·P(H)Ph 2 and (Me 3SiCH 2) 3In·P(H)Ph 2 were attempted but room temperature elimination reactions, which produced CMe 4 and SiMe 4, respectively, and the appropriate organoindium phosphides, precluded the isolation of adducts. Simple kinetic studies revealed that In(CH 2CMe 3) 3-P(H)Ph 2 eliminated CMe 4 at 17°C significantly faster than In(CH 2SiMe 3) 3-P(H)Ph 2 produced SiMe 4.

Preparation of some Lewis base adducts of tris(methyltrihydroborato)Ho and Yb and crystal structures of tris(methyltrihydroborato)ytterbium(III)etherate and tris(methyltrihydroborato)holmium(III)bis(pyridine)

The complexes M(BH 3CH 3) 3·O(C 2H 5) 2 (M=Lu, Yb, Ho); M(BH 3CH 3) 3·OC 4H 8 (M=Lu, Yb, Ho); M(BH 3CH 3) 3·2OC 4H 8 (M=Ho, Yb); and Ho(BH 3CH 3) 3·2C 6H 5N have been prepared and characterized. The crystal structures of Yb(BH 3CH 3) 3·O(C 2H 5) 2 and Ho(BH 3CH 3) 3·2C 6H 5N have been determined. Crystals of (CH 3BH 3) 3Yb·O(C 2H 5) 2 are monoclinic, P2 1/ n, Z=4, with a=10.745(4), b= 15.647(4), c=9.215(3) Å, and β=90.78(2)° at 23 °C; crystals of (CH 3BH 3) 3Ho·2(C 5H 5N) are triclinic, P1, Z=2, with a=9.370(4), b=12.155(2), c=8.840(2) Å, α=80.47(2)°, β=107.41(2)° and γ=95.15(2)° at 23 °C. The structures were refined by least-squares to a conventional R factor of 0.023, [2767 data, F 2>;2σ( F 2)] for the Yb complex, and 0.040 [1554 data, F 2>;3σ( F 2)] for the Ho complex. Both complexes are monomeric. The ytterbium atom is tetrahedrally coordinated to three boron atoms and an ethyl oxygen atom with distances: YbB 2.40(2), 2.41(2), 2.43(2) Å, and YbO 2.23(1) Å. The holmium atom is at the center of a trigonal bipyramid that has three boron atoms on the equator and two nitrogen atoms at the apices with distances: HoB 2.483(6), 2.495(6) and 2.520(5) Å and HoN 2.535(4) and 2.555(4) Å.

Tris(2,2,2-trichloroethoxy)iron(III) complexes

The preparation, magnetic moments, i.r., reflectance and57Fe Mossbauer spectra of adducts of tris(2,2,2-trichloroethoxy)iron (III) complexes are reported. An alkoxybridged structure is supported by i.r. spectra.57Fe Mossbauer spectra are explained in terms of two inequivalent sites in highspin iron(III) octahedral symmetry.

Mixed-ligand lanthanide complexes—II : Complexes of β-diketone and heterocyclic amine. Synthesis and spectroscopic studies

The imidazole adducts of tris(heptafluorooctanedionato)lanthanide(III), [Ln(fod) 3 · im] have been synthesized and characterized. The electronic spectra in the visible region have been analysed and spectral parameters ( β , b 1/2, δ and T λ) and oscillator strengths calculated and discussed. These complexes are more covalent than the analogous [Ln(fod) 3 · pz] complexes, pz = pyrazole. The covalency is more in solution than in the solid state. The experimental and the calculated oscillator strengths are in good agreement. The band shape for the hypersensitive transition in the solid and solution spectra is compared with the other known systems and discussed. The difference in the band shape of the hypersensitive transition in the solid and in solution is indicative of solvent molecule coordination. The Mössbauer spectrum of [Eu(fod) 3 · im] is reported. The dipolar shift produced in the NMR spectrum of [Eu(fod) 3 · im] is upfield in comparison to the signal of the organic moiety itself as well as in its diamagnetic analogues. The coordinated base does not dissociate even in DMSO solution. Due to their poor solubility these compounds are not suitable for use as induced NMR shift reagents.

Calorimetric titration studies of adduct formation between lanthanide β-diketonates and organic bases in benzene solution

The technique of titration calorimetry has been used to study the reactions of lanthanide shift reagents with organic substrates in benzene solution. Stability constants and enthalpies and entropies of formation have been determined for adducts of tris(2,2,6,6-tetramethylheptane-3,5-dionato)-europium(III) and -ytterbium(III) and tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dionato)-europium(III) and -praseodymium(III) with pyridine, 2-methyl-, 3-methyl-, and 4-methyl-pyridine, 2,4,6-trimethylpyridine, dimethyl sulphoxide, and pyridine N-oxide. Adduct-formation constants mostly lie in the range 2 < log K < 4 and enthalpies of adduct formation in the range 15 < –ΔH⊖ < 35 kJ mol–1 with some variations which can be related to steric effects. Unusual positive entropy changes associated with the formation of adducts of the fluorinated reagents can be correlated with their unusually high solubility.

Nuclear magnetic resonance studies of lanthanoid complexes. Part 3. Adducts of tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dionato)praseodymium with bidentate amines

Dynamic n.m.r. spectra have been obtained for adducts of the titie complex [Pr(fod)3] with substituted ethylenediamines. Four exchange processes have been characterized or observed: (i) intermolecular exchange; (ii) ring opening; (iii) ring inversion; and (iv) intramolecular rearrangement(s) of the eight-co-ordinate complex. Barriers to ring inversion are reported. For the NN′-dimethylethylenediamine adduct, DL. and meso isomers are present in a 3.0 : 1 ratio.