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Tris(pyrazol-1-yl)borate and tris(pyrazol-1-yl)methane: A DFT study of their different binding capability toward Ag(I) and Cu(I) cations
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Inorganica Chimica Acta
Volume 362, Issue 12, 15 September 2009, Pages 4358-4364
Tris(pyrazol-1-yl)borate and tris(pyrazol-1-yl)methane: A DFT study of their different binding capability toward Ag(I) and Cu(I) cations (Article)
Casarin, M.acd , Forrer, D.ad, Garau, F.a, Pandolfo, L.ad, Pettinari, C.b, Vittadini, A.cd
a Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
b Dipartimento di Scienze Chimiche, Camerino, Italy
c Istituto di Scienze Molecolari, CNR, Padova, Italy
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Abstract
Density functional theory has been used to study the electronic structure of [M(tp)] and [M(tpm)]+ conformers (M = Cu, Ag; tp = tris(pyrazol-1-yl)borate anion, tpm = tris(pyrazol-1-yl)methane) and the energetics of their interconversions. Results for the free tp ligand are similar to those of tpm [M. Casarin, D. Forrer, F. Garau, L. Pandolfo, C. Pettinari, A. Vittadini, J. Phys. Chem. A 112 (2008) 6723], indicating an intrinsic instability of the tripodal conformation (κ3-like). This points out that, though frequently observed, the κ3-coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the κ3-like tp/tpm conformer. Analogously to the [M(tpm)]+ molecular ions, the energy barrier for the κ2-[M(tp)] → κ3-[M(tp)] conversion is computed to be negligible. Though κn-[M(tp)] and κn-[M(tpm)]+ (n = 1, 2, 3) have similar metal-ligand covalent interactions, the negative charge associated to the tp ligand makes the M-tp bonding stronger
Da Agostino di Duccio, Ritratto di Sigismondo Pandolfo Malatesta (scheda I.40)
No full textLa scheda riguarda uno dei ritratti di Sigismondo Pandolfo Malatesta all'interno del Tempio Malatestiano di Rimin
Volume thermal expansion along the jadeite–diopside join
No full textAn in situ single-crystal high-temperature X-ray diffraction study was performed on clinopyroxene crystals along the jadeite, (NaAlSi2O6 Jd)–diopside (CaMgSi2O6 Di) join. In particular, natural samples of jadeite, diopside, P2/n omphacite and three C2/c synthetic samples with intermediate composition (i.e., Jd80, Jd60, Jd40) were investigated. In order to determine the unit-cell volume thermal expansion coefficient (αV), the unit-cell parameters for all these compositions have been measured up to c.a. 1,073 K. The evolution of the unit-cell volume thermal expansion coefficient (αV) along the Jd–Di join at different temperatures has been calculated by using a modified version of the equation proposed by Holland and Powell (J Metamorph Geol 16(3):309–343, 1998). The equation aV(303K,1bar) = 2.68(3) × 10-5 + [1.1(1) × 10-8 × XJd]-[7.1(1.7) × 10-10 × X2 Jd] obtained from the αV at room-T (i.e., αV303K,1bar) allows us to predict the room-T volume thermal expansion for Fe-free C2/c clinopyroxenes with intermediate composition along the binary join Jd-Di. The observed αV value for P2/n omphacite αV(303K,1bar) = 2.58 (5) × 10-5 K-1 was compared with that recalculated for disordered C2/c omphacite published by Pandolfo et al. (Phys Chem Miner 1–10, 2012) [αV(303K,1bar) = 2.4(5) × 10-5 K-1]. Despite the large e.s.d.’s for the latter, the difference of both values at room-T is small, indicating that convergent ordering has practically no influence on the room-T thermal expansion. However, at high-T, the smaller thermal expansion coefficient for the C2/c sample with respect to the P2/n one with identical composition could provide further evidence for its reduced stability relative to the ordered one
A depth-based classifier for circular data
No full textA depth-based procedure to perform supervised classification of circular data is developed. The proposed classifier is evaluated over a real data set by comparing its performance with the discriminant method introduced by Ackermann
New thermoelastic parameters of natural C2/c omphacite
No full textThe compressibility at room temperature and the thermal expansion at room pressure of two disordered crystals (space group C2/c) obtained by annealing a natural omphacite sample (space group P2/n) of composition close to Jd 56Di 44 and Jd 55Di 45, respectively, have been studied by single-crystal X-ray diffraction. Using a Birch-Murnaghan equation of state truncated at the third order [BM3-EoS], we have obtained the following coefficients: V 0 = 421.04(7) Å 3, K T0 = 119(2) GPa, K′ = 5.7(6). A parameterized form of the BM3 EoS was used to determine the axial moduli of a, b and c. The anisotropy scheme is β c ≤ β a ≤ β b, with an anisotropy ratio 1.05:1.00:1.07. A fitting of the lattice variation as a function of temperature, allowing for linear dependency of the thermal expansion coefficient on the temperature, yielded α V(1bar,303K) = 2.64(2) × 10 -5 K -1 and an axial thermal expansion anisotropy of α b ≫ α a > α c. Comparison of our results with available data on compressibility and thermal expansion shows that while a reasonable ideal behaviour can be proposed for the compressibility of clinopyroxenes in the jadeite-diopside binary join [K T0 as a function of Jd molar %: K T0 = 106(1) GPa + 0.28(2) × Jd (mol%)], the available data have not sufficient quality to extract the behaviour of thermal expansion for the same binary join in terms of composition
High-pressure behavior of space group P2/n omphacite
No full textA single-crystal X-ray diffraction (XRD) study, using a diamond-anvil cell at high pressure and room temperature, was performed on a crystal from a natural space group P2/n omphacite sample with composition very close to Jd 55Di 45 and with a high degree of order in cation distribution. Unit-cell pa-rameters were determined at 13 different pressures up to about 7.5 GPa. A third-order Birch-Murnaghan equation of state (BM3-EoS) fitted to the P-V data yielded V 0 = 421.43(4) Å 3, K T0 = 122(1) GPa, and K' = 5.1(3). The K T0 value for this sample lies between the data obtained for the two end-members jadeite and diopside, and describes a slight positive curvature trend. During the same experiment, intensity data were collected and crystal structures were refined at 5 pressures up to 7.3 GPa. Both M1 and M2 polyhedra volumes showed a slight but significant change in slope at about 4 GPa. This behavior can likely be explained in terms of tilt angle variation of TA and TB tetrahedral, which also showed a change in slope with pressure, rather than in terms of bond length compression anomaly
Tris(pyrazol-1-yl)borate and Tris(pyrazol-1-yl)methane: A DFT Study of Their Different Binding Capability Toward Ag(I) and Cu(I) Cations
No full textDensity functional theory has been used to study the electronic structure of [M(tp)] and [M(tpm)]+ conformers (M = Cu, Ag; tp = tris(pyrazol-1-yl)borate anion, tpm = tris(pyrazol-1-yl)methane) and the energetics of their interconversions. Results for the free tp ligand are similar to those of tpm [M. Casarin, D. Forrer, F. Garau, L. Pandolfo, C. Pettinari, A. Vittadini, J. Phys. Chem. A 112 (2008) 6723], indicating an intrinsic instability of the tripodal conformation (k3-like). This points out that, though frequently observed, the k3-coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the k3-like tp/tpm conformer. Analogously to the [M(tpm)]+ molecular ions, the energy barrier for the k2-[M(tp)] → k3-[M(tp)] conversion is computed to be negligible. Though kn-[M(tp)] and kn-[M(tpm)]+ (n = 1, 2, 3) have similar metal–ligand covalent interactions, the negative charge associated to the tp ligand makes the M-tp bonding stronger
Reactivity of keteylidenetriphenylphosphorane (Ph3PC=C=O) with Pt(II) complexes. Evidences of formation of an up to now unknown bis-eta(1)-ketenyl derivative
No full textKetenylidenetriphenylphosphorane, Ph3PC=C=O, 1, has been used to synthesize some Pt(II) η1-ketenyl derivatives, through reactions with dimeric and tetrameric chlorine-bridged compounds. Particularly it has been possible to isolate and characterize [Pt(η3-C3H5)Cl{η1-C(PPh 3)CO}], 2, and [PtCl2{η1-C(PPh3)CO}(PPh3)], 3. Moreover, the reaction of 2 with a further equivalent of 1, in the presence of AgBF4, lead to the formation of [Pt(η3-C3H5){η1-C(PPh 3)CO}2], 4, the first bis-η1-ketenyl derivative. Compound 4 is stable in solution only at low temperatures and its formation has been inferred unequivocally by IR, 1H and 31P-NMR measurements carried out at -50°C
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