Further Insights into the Structure of [M(η²(<i>C,C</i><i>‘</i>)-C₃O₂)(PPh₃)₂] (M = Ni, Pd, Pt) by Quasi-Relativistic Density Functional Calculations and Solid-State CP/MAS NMR

The molecular and electronic structures of [M(η2(C,C‘)-C3O2)(PPh3)2] (M = Ni, Pd, Pt) have been investigated by means of quasi-relativistic gradient-corrected density functional calculations and solid-state CP/MAS NMR spectroscopy. Theoretical outcomes are consistent with a square-planar coordination around the central metal atom and are in very good agreement with the bonding scheme emerging from IR and NMR data

Experimental and Theoretical Investigation of the Molecular and Electronic Structure of [Zn₄(μ₄-S){μ-S₂As(CH₃)₂}₆] and [Cd₄(μ₄-S){μ-S₂As(CH₃)₂}₆]: Two Possible Molecular Models of Extended Metal Chalcogenide Semiconductors^†

The molecular and electronic structure of hexakis[μ-(dimethylarsinodithioate-S:S‘)]-μ4-thioxotetrazinc has been investigated by combining X-ray diffraction measurements, electrospray mass spectrometry (ESI), UV absorption spectroscopy, and density functional calculations. The polynuclear zinc complex consists of discrete “tetrazinc sulfide” moieties held together by van der Waals interactions. The unit cell contains four independent molecules and four solvent molecules. Each independent unit is characterized by a central μ4-S coordinated to four Zn ions, each of them at the center of an irregular tetrahedron of S atoms. ESI measurements point out that the synthesis of the analogous Cd derivative was successful. Crystal data are as follows:  chemical formula, C12H36As6Cl1.5S13Zn4; monoclinic space group P21/n (no. 14); a = 30.4228(7) Å, b = 18.3720(5) Å, c = 32.3758(8) Å, β = 95.857(1)°; Z = 16. Theoretical calculations indicate that, despite their structural arrangement, neither the Zn nor the Cd complex can be considered molecular models of the extended ZnS and CdS. Nevertheless, the electronic transitions localized in the Zn4(μ4-S) and Cd4(μ4-S) inner cores of the title compounds have the same nature as those giving rise to the maxima in the excitation spectra of the extended Zn4S(BO2)6 and Cd4S(AlO2)6 [Blasse, G.; Dirksen, G. J.; Brenchley, M. E.; Weller, M. T. Chem. Phys. Lett. 1995, 234, 177]

Experimental and Theoretical Investigation of the Molecular and Electronic Structure of [Zn₄(μ₄-S){μ-S₂As(CH₃)₂}₆] and [Cd₄(μ₄-S){μ-S₂As(CH₃)₂}₆]: Two Possible Molecular Models of Extended Metal Chalcogenide Semiconductors^†

The molecular and electronic structure of hexakis[μ-(dimethylarsinodithioate-S:S‘)]-μ4-thioxotetrazinc has been investigated by combining X-ray diffraction measurements, electrospray mass spectrometry (ESI), UV absorption spectroscopy, and density functional calculations. The polynuclear zinc complex consists of discrete “tetrazinc sulfide” moieties held together by van der Waals interactions. The unit cell contains four independent molecules and four solvent molecules. Each independent unit is characterized by a central μ4-S coordinated to four Zn ions, each of them at the center of an irregular tetrahedron of S atoms. ESI measurements point out that the synthesis of the analogous Cd derivative was successful. Crystal data are as follows:  chemical formula, C12H36As6Cl1.5S13Zn4; monoclinic space group P21/n (no. 14); a = 30.4228(7) Å, b = 18.3720(5) Å, c = 32.3758(8) Å, β = 95.857(1)°; Z = 16. Theoretical calculations indicate that, despite their structural arrangement, neither the Zn nor the Cd complex can be considered molecular models of the extended ZnS and CdS. Nevertheless, the electronic transitions localized in the Zn4(μ4-S) and Cd4(μ4-S) inner cores of the title compounds have the same nature as those giving rise to the maxima in the excitation spectra of the extended Zn4S(BO2)6 and Cd4S(AlO2)6 [Blasse, G.; Dirksen, G. J.; Brenchley, M. E.; Weller, M. T. Chem. Phys. Lett. 1995, 234, 177]

Density Functional Theory Study of the Binding Capability of Tris(pyrazol-1-yl)methane toward Cu(I) and Ag(I) Cations

Density functional theory (DFT) has been used to look into the electronic structure of [M(tpm)]+ molecular ion conformers (M = Cu, Ag; tpm = tris(pyrazol-1-yl)methane) and to study the energetics of their interconversion. Theoretical data pertaining to the free tpm state the intrinsic instability of its κ3-like conformation, thus indicating that, even though frequently observed, the κ3-tripodal coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the κ3-like tpm conformer. It is also found that the energy barrier for the κ2-[M(tpm)]+ → κ3-[M(tpm)]+ conversion is negligible. As far as the bonding scheme is concerned, the tpm → M(I) donation, both σ and π in character, is the main source of the M(I)−tpm bonding, whereas back-donation from completely occupied M(I) d orbitals into tpm-based π* levels plays a negligible role

Sorption−Desorption Behavior of Bispyrazolato−Copper(II) 1D Coordination Polymers

A new polycrystalline vapochromic polymorph of the one-dimensional copper bispyrazolate polymer reversibly and selectively absorbs a number of small molecules; the crystal structures of the anhydrous and fully hydrated species, determined by powder diffraction methods, are markedly different despite their simple, fast, and reversible interconversion

Density Functional Theory Study of the Binding Capability of Tris(pyrazol-1-yl)methane toward Cu(I) and Ag(I) Cations

Density functional theory (DFT) has been used to look into the electronic structure of [M(tpm)]+ molecular ion conformers (M = Cu, Ag; tpm = tris(pyrazol-1-yl)methane) and to study the energetics of their interconversion. Theoretical data pertaining to the free tpm state the intrinsic instability of its κ3-like conformation, thus indicating that, even though frequently observed, the κ3-tripodal coordinative mode is unlikely to be directly achieved through the interaction of M(I) with the κ3-like tpm conformer. It is also found that the energy barrier for the κ2-[M(tpm)]+ → κ3-[M(tpm)]+ conversion is negligible. As far as the bonding scheme is concerned, the tpm → M(I) donation, both σ and π in character, is the main source of the M(I)−tpm bonding, whereas back-donation from completely occupied M(I) d orbitals into tpm-based π* levels plays a negligible role

Reaction of Copper(II) Chloroacetate with Pyrazole. Synthesis of a One-Dimensional Coordination Polymer and Unexpected Dehydrochlorination Reaction

The reaction of copper­(II) chloroacetate (<b>1d</b>) with pyrazole (Hpz) mainly yielded the mononuclear compound [Cu­(μ-ClCH₂COO)₂­(Hpz)₂] (<b>2m</b>), which self-assembled generating a one-dimensional coordination polymer. Moreover, the concomitant isolation of the tetranuclear [{Cu₂(μ-pz)­(μ-OCH₂COO)­(Hpz)­(MeOH)}₂­(μ-ClCH₂COO)₂] (<b>3t</b>) and hexanuclear [{Cu₃(μ₃-OH)­(μ-pz)₃­(Hpz)₂}₂­(μ-ClCH₂COO)₂]­(Cl)₂ (<b>4h</b>) species evidenced the occurrence of a peculiar, previously unreported, dehydrochlorination reaction and the formation of the trinuclear triangular moiety [Cu₃(μ₃-OH)­(μ-pz)₃]. Theoretical calculations based on density functional theory including solvation effects indicate a possible pathway for the formation of <b>3t</b>. Interestingly, besides the energy minimum corresponding to <b>3t</b>, a further relative energy minimum is found for a species which can be considered a possible reaction intermediate

Synthesis and Structural Characterizations of New Coordination Polymers Generated by the Interaction Between the Trinuclear Triangular SBU [Cu₃(μ₃‑OH)(μ-pz)₃]²⁺ and 4,4′-Bipyridine. 3°

The reactions of 4,4′-bipyridine with selected trinuclear triangular copper­(II) complexes, [Cu₃(μ₃-OH)­(μ-pz)₃(RCOO)₂L_<i>x</i>], [pz = pyrazolate anion, R = CH₃(CH₂)_<i>n</i> (2 ≤ <i>n</i> ≤ 5); L = H₂O, MeOH, EtOH] yielded a series of 1D coordination polymers (CPs) based on the repetition of [Cu₃(μ₃-OH)­(μ-pz)₃] secondary building units joined by bipyridine. The CPs were characterized by conventional analytical methods (elemental analyses, ESI-MS, IR spectra) and single crystal XRD determinations. An unprecedented 1D CP, generated through the bipyridine bridging hexanuclear copper clusters moieties, two 1D CPs presenting structural analogies, and two monodimensional tapes having almost exactly superimposable structures, were obtained. In one case, the crystal packing makes evident the presence of small, not-connected pores, accounting for ca. 6% of free cell volume

The Different Supramolecular Arrangements of the Triangular [Cu₃(μ₃-OH)(μ-pz)₃]²⁺ (pz = Pyrazolate) Secondary Building Units. Synthesis of a Coordination Polymer with Permanent Hexagonal Channels

By reaction of the trinuclear triangular copper(II) complex [Cu3(μ3-OH)(μ-pz)3(MeCOO)2(Hpz)] (Hpz = pyrazole), 1b, with aqueous HCl, four different crystalline species were formed and recovered through fractional crystallization. In order, the hexanuclear dicationic [{Cu3(μ3-OH)(μ-pz)3(Hpz)2}2(μ-MeCOO)2](Cl)2·2H2O, 2, the mononuclear [CuCl2(Hpz)4], 3, the heptanuclear neutral [{Cu3(μ3-OH)(μ-pz)3(Cl)2(Hpz)2(H2O)}2{CuCl2(Hpz)2}], 4, and the hexanuclear neutral [{Cu3(μ3-OH)(μ-pz)3(Cl)(Hpz)3}2(μ-Cl)2]·H2O, 5, complexes were obtained. Compounds 2, 4, and 5 all maintain the [Cu3(μ3-OH)(μ-pz)3]2+ core; nevertheless, they exhibit relevant differences in their molecular structures and supramolecular arrangements. In compound 2 a hexanuclear cluster, based on two monodentate acetate groups bridging two [Cu3(μ3-OH)(μ-pz)3(Hpz)2] units and clearly reminiscent of the structure of 1b, was observed, while the sequential replacement of the acetates by chloride ions generated 4 and 5. Although these two compounds were formed according to the same stoichiometry, they are characterized by very different molecular and supramolecular structures. The hexanuclear species 5 arranged, through hydrogen bonds, into a 3D, nonporous metal−organic framework (MOF), while the heptanuclear species 4 self-assembled through Cu−Cl bridges, giving rise to a 3D MOF having permanent hexagonal, star-shaped, parallel channels. The internal free diameter of these channels is about 4 Å, leading to a free space corresponding to ca. 9% of the total crystal volume

Reactions of a Coordination Polymer Based on the Triangular Cluster [Cu₃(μ₃-OH)(μ-pz)₃]²⁺ with Strong Acids. Crystal Structure and Supramolecular Assemblies of New Mono-, Tri-, and Hexanuclear Complexes and Coordination Polymers

A series of mono-, tri-, hexanuclear compounds, and coordination polymers were obtained from the reaction of [Cu3(μ3-OH)(μ-pz)3(MeCOO)2(Hpz)], 1, (Hpz = pyrazole) with H2SO4, H3PO4, HClO4, HNO3, CF3COOH, and CF3SO3H. The trinuclear [Cu3(μ3-OH)(μ-pz)3(SO4)(Hpz)3]·H2O, 2t, forms a one-dimensional coordination polymer through bridging SO42−. The mononuclear [Cu(H2PO4)2(Hpz)4], 3m, is instead the unique (pure) compound isolated in our conditions from the reaction of 1 with H3PO4, whereas both [Cu(ClO4)2(Hpz)4], 4m, and [{Cu3(μ3-OH)(μ-pz)3(ClO4)(Hpz)3}2(μ2-ClO4)2], 4h, have been isolated from the reaction with aqueous HClO4, the latter being a hexanuclear species formed by two trinuclear triangular units connected through two bridging perchlorates. Moreover, the three already reported species [Cu3(μ3-OH)(μ-pz)3(NO3)(μ3-NO3)(Hpz)2], 5t, [{Cu3(μ3-OH)(μ-pz)3(NO3)(Hpz)3}2(μ2-NO3)2], 5h, and [Cu(NO3)2(Hpz)4], 5m, are formed in the reaction of 1 with HNO3. Three pure fractions, containing crystals of the trinuclear [Cu3(μ3-OH)(μ-pz)3(CF3COO)2(Hpz)2], 6t, and two mononuclear adducts, [Cu(CF3COO)2(HPz)4], 6m(a), and [Cu(CF3COO)2(Hpz)2], 6m(b), have been isolated when 1 was reacted with aqueous CF3COOH. Analogously, in the reaction of 1 with CF3SO3H, three different species were obtained, the mononuclear [Cu(CF3SO3H)2(Hpz)4], 7m, the trinuclear [Cu3(μ3-OH)(μ-pz)3(CF3SO3)2(Hpz)3]·H2O, 7t, and the hexanuclear [{Cu3(μ3-OH)(μ-pz)3(Hpz)3}{Cu3(μ3-O)(μ-pz)3(Hpz)3}](CF3SO3)3, 7h, where the two trinuclear units are strongly bonded through an unequally shared H-bond involving (μ3-OH) and (μ3-O) [O···O 2.54(1) Å, O(2)−H(2)···O(1) 180°]. All compounds were fully characterized by single-crystal X-ray diffraction determinations, UV−vis and IR spectra, electrospray ionization mass spectrometry, and magnetic susceptibility measurements