ABSTRACT
The preparation and structures of seven new silver(I) complexes involving the parent tris(pyrazolyl)methane unit, [C(pz)(3)], as the donor set, {[C6H5CH2OCH2C(pz)3]Ag}(BF4), {[C6H5CH2OCH2C(pz)3]2Ag3}(CF3SO3)3, {[HOCH2C(pz)3]Ag}(BF4), {[HOCH2C(pz)3]Ag}(CF3SO3), {[HC(pz)3]2Ag2(CH3CN)}(BF4)2, {[HC(pz)3]Ag}(PF6), and {[HC(pz)3]Ag}(CF3SO3), are reported. This project is based on a retro-design of our multitopic C6H(6-n)[CH2OCH2C(pz)3]n (pz = pyrazolyl ring, n = 2, 3, 4, and 6) family of ligands in such a way that each new ligand has one fewer organizational feature. The kappa2-kappa1 bonding mode of the [C(pz)3] units to two silvers, also observed with the multitopic ligands, is the dominant structural feature in all cases. Changing the counterion has important effects on the local structures and on crystal packing. When these structures are compared to similar ones based on the multitopic C6H(6-n)[CH2OCH2C(pz)3]n ligands, it has been shown that the presence of the rigid parts (central arene core and the [C(pz)3] units) are important in order to observe highly organized supramolecular structures. The presence of the flexible ether linkage is also crucial, allowing all noncovalent forces to manifest themselves in a cumulative and complementary manner.
ABSTRACT
The room temperature iron K-edge X-ray absorption near edge structure spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) and (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) have been measured between ambient and 88 and 94 kbar, respectively, in an opposed diamond anvil cell. The iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2)undergoes the expected gradual spin-state crossover from the high-spin state to the low-spin state with increasing pressure. In contrast, the iron(II) in (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) remains high-spin between ambient and 78 kbar and is only transformed to the low-spin state at an applied pressure of between 78 and 94 kbar. No visible change is observed in the preedge peak in the spectra of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))I(2) with increasing pressure, whereas the preedge peak in the spectra of ((e[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) changes as expected for a high-spin to low-spin crossover with increasing pressure. The difference in the spin-state crossover behavior of these two complexes is likely related to the unusual behavior of (Fe[HC(3,5-(CH(3))(2)pz)(3)](2))(BF(4))(2) upon cooling.
ABSTRACT
The reaction of M(BF(4))(2).xH(2)O (M = Co, Ni, and Cu) and HC(3,5-Me(2)pz)(3) in a 1:2 ratio yields [Co[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (2), [Ni[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (3), and [Cu[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (4). Over the temperature range from 5 to 350, 345, or 320 K, Curie law behavior is observed for microcrystalline samples of all three compounds showing them to have three, two, and one unpaired electrons, respectively, with no spin-crossover observed for 2. Crystalline samples of these compounds torque in the applied magnetic field the first time the sample is cooled to 5 K. The solid-state structures of all three are isomorphous at 220 K, monoclinic in the space group C2/c. The metal is located on a unique crystallographic site and has a trigonally distorted octahedral structure, with 4 showing the expected Jahn-Teller distortions. Cooling crystals of all three to low temperatures leads to the observation of the same phase change to triclinic in the new space group P(-)1 with nonmerohedral twinning. This change is reversible and yields two crystallographically unique metal sites at low temperature. The bond angles and distances for the two different metal sites for each compound in the low temperature structures are very similar to each other and to those in the 220 K structures. The same phase change, monoclinic to triclinic, has been observed previously for [Fe[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) (1), except in this case, the phase change results in half of the cations changing over from the high-spin state to the low-spin state while the other half of the cations remain high-spin, with the low-spin form decreasing its Fe-N bond distances by 0.19 A. The new results with 2-4 show that it is the phase transition, which occurs in complexes of the type [M[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2) with first row transition metals, that is driving the unusual spin-crossover behavior of [Fe[HC(3,5-Me(2)pz)(3)](2)](BF(4))(2).
ABSTRACT
The reaction of NaI with 2 equiv of HC(pz)(3) or HC(3,5-Me(2)pz)(3) (pz = pyrazolyl ring) leads to the formation of [[HC(pz)(3)](2)Na](I) (1) and [[HC(3,5-Me(2)pz)(3)](2)Na](I) (2), respectively. Both compounds have trigonally distorted octahedral arrangements about the sodium. A similar reaction of KPF(6) with HC(3,5-Me(2)pz)(3) results in the formation of [[HC(3,5-Me(2)pz)(3)](2)K](PF(6)) (3), a complex also shown crystallographically to have a trigonally distorted octahedral arrangement about the potassium, which is an unusually low coordination number for this large metal ion. The complex [[HC(pz)(3)](2)Sr](BF(4))(2) (4) forms in the reaction of Sr(acac)(2) (acac = acetylacetonate) with HBF(4).Et(2)O followed by 2 equiv of HC(pz)(3). The structure is highly distorted, showing kappa(3) bonding of both tris(pyrazolyl)methane ligands and, in addition, interactions with the metal from three fluorine atoms from the BF(4)(-) counterions. The symmetrical structure of 1 and the nine-coordinate structure of 4 are both very different from the distorted, six-coordinate structure [[HC(pz)(3)](2)Pb](BF(4))(2), indicating that for this compound the lone pair on lead(II) is influencing the structure. The reaction of M(acac)(2) (M = Sr, Ca) with H[B[3,5-(CF(3))(2)C(6)H(3)](4)] followed by 2 equiv of HC(pz)(3) produces [[HC(pz)(3)](2)(Hacac)Sr][B[3,5-(CF(3))(2)C(6)H(3)](4)](2) (5) (when the reaction is done in CH(2)Cl(2)), [[HC(pz)(3)](2)(Me(2)CO)(2)Sr][B[3,5-(CF(3))(2)C(6)H(3)](4)](2) (6) (when the reaction is done in acetone), and [[HC(pz)(3)](2)(Hacac)Ca][B[3,5-(CF(3))(2)C(6)H(3)](4)](2)(7), respectively. The structures of all three complexes show a distorted eight-coordinate arrangement of the ligands about the metal. Crystal data: 1 is orthorhombic, Pnma, a = 16.931(1), b = 22.368(3), c = 7.937(2) A, alpha = 90, beta = 90, gamma = 90 degrees, Z = 4; 2 is trigonal, R3, a = 10.7483(8), b = 10.7483(8), c = 35.395(4) A, alpha = 90, beta = 90, gamma = 120 degrees, Z = 3; 3 is monoclinic, P2(1)/c, a = 9.144(4), b = 13.377(6), c = 15.988(7) A, alpha = 90, beta = 92.291(10), gamma = 90 degrees, Z = 2; 4 is hexagonal, P6(5), a = 9.42530(10), b = 9.42530(10), c = 55.3713(5) A, alpha = 90, beta = 90, gamma = 120 degrees, Z = 6; 5 is monoclinic, P2/n, a = 14.1601(3), b = 13.1756(3), c = 27.1826(6) A, alpha = 90, beta = 90.1744(7), gamma = 90 degrees, Z = 2; 6 is monoclinic, P2/n, a = 14.2709(7), b = 13.2646(7), c = 27.4189(13) A, alpha = 90, beta = 90.3850(10), gamma = 90 degrees, Z = 2; 7 is monoclinic, P2/n, a = 14.2388(2), b = 13.1919(2), c = 26.7879(3) A, alpha = 90, beta = 90.0650(8), gamma = 90 degrees, Z = 2.
