Structural, Magnetic and Mössbauer Spectral Studies of Salts of Bis[2,6-bis(pyrazol-3-yl)pyridine]iron(II)—a Spin Crossover System

1994 ◽  
Vol 47 (5) ◽  
pp. 869 ◽  
Author(s):  
KH Sugiyarto ◽  
DC Craig ◽  
AD Rae ◽  
HA Goodwin

The magnetic and Mossbauer spectral properties of hydrated and anhydrous complex salts [Fe( bpp )2] X2, where bpp = [2,6-bis(pyrazol-3-yl)pyridine] and X = PF6, BF4, Br, I, NO3, are indicative of a temperature-induced singlet (1A1) ↔ quintet (5T2) transition in the complex cation. The nature of the transition depends on the anion and the degree of hydration. The transition is displaced to lower temperatures in the anhydrous species and for the hydrated is only partial above room temperature. The transition in the hydrated hexafluorophosphate salt occurs in two steps, and that in the anhydrous hexafluorophosphate is incomplete, a high residual fraction of quintet state species being retained below the transition temperature. For the anhydrous complexes the transition is discontinuous and that in the complex iodide is associated with a narrow thermal hysteresis with transition temperatures Tc ↓ = 203 K and Tc ↑ = 205 K. The structures of [Fe( bpp )2]I2.4H2O and [Fe( bpp )2][BF4]2.3H2O have been determined at 298 K. Both complex salts are essentially low spin at this temperature and have an average Fe-N distance of 1.95 Ǻ. The structures reveal in both instances an extended hydrogen-bonded network involving the uncoordinated >NH groups of the ligands, the anions and lattice water. It is suggested that it is this bonding which is responsible for the favouring of the singlet state in the hydrated salts. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) diiodide tetrahydrate : triclinic, space group Pī , a 8.276(8), b 8.305(7), c 21.941(27) Ǻ, α 98.11(5), β 90.08(6), γ 90.82(6)°, Z 2. Bis [2,6-bis(pyrazol-3-yl)pyridine]iron(II) bis ( tetrafluoroborate ) trihydrate : monoclinic, space group C2/c, a 31.222(15), b 14.456(3), c 12.907(5) Ǻ, β 99.40(2)°, Z 8.

1997 ◽  
Vol 50 (2) ◽  
pp. 129 ◽  
Author(s):  
Bradley J. Childs ◽  
John M. Cadogan ◽  
Donald C. Craig ◽  
Marcia L. Scudder ◽  
Harold A. Goodwin

Complex salts containing the [FeIIN6]2+ derivative of 2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole (pzaptH) undergo continuous, temperature-induced singlet (1A1) quintet (5T2) transitions with the transition temperature being dependent on the nature of the counter anion and the presence of solvate water, the latter tending to stabilize the singlet state. A transition is also observed for the fluoroborate salt in methanol solution. The extent of stabilization of the singlet state for iron(II) in these complexes is somewhat greater than in those derived from the previously studied 2-(pyridin-2-ylamino)-4-(pyridin-2-yl)thiazole. The crystal structures of [Fe(pzaptH)2] [CF3SO3]2 and [Ni(pzaptH)2] [BF4]2.2H2O have been determined. The average Fe-N distance is 1·985 Å, a value consistent with the essentially low-spin nature of the complex at room temperature, and the average Ni-N distance is 2·089 Å. In both complexes the bridging >NH group is involved in hydrogen bonding to the anions and, in the nickel complex, also to the solvate water. The uncoordinated nitrogen of the pyrazine ring is not hydrogen-bonded. Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole]iron(II) triflate: triclinic, space group P -1, a 8·794(5), b 11·082(6), c 17·49(1) Å, α 77·59(4), β 86·80(4), γ 84·21(4)°, Z 2. Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazole]nickel(II) tetrafluoroborate dihydrate: monoclinic, space group P 21/c, a 8·784(3), b 8·795(2), c 41·16(1) Å, β 94·58(2)°, Z 4.


1995 ◽  
Vol 50 (7) ◽  
pp. 1018-1024 ◽  
Author(s):  
Axel Michalides ◽  
Dagmar Henschel ◽  
Armand Blaschette ◽  
Peter G. Jones

In a systematic search for supramolecular complexes involving all combinations of the cyclic polyethers 12-crown-4 (12C4), 15-crown-5 (15C 5), 18-crown-6 (18C 6) and dibenzo- 18-crown-6 (DB -18C6), and the geminal di- or trisulfones H2C(SO 2Me)2, H2C (SO2Et)2 and HC (SO2Me)3-n (SO2Et)n (n = 0 -3 ) , only the following four complexes could be isolated and unequivocally characterized by elemental analysis and 1H NMR spectroscopy: [(12C4){H2C (SO2Et)2}2] (3), [(18C6){H2C (S O2Me)2}] (4), [(DB -18C 6){H2C (SO2Et)2}] (5) and [(D B -18C 6)2{HC (SO2Me )(SO2Et)2}3] (6). The structure of 3 (triclinic, space group P1̄) consists of crystallographically centrosymmetric formula units, in which the disulfone molecules are bonded on each side of the ring by two C -H ··· O(crown) interactions originating from the central methylene group (H···O 213 pm) and from the methylene group of one EtSO2 moiety ( H ··· O 237 pm). Formula units related by translation are connected into parallel strands by a third type of reciprocal C -H ···O bond (H ···O 232 pm) between the second H atom of the central methylene group and a sulfonyl oxygen atom of the adjacent unit. The structure of 4 (monoclinic, space group C2/c) showed severe disorder of the crown ether and could not be refined satisfactorily. Compounds 5 and 6 crystallized as long and extremely thin fibres, indicative of linear-polymeric supramolecular structures; single crystals for X-ray crystallography were not available.


2005 ◽  
Vol 60 (9) ◽  
pp. 978-983 ◽  
Author(s):  
Sevim Hamamci ◽  
Veysel T. Yilmaz ◽  
William T. A. Harrison

Two new saccharinato-silver(I) (sac) complexes, [Ag(sac)(ampy)] (1), and [Ag2(sac)2(μ-aepy)2] (2), [ampy = 2-(aminomethyl)pyridine, aepy = 2-(2-aminoethyl)pyridine], have been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. Complexes 1 and 2 crystallize in the monoclinic space group P21/c and triclinic space group P1̄, respectively. The silver(I) ions in both complexes 1 and 2 exhibit a distorted T-shaped AgN3 coordination geometry. 1 consists of individual molecules connected into chains by N-H···O hydrogen bonds. There are two crystallographically distinct dimers in the unit cell of 2 and in each dimer, the aepy ligands act as a bridge between two silver(I) centers, resulting in short argentophilic contacts [Ag1···Ag1 = 3.0199(4) Å and Ag2···Ag2 = 2.9894(4) Å ]. Symmetry equivalent dimers of 2 are connected by N-H···O hydrogen bonds into chains, which are further linked by aromatic π(py)···π(py) stacking interactions into sheets.


1991 ◽  
Vol 46 (2) ◽  
pp. 235-244 ◽  
Author(s):  
S. Schmid ◽  
J. Strähle

PhNCO reacts with oxo ligands at metal centers to form phenyl nitrene complexes. As an intermediate of this reaction we obtained with ReO2I(PPh3)2 (1) the trimeric complex [ORe(OCONPh)I(PPh3)]3 (2) in which the PhNCO moiety was added to an oxo ligand to form an N -phenyl carbamato group. This group acts as a bridging ligand chelating one Re atom via its N and one O atom and coordinating an other Re atom by its second O atom . 2 crystallizes as 2 · 2 CHCl3 in the triclinic space group P1̄ with a = 1423.1(5), b = 2443.3(7), c = 1403.8(6) pm , α = 92.31(3), β = 94.76(3), γ = 81.48(3)°, and Z = 2. From the mother liquor of 2 after a few days Re(NPh)(NH2Ph)I2(PPh3)(OCONHPh) (3) is formed as a partial hydrolysis product. 3 is monoclinic with the space group P21/n and a = 1163.0(4), b = 2527.0(3), c = 1243.9(5) pm, β = 98.04°, Z = 4. The Re atom exhibits an octahedral coordination w ith the two I atom s in a ?ra«s-arrangem ent and the phenyl nitrene ligand trans to the m onodentate PhN HCO2 group. The coordination is completed by a phosphine and an aniline ligand. Reaction of 2 with excess PPh3 yields 1. It crystallizes from CHCl3 as 1 · CHCl3 in the monoclinic space group P21/n with a = 975.9(3), b = 2731(1), c = 1417.3(6) pm , β = 93.35° and Z = 4. In 1 the Re atom is pentacoordinated in form of a trigonal bipyram id with the two phosphine ligands in axial positions. A solution of 2 in THF forms Re(NPh)(NH2Ph)I2(PPh3) (OReO3) (4) upon exposure to air at room temperature. 4 is obtained as orthorhombic crystals with the space group Pca21 and a = 1727(1), b = 1064.2(4), c = 1765.7(9) pm , Z = 4, and is an analogue of 3 from which it can be derived by substituting the carbamato ligand by a perrhenat ion. In 3 and 4 the phenyl nitrene ligand is bound by a Re = N triple bond of 172 pm in a linear arrangement Re = N - Ph .


1995 ◽  
Vol 50 (1) ◽  
pp. 128-138 ◽  
Author(s):  
Dagmar Henschel ◽  
Armand Blaschette ◽  
Peter G. Jones

Complexes of Uncharged Molecules, Crystal StructureThe thermally labile ternary complexes 18C6 · 2MeOH · 2 HN(SO2Ph)2 (2a), 18C6 · 2MeOH · 2HN(SO2–C6H4-4-Cl)2 (2b) and 18C6 · 3 MeOH · HN(SO2Me)(SO2Ph) (3) were obtained by co-crystallization of 18-crown-6 (18C6) and the appropriate di(organosulfonyl)amine from methanolic solutions and characterized by low-temperature X-ray diffraction. The crystal structures of 2a (monoclinic, space group P21/n) and 2b (triclinic, space group P1̄) consist of monomeric, centrosymmetric formula units. Each di(arenesulfonyl)-amine molecule is connected to a methanol molecule by an N-Η ··· O hydrogen bond (H ··· O 203 pm in 2a, 190 pm in 2b). The methanol molecules are linked to three alternate crown oxygen atoms via one O-Η ··· O(crown) hydrogen-bond and two weaker C-Η ··· O(crown) interactions (OH ··· O 201 pm in 2a, 186 pm in 2b; CH ··· O 236 and 247 pm in 2a, 240 and 254 pm in 2b); two symmetry-related oxygen atoms of the crown are involved in O-Η ··· O and the other four in C-Η ··· O interactions. The structure of complex 3 (monoclinic, space group P21) is built of infinite chains parallel to [101]. The methyl group of the di(organosulfonyl)amine is bonded by C-Η ··· O(crown) interactions to a set of three alternate oxygen atoms of the cyclic polyether (H ··· O 228, 245 and 247 pm). Starting from the acidic NH function, a sequence of three methanol molecules catenated by hydrogen bonds curves around the bulky phenyl group and links with its terminal MeOH through one O-H ··· O(crown) and two C-Η ··· O(crown) bonds to the second set of alternate oxygen atoms in the adjacent symmetry-equivalent crown (OH ··· O 193 pm, CH ··· O 248 and 250 pm). Within the chain sequence N-H ··· O′(Me)H′ ··· O″(Me)H″ ··· O‴(Me)H, the H ··· O distances are H ··· O′ 184, H′ ··· O″ 189 and H″··· O‴ 183 pm. In the structures of 2a, 2b and 3, the crown rings adopt the frequently observed D3d pseudosymmetry.


1997 ◽  
Vol 52 (5) ◽  
pp. 587-592 ◽  
Author(s):  
Abdel-Fattah Shihada ◽  
Frank Weller

Abstract Ph2Sn(O2PMe2)2 has been synthesized by the reaction of HO2PMe2 with Ph2SnO in toluene or by treating HO2PMe2 with Ph2SnCl2 in methanol. X-ray diffraction studies of Et2Sn(O2PMe2)2 and Ph2Sn(O2PMe2)2 show that the O2PMe2 ligands function as bidentate bridges between the tin atoms. The ethyl and the phenyl groups are in trans-position in the resulting octahedral environment around tin. Et2Sn(O2PMe2)2 crystallizes in the monoclinic space group P21/n (a = 817.11(9), b = 974.1(1), c = 970.1(1) pm, β = 113.749(6)°, Z = 2 and R = 0.032) and con­sists of a polymeric layer structure with centrosymmetric (SnOPO)4 sixteen-membered rings. Ph2Sn(O2PMe2)2 also crystallizes monoclinically in the space group P21/n (a= 1060.9(1), b = 999.4 (1), c = 1768.9(2) pm, β = 90.93(1)°, Z = 4 and R = 0.057) and has a polymeric ring-chain structure with centrosymmetric (SnOPO)2 eight-membered rings. The IR and Raman spectra of Ph2Sn(O2PMe2)2 have been assigned and discussed in the light of structural information. The Sn(O2PMe2)+ ion represents the base peak in the mass spectrum of Ph2Sn(O2Me2)2.


1994 ◽  
Vol 49 (12) ◽  
pp. 1763-1773 ◽  
Author(s):  
Jochen Ellermann ◽  
Jörg Sutter ◽  
Falk A. Knoch ◽  
Matthias Moll ◽  
Walter Bauer

Reaction of (1) in CH2Cl2 with benzimidazole yields . The salt [4]+BPh4- has been prepared in THF by metathesis of [4]+Cl- with NaBPh4. Deprotonation of the cationic ring in [4]+BPh4- was accomplished using 1,8-diazabicyclo[5.4.01,7]undec-7-ene and resulted in the six-membered carbacyclophosphazene (6). Treating 1 with 8 -hydroxyquinoline in CH2Cl2 yields the octahedral cis-complex = 8-oxyquinolinate group). The com pounds [4]+BPh4-, 6 and 7 are characterized by their IR, Raman, 31P{1H} NMR, 13C{1H} NMR, 1H NMR and mass spectra. Crystals suitable for X-ray structure analyses have been obtained for [4]+BPh4- and 7×0.5 CH2Cl2. The colourless plates of [4]+BPh4- crystallize in the triclinic space group P1̄, with the lattice constants a = 1172.7(3), b = 1326.2(3), c = 1806.1(6) pm; α = 100.79(2), β = 103.71(3), γ = 108.18(2)°. The black blocks of 7×0.5 CH2Cl2 crystallize in the monoclinic space group P 21/c with the lattice constants a = 1159.0(10), b = 2008.9(10), c = 2034.6(12) pm; β = 105.86(5)°.


1998 ◽  
Vol 53 (8) ◽  
pp. 893-899 ◽  
Author(s):  
Nicolai Burzlaff ◽  
Michael Hagel ◽  
Wolfdieter A. Schenk

Abstract Reaction of the complex [CpRe(NO)(CO)2]BF4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(i-Pr)3}(CO)]BF4. The corresponding triphenylphosphite complex [CpRe(NO){P(OPh)3}(CO)]BF4 may be obtained by oxidative CO removal. Reduction of the remaining CO ligand with NaBH4 furnishes the corresponding methyl com­plexes [CpRe(NO)(L)(CH3)]. The structure of [CpRe(NO){P(i-Pr)3}(CH3)] was determined: triclinic space group P1̄ (No. 2), a = 8.442(4), b = 9.582(5), c -11.820(8) Å, α= 81.81 (4), β = 87.18(4), γ = 63.87(5)°, Z = 2. Reaction of the methyl complexes with HBF4 in the presence of thiols gives, after chromatographic workup, the thiolate derivatives [CpRe(NO)(L)(SR)] (L = CO, P(OPh)3, P(i-Pr)3, R = CH2Ph, CH2(4-C6H4Cl), CH2(4-C6H4OMe), CH3, C2H5). The structure of [CpRe(NO){P(i-Pr)3}(SCH3)] was determined: monoclinic space group P21 (No. 3), a = 7.0515(7), b = 17.3469(10), c = 7.9727(7) Å, β = 114.021(7)°, Z = 2. In both structures, a significant opening of the angle N-Re-X (X = C, S) suggests that antibonding interactions between orbitals of the ligand X and the second-highest MO of the [CpRe(NO)(L)] complex fragment are avoided.


1998 ◽  
Vol 53 (7) ◽  
pp. 641-652 ◽  
Author(s):  
Arista Gräfe-Kavoosian ◽  
Shida Nafepour ◽  
Klaus Nagel ◽  
Karl-Friedrich Tebbe

Abstract The new compound [(Crypt-2.2.2)H2]I8 has been prepared by the reaction of [(Crypt-2.2.2)H2](I3)2 with iodine in methanol. It crystallizes in the orthorhombic space group Pbcn with a = 11.476 (2), b = 13.589 (2), c = 22.888 (2) Å and Z = 4. The crystal structure has been refined to RF = 0.031 for 1618 reflections. It may be described as a layerlike packing of octaiodide anions I82-and diprotonated 2.2.2-Crypt as cations. The non planar octaiodide anion is built up from two triiodide groups and a bridging iodine molecule.Tris(1, 10-phenanthroline)nickel(II) octaiodide bis(chloroform) crystallizes in the monoclinic space group P21/n with a = 11.683 (8), b = 21.717 (8), c = 20.752 (5) Å, β = 95.03 (5)° and Z = 4 formula units. The crystal structure has been refined to RF = 0.058 for 3894 reflections. The structure consists of two chloroform molecules, octahedrally coordinated complex cations [Ni(phen)3]2+ and nonplanar octaiodide anions I82- each composed of two asymmetric triiodide units I3- weakly associated with an elongated bridging iodine molecule I2.The already known structure of bis(N-methylurotropinium) octaiodide, (UrMe)2I8, has been verified and more accurate crystal data have been collected. The crystal structure has been refined to RF = 0.045 for 1908 reflections. The compound crystallizes in the monoclinic space group P21/c with a = 11.302 (2), b = 9.850 (2), c = 14.188 (2) Å , β = 92.59 (1)° and Z = 2. The anion has the shape of a stretched Z.The structure of bis(N-ethylurotropinium) octaiodide (UrEt)2I8 has been determined and a new configuration (I3-, I5-) for octaiodide ions between Z (I3- · I2 ·I3-) and a “broken” configuration (I3-, I5-) has been observed. The compound crystallizes in the triclinic space group P1̄ with a = 9.741 (3), b = 11.815 (3), c = 15.426 (3) Å, α = 91.80 (2), β = 107.14 (2), γ = 90.04 (2)° and Z = 2. The crystal structure has been refined to RF = 0.037 for 3657 reflections.


2000 ◽  
Vol 56 (4) ◽  
pp. 744-744 ◽  
Author(s):  
Richard E. Marsh

The structure of bis((phenyl-O,N,N-azoxy)oxy)methane, C_{13}H_{12}N_4O_4, originally reported as triclinic, space group P1 [Zyuzin et al. (1997). Isz. Akad. Nauk SSSR Ser. Khim. pp. 1486–1492; CSD refcode NIXQAM] was recently revised to monoclinic, space group C2 [Marsh (1999). Acta Cryst. B55, 931–936]. It is properly described as orthorhombic, space group Fdd2.


Sign in / Sign up

Export Citation Format

Share Document