L. Randaccio

Cation‐site location in a natural chabazite

(Ca,Sr) chabazite, Cal.aSro.3A13.sSis.3024.13H20 from electron microprobe analysis, rhombohedral, R3m, a = 9.421(4)A, a = 94.20(1) °, U = 829 A 3, Z = 1, g(Mo Ka) = 0.82 mm-~; final R = 0.071 for 578 independent reflections. The location of three cation sites along the [ 1111 direction and of water molecules in the zeolitic cage is discussed and compared with that previously attributed on the basis of a two-dimensional analysis. Introduction. Chabazite is a natural zeolite of group 4, its framework being built up by double six-membered rings (D6R), linked by tilted four-membered rings (Fig. 1). The framework contains large ellipsoidal cavities of 6.7 x 10 A, entered by eight-membered rings (Breck, 1974). The ion-exchange properties and the role played by exchangeable cations in molecule-sieving properties justify the interest for a structural study of chabazites (Mortier, Pluth & Smith, 1977a,b; Pluth, Smith & Mortier, 1977; Barrer, 1978). On the other hand only two-dimensional X-ray diffraction analyses have been reported for hydrated natural chabazites (Smith, Rinaldi & Dent Glasser, 1963; Smith, Knowles & Rinaldi, 1964). From these results it was suggested that cations occupy but one site at x = 0.357, y = 0.494, z = 0.577, so that the crystal should contain two calcium ions and 13 water molecules per unit cell. To verify such an arrangement of cations and water molecules, we have undertaken the three-dimensional 0567-7408/82/020602-04501.00 X-ray analysis of a natural chabazite as the first step of a structural study of chabazites exchanged with transition-metal ions. The natural sample was from north-east Azerbaijan, Iran (Comin-Chiaramonti, Pongiluppi & Vezzalini, 1979). Wavelength dispersive microprobe analysis was carried out on eight single crystals of chabazite, using a fully automated ARLSEMQ instrument. The mean chemical analysis and the atomic ratios evaluated for 24 O atoms are given in Table 1. The chemical analysis indicates that the chabazite is particularly rich in strontium.

Structural effects of the co-ordination of quadridentate Schiff bases to transition-metal atoms. Structure of NN′-(o-phenylene)bis(salicylideneamine) and of its cobalt(II) complex

Geometrical variations which occur when a quadridentate Schiff-base co-ordinates to a cobalt(II) atom are compared on the basis of the crystal structure analysis of the ligand NN′-(o-phenylene) bis(salicylideneamine)(I) and its CoII derivative in its orthorhombic (II) and monoclinic (III) modifications. Crystals of (I) are monoclinic, space group P21/c, with cell parameters: a= 6.064(3), b= 16.541(7), c= 13.306(7)A, β= 91.5(1)°. Crystals of (II) are orthorhombic, space group P212121, with a= 16.755(7), b= 17.532(8), c= 5.362(3)A, and of (III) are monoclinic, space group P21/nwith a= 10.681(5), b= 8.354(4), c= 18.185(8)A, β= 105.3(1)°. A total of 1 277 (I). 1 113 (II), and 2 558 (III) independent reflexions were used : the structures were solved from diffractometer data by the heavy-atom method and refined to final R factors of 0.056 (I), 0.046 (II), and 0.041 (III). The enolimine form is established for (I) in the solid state. Upon co-ordination, with formation of (II) and (III), the geometrical data suggest that the contribution to the resonance of a ketamine form becomes as important as that of the enolimine. This is in agreementwith a π-orbital delocalization of the electronic charge over the planar complex molecule.

Cation sites and framework deformations in dehydrated chabazites. Crystal structure of a fully silver-exchanged chabazite

A sample of silver-chabazite, Ag3.7Al3.8Si8.3O24.10H2O, was completely dehydrated at suitable conditions of vacuum and temperature (2 × 10−6 Torr, 60°C). After dehydration, the symmetry of the Ag-CHA crystals was reduced from the usual rhombohedral space group R3m to the monoclinic C2m, with the following cell dimensions: a = 19.240(6)A, b = 13.771(4)A, c = 11.868(4)A, β = 113.28(3)A, Full matrix least-squares refinement reduced R index to 0.093 on the basis of 2305 reflections. The framework of d-Ag-CHA can be described as a tridimensional linkage of D6R units in alternate layers rotated about the monoclinic b-axis. The silver ions occupy eight independent positions, related to sites I, III and IV of the rhombohedral cell, near the centre of the 6-ring, at the centre (0, 12 12) of the D6R cage and near the 8-ring aperture, respectively. The positions and the populations of the cation sites of d-Ag-CHA are compared with those of h-Ag-CHA and related with the relevant variation of the framework.

Crystal structures of hydrated and dehydrated forms of a Co(II)-exchanged chabazite

Abstract Crystal structures were determined at room temperature in the rhombohedral space group R 3 m, for a cobalt(II)-exchanged chabazite from N.E. Azerbaijan, Iran (Co-chab(h): Co1.7Na0.4Al3.8Si8.2O24·9.4H2O), and its dehydrated form (Co-chab(d)). Unit cell parameters and R-indices were a = 9427(9) A , α = 94.02(7)° and 0.065 for Co-chab(h), and a = 9.351(9) A , α = 92.56(7)° and 0.046 for Co-chab(d). In Co-chab(h), Co ions were located in two sites of high occupancy on the triad axis, and in a third site of low occupancy in the centre of the D6R cage. Remaining extra-framework peaks were assigned to water molecules. Co ions moved during dehydration to two peaks of high occupancy, one on the triad axis near the 6-ring, the other in the centre of the D6R cage. Two other peaks of low occupancy near the 8-ring window were attributed to remaining Co and Na ions. Considerable distortion of the frame occurs during dehydration.

Organocobalt B12 models. Structures of trans-bis(glyoximato)(alkyl)(pyridine)cobalt(III), with alkyl=Me, Et, i-Pr

Abstract The crystal structures of the organocobalt complexes, pyCo(GH) 2 Me(1), pyCo(GH) 2 Et(2) and pyCo(GH) 2 Pr i (3) (py = pyridine, GH = monoanion of glyoxime) are reported. Compound (1) crystallizes in the space group P2 1 2 1 2 1 with cell parameters a = 8.508(1), b = 13.586(2) and c = 11.614(6) A; (2) crystallizes in the space group P 2 1 2 1 2 1 with cell parameters a = 8.448(4), b = 12.164(2) and c = 13.651(2) A; (3) crystallizes in the space group P 2 1 /c with cell parameters a = 8.443(7), b = 12.913(2), c = 14.341(2) A and β = 92.86(4). The three structures have been solved by Patterson and Fourier methods and refined by least squares methods to final R values of 0.045 (1) , 0.068 (2) and 0.057 (3) using 1819 (1) , 1653 (2) and 1582 (3) independent reflections. The pyCoalkyl fragment shows significant variation of CoN and CoC bond lengths. The latter increase from 2.003(4) to 2.084(9) A following the increase of the alkyl bulk. The CoN(py) distances increase from 2.064(3) to 2.101(6) A with the increasing σ-donor power of the alkyl group trans to pyridine. In comparison with cobaloximes having the same axial ligands, pyCo(DH) 2 alkyl (DH = monoanion of dimethylglyoxime) does not show significant differences on the pyCo alkyl fragment. CoN axial bond lengths and exchange rates of the axial neutral ligand are consistent for the two series, although changes in bond lengths are detected only when rate constants are from two to three orders of magnitude different.

The structure of CoSAPO-34, containing i-propylamine as a template

The crystal structure of a cobalt silicoaluminophosphate, CoSAPO-34, is reported. The crystals belong to the rhombohedral R— space group with unit cell parameters a = 13.797(7) and c = 14.898(7) A. The final R index was 0.055 for 771 independent reflections. The framework structure is very close to that of natural chabazite but with ordered tetrahedral sites, apparently (Al, Co) and (P, Si). The experimental evidence strongly supports the view that cobalt ions are incorporated into the framework. Each large cavity is occupied by one water molecule and by an isopropylamine molecule. The water O atom binds through weak hydrogen bonds to three O atoms of the six-membered ring, whereas the N atom binds in a similar way to the O atoms of the eight-membered window.

The crystal structure ofo-anisylcopper(I): An octameric copper(I) cluster compound

Abstract The cluster structure of o -anisylcopper(I), a novel type organocopper(I) compound, has been established by X-ray crystallographic techniques. The cell constants are a 39.24(1), b 25.91(1), and c 23.57(1)A˚; the space group is Fddd . The structure was refined by least-squares techniques to a conventional R index of 0.084. The crystals consist of octameric molecules having a distorted square antiprismatic arrangement of copper atoms. Two crystallographically independent molecules, both located at 222 crystallographic sites but differently oriented with respect to the crystallographic axes, have been found. On the basis of these results the structures of related organometallic compounds are discussed.

Quadridentate Schiff-base metal complexes as chelating ligands of alkali metals. Synthesis and structure of ammonium and sodium tetra-phenylborate addition complexes with [NN′-ethylenebis(salicylideneiminato)]nickel(II)

Transition-metal complexes of the Schiff-base NN′-erhylenebis(salicylaidimine)(H2salen) co-ordinate ammonium and alkali-metal cations to give addition complexes of different stoicheiometry. The complex [Ni(salen)] with ammonium or potassium tetraphenylborate, M′[BPh4], gives addition compounds of formula [{Ni(salen)3-,M′(BPh4)]·nL [L = solvent, e.g. tetrahydrofuran (thf), acetonitrile, or acetone]. For n= 2 and L = thf the complexes are isomorphous. Reaction with Na [BPh4] in acetonitrile yields again a compound with Ni : Na 3 : 1, from which [{Ni(salen)}2Na(NCMe)2(BPh4)]·2MeCN is obtained by very slow crystallization. The crystal structures of [{Ni(salen){3(NH4)(BPh4)]·2thf, (I), and [{Ni(salen)}2Na(NCMe)2]·2MeCN, (II), have been determined from three-dimensional X-ray data. Crystals of both compounds are triclinic, space group P, Z= 2, with cell parameters: (I), a= 18.93(1), b= 16.94(1), c= 14.84(1)A, α= 91.6(2), β= 111.4(2), γ= 116.8(2)°; (II), a= 14.64(1), b= 15.56(1), c= 14.91 A, α= 85.2(1), β= 114.2(1), γ= 98.7(1)°. The structures have been solved by Patterson and Fourier methods and refined by block-diagonal matrix least squares to R 0.11 for (I) and 0.080 for (II). The structure of (I) consists of discrete [BPh4]– anions and [{Ni(salen)}3(NH4)]+ macrocations in which the ammonium ion is surrounded by the six oxygen atoms (mean N H4+⋯ O 2.92 A) of the three Ni(salen) moieties. The co-ordination polyhedron is intermediate between a trigonal prism and an octahedron. as determined by a balance of steric and electrostatic factors. Similarly the structure of (II) has discrete [BPh4]– anions and [{Ni(salen)}2Na(NCMe)2]+ macrocations with the sodium ion on an approximately two-fold axis, co-ordinated by the four oxygen atoms of the two Ni(salen) molecules and by the nitrogen atoms of the two acetonitrile molecules occupying cis positions. The co-ordination polyhedron approximates to an octahedron with mean Na+⋯ O 2.41 and Na+⋯ N 2.49 A.

Reaction of PtOH complexes with CO2: synthesis and X-ray structure of (PBz3)4Pt2(Ph)2(η1,η1,μ-CO3)·(toluene)

Abstract The reaction of (diphoe)Pt(CH2CN)(OH) and trans-(PBz3)2Pt(Ph)(OH) with CO2 is reported as producing dimeric, bridged carbonato complexes of the type: P4Pt2(R)2(CO3). The crystal and molecular structure of (PBz3)4Pt2(Ph)2(μ-CO3)·(toluene) is also reported, showing η1, η1 bonding. The reaction is recognized to proceed in a stepwise fashion through bicarbonato intermediates.

Crystal and molecular structure of cis-chloro-p-tolyl-bis(triethylphosphine)platinum(II) and of cis-chloro-perfluorophenyl-bis(triethylphosphine)platinum(II)

Abstract The crystal structure of the title compounds has been determined from X-ray data and refined to R = 0.048 for both compounds. Crystals of (I) are orthorhombic, space group Pna21 with cell dimensions a = 19.91(1), b = 14.98(1), c = 7.82(1) A. Crystals of (II) are monoclinic, space group P21/n with a = 11.07(1), b = 21.64(1), c = 10.05(1) A, β = 91.24(3)°. The co-ordination of Pt(II) is nearly square planar in both complexes. The PtCl bond lengths of 2.392(8) (I) and 2.387(7) A (II) are equal within experimental errors, whereas the two chemically non-equivalent PtP bond lengths are significantly different in both (I) and (II). Their values are 2.320(9) A (trans to C6H4CH3) and 2.247(6) A (trans to Cl) for (I) and 2.326(7) A (trans to C6F5) and 2.226(7) A (trans to Cl) for (II). No significant difference is found in PtC bond lengths (2.05(3) in (I) and 2.08(2) A in (II)), which however appear significantly longer than the values reported for PtC bond lengths having partial double bond character.