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Single crystal X-ray structures of Fe(NO)2(CO)(PPh3) (I) and of Fe(NO)2(PPh3)2 (II) have been determined. Compound (I) form triclinic crystals of space group P 1 , with cell constants a 10.96(1)», b 10.20(1)», c 10.45(1)», α 115.84(8)°, β 117.33(8)°, γ 78.90(8)°, U 933.4»3, Z 2. Compound (II) forms monoclinic crystals of space group P2/c with cell constants a 11.70(1) », b 8.20(1) » c 17.24(2) », β 106.60(8)°, U 1584.6 »3, Z 2. Both cystals contain discrete molecules of distorted tetrahedral geometry. In compound (I) the CO and NO ligands are disordered; the principal bonding parameters are: FeC/N 1.709 », C/NO 1.148 », FeC/NO 177.9°, FeP 2.260(3) », C/NFeC/N 103.9° and PFeC/N 114.4°. In compound (II), which possesses C2 symmetry, the principal bonding parameters are: N 1.650(7) », NO 1.19(1) », FeNO 178.2(7)° NFeN 123.8(4)°, FeP 2.267(2) », PFeP 111.9(1)°. These values are compared with those found in other tetrahedral complexes of Group VIII metals and discussed in terms of π metalligand interactions.

The crystal and molecular structures of the title compound have been determined from three-dimensional X-ray data collected by counter methods. The crystals are triclinic, space group P 1 , with Z = 1; cell dimensions: a = 10.204(8), b = 11.602(8), c = 8.363(7)A, α = 106.04(8)°, β = 88.04(7)°, γ = 108.98(7)°. The structure, determined from 3435 reflections, has been refined by full-matrix least-squares methods down to R = 0.038. It consists of discrete centrosymmetric molecules; the Pt atom lies on an inversion centre. PtP and PtC bonds lengths are 2.302(2) and 2.059(7) A respectively. Essentially planar PtCOO moieties are present, which make an angle of 80.8° with the coordination plane. A trans configuration for a complex containing two Pt11C bonds is unexpected; alkoxycarbonyl ligands therefore show a peculiar behaviour which deserves further investigation.

The compound [W(OH)(CO)3H]4·4 OPPh2Et crystallizes in the monoclinic space group C2/c with the following unit cell constants: a = 25.06(2), b = 14.08(1), c = 24.60(2) A, β = 120°20′(10′) and Z = 4. The structure has been determined from a set of 1246 independent non-zero reflections, measured with counter methods, and refined by least-squares to a final R index of 0.049. It consists of tetrameric units [W(OH)(CO)3H]4, lying around the two-fold crystallographic axes. The tungsten atoms, which occupy the corners of a regular tetrahedron, are held together by four μ3-hydroxo groups, so that the W4O4 moiety forms a distorted cube. The W…W distances (mean value 3.48 A) are definitely non-bonding. The stereochemical arrangement of the ligands around the tungsten atoms identifies the hydridic hydrogen positions. The resulting coordination polyhedron in each (OH)3W(CO)3H moiety can be described as a combination, by apex sharing, of one triangular and one square pyramid, the triangle being formed by the OH oxygen atoms and the square by the CO carbon atoms plus the hydridic hydrogen. The four OPPh2Et molecules are joined to the tetramer through strong hydrogen bonds with the μ3-hydroxo groups (O…O contacts of 2.47 and 2.48 A).

The complex dicarbonylbis(diphenylethylphosphine)platinum, Pt(CO)2[P(C6H5)2(C2H5)]2, crystallizes in either of the enantiomorphous space groups P3121 (No. 152) and P3221 (No. 154) with cell dimensions a = 10.64(1), c = 22.06(1) A, U = 2163 A3; pc = 1.564 g/cm3 for Z = 3, pm = 1.55(3) g/cm3. The intensities of 1177 independent reflections have been determined by counter methods with MoKα monochromatized radiation. The structure has been solved by the heavy atom method. The refinement, carried out by full-matrix least squares down to a final R factor of 0.042, has enabled the absolute configuration of the crystal sample (space group P3121) to be ascertained. The molecule is roughly tetrahedral, and has the metal atom lying on a two-fold axis of the cell. Bond parameters are: PtC = 1.92(2) A, PtP = 2.360(4) A, CPtC = 117(1)° and PPtP = 97.9(2)°. The PtC2 and PtP2 moieties make a dihedral angle of 86.0(3)°. The overall C2 symmetry of the molecule is probably only a statistically averaged situation, a disorder in the PtCO interactions being apparent from the orientations of the thermal ellipsoids of the C and O atoms.

The structure of di-µ-chloro-tris(triphenylphosphine)dicopper(I), Cu2Cl2(PPh3)3 has been determined from three-dimensional X-ray data collected by counter methods. The crystals are monoclinic, space-group P21/c and have Z= 4 in a unit cell of dimensions a= 19·27(2), b= 9·81(1), c= 27·02(3)A, β= 112° 5′(8′). The structure was refined to R 0·055 for 2046 independent reflections. The crystal contains discrete molecules in which two copper atoms are held together by two chlorine bridges. Two of the three phosphine ligands are bonded to one of the copper atoms and the third to the other, so that one metal atom is four-and the other three-co-ordinate. The mean values for the bonds to four- and three-co-ordinate copper are Cu–P 2·240 and 2·183, and Cu–Cl 2·436 and 2·272 A. These values and certain angular distortions found in the molecule are discussed.

Este estudio investiga la eficacia de una secuencia de enseñanza-aprendizaje acerca de la minería sobre la comprensión de la naturaleza de la ciencia y la tecnología, en este caso centrada aspectos de la influencia de la minería sobre la sociedad y viceversa, la influencia de la sociedad sobre las tecnologías y explotaciones mineras. La investigación se ajusta a un diseño pre-posttest, donde la aplicación de la secuencia de aprendizaje tiene lugar entre ambas evaluaciones, inicial y final, cuyas diferencias mutuas son los indicadores de la eficacia de la enseñanza. Los resultados obtenidos son modestos, pues aunque se identifican algunas áreas de mejora, también existen otras áreas donde no se produce mejora y las diferencias de mejora observadas son pequeñas. El estudio presenta una estandarización de la evaluación que puede servir para comparar efectos de distintas secuencias didácticas o para comparar investigaciones diferentes.

Crystals of the title compound are triclinic, space group P, Z= 2, in a unit cell of dimensions: a= 12·55(2), b= 12·38(2), c= 15·55(2)A, α= 103·07(7), β= 97·73(7), γ= 116·28(7)°. 3699 Independent structure factor moduli were measured by counter methods, and the structure refined by full-matrix least squares to R 0·035. The metal atom, which displays a distorted octahedral co-ordination, is bonded to the terminal nitrogen atom, to C(2) of the aryldi-imide moiety [Ir–N 1·990(7), Ir–C 2·011 (8)A] and to two chloro-ligands [Ir–Cl 2·393(2) and 2·493(2)A, the bond being trans to C(2) of the aryldi-imide group], and to two mutually trans phosphine ligands [Ir–P 2·376(2) and 2·364(2)A]. There is evidence for the protonation of the nitrogen atom bonded to Ir.

The preparation and the spectra of Ir2 (CO)4 (PPh3)2 (SO2)2 and of the title compound are reported; in the molecular structure of the latter, determined by X-ray crystallographic analysis, there is a relatively long IrIr bond which is accounted for in terms of the acidic nature of SO2

Die Umsetzung des Iridiumtrihydrids (II) mit Stickstoffmonoxid in siedendem Tetrahydrofuran und in Gegenwart von.N-Methyl-N-nitroso-p-toluolsulfonamid (I) ergibt in hoher Ausbeute den Komplex (III).

Die Behandlung der komplexen Goldnitrate (I) mit Natriumborhydrid (II) in Athanol fuhrt zu den Komplexen (III).