Bruce R. Penfold

Molybdenum(VI) complexes with malic acid: their inter-relationships, and the crystal structure of dicaesium bis[(S)-malato(2–)]-cis-dioxomolybdate(VI)–water (1/1)

The complex anions obtainable in salts crystallising from aqueous solutions of molybdate and malic acid (H3mal) are of the types (i)[MoO2(Hmal)2]2–, (ia)[MoO2(mal)2]4–, and (ii)[Mo4O11(mal)2]4– The formation of each type is dependent primarily upon the reactant ratio, M+ : Mo : H3mal. With the structure of the type (ii) anion already known, the structure of the (simpler) anion (i) was determined by X-ray analysis of its salt, Cs2[MoO2(Hmal)2]·H2O. The complex is mononuclear, with each malato-ligand co-ordinated through the deprotonated hydroxy group and the vicinal carboxy group to form a five-membered chelate ring. The second carboxylate group is not co-ordinated, but there is inter-anion H-bonding between the two carboxy functions. The structural features of class (i) and (ii) anions show the importance of ligand characteristics in determining the type of molybdenum-oxygen core which forms. Compositional and i.r. evidence relating to class (ia) indicates it to be derived from (i) through proton replacement.

Structural studies of low-valent metal-fluorocarbon complexes

The crystal structure of bis(triphenylphosphine)hexafluoroacetone nickel(0), (Ph3P)2, has been determined. The crystals are monoclinic: space group P21/n, a=18·123(5), b=19·879(5), c=9·745(2) Å, β=93·46(2)° and Z=4. X-ray data were collected by counter methods using MoKα radiation, and least-squares refinement led toR = 0·087 for the 1406 independent reflexions for which ¦F0¦2> 2σ(¦F0¦2). In the complex, the hexafluoroacetone molecule is associated with the nickel atom by sideways coordination of the C=O group to form a three-membered ring in which the bond lengths are Ni-C, 1·89(2), Ni-O, 1·87(1) and C-O, 1·32(2) Å. The whole Ni, P, P, C, O coordination group forms an approximate plane with the two CF3 groups projecting on either side.

Preparative and structural studies of pentahalogeno-oxometallate(V) salts of the transition metals Cr, Mo, W, Tc, Re

Abstract Pentahalogeno-oxometallate(V) complex salts A 2 [MOX 5 ], A = K, Rb, Cs, M = Cr, Mo, W, Tc, Re and X = Cl, Br were studied in order to extend the series of salts. The isolation of a products depends on the inter-relation of factors such as solubility, redox stability of the anion and disproportionation reactions. The Cs + salts are all cubic and the K + and Rb + salts orthorhombic. The single crystal analysis of Cs 2 [MoOBr 5 ] was completed. Statistical disorder prevented accurate bond lengths being obtained, but MoO = 164 pm and MoBr =249.2(6) pm. The formation of low solubility A 2 [Tc(OH)X 5 ] salts is a common feature of technetium(IV) halogenochemistry.

The crystal and molecular structure of an isomer of ammine(diethylenetriamine)oxalatocobalt(III) nitrate

Abstract The crystal and molecular structure of one of the four possible isomers of ammine(diethylenetriamine) oxalatocobalt(III) nitrate has been determined from three-dimensional X-ray diffraction data collected on a four-circle diffractometer, using Mo-K α radiation. The compound crystallises in space group Cc with a = 7.72, b = 12.21, c = 14.88 A , β = 121.3°, and Z = 4. The structure was solved by conventional Patterson and Fourier techniques and full matrix least squares refinement of 878 observed reflections [(F o 2 > 3σ(F o 2 )] gave a final discrepancy factor of 0.074. The complex has a distorted octahedral configuration with the nitrogen atoms of the dien ligand in the same coordination plane as the Co, and the proton on the secondary nitrogen atom being directed toward the coordinated ammonia ligand.

The preparative and structural chemistries of hexahalogeno and trichlorostannato complexes of iridium

Abstract In a study of Ir(III) and Ir(IV) halogeno complexes it was found that oxidation of Ir(III) to Ir(IV) occurs readily, even in the presence of reducing agents such as tin(II) halides and from solutions containing predominantly the trivalent oxidation state. The three cubic (Fm3m) hexahalogenoiridates(IV) complexes; oxonium hexabromoiridate(IV), (H3O)2[IrBr6], a=1027.4(3) pm, IrBr=251.5(1) pm; ammonium hexabromoiridate(IV), (NH4)2[IrBr6], a=1044.0(2) pm, IrBr=254.9(3) pro; and caesium hexachloroiridate(IV), Cs2[IrCl6], a=1021.19(8) pm, IrCl=233.2(2) pm, were isolated from the solutions, and their single crystal and molecular structures determined. The iridium(III) and rhodium(III) trichlorostannato complexes A3[IrCl5(SnCl3)] for AK+, NH4+, and Rb3[RhCl3(SnCl3)3] have been prepared. The single crystal X-ray structure has been determined for K3[IrCl5(SnCl3)]. The complex and the isomorphous NH4+ salt belong to the orthorhombic crystal system a=958.73(13), b=951.70(15), c=784.80(9) pm, with space group Pmn21. The molecule has m symmetry and the IrCl bond length for the chlorine atom bound opposite the SnCl3− ligand is longer at 243.8(3) pm compared with the other IrCl bond lengths which lie in the range 233.9(3)–237.6(2) pm. The IrSn bond length of 249.6(1) pm is relatively short compared with other reported values.

Five coordination of tin involving a tridentate ligand: Crystal structure of N-(2-hydroxyphenyl)salicylaldimine dimethyl tin(IV)

The crystal structure of the title compound, (CH3)2Sn(C6H4O) CHN(OC6H4), has been determined from X-ray diffractometer data by Patterson and Fourier methods. The crystals are orthorhombic, space groupPbcn witha =19.304,b = 10.534,c = 13.398 Å andZ = 8. Full-matrix least-squares refinement of the 1024 reflexions having ¦F¦2 >σ(¦F¦2) led toR = 0.044. The tin atom is pentacoordinate with the two oxygen atoms forming the apices and the two methyl groups and nitrogen atom forming the equatorial plane of a distorted trigonal bypyramid. The Schiff base ligand is thus tridentate. The bond lengths involving the tin atom are Sn-O, 2.108(6) and 2.130(6); Sn-N, 2.224(8); Sn-C, 2.10(1) and 2.12(1) Å.

Molybdenum(VI) complexes from diols and aminoalchols: the occurrence of MoO2, Mo2O3, and Mo2O5 core structures

The co-ordination behaviour of molybdenum(VI) towards diols and aminoalcohols is discussed, particularly in relation to newly determined reference structures. A pinacol (H2pin) complex, typical of the yellow vicinal diol derivatives, is constituted [MoO(pin)(Hpin)]2O, with an Mo2O3 core. An Mo2O5 core is present in the anion [{MoO2(Hnta)}2O]2–, formed by nitrilotriacetic acid (H3nta) at low pH. Several new complexes in which ligand bridging is inferred have been prepared. One of these, [{MoO2(Hpin)(OMe)}2]·2MeOH, which is derived from the yellow pinacolate, is shown by X-ray analysis to have methoxy-bridging. The bridge vibration from an Mo2O3 core is close to 750 cm–1, but the pattern of bands from an Mo2O5 core is variable. The MoO1bMo vibration involving an oxygen bridge provided by a chelating ligand gives an i.r. band in the region 625–650 cm–1.

X-Ray crystal and molecular structures of three methinyl tricobalt enneacarbonyl derivatives

Crystal structures have been determined of three derivatives of YCCo3(CO)9, all containing the tetrahedral CCo3 cluster of the parent compound: in PhCCo3(CO)6·π-C6H3Me3 a mesitylene molecule is π-bonded to a single Co atom of the Co3 triangle, having replaced three CO groups; in PhCCo3(CO)6·π-C8H8, a cyclo-octatetraene molecule has replaced the three axial CO groups of the parent molecule and is π-bonded to the Co3 triangle through three of its double bonds, and in the dimer, [CCo3(CO)9]2 the length of the central formally single C–C bond is 1.37(2)A.

Crystal structure of bis(dipyrromethene)copper(II)

The structure of bis(diethyl 3,3′,5,5′-tetramethyldipyrromethene-4,4′-dicarboxylate)copper(II) in one of its crystalline modifications has been established by X-ray analysis at room temperature. The crystals are monoclinic, space group P21/c with a= 8·09, b= 30·16, c= 16·01 A, β= 91·7° and Z= 4. Blocked least squares refinement using 683 photographically measured intensities led to a conventional R of 12·6%. The two approximately planar dipyrromethene ligands are inclined at an angle of 66°, making the copper environment distorted tetrahedral. The mean Cu–N bond length is 1·99(2)A. Three other crystalline modifications, one of them stable only at reduced temperatures, have been identified.

Crystal and molecular structures of hexafluoroacetone and hexafluoroisopropylideneamine complexes of nickel

Crystal structure determinations on (Ph3P)2[graphic omitted] and (ButNC)2N[graphic omitted] have established the geometries of two classes of compounds formed by co-ordination of fluorocarbon molecules to transition metals; in the first case a symmetrical three-membered ring is formed by co-ordination of one molecule of (CF3)2CO and in the second case a five-membered ring is formed by co-ordination of one molecule of (CF3)2CO and one molecule of (CF3)2CNH.