Michael L. Post

Crystal structure of di-µ-tropolonato-bis[aquo(tropolonato)nickel(II)]

Crystals of the title compound are monoclinic, a= 9·720(7), b= 18·888(17), c= 7·146(3)A, β= 97·97(5)°, Z= 4, space group P21/n. The structure was determined from diffractometer data by the heavy-atom method and refined by full-matrix least squares to R 0·082 for 1191 observed reflections. The molecule exists as a centrosymmetric dimer and contains two types of tropolone ligand: one co-ordinated to one nickel atom only, the other, co-ordinated both to the first nickel atom, and to a second nickel via a bridging oxygen atom. This, together with a co-ordinated water molecule gives the nickel atoms six-co-ordination. There is evidence for hydrogen bonding, via the water molecule, between adjacent dimers.

Crystal and molecular structure of a tetranuclear cobalt(II)–tropolonate complex: [Co4(C7H5O2)8(H2O)2]

Crystals of the title compound are monoclinic, a= 13.341 (5), b= 18.634(9), c= 11.603(5)A, β= 171.43(3)°, Z= 2, space group P21/c. The structure was determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0.067 for 2 070 observed reflections. There are two distinct cobalt atoms in the structure, both achieving a co-ordination number of six but with considerably distorted octahedral geometry. Of the four independent tropolone ligands in the asymmetric unit, three chelate and have one bridging oxygen atom while the other ligand chelates and does not bridge. A water molecule completes the co-ordination polyhedra. The Co–O distances vary from 2.051 (6) to 2.1 49(9)A, with mean distances corresponding to whether the ligand chelates (2.060 A), chelates and bridges (2.084 A), or forms a bridging bond (2.137 A). The molecules are hydrogen-bonded via the water molecules and tropolone oxygen atoms. The stability of the structure is due to efficient lattice packing and hydrogen bonding, both facilitated by the compact planar structure of the ligand.

X-Ray crystal-structure analysis and magnetic and spectral properties of tetrachlorotris[dichloro(methyl)phosphine]molybdenum(IV)–carbon disulphide (3/1)

The title complex (1) is one product of the reaction between MoCl5, PMeCl2, and ButCl. It can also be prepared by direct reaction between MoCl5 and the phosphine. Crystals of (1) are trigonal, with unit-cell dimensions a=b= 9.760(2), c= 71.167(16)A, α=β= 90, γ= 120°, Z= 12, and space group Rc. The structure has been determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0.061 for 726 observed reflections (3σ). The Mo and Cl(1) atoms lie on three-fold special positions and a CS2 solvent molecule straddles a six-fold site, but with-two thirds occupancy. The Mo atom is seven-co-ordinate having capped-octahedral stereochemistry. Three Cl atoms occupy an uncapped face whilst the fourth caps a face occupied by the three P atoms. The magnetic properties of (1) are consistent with a strong-field, high delocalisation of the metal d electrons, and a low-symmetry ligand-field component. The Mo–Cl bond-stretching frequencies and a spin-forbidden electronic transition have been identified.

Crystal structure of polymeric cadmium(II) malonate monohydrate

Crystals of the title compound are trigonal (based on hexagonal axes), space group R, a=b= 17·216(9), c= 10·894(4)A, α=β= 90, γ= 120°, Z= 18. The structure was determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0·048 for 1071 observed reflections. Each malonate ligand chelates three symmetry-related cadmium atoms with two of the oxygen atoms also in bridging positions. The lattice formed is polymeric and further strengthened by hydrogen bonding via a co-ordinated water molecule. The cadium atom is seven-co-ordinate in nearly pentagonal bipyramidal geometry with Cd–O 2·272(7)–2·501(7)A. The mode of chelation exhibited by the malonate ion has not previously been reported.

Crystal and molecular structure of cadmium(II) cyanoacetate

Crystals of the title compound are monoclinic, a= 4·465(1), b= 10·262(2), c= 17·567(5)A, β= 95·44(2)°, Z= 4, space group P21/n. The structure was determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0·046 for 1656 observed reflections. The cadmium is co-ordinated to one nitrogen and five oxygen atoms in distorted octahedral geometry. Each of the two independent cyanoacetate ligands co-ordinates to three symmetry-related cadmium atoms to give a three-dimensional polymeric lattice. One ligand co-ordinates through two oxygen atoms, one of which is also bridging, while the other co-ordinates through two oxygen atoms and the nitrogen atom. In common with many other acetates, the metal atom is not chelated, the ligands acting as bridging molecules.