Trigonal Bipyramidal Arrangement Research Articles

Nuclear magnetic resonance studies on fluorine-containing compounds. Part III. The tetrafluoro-oxovandate(V) ion

The preparation of the caesium salt of the VOF4– ion is described. I.r. and Raman studies indicate that it has C4v symmetry in the solid state. 19F and 51V N.m.r. data suggest that in HF solution there is rapid fluorine rearrangement between square pyramidal and trigonal bipyramidal stereochemical arrangements.

Crystal structure of (Me3Sn)2N2C

The crystal structure of (Me3Sn)2N2C has been determined by single-crystal X-ray diffraction, and the absolute configuration established for the particular crystal employed. The crystals are hexagonal, space group P6422, a= 8·74(1), c= 14·28(2)A, Z= 3. The structure consists of an infinite helical network of planar trimethyltin groups linked by linear NCN units. The nitrogen atoms complete a trigonal-bipyramidal arrangement about tin, with Sn–N 2·47(1) and Sn–C (mean) 2·14(2)A. The Sn2NCNSn2 moieties have exact D2(222) symmetry with a dihedral angle of 68° between the two Sn2NC planes; C–N 1·24(2)A and angle SnNC 117·6(4)°. The structure can be considered to be intermediate between carbodi-imide, cyanamide, and ionic extremes.

Far-infrared and Raman spectra of tetrahalogeno-complexes of arsenic(III), antimony(III), and bismuth(III)

Tetra-alkylammonium salts of [MX4]– anions (M = As; X = Cl or Br; M = Sb or Bi; X = Cl, Br, or I) have been prepared and their low-frequency (<400 cm.–1) i.r. and Raman spectra studied in the solid state (i.r. and Raman) and in solution (Raman). Excepting for solid [Et4N][AsCl4] and [Bun4N][SbI4], the results point to distorted tetrahedral structures (C2v symmetry) for the anions in both phases, arising from trigonal bipyramidal arrangements of electron pairs with a lone pair occupying an equatorial position.

The far-infrared and Raman spectra of the tetra-alkylammonium salts of mixed tetrahalogeno-complexes of arsenic(III), antimony(III), and bismuth(III), [R4N][MX3Y

The far-i.r. and Raman spectra are reported for tetra-alkylammonium salts of [MX3Y]– anions (X ≠ Y: M = As, X or Y = Cl or Br; M = Sb, X or Y = Cl, Br, or I; M = Bi, X or Y = Cl, Br, or I; excluding [BiBr3Cl]–). Except in the cases of [Et4N][SbBr3Cl] and [Bun4N][Sbl3Br] in the solid state, the spectra are indicative of structures of Cs symmetry based on trigonal bipyramidal arrangements of electron pairs around the group VB element. For M = Sb or Bi, and X = Cl, either Y or the lone pair of electrons occupies an axial position, whereas for all the other [MX3Y]– species both axial sites are occupied by X atoms.

Crystal and molecular structure of 1-acetonyl-1-thionia-5-thiacyclo-octane perchlorate

The crystal structure analysis of 1-acetonyl-1-thionia-5-thiacyclo-octane perchlorate has been carried out using three-dimensional X-ray diffraction film data measured visually. The crystals belong to the orthorhombic system, a= 13·67(3), b= 9·12(4), and c= 21·09(5)Å; the space group is Pbca and there are eight molecules of [C9H17OS2]+[ClO4]– in the unit cell. The structure has been refined to R 0·107 on 1117 independent non-zero reflexions. There is a transannular S(1)⋯S(5) distance of 3·121(5)Å and an intramolecular S(1)⋯O distance of 2·81(1)Å; these contacts result in a distorted trigonal-bipyramidal arrangement around S(1). The eight-membered ring is in the boat–chair (BC) conformation.

The crystal structure of germanium difluoride

Crystals of germanium difluoride are orthorhombic, a= 4·682, b= 5·178, c= 8·312 A, Z= 4, space group P212121. The structure was determined from the three-dimensional Patterson function, and refined by least-squares, the final R being 0·129 for 225 reflexions.The fluoride is a strong fluorine-bridged chain polymer, in which the parallel chains are cross-linked by weak fluorine bridges. The structural unit of the strongly bridged chains is a trigonal pyramid of three fluorine atoms and an apical germanium atom, with Ge–F distances of 1·79, 1·91, and 2·09 A and F–Ge–F angles of 85·0, 85·6, and 91·6°. The two longer-bonded fluorine atoms are structurally equivalent and join each germanium atom to its two neighbours in the chain. The fluorine atom 1·79 A distant from each germanium atom makes a weak bridge bond with a germanium atom in an adjacent chain, 2·57 A distant. This longest-bonded fluorine atom is almost opposite the fluorine atom at 2·09 A, the F–Ge–F angle being 163°. The poor fluorine atom packing and the geometry of the [GeF4] group are consistent with steric activity of the non-bonding valence electron pair. The [GeF4] group may be described as a distorted trigonal bipyramidal arrangement of four fluorine ligands and an (equatorial) electron pair, about a germanium atom.

Addition of Alcohols to a Schiff Base co-ordinated to Copper(II)

WE have been interested in the Schiff base quadridentate I (1,2-bis-(2′-pyridylmethyleneamino)-ethane, BPE) in order to ascertain whether it forms five-coordinated copper(II) complexes [Cu(BPE)X]+ (X = univalent anion) similar to those reported with 2,2′-bipyridyl and 1,10-phenanthroline1. These are of the type [Cu(chelate)2X]+, and the iodo-complex [Cu(bipy)2I]+ possesses an approximately trigonal bipyramidal arrangement about the copper atom2.

BOND LENGTHS AND BOND ANGLES IN OCTAHEDRAL, TRIGONAL- BIPYRAMIDAL, AND RELATED MOLECULES OF THE NON-TRANSITION ELEMENTS

The stereochemistry of molecules in which there are five or six pairs of electrons in the valency shell of a central atom is discussed in terms of the repulsions that exist between pairs of electrons in the valency shell as a consequence of the operation of the Pauli exclusion principle. An explanation is given for the difference in lengths of the axial and equatorial bonds in molecules such as PCl5 and ClF3 whose structures are based on the trigonal-bipyramidal arrangement of five valency-shell electron pairs. The fact that in molecules with a central atom with a valency shell of six electron pairs, one of which is a lone pair and which have the structure of a square pyramid, the central atom always lies below rather than in, or above, the base of the square pyramid, is also accounted for.

Rare sugar produced cheaply by new method

The synthesis of diorganotincarbohydrates {R2SnL [R = Me, Bu or Oct; L = aldotetrose (erythrose), aldopentoses (arabinose or ribose), ketohexoses (fructose or sorbose), aldohexoses (galactose or glucose) or 6-deoxyaldohexose (rhamnose)]} is reported. Ir and 119Sn Mössbauer spectra are consistent with the presence of tin-carbohydrate oxygen bonds in the compounds and with a trigonal bipyramidal arrangement of two alkyl and three O-containing groups about the tin atoms. The thermal decomposition of the compounds is shown to fall into one of three categories, viz: (1) aldose derivatives that decompose without melting to give SnO as the final tin-containing product, (2) ketose derivatives that decompose without melting to give SnO2 as the final tin-containing product, and (3) aldose derivatives that melt and then decompose to give either SnO or SnO2.