Difluoride molecular structure

Xenon difluoride XeF2 and calcium carbide (form I) CaC2 are isomorphous with Z = 2, the linear triatomic molecule occupies Wyckoff position 2(a) of site symmetry 4/mmm. Hg2Cl2 (calomel) has a very similar crystal structure, although it is tetraatomic. The molecular structure and crystal packing of XeF2 and Hg2Cl2 are compared in Fig. 9.6.15. 

Polycondensation Routes.—Nylon 4,6 has been synthesized by melt-polycondensation and characterized by a variety of techniques, with emphasis on molecular structure determination. Routes to nylon 6,6 via phosphorylation of the salt in organic solvents in the presence of organic bases such as imidazole have been assessed. Similarly, the conditions for polycondensation of carboxylic acid difluorides with diamines in homogeneous aqueous organic media have been described. ... 

The crystal and molecular structure of xenon difluoride, Xep2, has been determined by a three-dimensional neutron diffraction study. The crystals are tetragonal with a = 4.315, c = 6.990 A. The space group is lA/mmm and there are two molecules in the unit cell. Special positions of four-fold and two-fold multiplicity are ... 

The starting point for the synthesis of xenon compounds is the preparation of xenon difluoride, XeF2, and xenon tetrafluoride, XeF4, by heating a mixture of the elements to 400°C at 6 atm. At higher pressures, fluorination proceeds as far as xenon hexafluoride, XeFfi. All three fluorides are crystalline solids (Fig. 15.27). In the gas phase, all are molecular compounds. Solid xenon hexafluoride, however, is ionic, with a complex structure consisting of XeF< + cations bridged by F anions. 

In discussing the states of aggregation of solid fluorides as solutes, there is some overlap between the structures of the transition metal pentafluorides, discussed above, and those of corresponding tetra-, tri- and difluorides of d- and /-transition metals. The intermediate and lower fluorides of the transition metals are fluorine-bridged polymeric lattices, whereas the alkali metal and alkaline earth fluorides are essentially ionic and the non-metal fluorides are molecular. 

All observed X-ray reflexions, were with the exception of the faint lines of palladium metal, indexed on a tetragonal cell of the rutile type. Since only one of the palladium reflexions overlapped with a difluoride reflexion the presence of metal did not interfere with the structure determination. The dimensions of the bi-molecular imit cell are compared below with those given by Ebert. 

G. R. Jones, R. D. Burbank and N. Bartlett, The Crystal Structure of the 1 1 Molecular Addition Compound Xenon Difluoride-Iodine Pentafluoride, XeF2.IF5, Inorg. Chem. 9 (1970) 2264-2268. 

Use Lewis structures to predict the molecular polarities for sulfur difluoride, sulfur tetrafluoride, and sulfur hexafluoride. 

In the present study, we synthesized dibromo(l,4,8,ll-tetraazacyclotetradecane)copper(II) ([CuBr2(cyclam)]) and diaqua(l,4,8,ll-tetraazacyclotetradecane)copper(II) difluoride four hydrate ([Cu(cyclam)-(H20)2]F2 4H20) complexes and performed single crystal structure analysis and X-ray absorption near-edge structure (XANES) measurements in crystals and in aqueous solution. Furthermore, DV-Xa molecular orbital calculations have been made for models based on these results, and the structures and electronic states of the [Cu(cyclam)] complexes in crystals and in aqueous solution are discussed, in particular, on the axial coordination to Cu(II). 

Structural and dynamic parameters for trifluoromethyliminosulphur difluoride [F3CNSF2], in the gas phase, have been determined from molecular-electron scattering functions. The parameters are C—F= 1.332, [S=N]= 1.447, N—C =... 

The structure of the alkoxyboron difluorides has recently aroused some interest, and the historical consideration of the structure of these compounds has been outlined. Although the chemical shifts of these compounds are comparatively high (+01 to -f0 8) this does not imply quadricovalency (see above discussion) > however, the formation of the pyridine co-ordination complexes of the alkoxyboron difluorides (11) did not give appreciably higher B chemical shifts, and it was concluded that the boron atom in alkoxyboron difluorides was already tetracovalent. Molecular-weight determination confirmed the trimeric structure similar to the boroxole ring system. 

The relatively small radius of F", 1.19 A, is almost identical with that of the oxide, O2-, ion (1.25 A) consequently, many fluorides and oxides are ionic with similar formulae and crystal structures, for example, CaO and NaF. The compounds of the other halogens with the same formula usually form quite different lattices and may even give molecular lattices. Thus chlorides and other halides often resemble sulfides, just as the fluorides often resemble oxides. In several cases the fluorides are completely ionic, whereas the other halides are covalent for example, CdF2 and SrF2 have the CaF2 lattice (nearly all difluorides have the fluorite or rutile structure), but CdCl2 and MgCl2 have layer lattices with the metal atoms octahedrally surrounded - by chlorine atoms.-----------------------------... 

A Yes. The high values for KF and CaFj are those expected for ionic compounds. The increase in m.p. from KF to CaF, is expected from the doubly charged Ca ion and its effect on the lattice enthalpy of the difluoride. The lower value for GaF, is an indication of the onset of covalency in the polymeric structure. That the compound sublimes instead of melting is another indication of its polymeric nature, the bridging between units persisting in the vapour phase, Ga,Fg. The sharp fall in melting points in the other fluorides marks the transition to discrete molecular (i.e. covalent) forms. 

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