Selenium tetrafluoride, with

The reaction of selenium tetrafluoride with platinum hexafluoride. When selenium tetrafluoride and platinum hexafluoride were mixed in a silica bulb, there was an immediate and vigorous reaction at —9°, which evolved much gas, presumed to be selenium hexafluoride. Selenium tetrafluoride, which was present in a large excess, was removed by vacuum distillation. X-Ray examination showed the yellow residue to be the 2 1 selenium tetrafluoride-platinum tetrafluoride adduct. 

The tetrafluorides of selenium and tellurium are similar to SF4 both structurally (in the gaseous molecules) and in terms of reactivity, ffowever, the bonding in condensed phases is different and leads to several types of structures. Selenium tetrafluoride can be prepared by combining the elements, but it can also be obtained by the reaction of Se02 with SF4 at high temperature. The tellurium compound can be prepared by the reaction of SeF4 and Te02 at 80 °C. 

Fluorination with Selenium Tetrafluoride and Its Pyridine Complex... 

The preparation of selenium tetrafluoride in normal glass apparatus has been reported by the reaction of selenium metal with chlorine trifluoride and selenium tetrafluoride as the solvent.81 Caution chlorine trifluoride (C1F3) is extremely reactive and must be handled with care, avoiding organic compounds and moisture. 

Although alcohols can be fluorinated directly with selenium tetrafluoride, yields can be disappointing because of rearrangement/polymerization due to the presence of hydrogen fluoride produced during the reaction. Higher yields have been obtained when the reaction is performed in the presence of 1 equivalent of pyridine, which forms a 1 1 donor-acceptor complex with selenium tetrafluoride. The reaction proceeds in two distinct steps first is the reaction of the alcohol with the complex to form an alkoxyselenium trifluoride, the second is the thermal decomposition to the alkyl fluoride. 

For example, treatment of benzyl alcohol with selenium tetrafluoride-pyridine quantitatively yields benzyl fluoride.81... 

Potassium hexafluorovanadate(IV) can be prepared from [VF4] and KF in selenium tetrafluoride(III)416 or by fluorination of K2VF5 for example. K+, Rb+ and Cs+ salts obey the Curie-Weiss law with high values of 6. [VF4] reacts with py and NH3 forming [VF4L], probably fluorine-bridged polymers.416... 

Selenium hexafluoride, SeFg, the only clearly defined hexahalide, is formed by reaction of fluorine with molten selenium, It is more reactive than the corresponding sulfur compound, SFs, undergoing slow hydrolysis. Selenium forms tetrahalides with fluorine, chlorine, and bromine, and dihalides with chlorine and bromine. However, other halides can be found in complexes, e.g,. treatment of the pyridine complex of SeF/i in ether solution with HBr yields (py)2SeBrc Selenium tetrafluoride also forms complexes with metal fluorides, giving MSeF complexes with the alkali metals. 

The SeF4 molecule has a distorted structure similar to that of SF4, and its dipole moment is 1.78 D. Chemically, the tetrafluorides of Se and Te behave in much the same way as SF4. Selenium tetrafluoride can be prepared by direct combination of the elements or by the reaction of SF4 with Se02 at elevated temperatures. Tellurium tetrafluoride can be prepared by the reaction of SeF4 and Te02 at 80 °C. 

Selenium tetrafluoride, which can be prepared from selenium metal and chlorine trifluoridc (CIF3), was introduced by Olah as a fluorinating agent for carbonyl compounds and alcoholsT It is generally necessary to add pyridine in the reactions with alcohols I. Pyridine forms a I 1 complex with selenium tetrafluoride and neutralizes the hydrogen fluoride which is formed in the fluorination reaction. 

Selenium tetrafluoride, which is a liquid at room temperature, reacts with aldehydes and ketones to form, gcm-difluoro compounds in good yields (Table 3). The reaction is run under mild conditions in halogenated solvents or without solvent. 

Both tetraflnorides can be synthesized from the action of SF4 on the dioxides. Selenium tetrafluoride is a white solid that melts to a colorless liquid. It can be handled in rigoronsly dried Pyrex, reacting slowly with glass but violently with H2O. Selenium tetrafluoride can solvate many fluorides. Selenium tetrafluoride and other organic Se fluorides have been ntilized as flnorinating agents for alcohols and carbonyl componnds. 

Violent reacdon with acids (e.g., nitric or sulfuric), chromium trioxide, ruthenium, selenium tetrafluoride (above 106°C), metals, metal oxides, metal salts, nonmetals, nonmetal salts, organic matter, glass wool, acedc acid, Al, Sb, As, Cu, Ir, Fe, Pb, Mg, Mo, Os, P, K, Rh, Se, Si, Ag, Na, S, Te, Sn, W, Zn, oxides, CO, graphite, HgL, HNO3,... 

Tris(morpholine)selenonium fluoride (33), easily prepared by the reaction of JV-trimethylsilylmorpholine (34) with selenium tetrafluoride (35), is a very useful reagent for chloride/fluoride exchange reactions (121. Thus, benzenesulfonyl chloride (36) and diphenylphosphinyl chloride (37) gave upon treatment with 33 the corresponding fluorides 38 and 39 in good yields (Scheme 5). 

Essentially the same route as that of Ruff has been followed by us, except that two new reducing agents whose chemistry is under study in these laboratories, namely sulphur and selenium tetrafluorides, have been used. Attention has already been drawn to the usefulness of selenium tetrafiuoride as a mild reducing agent in fluorine chemistry while sulphur tetrafiuoride also gives evidence of possessing similar properties. In the first series of experiments, palladium trifluoride, formed by the reaction between palladous iodide and elementary fluorine at room temperature, was treated with a stream of sulphur tetrafluoride at 250-300°. The violet-coloured powder which resulted was proved, by Af-ray examination, to contain palladium difluoride in admixture with about 10% of palladium metal. 

This suggests that selenium tetrafluoride is able to act as a fluoride-ion donor and that the adduct with palladium tetrafluoride is the salt (SeF3+)2[PdFg]2 . Since the platinum tetrafluoride and germanium tetrafluoride adducts are isomorphous with the palladium P compound they should also be given the ionic formulation. 

---