Caesium dimer , reaction

The reaction of the bromosilane with caesium fluoride in DMF at room temperature in the presence of (Ph3P)4Ni leads to the dimer 89, apparently resulting from Ni(O) catalysed reaction of the cumulene 87204. 

The synthesis starts from 2,4,4-trimethyl-4,5-dihydrooxazole, a compound with marked C—H acidity in the exocyclic methyl group. Triple lithiation followed by derivatiza-tion with chlorotrimethylsilane affords a triply silylated, open-chain ketenimine which is reacted with [AuCl(PPh3)] in the presence of caesium fluoride to give a dimeric, octanu-clear gold(I) cluster. The reaction proceeds beyond the stage of a triauriomethyl oxazolinyl derivative which, in fact, can only be observed as a side product. 

Andrews and co-workers have used the matrix reaction between lithium atoms and some inorganic compounds to produce species of spectroscopic interest. Reaction of lithium with molecular oxygen [301] produces, in addition to the molecule Li02, the molecule LiO and a dimer Li2 02. Reaction with nitric oxide produced a nitroxide compound [302], but analysis of the infrared spectrum indicated that in this compound the lithium atom was bound to the oxygen atom (LiON), rather than to the nitrogen atom (LiNO), as would be expected by analogy with the known compounds HNO and RNO. The matrix deposition of lithium and nitrous oxide [303] leads to the formation of LiO and LijO. The other alkali metals have also been reacted in the same way with nitrous oxide [304]. Potassium, rubidium and caesium all led to the formation of the compounds MO and M2O. No sodium oxides were produced when sodium and nitrous oxide were co-deposited. This is to be compared with the mechanism advanced for the sodium-catalysed gas-phase reaction between N2O and CO, where sodium is assumed to react with N2O, (Section 4, ref. 

Reactions of perfluorocarbanions, from fluoro-olefins and alkali-metal fluorides, have been extensively studied during the period of this Report. During the course of a study of the reactions perfluorocycloalkyl anions with pentafluoropyridine and tetrafluoropyridazine it was found that caesium fluoride in tetramethylenesulphone at 125 °C caused the dimerization of perfluorocyclopentene to the dimer (76), per-fluorocyclohexene at 170 °C yielded dimer (77) (19, and, unexpectedly, the diene (78) (57%), which was, however, a minor product at 150 C, and perfluoroQrclo-butene at 125 °C yielded trimer (79). Reaction of CzFs", from tetrafluoro-... 

Phenylbenzocyclobutadiene is an intermediate in the photolysis of diphenyl-acetylene, but is too unstable to be isolated and undergoes dimerization. A cyclobutadiene has also been proposed as an intermediate in the complex reaction of perfluoro-l,l-dimethylallene with chloroform and caesium fluoride. Cyclobutadiene is generally trapped and stored as its iron tricarbonyl complex. A normal co-ordinate analysis of the latter has been reported, as has a convenient synthesis of the carboxylic acid complex (823), ... 

Chapman and co-workers have reported the direct spectroscopic observation of benzocyclobutadiene itself by reaction of cis-1,2-di-iodobenzocyclobutene with zinc powder at 230 °C. Initial cooling of the resultant vapour deposited a mixture of dimeric material and traws-l,2-di iodobenzocyclobutene. The benzocyclobutadiene was trapped in an argon matrix at 20 K on either a caesium iodide or a sapphire plate for spectroscopic examination. The infrared spectrum showed a band at 700 cm which is probably due to one of the C—H bond deformations of the four-membered ring. The ultraviolet spectrum showed at 243, 246.5,256, 270, 281.5, and 289 nm. On warming above 75 K, the known benzocyclobutadiene dimer (150) was formed and identified by comparison with authentic material. 

Reaction of perfluoroisobutene with sulphur in the presence of caesium fluoride yields 2,4-bis(hexafluoroisopropylidene)-l,3-dithietan (bistrifluoro-methylthioketen dimer) together with the polysulphides (CF3)3C Sn-C(CF,), (n = 3 or 4). Bistrifluoromethylthioketen dimer is available by the reaction of a variety of sulphur nucleophiles, alkali-metal salts of thiocarbamates, thiocarbonates, thiocarboxylates, thiophosphates, thiosulphate, thiocyanate, hydrosulphide, etc. with perfluoroisobutene. - The reaction with... 

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