Pentachloride fluoride complexes

Fluorides and Fluoride Complexes. The pentafluorides are made by direct fluorination of the metals or the pentachlorides. Both are volatile white solids (Nb, m.p. 80°, b.p. 235° Ta, m.p. 95°, b.p. 229°), giving colorless liquids and vapors. They have the tetrameric structure shown in Fig. 26-B-2 they appear to be polymeric also when molten. The oxide fluorides MOF3 and MOzF are known. 

The effectiveness of antimony fluoride is increased if it is used in conjunction with chlorine or with antimony pentachloride. The formation of either SbCl2F2 or a complex of SbF and SbCl probably accounts for the increased activity (4). 

Tetrakis(phenyldifluorophosphine)nickel-(0) could also be obtained, using arsenic trifluoride in the presence of catalytic amounts of antimony pentachloride, or zinc fluoride as fluorinating agents. Yields as high as 50% could be obtained, but sizable decomposition on the process of fluorination of the chlorophosphine nickel-(0) complexes in solution could not be entirely suppressed. The marked instability of zerovalent nickel-phosphine complexes in solution in organic solvents, even under strictly anhydrous and anaerobic conditions, has been noted by several workers (16,20), but is still lacking a detailed explanation. A closer examination of the system carbon tetrachloride-tetrakis(trichlorophosphine)nickel-(0) (23) showed the main pa h of the reaction to consist in the formation of hexachloro-ethane with conversion of zerovalent into bivalent nickel, while the coordinated... 

As the inner salts are generally unstable and insoluble, they cannot be manipulated and their structures were therefore inferred from those of the more stable nitrogen analogues. The inner oxonium salt from boron fluoride, when examined at low temperatures, was found to contain a molecule of ether of crystallization which was held very tenaciously and was involved in the complex decomposition of the salt at higher temperatures. The salt from antimony pentachloride did not contain this molecule of ether and decomposed to ethyl chloride and a mixture of alkoxy antimony tetrachlorides. The stannic chloride decomposed in at least two ways,... 

While the first two allow the isolation of the reaction products, the third does not. When a Lewis acid is mixed with an acyl halide, a donor-acceptor complex RCOX. .. MtX , or full ionisation by halide ion transfer, to give RCO MtX +i, or both, take place. The extent of ionisation depends mostly on the nature and strength of the Lewis acid used Thus, for example, acetyl halides react with stannic chloride and titanium tetrachloride to give mostly the coordination complex while with antimony pentachloride, pen-tafluoride and boron fluoride they give the conesponding acylium salts. Many of these... 

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