Group 2 Fluorides

Thin films of NaF have been deposited on Si and Si02 substrates by chemical vapor deposition from sodium hexafluoro-wo-propoxide (1), sodium perfluoro/m-butoxide 

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In general, Group 5 fluorides tend to adopt a preference for higher oxidation states, and as a consequence, over the past few years, there have been virtually no reported examples of low valent fluoro complexes of vanadium, niobium or tantalum. 

Table 3.32. Symmetry, bond lengths, and bond angles for ordinary covalent (M—F) and uo-bonded (M—I cu) fluoride bonds of normal-valent and hypervalent second-row main-group fluorides MF (M = P, S, Cl) see Fig. 3.87...

Hirakawa, K., and T. HasMmoto Magnetic properties of potassium iron group fluorides KMFj. J. Phys. Soc. Japan 15, 2063 (1960). 

Jaccarino, V., and if. G. Shulman Nuclear magnetic resonance in paramagnetic iron group fluorides. Phys. Rev. 106, 602 (1957). 

Though not available commercially, trifluoronitroethane shows some interesting chemistry consistent with the powerful electron-withdrawing effect exerted by the nitro group. Fluoride-mediated nitroaldol reactions were reported [144] with aldehydes affording a valuable entry to trifluoromethyl amino alcohols... 

In the first nucleophilic aromatic substitution that we showed you, we used fluoride ion as a leaving group. Fluoride works very well in these reactions, and even such a simple compound as 2-nitro-fluorobenzene reacts efficiently with a variety of nucleophiles, as in these examples. 

The mechanism obviously involves attack by the enol (or boron enolate ) of the ketone on the anhydride, catalysed by the Lewis acid. Probably BF3 or BF2 groups (fluoride can come and go from boron easily) hold the reagent together at all times, much like lithium in the aldol reaction (p. 698). 

The use of elemental fluorine in the preparation of main group fluorides is carried out in batch and flow systems... 

Table 3 Mean thermochemical bond energies of some main group fluorides ...

Nomnetal fluorides and oxyfluorides have been studied by nearly every available modem spectroscopic and diffraction technique. This is due in part to the strong practical and theoretical interest in the stracture and reactivity of simple molecules of this type, the diversity of compounds that can be obtained, and their amenability to study by many different techniques. Many stractures of simple ffnorides and oxyfluorides have been determined by electron diffraction, microwave specttoscopy. X-ray diffraction, and vibrational analysis. For many chemists interested in the synthesis and reactivity of main group fluorides and derivatives, F NMR, IR, and Raman spectroscopy, and mass spectrometry are the indispensable routine tools of analysis. 

Figure 1. Reaction of soman (GD) with acetylcholinesterase (AChE). (a) Soman and the active site of AChE shown together but not having undergone any reaction, (b) Soman combined with AChE to form an inhibitor-enzyme intermediate, (c) The leaving group (fluoride) has been lost, leaving a complex of soman with AChE. (d) The ester link in the phosphonylated AChE has been hydrolyzed, the enzyme has reactivated and an alkylphosphate has been formed, (e) The link between the large pinacolyl group and phosphorus has been cleaved with the formation of a stable monoalkylphosphonylated complex with AChE and pinacolyl alcohol. The process is known as ageing .

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