Acyclic cation, N

A different type of behaviour is observed with the chloro Lewis acid BCI3. With this reagent halogen exchange occurs to produce the acyclic cation [N(SC1)2] , as the [BCU] salt, rather than NSCf. " Thiazyl trichloride NSCI3 is predicted to be unstable with respect to NSCl -1-Cl2. ... 

Reaction of NSF3 with BCI3 yields the acyclic cation [N(SC1)2]" as its BCI4" salt (Fig. 15.48c) the compound is very hygroscopic and readily decomposes to BCI3, SCI2, S2CI2, and N2. 

Acyclic Se-N chlorides that are potential building blocks (as a source of the SeNSe unit) for cyclic Se-N systems are generated by the reactions of [SeChJiAsEg] or SeCU with (Mc3Si)3N as illustrated by the sequence of transformations that produce the five-membered [Se3N2Cl] cation (Scheme 2.4 and Section 8.4). 

The principle of the action of fluorescent enolimine/ketoenamine chemosensors is usually based on two fundamentally different effects - CHEF (Chelation-Enhanced Fluorescence) and CHEQ (Chelation-Enhanced Fluorescence Quenching). The former is connected with hindering the enolimine C=N bond rotation by complexation with cations. As a result, the fluorescence intensity of compounds 23 (Figure 10.15) is selectively and significantly enhanced by adding of, for example, Cd " " cations [92, 93]. This enhancement was attributed to the formation of a 1 1 complex in which the rotation around the acyclic C=N bond is frozen. 

Scheme 2.4 Formation of acyclic and cyclic Se-N cations (i) -3Me3SiCl, -CI2 (ii) GaCl3 (iii) Ph3Sb...

The thiazyl cation is used for the preparation of other important S-N compounds. For example, the insertion reactions with S4N4 or SC12 produce [S5N5]"1" or the acyclic [C1SNSC1]+ cation,62 respectively, and the reaction with sulfur gives [S2N]+ salts. 

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