Isothiocyanate anions

Isoihamnetin la 323 Isothiazolone, microbiocidal la 45 Isothiocyanates la 75 lb 312 Isothiocyanate anions lb 307 Isotopes, detection limits la 41 Itaconic acid, reduction la 61 lodazide reaction lb 301,303... 

From this study, the authors concluded that most isothiocyanates (II) must be due to a N-condensation of the thiocyanate anion rather than an isomerization. Because N=C=S is harder nucleophile than "SCN, attack of the isothiocyanate anion to the carbonyl will explain the observed decomposition. 

Fig. 12 Top ionic liquids of the type [Bmim]4[Ln(NCS)7(H20)] with Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, and Yb. The color is due to the metallate anion. Bottom molecular structure of the anionic unit [La(NCS)7(H20)]4 showing the hydrogen bonding from coordinated water molecules to the isothiocyanate anions. The [Bmim] cations were omitted for clarity. Image adapted from [67]. Image copyright American Chemical Society (2006). For color image see online version...

The 16 KNCS complex forms a complicated polymeric structure as depicted in Fig. 50 An important feature of this complex is the classical double action displayed by a water molecule which is hydrogen-bonded to an SCN" anion, thus shielding it from the cation. The other isothiocyanate anion accepts a hydrogen bond from the amide N—H grouping. 

Reaction of dimsyl anion with isothiocyanates gives a-thioamidosulphoxides 478 in 12-59% yield, whereas with isocyanates it affords a mixture of a-amidosulphoxides 479 and methylsulphinylmalonoamides 480, the products of a double addition549 (equation 289). 

Glutaconaldehyde anion serves as an interesting intermediate for the synthesis of heterocyclic compounds. The parent pyrylium perchlorate has been prepared from glutaconaldehyde and 70% perchloric acid in ether at -55°.° The reaction of glutaconaldehyde anion with alkyl and aryl isothiocyanates and... 

The 3-formyl-2(IH)-pyridinethiones were prepared by reaction of glutaconaldehyde anion with the corresponding isothiocyanates (RN—C==S). 

Other approaches to tetrazoles were also recently published. Primary and secondary amines 195 were reacted with isothiocyanates to afford thioureas 196, which underwent mercury(II)-promoted attack of azide anion, to provide 5-aminotetrazoles 197 . A modified Ugi reaction of substituted methylisocyanoacetates 198, ketones, primary amines, and trimethylsilyldiazomethane afforded the one-pot solution phase preparation of fused tetrazole-ketopiperazines 200 via intermediate 199 <00TL8729>. Microwave-assisted preparation of aryl cyanides, prepared from aryl bromides 201, with sodium azide afforded aryl tetrazoles 202 . 

The choice of isothiocyanate as the anionic ligand is to some extent historical, but it seems to be a very appropriate ligand with an intermediate ligand field strength. The variation in ligand field strengths for a list of cyanide ligands is ... 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

Thiols react directly with non-activated alkynes [15] and with 1-alkynyl thioethers [16] to yield alkenyl thioethers in good yield (>76%), whereas thiocyanate anions only add to non-activated alkynes under acidic phase-transfer catalytic conditions on the addition of mercury(II) thiocyanate. Terminal alkynes are converted into vinyl thiocyanates, but disubstituted alkynes also form vinyl isothiocyanates [17]. Major by-products are the ketones formed by solvolysis of the alkynes. 

Complexes of picolinamide with lanthanide perchlorates, nitrates, and isothiocyanates have been isolated by Condorelli et al. (59). All these complexes show changes in the stoichiometry on going from La(III) to Lu(III). The ligand acts as bi-dentate with the oxygen of the amide group as well as the heterocyclic nitrogen coordinating to the metal (Structure I). While the anions in the perchlorate complexes are not coordinated to lanthanide ions, those in the nitrate and isothiocyanate complexes are coordinated. 

Vicentini and Dunstan (227) have obtained tetrakis-DDPA complexes with lanthanide perchlorates in which the perchlorate groups are shown to be coordinated to the metal ion. DDPA also yields complexes with lanthanide isothiocyanates (228) and nitrates (229). All the anions in these complexes are coordinated. DPPM behaves more or less like DDPA which is reflected in the stoichiometry of the complexes of DPPM with lanthanide perchlorates (230), nitrates, and isothiocyanates (231). Hexakis-DMMP complexes of lanthanide perchlorates were recently reported by Mikulski et al. (210). One of the perchlorate groups is coordinated to the metal ion in the lighter lanthanide complexes, and in the heavier ones all the perchlorate groups are ionic. 

Complexes of TSO with lanthanide perchlorates which have the formula Ln(TS0)9(C104)3 have been reported by Edwards et al. (266) (Ln = Ce or Y). Later, Vicentini and Perrier (267) have prepared the whole series of complexes of TSO with lanthanide perchlorates and have shown that the L M in these complexes gradually decreases from 9 1 to 7 1 as the cationic size decreases. These authors could not prepare Y(TS0)g(C104)3 reported by Edwards et al. (266). Instead, they obtained the complex of the composition Y(TS0)7(C104)3. Two series of complexes of TSO with lanthanide hexafluorophosphates are known (268, 269). While the L M in one of the series is 7.5 1, in the other series it is found to be 8 1. The change in the stoichiometry of the two series of compounds is attributed to the preparative procedures adopted. In both the series of complexes, the PFg ion remains ionic. Lanthanide nitrates (270), chlorides (270), and isothiocyanates (271) also yield complexes with TSO. In all these complexes, changes in the stoichiometry could be observed when the lanthanide series was traversed. In all these complexes the anions are coordinated to the metal ion. 

Crystalline salts containing tetra-, penta- and hexa-isothiocyanate complex anions can be isolated from aqueous or methanolic solutions.507 Frequencies v(Ga—NCS) occur in IR spectra at 350 cm-1 in four-coordinate or 250 cm-1 in six-coordinate species. Although powder patterns have been reported, single-crystal X-ray data are lacking for gallium thiocyanates. Some gallium selenocyanide complexes Ga(NCSe)3Ls and Ga(NCSe)4 have been prepared.508 Attempts to obtain Ga(NCS)3 or Ga(NCSe)3 appear to have failed. 

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