Isothiocyanate complexes

These authors noted that if the last group in the Fe(II) coordination sphere is acetonitrile a low-spin complex is obtained [22]. We found [23] that the aqua complex is high-spin (Mossbauer spectral parameters for the sulfate <5=1.15 mm s 1, A q=3.23 mm s 1), whereas the corresponding isothiocyanate complex is a crossover complex [23]. 

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). 

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. 

The photodissociation spectra of the Mg(L) complexes of ethyl isocyanate and ethyl isothiocyanate show some common photofragments. Aside from the ubiquitous formation of Mg+ (cf equation 39), both ethyl isocyanate and ethyl isothiocyanate yield products from attack of the N—C single bond (equations 57 and 58). The ethyl isothiocyanate complex also yields MgS via equation 59. The photodissociation spectrum of the ethyl thiocyanate isomer was also examined and gave the products shown in equations 60-62. Thus each isomer gives a unique ionic product [Mgs for ethyl isothiocyanate (equation 59) vs MgNC+ for ethyl thiocyanate (equation 62)] which allows their distinction. Finally, the Mg(ethyl isocyanate) +" complexes simply undergo solvent evaporation for n = 2 and 3 (cf equation 52). 

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. 

One of the earliest references to a reaction in solution, which, as we now realize, depends upon the formation of a coordination compound, was recorded by Pliny who stated that the adulteration of copper sulfate by iron sulfate could be detected by testing with a strip of papyrus soaked in gall-nuts, when a black colour developed if iron were present. A. Libavius (1540-1616) noted how ammmonia present in water could be detected by the blue colour formed with a copper salt and A. Jacquelain (1846) actually determined copper salts in terms of the blue colour formed on adding ammonia. Later developments used coordination compounds formed from ethylenediamine and other polyamines.3 T. J. Herapath determined iron(III) as its red isothiocyanate complex in 1852 and the basic procedure is used today.3... 

Finally, it is interesting to note the eight-coordination about Zr in the Zr-isothiocyanate complex which contains four linear N-bonded —NCO ligands.239... 

The two reported structures of Rh thiocyanate complexes both contain an S-bonded NCS unit.275,283 The N-bonded isothiocyanate complex IrCl(CN)(NCSXCO)(PPh3)2284 is obtained by recrystallization of the S-bonded isomer (linkage isomerization). Its structure could not be refined and of the Ir-NCS fragment only the C—S distance (1.62 A) has been given. 

Furthermore, isothiocyanate complexes can be prepared starting from the metal-azido complexes and reacting these with CS2. These reactions most probably proceed via 1,3-dipolar cycloaddition reactions.354 Syntheses of isothiocyanato complexes via this route are known for several metals (see, for example, ref. 355 for a synthesis involving Co). In these reactions formation of a cyclic intermediate (cf. equation 24) could be established. 

Lo and co-workers synthesised a series of rhenium(I) polypyridine isothiocyanate [Re(NAN)(CO)3(py-3-NCS)]+ (7) [26] and maleimide [Re(NAN)(CO)3 (py-3-mal)]+ (8) [27] complexes that can act as biological labels. Similar to most rhenium(I) diimines, irradiation of all the complexes results in intense and long-lived 3MLCT (dir(Rc) —> ir (NAN)) emission. The isothiocyanate complex [Re(phen)(CO)3(py-3-NCS)]+ has been used to label a universal M13 reverse sequencing primer that has been modified with an aminohexyl group at the 5 -end,... 

Electronic spectral data (cm ) and related bonding parameters of lanthanide(IH) isothiocyanate complexes of MBAAP. Ref. [299]. 

A preponderance of the transition-metal pseudohalogen complexes reported in the literature are prepared in aqueous media. Several oxidation states of many transition metals are either unstable in the presence of water or form only oxygen-coordinated species. Thus, these metal ions will not form pseudohalogen complexes in the normal manner. The following method, using polar, nonaqueous solvents is suitable for the preparation of isothiocyanate complexes of several of these ions. As an example of the preparation of such complexes, the synthesis of potassium hexakis(isothiocyanato)niobate(V) is described. 

C31H3gNOgS Na,Rb), 2,3,11,12-Dibenzo-1,4,7,10,13,16,-hexaoxocyclo-octadeca-2,11-diene(dibenzo-18-crown-6)-rubidium sodium isothiocyanate complex, 35B, 476... 

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