Cyanate complex

For colorimetric or gravimetric determination l-nitroso-2-naphthol can be used. For chromatographic ion exchange (qv), cobalt is isolated as the nitroso-(R)-salt complex. The cyanate complex is used for photometric determination and the thiocyanate for colorimetry. A rapid chemical analysis of... 

It now appears that the most usual coordination mode in c/s-di(thio-cyanate) complexes is one N-bound and one S-bound thiocyanate, as an angular Pd—SCN bond minimizes interaction with the other bound thiocyanate and with the other ligands. 

Both complexes (867) and (868) promote the hydrolysis of urea in a two-step process.2080 Heating of (867) or (868) in acetonitrile solution produced ammonia with kinetic first-order dependence on complex concentration and an observed rate constant of (7.7 0.5) x 10-4 h-1 to yield a cyanate complex as the reaction product. When the reaction was carried out in 50% aqueous acetonitrile solution, ammonia was produced at the same rate but without buildup of the cyanate-containing product, suggesting that the latter is hydrolyzed in the presence of water. The hydrolysis rate was also first order in water, indicating that it occurred by attack of an external water on the coordinated cyanate.2080... 

In an analogous reaction, urea substrates having alkyl substituents at only one of the N atoms undergo alkylamine elimination to form a dinickel cyanate complex.2081 In contrast, no reaction was observed for A ,A7-dialkylated substrates. 

A precipitate, explosive when touched after drying, which appeared from a neutralised solution stood overnight with a large excess of potassium cyanate, was described as a fulminate. This is unlikely, though fulminating gold is probable, cyanate hydrolysing to release ammonia (see above). Existence of explosive cyanate complexes is also conceivable. 

It is more convenient to start with the triflate ion [Rh(NH3)5(CF3S03)]2+ since triflate is a much better leaving group than chloride and is immediately replaced by liquid ammonia [87]. A third route involves acid hydrolysis of the cyanate complex [Rh(NH3)5(NCO)]2+, which proceeds quantitatively (probably via a carbamic acid complex). Vibrational studies on Rh(NH3) + assign stretching vibrations as i(Alg) at 514cm-1, i/2(Eg) at 483 cm-1 and i/j(T,u) at 472 cm-1 [88],... 

Table 2. Molar conductance (A) for the hexachloride and the hexaisothio-cyanate complexes of the lanthanides in nitrobenzene 35, 36)...

Only a few cyanate complexes have been reported for Cr250 and Mo.2SI Both in these complexes and in related thiocyanate complexes of Cr,252,253 Mo253,256 and W254 the NCX ligands are terminal N-bonded. 

Only one structure for a transition metal cyanate complex has been reported. In trigonal-bipyramidal Co(terpy)(NCO)2 (98)277 the cyanate ligand is terminal N-bonded. Based on the M—N—C bond angle (160.9°) an M—N(CO) bond distance of about 1.16 A is expected whereas a much shorter bond is found. 

The cyanate complexes of the Group VIII metals are less common. A terminal N-bonded ligand is present in Ni(NCO)2(phen)2263a and a l,3-/i-bonded NCO in dimeric [BPh4][Ni2(tren)2(NCO)2] (cf. 100).230... 

Asymmetric 1,1 -p, bridging azides are present in Hg(CF3)N3330 and the corresponding cyanate complex (112). In the latter complex the Hg—N bond distances differ considerably (2.03 vs. 2.88 A). 

It is necessary to consider that the competitive reactions are characteristic also for ligands having two or more hard and soft donor centers. The first of them are NCO, NO2, NO., and other anions [2,7,44], The synthesis of cyanate complexes is mainly carried out by the method of immediate interaction of ligands and metal cyanates [(3.274), X - O] or by exchange of ligands, for example (4.16) [44] ... 

Apart from the preceding example, which depends on a rather indirect argument, electronic spectra are only useful to provide supporting evidence for the mode of coordination of cyanate and seleno-cyanate complexes. The arguments must necessarily be based on the magnitudes of crystal field parameters, and these can be assessed only by comparison with other related values. 

A number of metallocene cyanate complexes have been reported for these metals. Samuel (648) and Coutts and Wailes (219) reported cp2M(CNO)2 (M = Ti, Zr) independently in 1966. Samuel made no definite assignments of the structure, but Coutts and Wailes suggested the compounds were JV-cyanato complexes. Later, Burmeister et al. (145, 146) reexamined the compounds in more detail and argued that they, and the hafnium analog, were 0-cyanato complexes. This was... 

Metallocene-thiocyanate complexes have been reported similar to the cyanate complexes described previously. There is general agreement that these are N-thiocyanato complexes, cp2M(NCS)2 (M = Ti, Zr, Hf) 145, 146, 219, 320, 648). The compound cpTi(NCS)3 has been prepared, and infrared measurements show it to be as Avritten 458) cp2Ti(NCS) is trimeric but the mode of bridging is not known 220). 

The preceding sections have shown that the behavior of the thiocyanate and selenocyanate groups in homogeneous complex anions is identical in both cases the nitrogen atom coordinates to the class a metal, and the sulfur or selenium atoms coordinate to the class b metal. Although fewer comparable cyanate complexes are known, it is quite clear that the coordination of the cyanate group is not governed by the same factors. 

To facilitate the program it was decided to study the cobalt(II)-thio-cyanate complex system which was as accessible to direct assay in the exchanger phase as it was in the solution phase by absorption spectrophotometry in the visible region. Both Co(II) and Co(SCN) exhibit sizably different spectral absorption properties in the visible region. Assuming that the presence of higher complexes than one to one in the cation... 

Since neither protons nor phosphorus nuclei are present in this case, similar investigations of (poly)tungsten carbonyl, nitrile, cyanate complexes should be straightforward. 

Excluding organic ligands, there are few examples of complexes of M(14) with carbon donor ligands. Most cyanide and cyanate complexes have been known for some time, although there are always new examples to be found. The simplest examples of complexes with M(14)—C bonds are the carbides, and a number of new routes to such compounds have been reported. 

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