Se- and Te-donor ligands

A very convenient general synthesis for an extensive range of metal triazenido-complexes has been described (see p. 412). 

Complexes of the potentially bidentate ligands 3-(4-pyridyl)triazoline-5-thione, with Pd (Pt, Rh) have been prepared and were shown to be bonded through both N and S.72 The thermal stability of the compounds [PdX2L2] (X = Cl, I or N03  

Cardwell and P. S. McDonough, Inorg. Nuclear Chem. Letters, 1974, 10, 283. 

Condorelli, I. Fragela, G. Centineo, and E. Tondello, Inorg. Chim. Acta, 1973, 7, 725. 

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S-, Se-, and Te-donor Ligands. The TViV -dialkyldithiocarbamato-complexes [V0(R2NCS2)3] (where R = Me or Et, or R2N = 1-pyrrolidine) have been prepared. Their i.r. and mass spectra suggest that the compounds consist of discrete, seven-co-ordinate molecules.The [VOScj] " ion has been identified spectrophotometrically in the course of the reaction between an aqueous solution of [V04] and HjSe gas. CU3VX4 (X = S, Se, or Te) have been prepared and shown to have a sulvanite-type structure. ... 

Ketones form coloured solutions of 1 1 complexes which hydrolyse on contact with air i.r. spectra indicate solvation by a second molecule of ketone. Heats of solution of NbCl5 in MeCOR (R = Et, Pr, or Bu ) and cyclohexanone are reported.559 O-, S-, Se-, and Te-Donor Ligands. Table 4 summarizes much of the data reported on niobates, tantalates, and mixed oxides containing niobium(v) and tantalum(v) published this year. 

S, Se-, and Te-Donor Ligands. Photoconductive compounds of the type CU3VX4 (X = S, Se, or Te) have light.dark conductivity ratios of 10 1. V(S2CNEt)3 undergoes irreversible electrochemical oxidation in MeCN to both and V products. VO(S2CNEt2)3 forms as a seven-co-ordinate monomer which is reduced to VO-(S2CNEt2)2 this behaviour is different from that of the 8-hydroxyquinoline system (Vol. 5, p. 52). 

Complexes Containing S-, Se- and Te-donor Ligands 6.14.3.3.1 Thiolates, thiols, thioethers, and related ligands... 

Nickel(II) complexes with either bidentate mononegative ligands, such as dithiocarbamates, phosphorodithioates and thiocarboxylates, or monodentate neutral and anionic ligands are generally square planar. Nickel(II) complexes with Se and Te donors are strictly similar to those with S donors. 

There is also clear evidence of a change from predominantly class-a to class-b metal charactristics (p. 909) in passing down this group. Whereas cobalt(III) forms few complexes with the heavier donor atoms of Groups 15 and 16, rhodium(III), and more especially iridium (III), coordinate readily with P-, As- and S-donor ligands. Compounds with Se- and even Te- are also known. Thus infrared. X-ray and nmr studies show that, in complexes such as [Co(NH3)4(NCS)2]" ", the NCS acts as an A -donor ligand, whereas in [M(SCN)6] (M = Rh, Ir) it is an 5-donor. Likewise in the hexahalogeno complex anions, [MX ] ", cobalt forms only that with fluoride, whereas rhodium forms them with all the halides except iodide, and iridium forms them with all except fluoride. 

Arenetellurenyl halides are dihalogen-like electrophiles nucleophiles coordinate with tellurium and generate in many cases linear Y-Te-X arrangements (Y=0, S, Se, Te nucleophile donor atom, X=C1, Br, I). Examples with Se- or Te-containing ligands are not so numerous.9,83... 

The coordination chemistry of silver has historically been centred on the reaction of silver(I) ions with N-donor ligands and halides. However, an extensive chemistry now exists for P- and S-donor ligands, whilst for O-donor ligands only weak complexes are generally formed and they have been studied in much less detail. Based on the reactivity and stability of its coordination complexes, the silver(I) ion has been characterized as a class B or soft acid, for which the following stability order is observed N P>As>Sb 0 S Se Te FComparative studies between ligands with these donor atoms allowed the relative stability of silver bonds to be determined as P > S > N > O. 

The literature contains numerous reports of complexes formed between mercury(II) halides, HgX2 (X = Cl, Br, I), and neutral donor ligands containing the donor atoms N, P, As, Sb, S, Se or Te. Some of these species are described in subsequent sections. For a recent survey consult ref. 555 and papers cited therein. 

Sulfur participates as a donor center in sulfide complexes (Muller and Diemann, p. 515), dithiolenes (Miiller-Westerhoff and Vance, p. 595), and other S-containing ligands (thiosulfates, thiourea, mono-, and dithioketones) (Livingstone, p. 633). Some other complex compounds with Se and Te as donor centers have been described (Berry, p. 661). 

Complexes with S-Donor, Se-Donor, or Te-Donor Ligands. The interatomic distances and valence distributions in the chromium thiospinels have been reviewed.151 Several mixed-metal sulphides, selenides, and tellurides containing chromium(m) have been reported this year, as detailed in Table 2. 

Examples for square planar complexes of Se(II) and Te(II) with other sulfur and selenium donor ligands such as thio- and selenocarbamates are given (e.g., in 29,165, 205). When triarylphosphane ligands were introduced as two-electron donors by the reaction of triarylphosphane selenide with Br2, T-shaped Ar3PSeBr2 with the Br ligands in trans positions was prepared (435). Possibly, the molecules are dimerized via bromine bridges as in Se2(tmtu)2Br4 (445). 

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