1.1- Dithio complexes

The earlier literature containing work on 1,1-dithio complexes of iron has been covered in depth by Coucouvanis 1), and, since 1968, interest in these iron complexes has increased. 

The 1,1-dithio complexes of cobalt have been studied extensively (1). Most of the literature is concerned with Co(III) compounds, as the complexes with divalent cobalt are extremely air-sensitive and have only been synthesized in acidic solution under rigorously deoxygenated conditions. The recent complexes of cobalt with 1,1-dithio ligands are listed in Table III, together with some of their physical properties. 

Considerably less is known about the chemistry of palladium and platinum 1,1-dithio complexes. Of late, there has been only one report that dealt with the synthesis of a large number of palladium dithiocar-bamates 392). Twenty-five yellow palladium dithiocarbamate complexes were obtained by reaction of PdCla with NaR2dtc in methanol solution. Several other reports have appeared in which a few dithiocarbamate complexes of palladium were synthesized. Thus, the novel [Pd (OH)2dtc 2], which is soluble in water, was isolated 393). The synthesis of optically active palladium(II) complexes of AT-alkyl-a-phen-ethyldithiocarbamates, similar to (XXIV), via the reaction between the optically active amine, CS2, and PdCl2, has been described. From ORD and CD spectra, it has been established that the vicinal contribution of a remote, asymmetric carbon center could give rise to optical activity of the d—d transitions of palladium 394). Carbon disulfide has been shown to insert into the Pt-F bond of [PtF(PPh3)3]HF2, and X-ray studies indicated the structure (XXIX). 

With the advances in x-ray crystallographic instrumentation and computational facilities, the structural studies on the 1,1-dithio complexes have progressed at an amazing rate. Since the first reports of unusual oxidation states of the dithiocarbamate complexes, the electrochemical properties of these molecules have been investigated extensively. New ligands have been designed to test various hypotheses regarding structural and electronic properties of the complexes. 

Fig. 6. The MS4 core structure in divalent Sn and Pb 1,1-dithio complexes. The heavy lines correspond with the short M-S distances (Table IV).

Structural Details of the Quadrivalent Sn, 1,1-Dithio Complexes and (Et4N)Pb(EtXant),... 

Numerous synthetic and crystallographic studies of the Group V 1,1-dithio complexes have been reported in the literature since 1970. 

A considerable amount of research has been devoted to the chemistry of V(IV) 1,1-dithio complexes. The 1 1 base adducts of the VO(R2Dtc)2 complexes (445, 446, 610) have been isolated and characterized (R2 =Me2, Pyrrol with pyridine and 4-methylpyridine, respectively (444). 

Selected Structural Parameters of the Group V Transition Element 1,1-Dithio Complexes. 

Selected Structural Parameters and Electrochemical Properties of the Ruthenium 1,1-Dithio Complexes. 

Selected Structural Parameters and Redox Potentials for Nickel 1,1 dithio complexes. 

Sulfur addition to 1,1-dithio complexes of Ni(II) was first reported by Coucouvanis and Fackler (156). The initial proposal that sulfur addition was accompanied by ring expansion was verified by the crystal structure determination of the FeL3S complex (160) (L = p-dithiotoluate). Since then,several studies that dealt with the synthesis, structures, and reactivities of perthio complexes have appeared. 

Theoretical studies for the 1,1-dithio complexes of the extended Hiickel or LCAO-MO--SCF type are few, and accounts of such studies are briefly given in the appropriate sections, which are arranged according to element. 

T2 >47 2(P) transitions at 15, 300, and 22,000 cm-1. The energy of the 4A2 - 4T2 transition, which is a direct measure of 10Dq, when compared to that of other Cr(lll) 1,1-dithio complexes, places the R2DEI) ligand between j -MNT and R2Dtc in the spectrochemical series. 

Since the first report of the sulfur-addition reaction to 1,1-dithio complexes (156), a number of structural studies have verified the originally proposed ring expansion of the MS2C ring following this reaction. In addition, mechanistic studies on the sulfur insertion reaction and electronic spectral studies of the perthiocarboxylate Ni(II) complexes have been reported. 

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