Homoleptic dithiocarbamates

Group 13 (III PETER J. HEARD TABEE I A) Homoleptic Dithiocarbamate Complexes ... 

The homoleptic dithiocarbamate complexes of both Sn and Pb have been investigated recently as possible single source precursors for the deposition of metal sulfide materials (98, 105, 106) and dithiocarbamates have also been used for the extraction of lead from environmental samples (107). 

Homoleptic dithiocarbamate complexes of both teUurium(II) (215, 293, 294, 296, 302-311) and tellurium(lV) (293, 294, 296, 302, 304-306, 309, 310, 312-315) are well known. The molecular structures of the bis(dithiocarbamate)tel-lurium(II) compounds, [Te(S2CNR2)2], are analogous to those of the corresponding Se compounds The Te atom exhibits a planar trapezoidal coordination geometry, with the two dithiocarbamate ligands bound in an anisobidentate fashion [Te—S(ave) = 2.52 (short) and 2.83 A (long)]. Tellurium(II) has a tendency for pentacoordination and, with the exception of [Te(S2CNCy2)2], which is monomeric (311), there is a short intermolecular Te-- S contact (av... 

Homoleptic gold(III) derivatives with dithiolate, ligands of the type [Au(S-S)2] are well known and are usually prepared from [AuC14] with the dithiol some examples are with 1,2-benzene dithiolate, maleonitriledithiolate, dmit, and so on, [164, 336]. Similar complexes have been reported for bidentate sulfur ligands such as dithiocarbamates, dithiophosphates, and so on, [41]. Other derivatives as the trinuclear species [Au(C6F5)(S2C6H4)]3 [337] or the complex with one nido and one closo-carborane dithiolate are known [338]. Figure 1.72 collects some of these complexes. 

Typical examples of this reaction involve the heterocumulenes C02, CS2, COS, RNCO, RNCS and other related molecules such as S02, S03, RC=N and RNC, and activated alkynes bearing strongly electron-withdrawing substituents such as C02Me. These reactions find utility in the syntheses of homoleptic carbamates (equation 77),223 monothiocarbamates and dithiocarbamates from homoleptic amides though redox reactions can occur in some instances (equations 78102 and 79224). 

For sulfur, dithiocarbamates and thiolates have long been known, some recent examples being U(SBu")4, [U(SBu")6]2 , [U(SPh)6]2-, and [Li dme]4[U(SCH2-CH2S)4].M The homoleptic polychalcogenide K([U(Se2)4] was made by heating U with Se and K2Se at 300°C the anion has four Tj2-Se2 units in a distorted dodecahedral structure.37... 

A unique homoleptic molybdenum thiolate, Mo(//r -dmpt)(dmpt)2 (388), is produced in the reaction of MoCl3(thf)3 with Li(2,6-dimesitylphenylthiolate) in diethyl ether at 0°C. The paramagnetic (/rB = 3.6), pseudo-tetrahedral complex features two monodentate thiolates, the third being bound through sulfur and 7r-arene interactions.893 The investigation of Mo111 and MoIV dithiocarbamates as oil additives and lubricant precursors continues. 

The homoleptic tris(dithiocarbamate) complexes [M(S2CNR2)3] (M = As, Sb, or Bi) have been studied extensively (93, 212-245). The arsenic complexes are mononuclear with three short As—S bonds (As—S = 2.31-2.39 A) that are essentially cis each other, and three long As—S bonds (As—S = 2.77-2.94 A). Valence bond sum (VBS) calculations show that the valency of the As atom is, as expected, close to three (224). The geometry at arsenic in the [As(S2CNR2)3] is best described as a distorted octahedron with the stereochemically active lone pair directed along the pseudo threefold axis, capping the triangular face defined by the three weakly coordinated S atoms (Fig. 16) (222-224, 230). 

Reaction of selenium(IV) dioxide with sodium dithiocarbamate salts yields the homoleptic selenium(II) bis(dithiocarbamate) complexes [Se(S2CNR2)2] (293-297). No selenium(IV) dithiocarbamate complexes appear to have been authenticated and dithiocarbamate ligands have been successfully employed as a method of separating selenites from selenates (298), as well as from other metal... 

With the exception of perchloric acid media, in which ttis(dithiocarbama-te)tellmiiun(lV) perchlorate species are formed (319), Te02 reacts with dithio-carbamate salts under acidic conditions to give the intensely colored homoleptic tetrakis(dithiocarbamate)teUurium(lV) complexes, [Te(S2CNR2)4]. The intense coloration results form Ugand-to-metal charge transfer (LMCT) bands in the visible region (293). 

Nickel(II) complexes with two different dithiocarbamate ligands, [Ni(S2CNR2) (S2CNR2)], can be prepared via ligand exchange between pairs of homoleptic complexes (1484). These reactions have been followed HPLC activation parameters suggest an Sn2 mechanism. While the steric properties of the... 

There are two types of neutral complexes homoleptic and heteroleptic. The former are generally dimers, with two cadmium atoms penta-coordinated by two molecules of dithiocarbamate, which acts as an anisobidentate ligand (Figure 31). One sulfur atom from one of the molecules coordinated to the cadmium ion acts as a bridge to the other cadmium atom, bringing about a distorted square pyramidal coordination geometry with the axial position occupied by the bridging sulfur atom [117]. 

---