Nickel xanthate structures

Of the transition metals, the nickel triad has been the most studied in terms of xanthate structures, especially nickel xanthates. Thus, binary xanthate structures are known for all elements with no less than 15 binary nickel xanthate structures known and these aggregate in the solid state in six distinct supramolecular architectures. There is also a rich diversity of adducts as well as mixed-ligand complexes, in particular for nickel. 

VIII. XANTHATE STRUCTURES OF NICKEL, PALLADIUM, AND PLATINUM 167... 

CH2CH2 -Pr (78, 79), CH2CH2 f-Bu (80), hex (68), CH2CF3 (81, 82), CH2CH2OMe (83), CH2Ph (84), Cy (68), 4-MeCy (85), and 4-f-BuC6H4 (60). Table II summarizes the salient features of the structural chemistry of the binary nickel xanthates with data from the most precise structure determination included for cases where more than one determination is available in the... 

Structural Data for Binary Nickel Xanthates, Ni(S2COR)2... 

There is a rich structural chemistry in the Lewis base adducts of the nickel xanthates so that a variety of coordination geometries are found as well as... 

Structural Data for Nickel Xanthate Adducts of the General Formula Ni(S2COR)2(NnN)... 

The second nickel xanthate cluster is that of [Ni(OCH2C5H4N)(S2COEt)]4, characterized as an acetone solvate (116), and this is represented in Fig. 63(a). The structure is built up about a Ni404 core, see Fig. 63(h), which approximates... 

There is no apparent correlation between the magnitude of the intermolecular Au- -O or Au- -S interaction and the distortion from the ideal linear geometry about the gold atom. For example, the structure of (o-MeCgH PAu CO—i-Pr) (141) features the closest intramolecular Au- - -O contact of 2.892(7) A, but the smallest deviation from linearity [i.e., 179.6(1)°]. This emphasizes the weak nature of these intramolecular interactions. As for the nickel xanthates, there are... 

The important point to appreciate is that the formal valency of zinc is satisfied by two bonds to sulfur so that the additional interactions are indeed hypervalent interactions. Thus, the nature of the adopted structures arises from the ability of the central element to form hypervalent, or secondary, interactions and it is proposed that this ability is moderated by steric considerations associated with the alkyl substituents. As noted from the structural studies for the uncoordinated xanthate anions summarized earlier in Section II, there are no electronic differences among the xanthate ligands that can be correlated with the nature of the oxygen-bound substituent. This conclusion is vindicated by the homogeneity of the molecular structures of the binary nickel xanthates as... 

With P-donors a variety of different structures are formed. Two complexes (359a,b) with a five-coordinate square pyramidal geometry and one S-donor in the apical position are reported.934,933 In a related complex (360) the nickel center reveals a distorted square planar geometry, because one xanthate ligand switched to a monodentate coordination mode. 6 By reaction of [NiL2] complexes with Ph2P(CH2)2P(Ph)(CH2)2PPh2, compound (362) is formed, which consists of a five-coordinate cation and a hexacoordinate anion. 7... 

Substituted dithioformate anions as ligands R C(S)S are usually called dithiocarbamates (R = R2N), alkyl and aryl dithiocarbonates or xanthates (R = RO), alkyl and aryl trithiocar-bonates or thioxanthates (R = RS). Dithioacid anions (R = alkyl, aryl) have been rarely used as ligands of nickel(II) because of their instability. Structural properties of selected nickel(II) complexes with substituted dithioformate, dithiolene and related ligands are shown in Table 90. 

The ligand field strength of the ligands is between that of the dithiocarbamates and water.49 IR studies show characteristic bands near 1250, 1100, 1020 and 550 cm-1.93 The contribution of the resonance form (85) in transition metal complexes is less than that of the analogous structure in the dithiocarbamates.60 The electron density on the metal is not very high, which accounts for the fact that abnormal high oxidation states are exceptional and a strong interaction of bases with the square planar nickel (and some other metal) xanthates is found.94... 

Figure 55. The structure of polymeric [Ni(S2CO—i-Pr)2(pyr)]oo showing (a) the linear polymeric chain aligned along the b axis, and (b) highlighting the orthogonal relationship between the xanthate and pyrazine ligands. The structure has symmetry in that the nickel atom is located on a center of inversion and the pyrazine ligand is disposed about a center of inversion.

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