Glyoximate metal complexes

Figure 4.13 Molecular structures of macrocyclic metal complexes metal bis(glyoximate), metal tetraazaanulene and metal phthalocyanine complexes...

Among the more widely studied 2,3-C-disubstituted ligands related to ethylenediamine are sbn and stien (Table 3). These ligands can exist in meso and racemo forms and the properties e.g. solubility) of transition metal complexes (especially Co" ) with the two forms of this type of ligand are often sufficiently different as to allow amine isomer separation to be achieved without separation of the amine mixture. Meso and racemic 5bn are prepared together by the reduction of dimethyl-glyoxime and can be separated by fractional crystallization of the dihydrochloride salts. There are, however, stereospecific synthetic routes available for the meso and racemo forms of stien (Table 6). 

Most of the separation procedures are based on the precipitation [27, 68, 72, 76, 80, 89, 99, 110, 139, 158, 170] or extraction [11, 72, 81, 119, 122, 124, 139, 162] of the Pd dimethyl-glyoxime (DMG) complex. In combination with the commonly used scavenger precipitations of Fe, La, or Zr hydroxides and Ag halides quite high decontamination factors can be achieved (see for example procedure 1 below). The samples for counting are prepared using either Pd metal or insoluble Pd compounds, like DMG complex, sulfide, or iodide. 

Replacement of the hydrogen bonds in oxime complexes with boron bridges leads to macrocyclic complexes such as those from dimethyl glyoxime (equation 59).201,202 This kinetic template technique has been used for the encapsulation of metals inside cage ligands.203 204... 

Conducting halogenated linear metal atom chain systems were first reported in 195095 and are now known for Ni and/or Pd complexes of glyoxime (GLY), DPG and BQD. The compounds are usually produced by treating a hot solution of the neutral complex in o-C6H4C12 with I2 and lustrous coloured crystals of the NIOS compound are obtained on cooling the solution. The limited range of compounds studied is shown in Table 3 and all have metal-over-metal stacked structures. 

Halogen oxidation of planar complexes, particularly of the nickel triads that contain bidentate glyoximes or macrocyclic ligands, such as, phthalocyanines, substituted porphyrins, or tetraazaannulenes, leads to highly conducting substances that may possess chains of metal atoms as well as chains of polyhalides ... 

Ni(ii) forming 4 coplanar bonds. Planar diamagnetic complexes include the Ni(CN)4 ion, which has been studied in the and other salts (Ni-C, 1-85 A), and molecules such as (a) and (b). The numerous complexes with bidentate ligands include the thio-oxalate ion, (c), molecules of the types (d) ) and (e), and the glyoximes, (0> notable for the short intramolecular hydrogen bonds. Many divalent metals form phthalocyanins, M(ii) replacing 2 H in C32H18N8 (Fig. 27.9). 

Besides complexes of o-phenylenediamine, a variety of glyoximes, 24 (R = methyl dimethylglyoxime, HsDMG), and the related salicylaldimines, 25, form neutral square planar complexes which exhibit short metal-metal bonds in the solid state (398). 

Rhodium(II) forms dimeric diamagnetic glyoximes, for example, Rh -(HDMG)4(Lewis base)2 (225, 226), which do not have intermolecular metal-metal interactions. The compaction conductivity of [Rh(HDMG)2py]2 (3.3 X 10-1 Q-i cm-i) (225) and the isostructural Rh2(HDMG)2(CO)2Cl2 (< 10 cm-i) (313) is consistent with the lack of metal-metal bonds between molecules. Iridium glyoxime complexes have not been reported. 

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