Germanium complex

Germanium, eyclopentadienyl-, 3, 218 Germanium, tris(acetyiacetone)-structure, 1, 65 Germanium alkoxides physical properties, 2, 346 Germanium complexes, 3,183-223 acetylacetone isomerization, 2,383 bivalent... 

Another example for a five-coordinated germanium complex (10-Ge-5 anionic complex) has already been described above (see Section IV.B.2.a.ii Figure 23). An unusual rectangular pyramidal germanium(IV) anion was synthesized according to the reaction shown in Figure 30. The anion was characterized by 31P and 1H NMR studies125. 

There are many examples of tris-bidentate complexes ML3. An early example is provided by the germanium complex [GeCmaltjs], whose formation, along with [Ge(OH)2(malt)2], was documented in 1966 149). Better-characterized examples are provided by the series of tin(IV) compounds [SnLaJX with L — l,2-dimethyl-3-hydroxy-4-pyri-... 

On the other hand, for cobalt-germanium complexes, the stereochemistry strongly depends on ligand (Table 3). 

In cobalt-germanium complexes, substitution of one carbonyl by electron-donating ligands should increase the nucleophilicity of the transition metal moiety . ... 

In the 80 MHz H-NMR spectrum of Sn(OMC)Cl, and in the analogous germanium complex, the meso-protons appear as two signals while in the spectra of the acetate derivatives a single resonance has been observed. No linewidth data have been reported and the results have been explained considering that the behavior of acetate as a bidentate ligand, discussed in Sect. 4.2, would introduce distortions into the molecule causing accidental isochrony of the meso-proton resonances. 

Germanium-carbon multiple bonds, formation, 3, 709 Germanium-chalcogen bonds, reactivity, 3, 745 Germanium complexes with alkali metal bonds, 3, 748 with Isis // -arcnc chromium heteroatoms, 5, 340 with chromium carbonyls, 5, 208 coupling reactions, 3, 711 with CpMoCO, 5, 463... 

Holmes and his coworkers described a number of pentacoordinated anionic germanium complexes containing a spirocyclic framework with methyl, phenyl, halogen or hydroxyl ligand at the acyclic site307,332,333. Reaction of an organogermanium trichloride with a catechol or thiocatechol derivative in the presence of triethylamine, followed by a metathetical exchange, led to desired products as illustrated by the formation of the phenyl-substituted derivatives 90 and 91 (equation 16)333. 

As in the spirocyclic five-coordinated germanium complexes discussed above, the geometry about the tin atom in some of the mono- and bi-cyclic stannates, listed in... 

Tacke and his coworkers have recently reported the synthesis and structural characterization of a series of pentacoordinated anionic germanium complexes based on the Ge04C ligand framework340-344. The route to these compounds involves the reaction of (chloromethyl)trimethoxygermane with a secondary amine in the presence of triethy-lamine, followed by an exchange with two equivalents of bidentate ligands, such as aromatic 1,2-diols or a-hydroxycarboxylic acids, as shown for the synthesis of 114340 (equations 22 and 23). 

Among neutral pentacoordinate intramolecular germanium complexes, compounds containing a C,0-chelating ligand have been most extensively studied. 

The structures of germanium complexes 494a995, 494b"6, 495a"7 and 495b"8 show that the central Ge atom has an octahedral structure with two bidentate deprotonated catechol moieties in equatorial positions. 

A germanium complex with ethylenediaminetetraacetic acid (Hedta) 532 has a pen-tadentate edta ligand with one protonated acetate group which does not coordinate, forming a six-coordinate complex1150. 

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