Germanium ligands transition metal complexes

W. Petz, Transition Metal Complexes with Derivatives of Divalent Silicon, Germanium, Tin, and Lead as Ligand", Chem. Rev. 1986, 86, 1019. 

The chemistry of silicon, germanium, and tin transition metal compounds has been the subject of several reviews (12, 180). Optically active silyl ligands have been introduced in a transition metal complex by reaction of chiral functional organosilanes. However chiral silyl ligands containing complexes are limited to a few metal centers we shall discuss in turn iron, cobalt, platinum, and manganese complexes. 

We must however keep in mind that some of the above reactions may not be simple reactions at the silicon atom, since transition metal complexes show multicenter reactivity (metal atom, ligands) as exemplified in the chemistry of triphenylgermyl-carbene complexes of cobalt carbonyl (253). Thus, displacements of a silyl ligand may result from a multistep process and a thorough examination of these reactions has to be made. An example can be drawn from molybdenum-germanium chemistry (247). As shown in Scheme 59, germanium is displaced from complex 167 by HO with retention of configuration. Actually,... 

The stereochemistry of displacement of chiral germyl ligand in germanium transition metal complexes [which has been reviewed elsewhere (12)] will also be discussed here, since silicon and germanium resemble each other and since complementary experiments have been undertaken. 

Substantial progress has also been made in the area of transition metal complexes containing germanium ligands. The metal-germanium bond nexus has been shown to be active to a variety of small molecule activations and to undergo facile reaction in the formal 2 - - 2 sense. 

TM=tetrel complexes (1) W. Petz, Chem. Rea, 86, 1019 (1986). Transition Metal Complexes with Derivatives of Divalent Silicon, Germanium, Tin, and Lead as Ligands, (m) W. A. Herrmann, Angew. Chem., Int. Ed. Engl., 25, 56 (1986). Multiple Bonds Between Transition Metals and Bare Main Group Elements Links Between Inorganic Solid State Chemistry and Organometallic Chemistry. 

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

TABLE 8. X-ray structural data of transition metal germanium complexes with bridging germylene ligands... 

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