Germanium complexes divalent

A truly divalent germanium complex with a Cr—Ge bond is found in the macrocycle-containing compound (tmtaa)Ge—Cr(CO)5174 in which the local geome-... 

C. Cyclopropenylidene Complexes of Divalent Germanium, Tin, and Lead Amides... 

Scheme 7. Cyclopropenylidene complexes of divalent germanium, tin, and lead.

NMR spectra, 20 347 structural parameters, 20 297, 299 structure of, 20 300 chalcogenide halides, 23 381-382 structure, 23 382 complexes, 6 2 anation reactions, 34 225 with bipy and phen, 12 185-187 5-coordinate, 34 229, 234, 236-238 with divalent tin, 11 119 with germanium, 11 107-108, 112 homoleptic, 2,2 -bipyridine, 34 28-30 with olefins, 12 311-316 sulfoxides, 24 166 carbonylation reactions, 24 143 and catalyzed decomposition of H2O2, 24 150-151... 

It is apparent from most of the examples previously described that the most common formal oxidation state found for the Group 14 element is E(IV) (E = Ge, Sn, Pb). Relatively few examples of divalent germanium, tin, or lead complexes have been described, and of these, many are not well characterized. Cobalt-containing compounds are no exception in this regard and there appears to be only one report in the literature that describes a species of this type, viz. [Ge Co(CO)4 2], 67, although the precise structure of this complex is unknown (77). Two main synthetic routes are described, Eqs. (4) and (S), the starting complex in the latter reaction being... 

Reactivity is an intriguing aspect of these complexes not only because of the previously mentioned unique bonding mode, but also because these complexes can serve as good models for surface-bound divalent silicon and germanium species. Unfortunately, only a limited number of the reactions with small molecules and catalytic reactions have been reported so far. In contrast, the dynamic behaviors and isomerization reactions of these complexes, which give plentiful information about their chemical properties, are well documented. 

In contrast to the sulfide of silicon (p. 187). the sulfides of tetravalent germanium (white) and tetravalent tin (yellow) are stable in water, but form complexes in the presence of excess sulfide ion. The sulfides of divalent tin and lead (both black) dissolve neither in strong base, in excess sulfide, nor in dilute acids. Note that PbS has the same structure as sodium chloride and is probably the most nearly covalent salt known having this structure, its color and metallic lustre setting it apart from the structurally similar ionic halides and oxides. 

Other divalent germanium compounds include salts of GeClj, such as the substituted pyrazolyl complexes [Ge2(pz )3][GeCl3] (8-XXII) which is obtained in the reaction of Ba(pz )2 with GeCl2-dioxane.148 There are also a sulfide, GeS, several thiolato complexes,149 and a white to yellow hydroxide of no definite stoichiometry that is converted by NaOH to a brown material that has Ge—H bonds. 

An interesting part of chemistry comprises the divalent complexes of the Group 14 elements, germanium, tin and lead, supported by tetradentate nitrogen and oxygen donor ligands. The [Salen ] ligand system, obtained by condensation of a salicylaldehyde... 

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

Silicon and germanium require rather drastic reaction conditions for complexation to porphyrins. SiCU or GeCU must be heated with the porphyrin at 170°C for several hours in pyridine in a sealed tube, and the complex is obtained as the dimethoxy form, M (Por)(OMe)2, by crystallization in the presence of excess methanol after hydrolysis and chromatographic isolation. Ge(Por)Cl2 is also obtained by the reaction of GeC and porphyrin in quinoline at 230 °C. Sn and Pb porphyrins are easily prepared from the divalent metal salts in pyridine. Sn (Por) is air sensitive and oxidized to the Sn complex, Sn (Por)X2. In Sn(TPP)Cl2, the porphyrin ring is expanded to accommodate the large Sn atom (Sn—= 2.098(2) A). The Pb atom in Pb" meso-tetrapropylporphyrin (A(N ) 1.174 A, Pb—Np r 2.37A) is easily dissociated from it. Pb (Por) can be oxidized to Pb" (Por)Cl2 by chlorine. ... 

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. 

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