Germanium divalent

Germanium forms divalent compounds with all the halogens. Germaniunil 1) chloride can be prepared by passing the vapour of germanium(IV) chloride (see below) over heated germanium. The reaction is reversible and disproportionation of germanium(II) chloride is complete at about 720 K at atmospheric pressure ... 

It has become common to classify all molecular compounds, which fulfill the above characteristics, as carbene analogs 9,13>. As a consequence, compounds of divalent silicon, germanium, tin, and lead may be regarded as carbene-like and are therefore called silylenes, germylenes, stannylenes, and plumbylenes. In contrast to carbenes they have one property in common the energetically most favorable electronic state is the singlet 1a2 found by experiments and calculations 9). 

The decamethylmetallocenes of germanium, tin and lead as well as the parent metallocenes were prepared by reaction of divalent inorganic... 

In contrast to silicon, germanium has a well-established though limited chemistry of inorganic compounds in the +11 state which are of reasonable thermal stability though usually air-sensitive. Divalent organogermanium(II) species known at present fall into three groups ... 

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

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

Interest in divalent compounds of germanium has increased steadily over the past several years, and many new species have been prepared. In particular, unsymmetrical heteroleptic species GeLL have become much more prevalent. Several reviews covering the synthesis and chemistry of germylenes have appeared, and the... 

Chalcogenation of a divalent germanium compound with styrene sulfide has been examined as an alternative route to the first free germanethione Tbt(Tip)Ge = S 165142 (Scheme 32) and later on allowed the synthesis of new base-stabilized germanethiones 187 and 188156 [Eq. (37)]. Phenyl isocyanate also may serve as a sulfur source leading to 165, which was evidenced by electronic spectroscopy and underwent a subsequent [2 + 2] cycloaddition with phenyl isocyanate157 (Scheme 36). 

The chemical properties of germanium fall between those of silicon and tin. It forms both the divalent and tetravalent compounds, the oxidation state +4 being more stable than the +2 oxidation state. The metal is stable in air and water at ambient temperatures. However, it reacts with oxygen at elevated temperatures forming divalent and tetravalent oxides, GeO and Ge02. 

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... 

During the 1980s, several organosilylenes have been isolated and studied in argon or hydrocarbon matrices at very low temperatures such as 77 K, above which temperature they react rapidly with themselves or with solvent. By contrast, the divalent dicoordinate species of germanium, tin, and lead have been well characterized as stable molecules. 

Cyclic compounds containing Si2E2 rings (10.56, E = S, Se) are also formed from the reaction of a stable silylene with sulfur or selenium [eqn (10.37)]. The reaction of the divalent germanium compound Ge[N(SiMe3)2]2 with... 

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... 

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