Germanium multiple bonding

Compounds with Germanium-Germanium Multiple Bonds 796... 

The synthesis and chemistry of compounds where germanium is linked to a group 16 element has undergone a number of developments since the field was last surveyed,1 and a review on the subject has been published.162 New developments include the formation of new heterocyclic compounds and formation of multiple bonds to the heavier group 16 elements. A review has also appeared on this subject.163... 

Even though much effort has been directed toward the study of multiple bonding to germanium, compounds that exhibit Ge = 0 double bonding are almost completely limited to reactive intermediates.1,3... 

Element-element bonds, addition to G-G multiple bonds arsenic—selenium bonds, 10, 782 boron—boron bonds, 10, 727 boron—sulfur bonds, 10, 778 B-S and B-Ge bonds, 10, 758 chalcogen—chalcogen additions, 10, 752 germanium—germanium bonds, 10, 747 germanium-tin bonds, 10, 780 overview, 10, 725-787 phosphorus—phosphorus bonds, 10, 751 phosphorus—selenium bonds, 10, 782 phosphorus-sulfur bonds, 10, 781 Se-Si and Se-Ge bonds, 10, 779 silicon-germanium bonds, 10, 770 silicon-phosphorus bonds, 10, 780 silicon-silicon bonds, 10, 734 silicon-sulfur bonds, 10, 779 silicon-tin bonds, 10, 770 tin-boron bonds, 10, 767 tin-tin bonds, 10, 748... 

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... 

Homonuclear carbonyl dimers, palladium complexes, 8, 206 Homonuclear element-element bonds, addition to C-C multiple bonds boron-boron bonds, 10, 727 chalcogen-chalcogen additions, 10, 752 germanium-germanium bonds, 10, 747 phosphorus-phosphorus bonds, 10, 751 silicon—silicon bonds, 10, 734 tin—tin bonds, 10, 748... 

Of the linear clusters, the organogermanium-substituted transition metal carbonyl compounds are the simplest. In every case, the coordination at germanium is tetrahedral, while the transition element retains the geometry of the parent carbonyl compound (50,108,119,155, 157, 181). The Ge—M bond is almost without exception shorter than the sum of the Ge—M covalent radii (Table VI), which is cited as evidence for (d — d)-n multiple bonding. 

By analogy to the model used to describe a Sn=Sn double bond, the observed geometry of the digermyne molecule and its multiple bonding character can be rationalized as shown in Fig. 14.7.7. Each germanium atom is considered to be sp hybridized in the C-Ge-Ge-C plane a singly filled sp hybrid orbital is used to form a covalent bond with the terphenyl ligand, and the other sp hybrid is... 

The nature of multiple bonding between germanium and the heavier chalcogens in the complexes (/74-Megtaa)GeE (E = Se, Te) is best described as an intermediate between the Ge+— E and Ge=E resonance structures. The preparation of these complexes involves the addition of the elemental chalcogen to (/74-Mestaa)Ge, which is synthesized by the metathesis of GeCl2(l,4-dioxane) and Li2[Mestaa] (Mestaa = octamethyldibenzotetraaza[14]annulene dianion). The molecular structures of both complexes are shown in Figures 5 and 610. 

Experimentalists have been particularly well served by numerous reviews from some of the leading workers in the field. For example, Brook and Baines (76) have reviewed silenes, Wiberg (77) discussed M=C and M=N double bonds (M = Si and Ge), Cowley and Norman (78) have reviewed M=M (M, M = group 14 and 15 elements) double bonds, Raabe and Michl (79,80) have provided complementary reviews of multiple bonds to silicon, West (81) has reviewed disilene chemistry, Masamune (82) has reviewed the work of his group on Si=Si and Ge=Ge compounds, and most recently Barrau et al. (83) have summarized multiple bonds to germanium. Studies from the reactive intermediates era of this field are beautifully summarized by Gusel nikov and Nametkin (84). 

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