Germanium compounds, double

Although no 73Ge NMR spectra of stable doubly bonded germanium compounds have been recorded, NMR chemical shift data for the heteroatom of the double bond are available these are listed in Table II. The chemical shift of the, sp2-hybridized carbon atom of dimesitylneopentylger-mene (entry 1, Table II), without any polar substituents, falls at 8 124.2.26 The chemical shifts of the boron-substituted sp2-hybridized carbon atoms of two stable germenes (entry 2, Table II) fall in the upfield region of the... 

With the availability of stable geometric isomers of doubly bonded germanium compounds, experimental determinations of the 7r-bond strength can be made. The enthalpy of activation for double bond isomerization in Mes(Tip)Ge=Ge(Tip)Mes (Tip = 2,4,6-triisopropylphenyl) has been determined for the Z-E conversion, 22.2 . 3 kcal/mol and for the E-Z conversion, 20.0 0.3 kcal/mol.15 These values agree well with recent theoretical estimations.7 The isomerization barrier in germaphos-... 

Heteroatom-Substituted Germanium-Chalcogen Double Bond Compounds... 

Compounds containing germanium-oxygen double bonds which are transiently stable have emerged.167,168 A germanone which is temporarily stable in solution was prepared which undergoes intramolecular cyclization (Scheme 21), 7 and this species was also obtained from the cycloreversion of 72 (Scheme 22), as identified by its cyclization products.168... 

Reactivity of stable germanium-nitrogen double bond compounds has been widely documented in previous reviews.3,4,6,7,119... 

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... 

Comparison of theoretical data with experimental spectra led also to the identification of compounds which have germanium-nitrogen double and triple bonds. Foucat et al. report about the results of flash vacuum thermolysis of substituted germacyclopentenes and DFT (B3LYP) calculations of model compounds of possible reaction products114. The authors took the experimental photoelectron (PE) spectra and compared them with... 

Vibrational (IR and Raman), UV-visible, photoelectron, NMR, and Mossbauer spectroscopy have all been reported for bis(bistrimethylsilyl-methyl)tin(II) and analogous tin(II) amides. Since an unusual tin-tin double bond has been proposed for the solid state of [Sn[CH(SiMe3)2]2]2 the Raman spectrum of this compound was of interest. Unfortunately, the compound decomposed in the laser beam however, an intense band at 300 cm-1 has been assigned as the Ge—Ge stretching frequency for the analogous germanium compound (68). 

The synthesis and reactivity of germanium compounds containing double bonds to Si, Ge, and Sn has been a very active area of research over the past decade and has been extensively and recently reviewed. Particularly striking... 

The double-bonded germanium compound, 166 undergoes rapid oligomerization, and has not been isolated. 

Escendie, 1., Courte, C., Stage, J., Andrianarison, M., and Andrinizake, 1. D. (1985). 2,2,-Dimesityl-l-(2,4,6-tri-tert-butyl phenyl) germa-phosphene The first stable compound with a germanium-phosphorus double bond, Am. Chem. Soc. 107,3378. 

Unstable compounds with double-bonded silicon and germanium atoms... 

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