Hydrogermylation alkenes

Tri(2-furyl)germane63,127 130 has been shown to be a useful hydrogermylation reagent for alkenes,127,128 dienes,129 alkynes,129,130 and carbonyl species (Equations (97) and (98), Table 17).127 It has been employed to selectively hydrogermylate the double bond of a,/3-unsaturated carbonyl compounds (Equation (99)).127 This species can also be used to affect the hydrogermylcarbonylation of alkynes in the presence of CO (Equation (100)).130... 

Alkynes react with the bulky germanium hydride (MejSdjGeH to selectively yield (Z)-alkenes (Equation (105)).67 The hydrogermylation of alkynols or alkynes can be catalyzed by a rhodium complex (Equation (106), Table 18) and some of the intermediates were identified (Scheme 16).132 Similar rhodium species react with alkynes to yield alkenyl complexes,133 and other transition metal complexes have been employed as hydrogermylation catalysts including those containing palladium.134,135... 

A range of addition reactions of (TMS)3GeH with alkynes, alkenes, ketones, azines, and quinones has been studied using EPR. In addition, synthetic studies of hydrogermylation of alkynes have shown that the reaction proceeds regio- and stereo-selectively, whereas reactions with alkenes do not take place (presumably owing to the reversibility of the germyl radical addition) (Scheme 29). 

In fact, additions of tributylgermyl radical and tributyltin radical to activated alkenes occur at about the same rate (see refs, 38 and 101). This addition reaction is probably more readily reversible in the case of tin (because a weaker bond is formed) and therefore hydrostannylation is a less serious problem than hydrogermylation. Thus, very reactive precursors (preferably iodides) are required as precursors if germanium hydride is used with an electron deficient alkene but this is not because the germanium radical is less reactive towards halides than the tin radical. 

Hydrogermylation chemistry has been employed to make germanium-carbon bonds at surfaces via the reaction of alkynes and alkenes with the Ge-H bonds of HF-treated surfaces. Recently, this method has also been employed to functionalize the surface of germanium quantum dots (Figure 2). 

Additions of trihalogermanes to alkynes, alkenes and carbonyl compounds have been reviewed. Hydrogermylation of phenylacetylene with triphenylgermane in the presence of Pd(PPh3)4 gives a mixture of three vinylgermanes (equation 42). ... 

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