Out of several commercially available trialkylborohydrides, i.e. LiHBEt3, NaHBEt3, NaH(sec-Bu)3, and KHBEt3, it was the third one that exhibited the best selectivity and reactivity. As observed also in other research, lithium triethylborohydride turned out to promote unwanted side reactions, whereas its potassium congener led to formation of heavier products of consequent hydrogermylation (higher-order products). Decreasing the amount of sodium tri(sec-butyl)borohydride resulted in a decrease in conversion of diphenylgermane, and thus a loading of 10% has been maintained in the subsequent experiments. Several conjugated aromatic alkenes were hydrogermylated by phenyl-and diphenylgermane, as shown in the Chart 1. It is worth noting that tri(n-butyl)germane was inactive under the conditions used in this research. The isolation of adducts of phenylgermane turned out to be challenging. The instability of PhGeRH2 towards hydrolysis precluded chromatographic purification methods, as most of these products could not be retrieved from the chromatography column, even when silanised silica was used as a stationary phase. These compounds were identified only by gas chromatography coupled with mass spectrometry (GC-MS). It was, however, possible to purify six exemplary compounds, whose analysis further confirmed that hydrogermylation aided by tri(sec-butyl)borohydride yields products with anti-Markovnikov selectivity. Among those was the product of hydrogermylation of 2-vinylnaphthalene with phenylgermane, 6. To better explain these findings, we turned to the theoretical simulation of possible reaction pathways by means of DFT methods. ‡ It appeared natural to begin the theoretical investigation with an approach described in our previous research. After initial calculations (for details, see SI), the conclusion was drawn that regardless of the final regioselectivity, the reaction was initiated by a nucleophilic attack of a NaHBMe3 hydride anion on the terminal carbon atom of styrene (Chart 2, M superscript), which is preferred over the attack at the benzylic carbon (aM superscript). The observations for phenylgermane are almost identical as for phenylsilane.