A systematic theoretical investigation was carried out to study the reactions of various germylenes with germane. Molecular structures of the reactants (GeX2 and GeHX, where X = H, F, Cl and Br) plus GeH4, transition states, and products have been optimized to understand the effects of halo-substituted germylenes. The basis set used is of double-zeta plus polarization quality with additional s- and p-type diffuse functions. Consistent with experiment, the theoretical gas-phase reaction GeH2 + GeH4 -> Ge2H6 possesses a negative activation energy. The predicted activation energies reveal interesting trends for both mono- and di- halo-substituted germylenes, -1.5 [GeH2], +20.5 [GeHF], +59.9 [GeF2], +18.0 [GeHCl], +46.8 [GeCl2], +17.3 [GeHBr], and +42.9 kcal mol(-1) [GeBr2]. There is a noteworthy relationship between the activation energies and the singlet-triplet splittings of the divalent germylenes. We report For the first time rate constants for the transfer of hydrogen, evaluated using standard transition-state theory with tunneling corrections. These results are analyzed and compared to the available experimental and previous theoretical findings For the gas-phase reactions involving germylene derivatives and germanium analogues.