The reactions of Ge, Sn, Pb, Sb, Bi, and Te atoms with silane molecules were studied using matrix-isolation Fourier transform infrared spectroscopy and density functional theoretical (DFT) calculations. All metals generate the inserted complexes HM-SiH3, which were stabilized in an argon matrix, while H2M═SiH2 and H3M≡SiH were not observed. DFT and CCSD(T) calculations show the insertion complex HM-SiH3 is the most stable isomer with a near right angle H-M-Si moiety. However, silydene complexes H2M═SiH2 (M = C, Si) were calculated and identified as the most stable complexes with the lighter elements. The bonding difference is mainly due to relativistic effects, which is that for heavier metal atoms valence s and p orbitals have a lower tendency to form hybrid orbitals.