The new compounds [H2GaE(SiMe3)(2)](3) (E = P (1), As (2)), the first authenticated examples of a phosphinogallane and an arsinogallane containing the GaH2 moiety, an prepared via efficient dehydrosilylation from the respective combinations of H3Ga . NMe3 and E(SiMe3)(3) in diethyl ether or toluene. Compounds 1 and 2 are characterized by elemental analysis. NMR, IR, and mass spectrometry. Single-crystal X-ray structural studies show that the molecular structures of 1 and 2 feature a flattened six-member ring of alternating Ga and E centers. Both compounds are reasonably stable at -30 degrees C but spontaneously decompose at ambient temperatures, 2 noticeably faster than 1, with the evolution of HSiMe3, H-2, and E(SiMe3)(3). The pyrolysis of 1 yields nanocrystalline GaP while the pyrolysis of solids from decayed 2 results in nanocrystalline GaAs as determined from XRD studies. Under applied pyrolysis conditions, the thermally accelerated dehydrosilylation of the precursors is accompanied by a side-evolution of CH4 and retention of small quantities of amorphous Si/C phases.