Dimeric inorganic rings [X₂MYH₂]₂ and [XMYH]₂ (X=H,F,Cl,Br,I; M=Al,Ga,In; Y=N,P,As) and related monomer compounds X₂MYH₂, XMYH were theoretically investigated at B3LYP /LANL2DZP level of theory. Optimized structures and standard thermodynamic parameters of gas phase dissociation reactions were obtained. Nitrogen and Al-containing rings have higher stability compared to P,As and Ga,In systems; substituents × have minor effect on M-Y dissociation energy. [X₂MNH₂]₂ dimers are stable in the gas phase up to 1100-1300K.