“…Four-membered-ring compounds containing several different ligands (R, R‘) have been synthesized and characterized by single-crystal X-ray crystallography. − The four-membered-ring compounds studied here are divided into two groups: compounds containing two pnicogens of the general form R 2 ME(R‘) 2 M(R) 2 E‘(R‘) 2 (M = In, ,,− ,,,, Ga, − ,,, Al; ,,− ,, E, E‘ = P, As) and compounds containing one halogen and one pnicogen of the general form R 2 ME(R‘) 2 M(R) 2 X (M = In, ,, Ga; , E = P, As; X = Cl, Br). In our theoretical investigation we consider the case of R, R‘ = H (Figures and ).…”