The present work includes the formation and description of four-membered ring systems based on organometallic aluminum, gallium and indium compounds as well as the silylsubstituted pnicogen compounds of phosphorus and arsenic. Their chemical and spectroscopic characteristics and the reactivity towards N-heterocyclic carbenes are described. Regarding this, the cleavage of the ring systems with strong lewis bases is the main topic of this work. Therefore the structural and spectroscopic parameters as well as the thermal behaviour of the monomeric compounds is decribed and compared.