Donor-acceptor bonding in novel low-coordinated compounds of boron and group-14 atoms C-Sn

A summary of theoretical and experimental work in the area of low-coordinated compounds of boron and group-14 atoms C-Sn in the last decade is presented. The focus of the account lies on molecules EL2, E2L2 and E3L3, which possess dative bonds between one, two or three atoms E and sigma-donor ligands L that stabilize the atoms E through L -> E donor-acceptor interactions. The interplay between theory and experiment provides detailed insight into the bonding situation of the molecules, which serves as guideline for the synthesis of molecules that possess unusual bonding motifs.