Despite the prevalence of stable pi-complexes of most d(10) metals, such as Cu(I)and Ni(0), with ethylene and other olefins, complexation of d(10) Zn(II) to simple olefins is too weak to form isolable complexes due to the metal ion's limited capacity for pi-backdonation. By employing more strongly donating pi-ligands, namely neutral diborenes with a high-lying pi(B=B) orbital, monomeric 16-electron M(II)-diborene (M = Zn, Cd) pi-complexes were synthesized in good yields. Metal-B-2, pi-interactions in both the solid and solution state were confirmed by single-crystal X-ray analyses and their solution NMR and UV-vis absorption spectroscopy, respectively. The M(II) centers adopt a trigonal planar geometry and interact almost symmetrically with both boron atoms. The MB2 planes significantly twist out of the MX2 planes about the M-centroid(B-B) vector, with angles ranging from 47.0 degrees to 85.5 degrees, depending on the steric interactions between the diborene ligand and the MX2 fragment.