Spodium Bonding to Dicoordinated Group 12 Atoms

DFT calculations consider the interactions between linear MR₂ and a series of N-bases, where M is Hg or Zn and its R substituents are CCH, CN, or NO₂. NCH, NH₃, and NMe₃ were considered as three different N-bases. Zn forms stronger bonds with the N bases than does Hg, and they strengthen along with the electron-withdrawing power of the R substituent, varying over a wide range from 3.4 to 43.9 kcal/mol. Another factor contributing to the bond strength is the nucleophilicity of the base: NCH < NH₃ < NMe₃. All MR₂ Lewis acids can bind at least two bases, which are situated along the R-M-R bisecting plane, fairly close to one another, with θ(N-M-N) angles between 67° and 117°. The presence of a more electron-withdrawing substituent R and more powerful nucleophile allows up to 4 bases to bind to M. The properties of these bonds place them along a continuum, some clearly noncovalent, while other contain a good deal of covalent character.