Structure of methane comlexes according to the data of experimental and theoretical investigations

The results of experimental and theoretical studies of the structures of methane complexes with neutral metal atoms, metal ions M⁺ and molecular fragments ML_n are considered and generalised. The influence of the charge and electronic configuration of the central atom and the nature of stabilising ligands L on the mode of coordination of methane in the complexes is analysed. The data from theoretical calculations of the structures of methane complexes are compared with the results of structural studies of some classes of model compounds, namely, borane complexes M(CO)₅·BH₃L (M = Cr, Mo, W) and tetrahydroborate complexes ML_n(BH₄)_m containing BH₄^- anions as ligands. Some rules determining the mode of methane coordination in the complexes are elucidated and assumptions concerning the dependence of the mode of methane coordination on the electronic configuration of the central atom are made.