C-H center dot center dot center dot O hydrogen bonding in crystalline complexes carrying methylidyne (mu(3)-CH) and methylene (mu-CH2) ligands: a database study

The relationship between the molecular and crystal structures of organometallic complexes carrying methylidyne (mu(3)-CH) and methylene (mu-CH2) ligands has been investigated on data retrieved from the Cambridge Structural Database. It has been shown that mu(3)-CH and mu-CH, groups participate in intermolecular hydrogen-bonding networks of the C-H ... O type involving, in most cases, the oxygen atoms of CO ligands as accepters. The order of decreasing acidity, judged on purely geometrical grounds from the average length of the hydrogen-bonding interactions, is roughly eta(3)-CH > mu-CH2. These ligands establish C-H ... O interactions which are comparable in length to those established by hydrogen atoms bound to sp- and to sp(2)-hybridized carbon atoms consistent with experimental and theoretical evidence.