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 organ ometallic complexes carrying methylidyne (mu(3)-CH) and methylene (mu- CH2) ligands has been investigated on data retrieved from the Cambridg e Structural Database. It has been shown that mu(3)-CH and mu-CH, grou ps 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 geometri cal grounds from the average length of the hydrogen-bonding interactio ns, is roughly eta(3)-CH > mu-CH2. These ligands establish C-H ... O i nteractions which are comparable in length to those established by hyd rogen atoms bound to sp- and to sp(2)-hybridized carbon atoms consiste nt with experimental and theoretical evidence.