Abstract. Structure data on metal-alkoxides, metal-alcohol, metal-carboxylates, metal-carboxylic acid, metal-azolate and metal-azole coordination compounds from the Cambridge Structural Database (CSD) were analysed in terms of bond lengths. In general the anionic ligands form shorter metal-ligand bonds by about 0.02-0.05 Å compared to neutral ligands, a clear indication of a charge contribution to the bonding interactions. This small difference is not, however, deemed as sufficient to generate two distinct classes of metal-ligand bonding. Instead, the anionic ligands can be viewed as having "charge assisted" metalligand bonding, corresponding to the same term used for "charge-assisted hydrogen bonding".

Almost 700 Swedish and South African students from the upper secondary school and first-term chemistry university level responded to our survey on concepts of chemical bonding. The national secondary school curricula and most common textbooks for both countries were also surveyed and compared for their content on chemical bonding. Notable differences between the countries were found in textbooks and in the curriculum regarding the topics of ionic bonding, bond energetics and use of the VSEPR model, the latter being absent in the Swedish curriculum and ionic bonding not explicitly mentioned in the South African curriculum. To some extent these differences are reflected in the students’ responses to the survey. It is also clear that university teachers in both countries must prepare effective counter-measures against deep rooted misunderstandings. For the upper secondary school level it is suggested that the bond energetics and exothermic and endothermic reactions be clearly and carefully presented and separated as the study indicates that mixing of these two concepts is a major cause of confusion.