On the negative oxidation state and chemical bonding of late transition metal elements in their compounds with electropositive main group elements

PHYS 215

Myung-Hwan Whangbo, mike_whangbo@ncsu.edu1, Changhoon Lee, clee10@ncsu.edu1, and Juergen Koehler, j.koehler@fkf.mpg.de2. (1) Department of Chemistry, North Carolina State University, Box 8204, Raleigh, NC 27695, (2) Festkoerperforschung, Max-Planck-Institut, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
In qualitatively predicting the nature of the frontier energy levels, one commonly employs electron counting rules such as ionic and covalent electron counting rules in which the concept of oxidation state plays an important role. Such a simple picture of bonding breaks down for compounds of late transition metal elements with electropositive ligands for which the transition metal d-level lies in between the s- and p-levels of the ligands or lies lower than the s- and p-levels of the ligands. For such compounds, a blind use of the conventional (i.e., ionic and covalent) electron counting rule leads to incorrect predictions. To correct this deficiency of the conventional electron counting rules, a modified electron counting rule is necessary. In the present talk, a brief review will be given for those extended solids of late transition metal elements in which their oxidation states are best described as zero or negative. The electronic structures of such compounds, determined from density functional calculations, were analyzed to find the bonding picture that captures the essence of their electronic structures. Specific examples to be discussed include those compounds in which the electron configuration of the transition metal element is best described as nd10, (n+1)s2nd10, (n+1)s2nd10(n+1)p1 and (n+1)s2nd10(n+1)p2.